Seeing The Earth From Space : What the Man-Made Moons Tell Us 0451020502, 9780451020505

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Seeing The Earth From Space : What the Man-Made Moons Tell Us
 0451020502, 9780451020505

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the way up The launching of earth satellites is one of the greatest achievements of human history. It has opened the door on dramatic new vistas of knowledge . . . man now has a possibility of peereine his world far beyond the confines of earth.

This fascinating book by 2 noted scientist and writer tells in clear, nontechnical language just what our assault on space has accomplished to date. Irving Adler reports actual results of both Russian and American satellite launchings.

He describes findings regarding the shape of the earth, density of electrons, temperature of upper air, noting particularly the Van Allen radiation belts— two rings of charged particles encircling the earth, one of which was predicted by the Norwegian physicist Carl Stormer some fifty years ago.

The text is illustrated with Ruth Adler’s informative drawings. The author also includes eight ages of photographs, and a valuable table showing the date of launching, weight, distance from earth, and length of life of the first fifty satellites that America and Russia have placed in orbit.

Other SIGNET SCIENCE LIBRARY Books Tue Sun Anv Its Famity by Irving Adler A popular book on astronomy which traces the scientific discoveries about the solar system from earliest times to the present. (# P2037—60¢) TuHinkinc Macuines by Irving Adler The uses of logic and algebra in connection with today’s electric computers, and how these computers work, (# P2065—60¢)

ReELativiry FoR THE LAYMAN by James A. Coleman A concise history and account of the theory of relativity, written with a minimum of technical language and profusely illustrated. (# P2049—60¢) THe Wetsprines or Lire by Isaac Asimov The chemistry of the living cell and its relation to evolution, heredity, growth and development. (# P2066—60¢)

TO OUR READERS: We welcome your request for our free catalog of Stcnet and Mentor books. If your dealer -does not have the books you want, you may order them by mail, enclosing the list price plus 5¢ a copy to cover mailing. The New American Library of World Literature, tare Box 2310, Grand Central Station, New York Tey NER §,


aech£9 : “inAt


Seeing 4 The Earth ‘

From Space

7 Ts

- What the Man-Made Moons Tell Us :

By Irving Adler — ss

Illustrated by Ruth Adlet i fi Based in parton

MAN-MADE MOONS, — v2Irving Adler |


© 1957, 1959, 1961 By IRVING AND RUTH ADLER All rights reserved. This book, or parts thereof, must not be reproduced in any form without permission. For information address The John Day Company, Inc.,

62 West 45th Street, New York 36, New York.


By Arrangement with The John Day Company, Inc. Fmsr PrintTinG, JANuARY, 1962

Material on the findings made by earth satellites constitutes approximately two-fifths of the text and illustrations of this book. The remainder is background material from the author’s earlier book, Man-Made Moons. SIGNET TRADEMARE REG. U.S. PAT. OFF. AND FOREIGN REGISTERED TRADEMARK—MAROA BHGISTRADA HECHO EN OHICAGO, U.S.A.


SIGNET SCIENCE BOOKS are published by The New American Library of World Literature, Inc. 501 Madison Avenue, New York 22, New








Contents . The Earth Satellite



. The Shape of the Earth


iil. The Earth’s Blanket of Air

7 tv. Light We Never See . The Earth as Seen from Space vi. Electricity in the Air Vit. The Earth’s Magnetism


Next Steps in Space




First Satellites Successfully Placed in Orbit 137 Index







mF G7St



The Earth Satellite af Yew Moons and New Planets

Every month we say there is a new moon in the sky, al-

though it really isn’t a new moon at all. It is only the old moon hiding its face again in its own shadow. But now

are there are moons in the sky that are really new. They ‘man-made moons, designed by scientists, built in labora-

tories, and hurled into space from the ground. They to are tiny compared to the old moon, and much closer of _ satellite a is each moon, old the like But, the earth.

the earth in an orbit of its |

‘the earth, revolving around

; own. were There are also new planets in the sky. They

but unched from the earth in the direction of the moon, the around circle fe y sped past the moon and began to gun.

was launched by scientists

The first man-made moon

day of the Soviet Union on October 4, 1957. On that the sputnik, the whole world began using a new word, second Russian word for satellite. One month later a

a _sputnik was in the sky carrying the first space traveler, satellites earth more six 1958, In Laika. all dog called were © successfully placed into orbit. Five of them — the SoO space by the United States, and one by ; sph













spre BD) f'y






viet Union. In February and April, 1959, the United States launched two more earth satellites, and there will be many more following them into the sky. At the time that .this is being written, only six of the first ten man-made moons are still revolving around the earth. The other four have already fallen back to the earth, burning up as they fell. The new planets are accidental results of attempts to fire rockets to the moon. A Soviet moon rocket, fired on January 2, 1959, took about two days to travel the 240,000-mile distance to the moon. But it didn’t get close enough to the moon to hit it or begin circling around it. It passed the moon at a distance of about 5,000 miles, and went on into an orbit around the sun. An American moon

rocket, fired on March

3, 1959,


to within

37,000 miles from the moon, and then, like the Soviet rocket, sped on into an orbit around the sun. First Steps into Space

The launchings of the earth satellites and moon rockets are important as man’s first steps into outer space. For hundreds of years men have dreamed of being able to travel away from the earth. Gifted writers like Edgar Allan Poe, Jules Verne, and H. G. Wells have told exciting stories about spaceships that carried men to the moon. Magazine stories, radio programs, and motion

pictures have described voyages to Venus and Mars. But all these journeys through space have existed only in the imaginations of their authors, While man’s mind has reached out to the stars, his body has been a prisoner on the earth. The force of gravity has been like an invisible chain binding him to the earth’s surface. But when the first earth satellite rose out of the earth’s atmosphere to circle the earth hundreds of miles above the ground, it proved that this chain had been broken. The first manmade moon, was only a small sphere carrying™scientific instruments. But its successful journey paved the way for passenger ships that will some day follow it into space.




Rising above the Air

The earth is surrounded by a blanket of air that extends for many miles above the ground. Beyond the air is space, senarating the earth from its nearest neighbors ing stories about spaceships that carried men to the

air is the gateway to space. Before man could consider venturing into space he had to learn first how to rise above the ground into the air. In 1783 he invented the balloon, and in 1903 he invented the airplane. In an airplane, man has climbed as high as 91,243 feet, or 17 miles above the ground. In a balloon he has reached a height of 101,500 feet, or 19 miles. Balloons without 30 miles UNMANNED:




25 miles

20 miles [Be

Heights reached by aircraft

_ passengers





a height


balloon 140,000 feet, or almost 27 miles. But while the

into and the airplane can carry men or their instruments

and the air, they cannot carry them out of it. Balloons above airplanes need the help of the air in order to-rise comes up n balloo a pushes the ground. The force that

Se 10






from the pressure of the air. The force that pushes an airplane up comes from the combined action of air pressure and the flow of air across the airplane’s winzs. An . airplane with a gasoline engine or a jet engine also needs air to make its engine work. The air supplies the oxygen with which the engine’s fuel combines as it burns. In balloons and airplanes, men escape from the ground only to become prisoners of the air. In order to escape from the air into surrounding space, we need a ship that does not depend on the air to lift it. The ship must also have an ensine that does not need air in order to burn its fuel. A ship that is powered by rockets satisfies these conditions. That is why rocket engines are included in all designs for spaceships, and that is why rockets are used to hurl an eart' satellite into its orbit. How a Rocket Works

To see in action the principle on which a rocket works, try this simple experiment with an ordinary rubber bal- — loon. First blow up the balloon, and notice how it swells. It swells because you are pushing compressed air into it, and the compressed air is pushing against the rubber —

wall of the balloon. This shows that a compressed gas is ;





capable of exerting a push. Now stop blowing up the balloon, and hold it by its neck without pinching it shut. The compressed air in the balloon, still pushing, takes advantage of the open mouth of the balloon. It pushes its way out of the balloon with a noisy rush. Now blow the balloon up again. Then, instead of holding the bal‘loon, let it go. This time, a surprising thing happens. As balloon the air rushes out of the mouth of the balloon, the direction. opposite the in room the darts across

To think when wall

understand why the balloon of this experience you must you use your roller skates. and push against the wall

begin rolling backward

sails across the room, have had many times If you stand next to a with your hands, you

away from

the wall. You


the wall - pack because when you push against the wall,of an imle examp an _ pushes back against you. This is action and - portant law of nature known as the law of gets pushed reaction. This law says that anything that what happens ~ pushes back. This law helps us understand mouth of the the of out to the balloon. The air rushes ure. But, as press own its by d balloon because it is pushe

back against the balloon. the air is pushed out, it pushes sends the balloon sailing across the

_ This backward push forward for the room. A rocket, when it is fired, darts d by their own pushe are gases - same reason. Compressed end of the rocket. _ pressure out of an opening in the tail pushed away~ from the - As the compressed gases are the opposite direction. in rocket, they push the rocket

i eae ‘ see a

| 12






Burning without Air

The gases that are pushed out of a rocket come from ’ the rocket engine that is inside. The engine is simply a combustion chamber in which some fuel is being burned. The burning fuel produces hot gases with a high pressure. In an ordinary fire, like those we see in a fireplace or a stove, air is needed to feed oxygen to the fire. Oxygen is needed for the fire because burning is a chemical reaction in which the fuel combines with oxygen. The fire in a rocket engine needs oxygen, too, but it does not need air. It manages to burn without air because the rocket carries its own oxygen supply. In some, rocket engines the oxygen is stored in a tank in the form of COMBUSTION


liquid oxygen. In other rocket engines, the oxygen is hidden in some chemical compound like nitric acid. The fuel in a rocket engine may bea liquid, like alcohol or —

gasoline, or it may be a solid.

New Use of an Old Idea The rockets used to launch earth satellites are a modern development of a very old invention. The rocket was invented in China over seven hundred years ago. The Chinese rockets were powered by gunpowder, which is a mixture of sulphur, charcoal, and saltpeter. The sulphur and charcoal were solid fuels that burned in the rockets. The saltpeter, a chemical compound.that contains oxygen, served as the rockets’ oxygen supply. The Chinese used the rockets as weapons in warfare. The use of gunpowder and rockets spread from China across

— — —

— © 4






Asia, into Europe. But the invention of guns and cannon gradually displaced the rocket as a weapon. By the time of World War I (1914-18), rockets were used chiefly to fire signal flares into the air, and for fireworks displays in holiday celebrations. It looked as though the rocket would soon be nothing but a toy and ahistorical curiosity, like the bow and arrow. But, shortly after the war, new interest in rockets was aroused when two scientists proposed new uses for which rockets are ideally suited. In 1919, Dr. Robert H. God-

dard, an American

scientist interested

in studying the

upper layers of the earth’s atmosphere, published an article suggesting that rockets might be used to carry measuring instruments high up into the air. In 1923, Professor Hermann Oberth, a German mathematician, wrote a book showing that rockets could also be used for

flying out of the air into interplanetary space. For both

purposes, however, it was necessary to make rockets far more powerful than any that had been used before. To give rockets a stronger push or thrust, Dr. Goddard and rocket other scientists and engineers began to design Goddard Dr. 1926, In fuels. engines that burn liquid fired his first liquid-fuel rocket at Auburn, Massachusetts.

=e wns

|ie es ie

designed and In Germany, a society of rocket enthusiasts travel

that space tested rockets, and confidently predicted fact. into n fictio from rted conve be soon - would

eo aoa.


ae fg ae 14





Old Use of a New Idea

With the outbreak of World War II (1939-45), the new rocket designs were exploited for an old purpose.

The rocket was restored as an important weapon of war. Germany developed an airplane with a rocket engine, and created the V-2 rocket, a guided missile that traveled 200 miles to reach its targets in England. The V-2 rocket was a bullet-shaped barrel about 46 feet long and over five feet wide in the middle, and carried almost a ton of high explosives in its nose or warhead. Its engine used liquid oxygen to burn alcohol as a fuel. The oxygen and the fuel were forced into the combustion chamber by pumps and operated by a steam turbine. The burnt gases — rushed out of the nozzle at the tail end of the rocket ata — speed of 4,500 miles per hour, giving the rocket a thrust of over thirty tons and a speed of about 3,500 miles per hour. The rocket, aimed at London from a launching platform 200 miles away, followed a curved path that took it as high as 60 miles above the ground. It took less than five minutes to reach its target, and arrived without being heard in flight, because the rocket traveled three

times as fast as the sound it made in the air.



a V-2 on Its Course

A V-2 rocket was carefully aimed at its ae: But it




was impossible to predict all the forces that might influence it while it was in flight, and might turn it aside trom the path that it should follow. So, to keep it on its course, it was provided with steering gear, and an automatic pilot to control it. The steering gear consisted of movable rudders in the tail fins, and vanes mounted so that they could be turned into the path of the gases that rushed out of the rocket engine. The automatic pilot controlled the movements of the rudders and vanes by means of electrical signals to the motors that turned them.

The heart of the automatic pilot is a set of gyroscopes. A gyroscope is simply a wheel that is spinning around on its axis like a top. A spinning gyroscope, if it is not disturbed, tends to keep its axis pointing in the same tilt direction all the time. But if any attempt is made to

a it, the axis begins to wobble. Because of this property, the If n. directio in changes “sense” can set of gyroscopes the changes in direction turn the rocket off its course, it back. automatic pilot signals the steering gear to turn

Exploring the Upper Air



was defeated in the war, American

er with a forces captured the V-2 launching sites, togeth s. The rocket ed finish supply of completed and partly d

be studie rockets were brought to the United States, to might be forces ry milita can Ameri that so and improved hile Meanw es. equipped with long-range guided missil

7 Se


tg RHC:

i gOS

Se ee os





the rockets were put to work to realize Dr. Goddard’s - original purpose, the scientific study of the upper air. The rockets were fired from launching platforms at the ‘ White Sands Proving Ground in New Mexico. Instead. _ of being aimed at a target on the ground, they were fired almost straight up into the air. Instead of carrying a ton of high explosives, the warheads were now packed with scientific instruments. The rockets carried cameras for photographing the earth, and spectrographs for analyzing the sun’s light. They took aloft cloud chambers and ~ other instruments for catching, counting, and identifying the cosmic ray particles that crash in on the earth from outer space. They measured the magnetism of the earth, and scooped up for study samples of high-level air. Some of the information gathered by the instruments was converted into electrical signals and broadcast to the ground © immediately by specially designed radio transmitters. Other information was obtained only when the instruments themselves were recovered from the wreckage of — the rockets, after they fell to the ground. Successors of the V-2

The supply To take their especially for was ready for

of captured V-2 rockets was soon place, new rockets were built, upper air research. In 1948 the use. The Aerobee is smaller and

used up. designed Aerobee slimmer


than the V 2 and doesn’t go so high. While the V 2 has — gone as high as 114 miles, the Aerobee, which is only 19 feet long and 15 inches wide, was designed to reach aheight of about 80 miles. In 1949, the Viking was completed. The Viking is as long as the V-2, but is only 32. inches wide. It is capable of reaching heights above 150 miles. The Viking has been outreached by the AerobeeHi, which has climbed to a height of 180 miles.

Rockets That Ride Pickaback



When a rocket is launched from the ground, it has to © fight its way up against the force of gravity and» the 3 a 1 tt

al taal




ee =



stance of the air that surrounds it. By the time it a— vs,

aches. a height where

air resistance

is small, its fuel


supply has been used up, and it has been slowed down

so much that it begins to fall. Gravity and air resistance

‘put a limit on the height that a single rocket launched

= from the ground can reach. It is possible to bypass this—

limit by launching

the rocket, high above

the ground,—

where the air is already thin. But then the rocket has to

be carried up first, before it is fired. One way of doing this is to use a rockoon, a balloon and rocket combination. First the balloon

the rocket


into the air.

Then, when the balloon has reached its maximum height,

e the rocket is fired. Another way is to have a two-stag ride, a rocket rocket, in which one rocket gives another ‘In 1949, a V-2 rocket was launched with a small rocket, ‘known as the WAC-Corporal, mounted in its nose. CorWhen the V-2 reached a height of 20 miles, the e of altitud an to was fired, and went up from there

kets that launch earth satellites have thrée’ or 4







four stages. First one stage is fired, and carries-the others

high into the air. When

the fuel of the first stage has

been used up, it drops. off, and the second stage is fired, boosting the speed of the stages that remain. Then the

second stage drops off and the third stage is fired, giving its speed another boost. If there is a fourth stage, it is fired last. The successive pushes given by the rockets| raise the last stage to a height of 300 miles or more. Then > the satellite, carried up to this point by the final stage rocket, is released into its orbit. ‘|

In the United States, a three-stage rocket known as

Vanguard was designed by the Navy for the special purpose of putting earth satellites into space. At the same time, other rockets were being developed for military uses. Among these were the Air Force Thor and Atlas and the Army Redstone and Jupiter. Although not originally intended for that purpose, these rockets were used for launching some of the American earth satellites. The wartime use of V-2 rockets had the same effect on | the Soviet Union as it did on the United States. It stim-



great interest in rockets and missiles, Using the —= ;; ,-

rman experience with V-2 rockets as the starting point, viet scientists and engineers built rockets for upper-air .

search and for military purposes. By 1957, the United ‘States and the Soviet Union, as the two leading industrial a military powers, were engaged in a race, each trying | Ko be the first to get its earth satellites off the ground.

An Eight-Minute View By rising higher than any airplane or balloon can — reach, to a position above the greatest part of the earth’s ‘atmosphere, rockets made it possible for scientists to. gather important new information about the earth. The instruments in the rockets look down on the earth to see

Sy .



& ok




200 miles ——









] 100 mites



Heights reached by rockets before the first shots at the moon

sun, how it looks from the outside. They look up at theit and ee what sunlight is like before tie air stops a good part of it. They look around at the surters upper air and observe conditions that could “be he bot,


pts AE








a .3. Pee es ee

ate Ct




isee ied o a ipitee is rind byit its ce the short duration of its flight. A rocket like the \ + Corporal is fired almost straight up, and lands not ma: ‘. miles from its launching site. So its instruments observe — conditions in the upper air only over a small region of t earth. They get only a quick look around, because | rocket goes up and down so fast, the instruments have at most eight minutes in which to make their observations. - These disadvantages are overcome by the use of earth~

satellites. Each satellite circles the globe many times and—

-makes world-wide observations. For example, the first— earth satellite, Sputnik I, made 1,400 trips around ee l earth before it fell. Satellites also stay aloft for a long period of time. ie



The years 1957 and 1958 were chosen for the birth of the first man-made moons so that they could share in the activities of the International Geophysical Y:

The IGY extended for an eighteen-month period be ning with July 1, 1957. Sixty-four nations cooper in the most extensive study of the earth and its roundings ever made. Teams of scientists studied _ ground, the oceans, the great ice sheets that cover

polar regions, and the sea of air that lies above them a About 30,000 scientists, engineers, and technicians, and an equal number of volunteers took part in these activve -ities. Seven of the participating nations launched rockets _ to take soundings of the upper air. The rocket launchers oo were Australia, Canada, France, Great Britain, Ja _ the Soviet Union, and the United States. A total of 3 sounding rockets were fired. Each was equipped w instruments for making a variety of measurements in t air. The instruments that went the highest and tray

the farthest were those carried by the earth satellites the moon*rockets launched by the Soviet Union and : rs



came to an citsonnee




‘their cooperative study of the earth for another year —

through a special organization known as IGC-1959 (International Geophysical Cooperation), and to join forces / again in the International Year of the Quiet Sun (IQSY) ‘in 1964-65 when sun-spot activity will be at a minimum. The Names of Earth Satellites

Each of the earth satellites has. two names. One is the popular name, generally used in all public discussion about the satellites. The other is the scientific name, con-

sisting of the year the satellite was launched and the name of a letter in the Greek alphabet. This kind of name for _ objects seen in the sky is commonly used by astronomers. The popular name for all the Russian earth satellites is

_ Sputnik. The American satellites carry such names as Explorer, Vanguard, and Atlas, taken from the name of

the project or the rocket that launched it. Here are the ‘names of the first ten earth satellites, listed in the order in which they were put into orbit: Sputnik I (1957 Alpha), Sputnik Il (1957 Beta), Explorer I (1958 Alpha), Vanguard I Gamma), Sputnik III Epsilon), Atlas (1958 Discoverer II (1959

(1958 Beta), Explorer III (1958 (1958 Delta), Explorer [IV (1958 Zeta), Vanguard II (1959 Alpha), Beta). Notice that the list skips

Explorer IJ. This was the name of a satellite that never ground, went into orbit because, although it went off the It also fire. to failed ly assemb rocket the of stave the last mee : : . ry, Februa in ed _ skips Discoverer I, which was launch days. few 1959. It had a life of only a ‘The first Russian moon rocket, while it was on its way word toward the moon, was called Lunik, from the Latin Rusthe moon, luna, meaning moon. After it passed the dream. means which , Mechta to sians changed the name

The first American moon rocket is called Pioneer IV.

Basketball in the Sky Sputnik

I, the earth

satellite that opened

the space

22-inch ball, not much 3 ‘on October 4, 1957, was a ot

Bee a:




“tt ew about 184 onde It carried two sete ra mitters for sending out “beep” signals to the ground.



The transmitters were operated by batteries that supplied each with one watt of power. (This is about one-— hundredth the amount of power used to light an ordinary — electric light bulb.) Sputnik followed an oval-shaped path — known as an ellipse. It was not always the same height } above the ground. When it was closest to the earth, in the position


as perigee,

its height




When it was farthest away, in the position known

as |

traveled at a speed of about 18,000 miles per hour. Thi : speed was great enough to carry it completely around the world in 96 minutes. This time is referred to as the period of the satellite. The orbit of Sputnik I made an angle sixty-five degrees with the equator. Because of this fact, kept passing from the northern hemisphere to the south-— ern hemisphere and back again. Since the earth was turn-_ ing under it, the satellite passed over a different part of the equator every time it crossed it. The orbits of the other earth satellites also made an angle with the equator, so they too passed back and forth between the nor ern and southern hemispheres. Those that are still in or_ bit are doing it right now. ; Sputnik I was released from the third stage of a threoll _ Stage rocket. The third stage rocket went into orbit

the satellite, trailing behind it. The rocket fell eart ‘December, 1957. The satellite fell on January 4, 1 _ By that time, it had traveled a total of 38 million mil Flying Dog Kennel .

ry J


Sputnik I, launched on November 3, 1957, was of heavier than Sputnik I. It weighed 1,120 pounds. It

Tied instruments for measuring X-rays and ultra-v “rays, and radio transmitters for reporting fts mea _tnents to the ground. It also carried the dog, Laika, first passenger ever to travel in a spaceship. L a space suit,pond sat in a setlecs air-conditio: ig





Special instruments measured her pulse, blood pressure, and breathing rate, and fed the information, in the form of electrical signals, to the radio transmitters. Laika died when her oxygen supply was used up. In its trips around its orbit, Sputnik II rose as high as 1,056 miles above the ground, and dipped as low as 145

Laika in her compartment

miles above the ground. Its period, or round-trip time, was 103.7 minutes. It fell and burned up on April 13, 1958.

_ Radiation Detective - Explorer I was Jaunched on January 31, 1958, by a four-stage Jupiter-C rocket using a Redstone rocket as its first stage. The satellite, built into the last rocket stage, was a cylinder 80 inches long and six inches wide. It weighed 30.8 pounds, and carried a pay load of 18 pounds of scientific instruments, batteries, and radio transmitters. One of the instruments was a geiger Coun3 for detecting and measuring the amount of radiation

S an camoraitPaceay ee ae ae space surrounding the earth. (See page 113.) The hi Eand lowest points of the orbit of Explorer I were 1, miles and 224 miles above the ground. Its period 115 minutes. At the time that this paragraph is being _ written, Explorer I is still in orbit, with a filenege of a _ few more years ahead of it.

sy ae hae

_ High Flyer

Vanguard I, the satellite launched on March 17, 1958,— has the distinction of being the smallest and the highest

of the first nine satellites, and the one that will last the longest. It is a sphere that is only 6.4 inches wide, a weighs 3142 pounds. The highest point in its orbit is _ 2,453 miles above the ground. Calculations show that it will stay aloft about two hundred years. It was launch with two radio transmitters aboard. One of them, ered by a chemical battery, went dead when the batte p | ran down. The other one, powered bya solar battery, which gets its energy from sunlight, is still working,and _ will continue to work indefinitely. Its steady beeping helps —


tracking stations locate its position in space with gr accuracy. A careful study of its motion has led to


portant information about the shape of the earth, includ- —

ing the discovery that the earth is slightlypear-shaped. ee page 61.)


ie Tape Records from Space ; The geiger counter aboard Explorer I fed its measurements

to the radio transmitters, which broadcasted the

to the ground


When the satellite passed

iover a tracking station, the station received its message. peut during a large part of ‘each of its round trips, t satellite was too far from any tracking station fomits _ broadcasts to be picked up. At these times, theiinfor f -mation it was sending down to the ground was| was caurecteg in Explorer III, |: aeweakness Piatt







March 26, 1958. Explorer III carried a geiger counter similar to the one on Explorer J. But its measurements were not broadcasted as soon as they were made. They were recorded on a magnetic tape instead. Then, when the satellite passed over a tracking station, a signal from the ground caused the transmitter to broadcast the infor‘mation stored on the tape. In this way, measurements made out of range of the tracking stations were not lost. Explorer III fell on June 27, 1958. Flying Laboratory

Sputnik III, launched on May 15, 1958, was a fully equipped scientific laboratory. It was shaped like a cone, 11 feet, 9 inches high, and 5 feet, 8 inches wide at the base. It weighed 2,925 pounds, and carried 2,134 pounds of instruments. The instruments were designed to measure air pressure near the satellite, temperature inside and outside the cone, electric charge, rays from the sun, and the magnetic field of the earth. They counted the tiny meteorites that struck the satellite, and weighed the heavier

of the cosmic rays that entered it. As in Explorer III, all measurements were recorded on tape, and were broadcasted to ground stations only when signaled to do so. Sputnik III is believed to have fallen on April 6, 1960. Improving the Count

A geiger counter counts radiation particles by releasing a brief pulse of electricity for every particle that strikes it. When

the particles come

in rapid succession,

the electrical pulses do, too. If the particles come too rapidly, the geiger counter becomes tongue-tied, like a man trying to talk too fast, and it jams. This happened to the counters that were carried by both Explorer I and

Explorer II. The jamming showed the existence of a high


of radiation,





couldn’t measure exactly how high it is, To eliminate this difficulty and get more accurate information about

_ radiation 4


in space,

a less sensitive geiger counter® was







placed aboard Explorer IV, which was put into orbit on July 26, 1958. This counter had a window only one — seventy-fifth the area of the windows of the counters on the earlier satellites, so it admitted fewer particles. Even - then, it admitted about five thousand particles per second. The information obtained from Explorer IV confirmed the important discovery made by Explorer I. The meaning of this discovery is discussed in Chapter VIL. Flying Relay Station On December

18, 1958, the Atlas earth satellite was

launched, with a pay load of 150 pounds. Atlas served — as the first radio relay station in space. President Eisenhower’s Christmas peace message to the world was broadcasted to it before the rocket left the ground. The satellite — recorded the message on tape, and then, when the satellite — was in orbit, rebroadcasted it when ordered to do so by a radio signal. Later, Atlas erased this message from its tape, picked up new ones beamed up from ground stations in Texas, Arizona and Georgia, and broadcasted them, too. What this means for future world-wide radio

and television broadcasting is discussed in Chapter VIII. — Atlas fell on January 21, 1959. A Weather Satellite

The ninth earth satellite, Vanguard II, was put into — orbit on February 17, 1959. Vanguard II has special equipment for observing and reporting the position of — clouds in the air. (See page 58.) This information will—

be of great value in working out methods of making —

more accurate weather forecasts. Vanguard II will re-— main in orbit for several decades. Other space weather — stations will soon join it to gather information of different | kinds. Spy in the,sSky

®, te,

The tenth earth satellite, Discoverer II, was success-

fully launched on April 13, 1959, It followed an orbit— ae







that took it repeatedly over the north and south poles.

Meanwhile, the orbit swung around the earth. As a result, the satellite was in a position to view every part of the earth at some time during its flight. Discoverer II was designed to keep a fixed orientation, without spinning or tumbling. This design has made it possible for later satellites like it to view the ground through television cameras, and gather important military information. Discoverer II was also the first in a series of satellites which were used in attempts to bring a space capsule safely back to the ground; at the time this edition goes to press there have been 21 launchings. The Discoverer II satellite contained a 195-pound hemispherical capsule 27 inches long by 33 inches base diameter in which were packs of photographic emulsion to study radiation in space and equipment to maintain the internal temperature at a level sufficient to sustain life. A timer in the satellite ejected the capsule on April 14 but it was not recovered. The method of recovering the capsules was to involve descent through the atmosphere while protected by a heat shield, then braking with a parachute and finally catching the parachute lines with cables slung out behind aircraft sent to the predicted point of descent. If all went well, there would be time enough for the aircraft to have two or three shots at catching a capsule. But all did not go well at first; there was a long series of disappointments. Discoverer II was not recovered, and Discoverers III and IV (launched on June 3 and 25,

1959) failed to orbit, owing to second-stage failures in erer the U.S.A.F. Thor-Hustler launching vehicles. Discov same the using 1959, 13, V was placed in orbit on August but fuel, stage first ic energet more a type of vehicle with ed. recover be not could it ejected was e capsul the when ber ‘The satellite burned up in the atmosphere on Septem debeen have to t though also 28, and the capsule was being first (after overed redisc later was stroyed, but it thought to be an unidentified


satellite). It was

sevstill in orbit early in 1961, with an estimated life of

‘eral months. he



For subsequent attempts, the Thor-Agena two-stage launching vehicle was used. Discoverers VI, VII and

VIII all achieved their orbits when they were launched

on August 19, November 7 and November 20 respectively; as is usual for this series of satellites a polar orbit was employed. The capsule of Discoverer VI was ejected but not recovered; that of Discoverer VII did not eject as planned on the seventeenth orbit (the satellite was not stabilized in its orbit), and there were several troubles with Discoverer VIII (the satellite went into an elongated orbit, the capsule was ejected on the fifteenth instead of the seventeenth orbit, and its parachute failed to open). There was no improvement with the next two attempts; in both cases the satellite was not placed in orbit. When Discoverer IX was launched on February 4, 1960, — a fault in the fuel connection in the servicing gantry re_sulted in a premature shut-down of the first stage and damage to the second stage of the launching vehicle. On February 19, 1960, the Range Safety Officer had to destroy the rocket carrying Discoverer X 52 seconds after take-off when a control fault developed at an alltitude of 20,000 ft. These failures represent the waste of considerable effort and ingenuity; apart from the launching rocket and satellite, the capsule contained a variety — of equipment: a retro-rocket (fired to start the descent — of the capsule), a parachute, a radio beacon (to assist — in location of the capsule during descent), radar devices, and a rotating high-frequency stroboscopic light to act © as a recovery aid. ; The same equipment was carried by Discoverer XI, launched on April 15, 1960. This attained its orbit, and — the capsule was ejected successfully. However, despite the equipment, contact was lost with the capsule so that recovery was hopeless. Discoverer XII carried additional { instrumentation to check the orientation system of the — satellite and the ejection of the capsule, but when this was launched on June 29, 1960, it did not achieve orbital © velocity—it immediately re-entered the atmosphere and

was burned up.


But these eleven unsuccessful attempts were to be foloa se





lowed by brilliant success. On August 10, 1960, Discov-

erer XIII was launched into orbit, and after seventeen circuits of the earth over a period of twenty-seven hours a timing device triggered gas jets which turned the satel-

lite into a position 60° down from horizontal. Separation of the re-entry capsule was accomplished by a series of explosive bolts and springs. A retro-rocket was fired immediately after separation. When this rocket had burned out, the vehicle was traveling at only slightly less than orbital speed and following a path less than five degrees from horizontal. The trajectory became more and more vertical as the vehicle descended, until finally the drag forces operated a switch and a parachute was released. The capsule weighed 300 pounds when it left the satellite, but the shedding of its retro-rocket, parachute cover and heat shield during descent reduced the weight to 85 pounds. Broken clouds delayed sighting of the satellite by aircraft waiting to catch it, and it landed in the Pacific Ocean about 300 miles northwest of Hawaii on August 11. One of the aircraft spotted it floating in the water and it was picked up by a U.S. Navy frogman from a helicopter. This was 3 hours 54 minutes after it had been ejected over Alaska. When recovered it was still transmitting radio signals. Air Force Discoverer XIV, launched from Vandenberg The Base on August 18, 1960, was even more successful.

capsule released from the satellite was caught in mid-air by an aircraft piloted by Capt. Harold E. Mitchell. He before made two unsuccessful attempts to snatch it was aircraft hooking the parachute in his third try. The ping telesco two n fitted with “trapeze” gear slung betwee steel poles trailing beneath its fuselage. This was the first mid-air recovery. There have been next others since, but bad luck was experienced with the from sfully succes ted separa e capsul The ts. two attemp Discoverer



on September

13, 1960, and

was sighted by aircraft, but then lost in a storm. When



Discoverer XVI was launched on October 26, 1960, the

oe .







second stage of the rocket did not separate from the first stage, and the satellite was not even placed in orbit. Good fortune smiled on Discoverer XVII. This was sent up on November 12, 1960, and the capsule contained specimens of human tissue so that the effect of its exposure to severe radiation could be studied. For this reason, separation of the capsule was delayed until the thirty-first orbit; it was recovered by air snatch at a height of 9,000 feet 500 miles northeast of Hawaii by an aircraft piloted by Capt. Gene W. Jones. Whereas previously the capsule had been ejected by a timing device,

in this shot ejection


by a radio


from the ground. There were some other variations: the launching rocket had a more powerful second stage (a | modified Agena B rocket) and a new type of plastic nose — cone was used. This was said to be for the protection of animals to be sent up in future flights in this series, but. does not seem to have been a great improvement, as the capsule is reported to have been slightly scorched. Discoverer XVIII was launched on December 7, 1960, using an even more powerful vehicle, with an improved Thor rocket as first stage. The capsule contained human bone marrow, membrane from a human eyelid, algae,

spores and other materials for radiation studies. Ejection was delayed until after 48 revolutions and the capsule was caught in mid-air at 14,000 feet near Hawaii. The pilot was again Capt. Gene Jones. A recoverable capsule was not included in Discoverer XIX, launched from Vandenberg on December 20, 1960. — Instead, it carried instruments to study the heat (infrared) radiation given out by the earth beneath, equipment similar to that to be used in the Midas satellites to detect © _. the launching of enemy ballistic missiles. The radio of the satellite ceased transmitting on Christmas Day, much ' earlier than expected. : The heaviest satellites in this series were«Discoverers — XX and XXI, launched on February 17 and 18, 1961.




A further success


1 ton and carried Midas was achieved


with Discoverer _





XXI. After it had been placed in orbit, its Agena B rocket engine was restarted on command from the ground. This opened the way to the development of maneuverable spacecraft and of satellites which could stay in orbit indefinitely. (With engines that can be switched on and off at will, it is possible to correct deviations from the desired orbit.) We have seen that the Discoverer series (which may include over fifty launchings by the time it is completed) has had two main objectives, namely, mastering the technique of recovering a satellite from space, and developing an infrared detection system for missile detection. This is not the only “Spy in the Sky” system. There is also Samos

(the Satellite and Missile Obser-

vation System), which is designed to do a job previously carried out by the U-2 aircraft: the photographing of ground installations and troop movements in other countries. The satellites contain cameras capable of taking photographs equivalent to what the eye would see from a height of 100 feet. These are developed aboard the satellite and later relayed by television to the ground on command. Samos I failed to achieve orbit on October 11, 1960, owing to damage to the second stage in take-off. Samos II was launched successfully on January 31, 1961, and was then expected to remain in orbit for at least a year, but to be useful as a spy for only about twenty days. The factors limiting its useful life were the life of the television transmitter and the exhaustion of a gas supply to jets used to keep the cigar-shaped satellite in a nosedown attitude (to aim the camera at the ground). The Discoverers are really R & D (research and decarry velopment) devices. The satellite that will actually launchnary Prelimi Midas. is es activiti out spy or police Febings of this have already taken place. The first (on not did e - ruary 26, 1960) was a failure, as the satellit The stage. first as separate from the Atlas rocket acting 2,500 assembly re-entered the atmosphere and burned up

_ miles from its launching pad at Cape Canaveral. Midaé II =



was put satellites between * factories

in orbit on April 24, 1960. 1 he equipment Midas will carry is designed to be able to discriminate the exhaust of a ballistic missile and heat from and furnaces.

The Vanguard Satellites

The Vanguard satellites were the first ones planned by America. Apart from Vanguard I and I mentioned above, only one other satellite in this series was placed in orbit. (Note that numbers were only given to successful Vanguards, whereas the Discoverer satellites are numbered by attempted launchings, whether successful or not.) Vanguard III was fired up on September 18, 1959, and contained instruments to measure the earth’s magnetic field, X-rays emitted by the sun and other conditions in space. Advanced Weather Satellites

The weather satellite Vanguard II has been followed by more advanced meteorological stations. On April 1, 1960, the 270-pound Tiros I was placed in orbit. Shaped like a giant pillbox,

it was






solar cells to absorb light from the sun and convert it into electricity to power the instruments and radio transmitters it contained. Tiros I was equipped with two TV cameras, one with a wide-angle lens taking a picture showing a strip of the earth measuring about 135 by 800 miles, the other taking — a close-up. The pictures were converted into an elec_ trical signal and then stored on magnetic tape, so that ' when the satellite later came over a ground station the | tape could be played back and broadcast to the ground. Provision was made for pictures to be transmitted direct to the ground when the satellite was within meas of a station.

The photographs were examined to study edba for— mation and distribution. Over 22,000 pictures were trans-

; i

mitted in 13 weeks before the investigation stopped; the zi‘




satellite itself will remain in orbit for fifty to a hundred — years. Another weather satellite, Tiros II, was launched suc- — cessfully on November 23, 1960, and has given many — useful photographs, although trouble was experienced with the wide-angle camera. At least one more Tiros is planned; it will be followed by the Nimbus “secondgeneration” weather satellites. The Later Explorers After Explorer IV (see page 26) there were two failures in this series: Explorer V and the U.S. Army’s Explorer VI (August 24, 1958, and July 16, 1959). The first

mishap was due to collision between the first stage and the rest of the vehicle after the first stage separated, while there was a control failure in Explorer VI imme; diately after take-off. A second Explorer VI was launched successfully by the U.S. Air Force on August 7, 1959. This was a more ambitious satellite than the Army’s and contained fifteen experiments. These simultaneously investigated the behavior of radio waves in the ionosphere (see Chapter ‘V), the earth’s magnetic field, the bombardment of the earth by micrometeorites, the earth’s cloud cover, etc.

_ Explorer VII, launched on October a replica of the U.S. Army’s


13, 1959, was

earlier shot. It

contained seven experiments, including weather study, “measurement of the heat radiation of sun and earth, — ‘measurement of the Lyman alpha and X-ray radiation ‘from the sun (see Chapter IV) and investigation of “micrometeorites.

~ Another Explorer failed on March 23, 1960, ‘because the later stages of the rocket did not ‘next achievement in the series was on November when Explorer VIII was sent up to investigate ‘sphere. It carried eight different experiments, it obtained



probably fire. The 3, 1960, the ionoThe data

for designing the engines that

will succeed the chemical rockets now in use—the nuclear me”“ee









Pea ees}

~~ rate

rocket and the ion ieee


rr TF Aq MtAIX



ang for future



tions technology.


p Giant Balloons in the Sky


Most of the artificial earth satellites could be deseaiaem 4 as queer-shaped metal boxes, but there are two that do not fit into this description. They are giant balloons,

_ made of thin plastic sheeting. Yet although they weigh —

dittle in comparison with the other satellites, they would -. never be able to rise unassisted to the altitudes they can

reach by means of rockets, and they can stay at those | altitudes only by whirling around the earth in the sane

way as other satellites. ! The first of the balloons was Echo I, which was placed Fi

in orbit on August 12, 1960. Weighing only about 165

pounds, it was lofted into a much higher orbit than usual for the metal satellites, an orbit at which the atmosphere — was extremely rarefied. This was necessary, for the high ratio of surface area to weight would make the satellite extremely susceptible to air resistance and drag. You can check this by throwing a balloon from one side of the — _ room both before and after blowing it up; you will find

it is much easier to do this when the balloon is empty. __ Echo I was blown up after reaching its orbit. It could

b B

, mA

not have been carried up when inflated, because it has a diameter of 100 feet. Its volume is greater than that of



the rocket which carried it aloft. When tested on the ground, 40,000 pounds of air were needed to inflate it;

in the near vacuum at an altitude of 1,000 miles only


_ few pounds would be necessary. However, it contai ee a trace of air; it was inflated with a white solic _ chemical





the balloon


released ~ into sunlight, the heat from the sun caused the

- benzoic acid to sublime—that is, to pass from solid to - vapor without intermediate'melting. This is a Pike ty

apeculiar to certain chemicals. ete

Is ae

contained 10 pounds |of benzoic.




Reenter Ary, a Pq






ee S| ng


Anthracene sublimes slowly; it was included so that if — the balloon was punctured by micrometeorites it would replace the benzoic acid as this leaked out.

The balloon was made of 82 orange-slice panels of Mylar plastic film coated with a thin film of aluminum deposited by evaporation in vacuum. This gave the surface a reflectivity of 98 per cent and made Echo readily visible from the earth; it also enabled it to reflect radio waves. A recorded message from President Eisenhower

was relayed right across America from the Jet Propul-

sion Laboratory

at Goldstone

Lake, California, to the

Bell Telephone Laboratories at Holmdell, New Jersey, by reflection from Echo when it was over the center of the United States, soon after launching. Other messages have since been relayed in the same way, thus demonstrating the practicality of a passive communications sys-

“tem (one in which the satellite acts only as a reflector,

and contains no electronic equipment for amplifying or

recording the message). Another balloon satellite, Explorer IX, was launched on February 16, 1960, and others are planned for the

future. Experiments with multiple satellites should take place in 1963-65, under the code named Project Rebound.

The Active Communications Satellite The alternative to the passive system is known as an active communications satellite. The first of these to be orbited successfully was Courier IB, launched from Cape

Canaveral on October 4, 1960, the third anniversary of

Sputnik I’s launching. On its first orbit it relayed a mes‘sage of President Eisenhower from Fort Monmouth, New Jersey, to Puerto Rico.

In contrast to the simple Echo I, the Courier satellite

is a complex mass

of electronic equipment, capable of

functioning either as a diréct relay or as a delayed‘repeater station. It was designed to operate only on command, to prevent unauthorized interception of messages. When in orbit the satellite transmits a low-powe radio signal; on receiving this signal a ground






station can send a coded command



to the satellite to

switch it from stand-by to active operation. The satellite acknowledges receipt of the signal and then transmits “messages to the ground station by VHF radio. The ground station also sends messages to the satellite. This is accomplished in the ten- to fifteen-minute period that the satellite is within range of the station. At the end of the transmission the satellite equipment is returned to the stand-by state, and this also happens if radio contact is lost for any reason. When the satellite passes over the next ground station, the process is repeated. Courier IB can provide twenty teleprinter channels or be used for voice transmission. Future communications satellites may contain as many as 600 channels. Navigation Satellites

The commercial use of satellites includes not only world-wide communications but also navigational assistance to shipping. The United States is putting into orbit a series of satellites that will enable any ship fitted with the necessary radio equipment to obtain accurate information about its position. The first experimental satellite launched as part of

this project—Transit IA, September, 1959—achieved the required altitude but did not go into orbit, owing to failure of the third stage rocket to ignite. Transit IB, launched on April 13, 1960, was a complete success. During its launching the first attempt at restarting a rocket in space was made, in order to correct its orbit. A second navigational satellite, Transit IIA, was

launched on June 22, 1960, and this time the required orbit was achieved. This was also a research device. When the operational system is put in place it will consist of four satellites orbiting simultaneously, to give world-wide coverage. The orbits will be determined accurately by ground stations, and ships using*the system will in effect do the same thing in reverse (knowing the time and where the satellite should be at that time, they obtain their own position).








a oe

Pickaback Satellites

Transit ITA was a rather special experiment. In addi-

tion to the navigational equipment it included a package of research equipment the Americans agreed to take up for Canada. This was to study radio-wave propagation in the ionosphere. It also carried up a second satellite, a small one developed by the Naval Research Laboratory, Washington. After Transit IIA was in orbit, ex-

plosive bolts were fired and a spring pushed the NRL Satellite (sometimes called Greb) away up into a higher orbit. Because it is higher, it is not quite as fast as its big brother, the difference in speed being about one foot per ; second. Just over a year later, on June 29, 1961, a triple launching was achieved. A Thor-Able-Star rocket carried

up not only Transit [VA and another Greb but also Injun, a forty-pound package designed to study Van Allen radiation.

Heavy Russian Satellites

The many American satellites reviewed above have been sent aloft for a variety of purposes: to obtain scientific data concerning space and the upper atmosphere, for weather forecasting, for communications, military requirements, navigation, and so on. The Russian program has involved launching fewer satellites and space probes and has but a single main objective: the conquest of space by man himself. Scientific data have been obtained because in the course of these investigations, but mainly venture safely can man that insure they are needed to proto ent equipm with d provide earth, the away from

tect him from the dangers he will encounter. have Before venturing to another planet, man must in a earth the g circlin of n missio undertaken the easier

satellite and returning to the sea level. Both the United

s for this States and Russia have been developing vehicle needed ent equipm the all and To contain a man

Santee Of pn






to attend to his bodily requirements, a large heavy vehicle must be provided. On May 15, 1960, Russia put a 4142-ton spaceship in a ‘nominal 200-mile orbit about the earth. It included within its heat-resistant shell an inner pressurized cabin containing a dummy spaceman and instrumentation. The cabin and its contents weighed 3,249 pounds. No attempt was made to retrieve this spaceship, Sputnik [V—or possibly an attempt was made but did not succeed—but a similar vessel launched on August 19, 1960, was successfully recovered the next day (nine days after America first recovered a Discoverer capsule). This spaceship, Sputnik V, carried television equipment and

two dogs, Strelka and Belka. They returned safely after seventeen trips around the earth; one of them has since been mated and produced a litter of healthy puppies. Sputnik VI, a similar vessel containing two dogs (Pchelka and Mushka), other animals, insects, plants and instruments, was launched on December 1, 1960, but

did not have the same luck as its predecessor. It went into orbit that approached too near to the earth. It was difficult to calculate the correct conditions for bringing it back to earth, and when this was attempted it took the wrong path and was burned up in the atmosphere. Even heavier Sputniks were launched in February, 1961, one of them being used as a launching platform for a probe rocket sent to the planet Venus. Then, after two successful test flights of the spaceship

Vostok in March 1961, the Russians reported that they had put into orbit on April 12 the first man to see the earth from space, Major Yuri Gagarin. Launched by a 450-ton rocket, he landed somewhat to the east of his launching place 108 minutes later. Through special windows in his spaceship he was able to look down on the earth which he said “has a beautiful blue color. When you leave the shadow of the earth you see all the colors of the

rainbow. As I flew in the shadow of the earth T-could see

nothing. The heavens have an absolutely -black color and — the sun has another color than on the earth. The stars

seemed brighter and more vivid.” «°

39 tn THE EARTH SATELLITE | Four weeks later, on May 5, 1961, America sent up Commander Alan Shepard, the world’s second spaceman,

as part of Project Mercury. (See Chapter VIII.) On July 21, 1961, Captain Virgil I. Grissom followed in another Mercury flight, and on August 6, 1961, the Soviet Union sent its second astronaut into orbit for 25 hours 18 minutes. Major Gherman S. Titov circled the earth more than 17 times in a five-ton space ship. He reported that he ate, slept, and exercised during flight and that he was

“standing weightlessness perfectly.” The First Moon Rockets

In August, 1958, the United States began a series of “space probes,” reaching farther and farther out into space with rockets aimed at the moon. The first attempt to launch such a rocket failed. The rocket fired on August 17, 1958, exploded two minutes after it left the ground. The second rocket was launched successfully on October 11, 1958. However, this rocket, now known as Pioneer I, did not travel fast enough to break away from the pull of the earth. After rising to a height of 71,300 miles, it fell back again into the earth’s atmosphere. A third attempt to reach the moon was made on November 8, 1958. This attempt failed when the third stage rocket did not fire. A fourth try, made with the rocket now known as Pioneer III, launched on December 6, 1958, repeated the performance of Pioneer I. It rose 63,580 miles, and then fell back again to the earth. Although Pioneer I and Pioneer III failed to reach the neighborhood of the

amoon, they were very valuable as space probes. Inform for e possibl it tion that they radioed back to earth made position scientists to form a more complete picture of the the Exby red discove space in es of the charged particl

- plorer satellites. (See pages Deas)

On January 2, 1959, the Soviet Union launched Lunik,

of “the first space rocket that broke away from the pull

made the earth. We do not know whether the Soviets the nce annou they e becaus failed, that ts earlier attemp orbit. in are .* of their space rockets only after they bi




es, SE



The part of the rocket that sped past the moon was the last of several stages. Without its fuel it weighed 1% tons. On January 3rd, when Lunik was 70,000 miles from - the earth, it released into space about two pounds of sodium vapor to make an artificial comet. The manmade comet appeared in that part of the sky where the constellation Virgo is located, and was photographed from the ground. Lunik carried two radio transmitters that sent down to earth the measurements made by scientific instruments on board. The transmitters became silent on January 4th when the rocket was 373,125 miles from

the earth. After passing the moon on that day, Lunik began circling around the sun, and so became the first man-made planet. As the earth and Lunik travel in their separate orbits, once every five years they may be close enough for astronomers

on the earth to see the rocket

through a powerful telescope. Lunik carried instruments that gathered information about the gas and radiation in space, and the magnetic field in space. They also counted meteor particles, and weighed cosmic-ray particles. On March 3, 1959, Pioneer IV, the fifth American space probe rocket, followed in Lunik’s footsteps. The pay load of Pioneer IV was a gold-plated cone weighing 13.4 pounds. It contained two geiger counters, a photoelectric cell, and a radio transmitter. The rocket that carried it into space was a Juno II, weighing 60 tons.

The first stage of this rocket assembly was a modified Jupiter rocket. The second stage was a cluster of eleven

Sergeant rockets. The third stage consisted of three Sergeant rockets. The fourth stage was a single Sergeant

rocket. The steps in the launching of Pioneer IV are shown on page 4 of insert. The transmitter on Pioneer IV continued working until it was 407,000 miles from the earth. This was the greatest distance across which man-made radio messages had ever been sent. Like Lunik, Pioneer IV is now an artificial planet travtling around the sun. It will make a round trip around the sun once every 394.75 days. The closest it ; ever comes to the sun is 91.7 million miles. When it is |

em PW ¢



farthest from the sun, the distance is 106.1 million miles. Its average speed with respect to the sun is 64,800 miles ; per hour. Assault on the Moon

On September 12, 1959, the Soviet Union sent Lunik Il toward the moon. It was designed to send back informoon, mation about the magnetism around the earth and ature temper the and space, in rays cosmic meteorites and tasks these out carried had it When there. e pressur and it m: perfor to one there was an even more spectacular accomwas task This moon. the was guided to land on probe’s plished—an excellent feat of navigation, The teleradio radio signal was received by the giant British durworld the to dcast scope at Jodrell Bank and rebroa rs listene of ns Millio . voyage the of ing the last stages

on the heard the signal suddenly stop as Lunik II landed t any withou was a “hard” landing—an impact

moon. -It to a heap of attempt at braking. This reduced the probe with the inions medall small ed releas wreckage but also signia of the Soviet Union. d out Lunik III, launched on October 4, 1959, carrie d passe it moon, the g achin Appro another remarkable feat. While earth. the d towar ned retur behind it and then s of the far passing behind the moon it took photograph earth. side, which is never seen from the 45,000 Lunik III’s photographs were taken 40,000 to a camer mm. 35 a using e, surfac lunar the miles above

processed - with two lenses. The film was automatically back to ed radio es pictur and scanned by TV and the in the form of an _ earth. They have since been published . The types of named es featur the of atlas, and many out to be much feature on the far side of the moon turn

_ the same as on its more familiar face. the pictures The Russians planned to rebroadcast earth, but. the of ty vicini the to ned retur III “when Lunik ment equip the se this proved impossible, probably becau been it Had rite. meteo a of had been damaged by impact

ned. ‘done, better quality pictures would have been obtai nay

tthe hoe acne, was iaciched on November 26, 1


This failed in its mission, owing to breakage of the nosecap during launching and subsequent failure of the second—

‘stage rocket to fire. It was one of the Pioneer series, but was not given a number.


Pioneer V, launched on March 11, 1960, was a paddlewheel probe sent out to gain information ‘about the sun. ae It became an artificial planet of the sun. By mid-June it _eg had transmitted sufficient information back to enable astronomers to correct their figure for the distance between earth and sun (the Astronomical Unit). This is an

important distance to both astronomers and space travelers, because all the other distances between planets are— reckoned i in terms of it. ‘ Pioneer V has also transmitted the results of measure- _ ments of solar radiation, magnetic fields out in space, etc. ; It should approach the vicinity of the earth late in 1965,— then again on April 1, 1966, and this pattern will repeat itself each 5.8 years afterward.


Launching a Vanguard Satellite ys

bem ere The steps by which a Vanguard satellite is launched ove — x! are typical of the way in which a man-made moon is put ;|

_ into orbit. A Vanguard satellite is carried off the ground ©

be: by a three stage rocket 72 feet long and almost four feet

ar wide. Although the satellite weighs only twenty pounds, |

the rocket assembly needed to raise it weighs eleven— _ tons, The first stage rocket burns a mixture of alcohol

and gasoline, Oxygen is supplied from a tank of liquid -

_ oxygen. The second stage rocket burns hydrazine, and

Ber: its Oxygen supply from nitric acid. The third stage

rocket burns a solid fuel, The satellite rides in the nose

a of the third stage rocket until it is released into its orbit , c 300 miles above the ground..

« .


_ Four Pushes and a Twist : The rocket is fired out over the Atlantic Ocean : the Patrick Air Hore paceson fans Canave.


Vv heading east, it gets help from the eastward motion of the earth’s rotation on its axis. The engine of the first NOSE CONE SATELLITE THIRD STAGE ROCKET



stage rocket pushes it up with a thrust of 27,000 pounds, lasting 140 seconds. This push carries the rocket to a height of 36 miles, and a speed of 3,600 miles per hour.

During the first part of its journey upward, the rocket has a streamlined nose cone that shields the satellite from the heat developed by friction with the dense lower

air. At higher altitudes, where the air is thinner, this

protection is not needed. So, when the rocket reaches the 36-mile level, the nose cone is dropped. The burned-

out first stage rocket also falls into the ocean, while the

‘second stage engine takes over. The firing of the second ‘rocket carries it to a height of 140 miles and a speed of 11,000 miles per hour. By the time it gets to this level,

e fuel of the second stage rocket is used up. But ‘the ,








motion that the rocket already has enables it to coast upward to a height of 300 miles, while its speed drops slightly to 9,000 miles per hour. At this point, some small explosions twist the rocket into a spinning motion. The second rocket falls, and the third stage rockets get to work, pushing hard enough to raise the speed to 18,000 miles per hour. Then a final explosion separates the satellite from the third rocket, giving it a horizontal kick that starts it in its orbit around the earth. All this action takes place in ten minutes. The burned-out third stage rocket foliows the satellite in its orbit for a while, and then falls. Automatic controls regulate the firing of the three engines and make sure that the rocket does not wander off its course. The Eyes and Ears of a Satellite

There are so many jobs the scientists want a satellite to do that no one satellite can do them all. There has to be a division of labor among the satellites that are

300 milelevel


200 mile level Rocket coasts from 140 mile level to 300 mile level

100 mile level

faa fom

Nose cone and burned out first mL, stage dropped






launched. Each contains a special set of instruments designed to gather information of a particular kind. Some concentrate on measuring the ultra-violet light they receive from the sun and surrounding space. Others have photocell eyes to see the light that comes from the earth, and microphone ears to hear the collisions every time they are struck by wandering meteorites that cross their paths. Later chapters in this book describe some of the instruments the satellites carry, and explain what the scientists hope to learn from them. Some satellites have been equipped with parachutes or other devices that returned them unharmed to the ground when they fell. But the first satellites had no parachutes. When they fell, friction with the air burned them up, and the instruments in them were destroyed. That is why it is necessary for such satellites to deliver the information that they gather while they are still moving in their orbits. The process they use of converting measurements into electrical signals that can be broadcasted to the ground by radio transmitters is called telemetering. Tracking the Satellites

Tracking a satellite and locating its position accurately are difficult because it is moving so fast. The job is being


successfully, however,

One is the method of set up to receive the by the satellites. The the United States are work is supervised by

by two different methods.

radio tracking, by special stations radio signals that are broadcasted radio tracking stations set up by in a chain called Minitrack. Their the Naval Research Laboratory in

Washington, D. C. The second method used is optical tracking, in which a satellite is observed by the sunlight that it reflects from its surface. The optical tracking is done by means of a special

telescope that was designed for the purpose, The tele- scope follows the satellite as it moves across the sky, and a camera attached to the telescope takes pictures of it in rapid succession. The motion of the telescope is

in small steps. It follows the satellite, then stops, “ahd





* i Tor ee , Pe oe. Perea fg" SEEING








follows and stops over and over again. When the camera follows the satellite, the satellite shows up on the film as a dot, while the stars in the sky make atrail across * the film. When the camera stops, the stars show up as dots, while the satellite makes a trail across the film. In this way, the picture of the satellite is separated from the pictures of the stars that appear on the same film. A clock that is synchronized with the shutter of the camera records the time of each picture.

The optical tracking is being supervised by the Smith-

sonian Institution’s Astrophysical Observatory, located at Cambridge, Massachusetts. To help locate a satellite when it first appears in the sky, two thousand amateur astronomers in the United States, organized in ninety Moonwatch teams, also make visual observations. One of the larger satellites is sometimes visible to the unaided eye. If it passes overhead shortly before dawn, or just after sunset, it reflects to the earth light from the © rising or setting sun. Then it is barely visible, looking like a faint star moving rapidly across the sky. Near big cities it is often hidden by the haze that fills the air. But people who live in the country may get a glimpse of a satellite when it passes by.


The Shape of the Earth Each of the satellites is packed with instruments that gather information as it journeys around the earth. Its radio transmitter sends this information down to observers on the ground. But even if it carried no instru-

ments, and had no radio transmitter, it would be a useful source of information. If it were nothing but an empty shell speeding around the earth, we could still watch it from the ground, notice where it is from moment to moment, and measure how fast it moves. Observations on the position and the motion of a satellite give us clues about the shape of the earth, the nature of the earth’s crust, and distances on the face of the earth. The meaning of these clues is explained in this chapter. The motion of a satellite also gives us clues about the air through which it moves.

These clues are

discussed in Chapter LI.

_If the Earth Vanished _ At the moment when asatellite is 300 miles above the ground, there ences acting on it. One of these is miles per hour. The other influence

pushed into its orbit are two main influits speed of 18,000 is its weight, causéd




by the pull of the earth’s gravity. To understand what happens when both influences act together, let us first see what would happen if one of them were acting alone. - Suppose the earth were to disappear suddenly, so that its force of gravity stopped pulling on the satellite. The satellite, because of its motion, would be headed in a definite direction with a definite speed. If no force acted to disturb it, it would continue moving in the same direction at the same speed. It would travel in a straight line, away from its starting point, and would never come back. Now let us put the earth and its force of gravity back into the picture. The speed of the satellite tries to

carry it forward over the ground. But, at the same time, —

the force of gravity tries to pull it down. Both influences

have their effect. The satellite moves forward.and down

at the sante time. It is pulled away from the straight —

line along which it was headed, and it follows a curved path instead,



Pulled to the Center

Here we have to stop for a moment to see exactly — what is meant by “down.” The word “down” refers to the direction in which a body falls when it is acted on ee by the force of gravity alone. We can find this direction easily by means of a plumb line made from a string with — a weight tied to it. Gravity pulls the weight “down,” and when the weight stops swinging, the string shows us which way is “down.” However, the meaning of the word is complicated by the fact that the earth is round. at The drawing on this page shows four people standing line plumb a holds different places on the earth. Each four showing which way is down for him. Notice that the

plumb lines point in different directions, but all these The directions come together at the center of the earth.

real meaning of “down”

is “toward the center of the


gto pull it earth.” As a satellite moves, gravity keeps tryin to the center of the earth. of what happens when a force pulls a

To get an idea







moving body toward a fixed center, let us make a simple — model with the same string and weight we used for a _ plumb line. Hold the string in one hand, and swing the weight in the air. The motion of the weight tries to carry it off in a straight line. Meanwhile the string pulls the weight back toward your hand. As a result the weight swings around in a circle with your hand as center. The circle is the “orbit” that the weight follows around your hand.

A Force That Changes

The swinging weight moves in a circle because the length of the string keeps it at the same distance from your hand all the time. The motion of a satellite is more complicated, because its distance from the center of the

earth can change, and the pull of gravity changes with | the distance. The closer the satellite comes to the earth,

the more


the earth

pulls it. In fact, if the

distance were divided by 2, the pull would be 2x2 or

four times as strong. If the distance were divided by 3, the pull would be 3x3 or nine times as strong. The way

in which the force of gravity changes with the distance


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combines with the speed of the satellite to fix the shape Ag

of the orbit that it follows.

It turns out that there are three kinds of path that a

satellite may follow. The orbit may be an ellipse, a parabola, or a hyperbola. In order to understand the motion of the satellite, we have to get acquainted with these curves. Three Curves

An ellipse is an oval-shaped curve that you see every time you drink a glass of water. When a partly filled glass of water is tilted without spilling the water, the

curve formed where the surface of the water meets the inside surface of the glass is an ellipse. It looks like a circle that has been stretched out of shape by being made wider in one direction. When the glass is turned upright, the ellipse shrinks to form a circle, which has

the same width in all directions. The line through theit center of the ellipse, drawn in the direction in which

h the is widest, is called its major axis. The line throug

h it is narrowest, “center, drawn in the direction in whic a special kind of is e circl ed the minor axis, A

is call

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minor axis

focus \

nerd major axis

ellipse in which the major axis and minor axis have the same length. You form an invisible parabola every time you play “catch” with a ball. The path of the ball, as it flies through the air, is a parabola. You can make avisible parabola when you squirt water into the air from a garden hose. Notice that while an ellipse is a closed curve, a parabola is an open curve. A hyperbola is shown in the diagram on page 53. It is a twin curve. Each of its two branches is shaped somewhat differently from a parabola, but, like a parabola, it is an open curve. No matter how far a parabola or


to form a hyperbola is extended, it does not close up é' — loop. er

laking an Ellipse



follow these _ To draw an ellipse accurately on paper, board, and— J ng directions. Place the paper on a drawi the board, + 7 into paper the ‘press two thumbtacks through string SO md of piece a Cut apart. at points several inches ce between that its length is more than double the distan to form a _ string the . ‘the two tacks, and tie the ends of a %









loop. Place the loop around the tacks, and then pull the string tight with the sharpened end of a pencil held _ inside the loop, as shown in the diagram. If you move the pencil around while it pulls the string tight, the pencil will trace out an ellipse on the paper. The point where each thumbtack has pierced the paper is called a focus of the ellipse. The line through the two foci-is the

major axis of the ellipse. A parabola also has a focus, located inside the bend. Each branch of a hyperbola has a focus, too.

The Orbit of a Satellite

The path of each earth satellite is an ellipse. The center of the earth is located at one focus of the ellipse. When the satellite is released from the final stage rocket that carries it, its speed of 18,000 miles per hour tends to carry it off in a straight line. But the force of gravity, pulling it toward the center of the earth, compels it to veer around and move along the ellipse instead. It is interesting and important to see what happens if a satellite is given a higher speed than 18,000 miles per hour. A higher speed, say 19,000 miles per hour, carries the

satellite farther away from the focus before the pull of

gravity compels it to swing around and come back. As a result, its path becomes an ellipse with a longer major axis. A speed of 20,000 miles per hour ‘would make the major axis still longer. Higher and higher launching © speeds would make the ellipse longer and longer. As the —








ellipses grow longer, the two foci are separated by a greater distance, and the part of the ellipse that is near a focus begins to look almost like a parabola. If the launching speed is 25,000 miles an hour, the orbit actu-

ally becomes a parabola. Since an ellipse is a closed curve, a satellite following an elliptical orbit comes back to its starting point and retraces its steps over and over

again. Since a parabola is an open curve, a satellite that starts out on a parabolic orbit never comes back. Once it goes around the bend in the parabola, it moves farther and farther away from the earth until another body like what the moon, the sun, or a planet captures it. This is

ng happened to Lunik and Pioncer IV. If the launchi a is orbit the hour, per miles 25,000 than speed is more a too, curve, open an is la hyperbo a Since hyperbola. into out shoot also satellite in a hyperbolic orbit would

miles - space and never come back. The speed of 25,000

earth. _ per hour is called the velocity of escape from the ad

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Choosing the Speed

The scientists who make the plans for an earth satellite and the rockets that launch it have to decide in advance what speed they want it to have at the moment when the final stage rocket kicks it into its orbit. They cannot choose a speed as high as 7 miles per second, or 25,000 miles per hour, because this is the velocity of escape. They cannot choose a speed as low as 4 miles per second, because then, when the satellite passes through the part of its orbit that is closest to the earth, it is less than 100 miles above the ground. If the satellite were to come too close to the earth, it would be slowed down too much —

by the air, and fall to the ground too soon. So they have to choose a speed between 4 and 7 miles per second. They decided on 5 miles per second, or 18,000 miles per © hour. With this speed when it starts in its orbit, the satellite does not escape from the earth. Its path is between 120 and 2,500 miles above the ground. It stays up there for at least several weeks, and, in some cases,

for years or centuries, before it slows down enough to fall. Placing the Orbit

The scientists are also free to choose where they will place the orbit of a satellite. If they were to launch a satellite eastward from a point on the equator, its orbit — would be a ring around the equator. Then, as the satellite moved around its orbit, it would run a race with —

the launching site on the ground. The satellite would win the race, because it would make a round trip every ninety minutes, while the launching site, carried by the spinning earth, would make a round trip only once every oe twenty-four hours. i If a satellite were launched southward, its orbit would pass over the north and south poles. If the earth were © not spinning, the satellite would remain over the same meridian, passing over the same points on the oe fin











So by the each time around. But the earth is spinning. trip round a time the satellite would have completed ard, eastw moved have over the poles, the earth would vers

To obser bringing another meridian under the orbit. orbit of the the h thoug as look would it on the earth ing hoop spinn a satellite had turned westward, like surrounding the earth. first satellites The scientists chose to launch each of the As a result, its in a direction between east and south. the time, nor all or orbit does not stay over the equat The orbit pole. south and does it go over the north back and moves te satelli the that so crosses the equator, pheres. hemis southern forth between the northern and r, equato the on point a - After the satellite crosses over So, ard. eastw point this s _ the spinning of the earth carrie her crossing, it passes when the satellite returns for anot g farther west. Its path over a point on the equator lyin line drawn round and over the ground looks like a wavy

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of orbit was chosen for the satellites because it carries they them over a large part of the earth’s surface, where a people many give and “see,” to things find many ed launch be will ‘chance to track them. Other satellites can in orbits that pass over the poles, so that they the over air upper the in ions condit observe the special earth. the of regions polar The Earth’s Big Belly

If the earth were spread out evenly in would be the same in a perfect sphere. It is

a perfect sphere, with its mass all directions, the pull of gravity all directions. But the earth is not flattened slightly at the poles, and

a big roll of fat bulges at the equator, like a man with because it has on his belly. Its surface is irregular, s.

valleys and plain continents and oceans, mountains, fact, the rocks in In y. evenl out ‘Its mass is not spread






some places are heavier than the rocks in others. As a

result, the pull of gravity is not the same in all directions. When an earth satellite passes over different regions of — the earth it receives a different pull. This has an effect on the way in which it moves. Its orbit is disturbed. Astronomers call the effects of such disturbances “aber- — rations.” By studying these aberrations, they get. infor-— ‘mation about the shape of the earth. The earth bulges at the equator because it is spinning— on its axis. To see why spinning makes it bulge, let us perform some simple experiments with spinning objects. —

Place an eraser on the turntable of a phonograph,


then turn on the motor. As soon as the turntable begins _ turning rapidly, the eraser will shoot off to the side, asi though some force were pushing it away from the center of the turntable. This force is known

as the centrifugal |

force. It acts on every part of a spinning object. We find it in action, for example, in the spinning wheels of an automobile. If there is mud on the wheels, the spinning

of the wheels sends the mud flying off the rim away from





s over . r the hubs. Automobile manufacturers put fender it from keep and mud flying this catch ‘the wheels to centrif- — the see also can We hing. everyt over ring spatte


ugal force in action if we twirl a weight in the air at the — of a string. The centrifugal force keeps the string

end away stretched taut. The force tries to push the weight

However, from the center, but the string holds it back. rubber, it like al materi if the string is made of an elastic force. In fugal centri the of pull the of stretches because

string fact, the faster we twirl the weight, the more the someis earth ng es. The behavior of the spinni

stretch of a rubber thing like that of a twirling weight at the end rotaearth’s the by caused force fugal string. The centri the from away tion tries to push the mass of the earth not does earth the so axis. The mass hangs: together, a spinning break into pieces that fly off like mud from to pull mass the ng allowi es, stretch it wheel. Instead r. _ equato the at away a bit from the axis to form the bulge expull a is ite satell a on The force of gravity acting of the satelerted by the mass of the earth on the mass close the how on s depend pull this of th lite. The streng at bulges earth the masses are to each other. Because of part greater a to closest the equator, the satellite is bulge. So, *very _ the earth’s mass when it comes near the it is subjected r, equato the over passes te | time the satelli shifting the — of effect "to an extra-hard pull that has the e moves satellit the while position of its orbit. As a result, turns ellipse the of axis major the around in an ellipse,

this shifting slowly. Careful measurements are made of ts

measuremen of the orbit of a satellite. From these satellite is the ly strong scientists can figure out how ation inform This t. momen each at _ being pulled by gravity at the out bulges earth the much how to clue a "serves as

“equator. Fa The Earth Is Pear-Shaped

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‘The Earth as Seen from Space An Outside View

When we look at other planets, like Venus or Mars, we are outsiders looking in. Each of these planets has its own atmosphere, and we see what they look like from outside their atmosphere. An earth satellite, by rising above most of the earth’s atmosphere, gives us a chance to get the same kind of view of the earth. Its photocell eyes, looking down from above the atmosphere, see the earth as it might look from a spaceship approaching it| , from another planet. We have a small sample of what an outside view of the earth can show in the photograph on page 7 of insert. This photograph was taken from a height of 86 miles above the ground by a camera placed in the nose cone of a United States Navy rocket. It is actually five separate photographs pieced together to make one continuous picture. The rocket, called a Nike-Cajun, was fired from

Wallops Island, Virginia. After it fell into the cone containing the camera and exposed nose ay _ picked up by a Navy ship. The picture shows formation extending for a distance of 700 miles Atlantic Ocean. The clouds were formed at an —~ ' _where warm air from the south meets cool air . ~—yre:

sea, the film was a cloud over the air front, from the

north. Pictures like this of cloud formations are useful nee







to the Weather Bureau for making weather forecasts. The earth satellite Vanguard II, which is especially ' equipped as a weather observer, looks down on the earth from a much greater height than 86 miles. So it can see more of the earth than the camera that took this picture did. Also, at each trip around its orbit, it passes over a different strip of territory, since its orbit is shifting steadily. By piecing together what it sees in each strip, a picture is formed of the clouds over almost a fourth of the earth. This picture is not made in the ordinary way by exposing film to visible light. It is made instead from electrical signals sent down by the satellite’s radio transmitter, after the photocell eyes of the satellite detect invisible infra-red rays coming from the earth. Earthshine

The sun glows, sending out light that it produces itself. The planets shine, but they do not glow. The visible light that they send us is not their own light. It is sunlight reflected from their surfaces and atmospheres. The

earth, like other planets,

also reflects some

of the

sunlight that strikes it. This earthshine can be seen from the earth satellite. It contains both visible and invisible light. The earth, in its behavior toward the sunlight it receives, is part sponge and part mirror. It behaves like a sponge because it soaks up or absorbs a large part of the sunlight that strikes it. It behaves like a mirror to the extent that it also reflects some of it back into space. The part of the light that it absorbs makes the earth warm and influences the weather. The part that it reflects does not. The scientists who try to explain and forecast changes in weather must take this difference into account, so they try to calculate the albedo, or reflecting power of the earth. It is a comparison of the brightnéss of the

earthshine with the brightness of the stnlight that the earth receives. To calculate it, it is necessary to measure the earthshine first.

Before we had rockets that could rise above the earth’s

1osphere, there oe no way of seeinghole

lirectly. Sp. we had to measure it indirectly, by ro about methods. The problem was complicated by _ fact that different parts of the earth’s surface do not w ‘, equally well as mirrors. Some parts of the earth’s surf: are covered with fresh snow, which reflects 80 to | t per cent of the light it receives. Some parts are covered — by forests, which reflect only 5 per cent of the light they — catch. Old snow reflects 40 per cent of the light, grass reflects 10 to 33 per cent, rock reflects 12 to 15 per cent, — the sea reflects 3 to 10 per cent, and deserts reflect 25 } per cent. A large part of the light is reflected even — before it reaches the ground, because clouds reflect from 7 50 to 75 per cent of. the sunlight that strikes them. To. “ calculate the earth’s albedo, scientists had to estimate how much of the earth is covered by clouds, how much| by snow, or forest, or sea, so that they could figure out how much reflected light each type of surface contributes to the total shine of the earth. By putting together facts like these, they estimated that the earth reflects about 35 per cent of the sunlight it receives. The moon,

_ which has no atmosphere, reflects only about 7 per cent. fe of the sunlight that shines on it. ee Another roundabout way of measuring earthshine made : use of the reflecting power of the moon. When the moon — - is not full, only part of its face shines brightly with reflected sunlight. But the rest of its face, even though — E :f

it receives no light from the sun, is not completely dark. ee It is lit up faintly by earthshine. The moon receives only | : bypasses which of most a small part of the earthshine, — a only reflects also It space. to lost is and the moon

small fraction of the earthshine it receives. Then we re- — ‘ ceive only a small part of the earthshine the moon re-_ ‘flects, because most of it. bypasses the earth. So the By doubly reflected light we finally receive, after it makes — : and back of about = a round-trip journey to the moon half a million miles, is only a tiny sample of the total ‘ ae But from this slender clue a rough estimate — -




Cy can be made. in. gabck: ae accuracy, es these roughesti,“te vip


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sea Forest

mates that were made by indirect methods. An earth satellite, looking down toward the ground, gets a direct view of the earthshine, and measures it. Looking out toward the sun, it also measures the brightness of the

— sunlight the earth receives. Comparing these two measures_ q will enable scientists to calculate the earth’s albedo. :4 ponds

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The Earth Is a Radiator

The earth is warmed by a steady supply of heat it receives every day. It is warmed up from the outside by the sunlight it receives and absorbs. It is also warmed up from the inside by heat released when radioactive minerals like uranium slowly break up as they lie in the ground. In spite of this fact, it does not grow warmer from year to year. The earth does not grow warmer because it also loses heat every day. Just as a warm oven radiates heat into a room,

the earth radiates

heat into

surrounding space. The incoming heat is balanced by the outgoing heat. Asa result, the average temperature of the earth remains fairly steady. The heat that the earth loses leaves the ground in the form of infra-red rays. The receiving instruments on Vanguard II were designed to detect infra-red rays, so that they could “see” the dark ground as well as bright clouds. The Weather Eyes of Vanguard II

The satellite Vanguard II is spinning steadily, as explained on page 90. Two photocells, called Weather Eyes by the engineers who designed them, are placed so that they look away from the satellite at an angle of 45 degrees with the axis around which it spins. When the height of the satellite is less than 1,700 miles, while one of the eyes faces away from the earth, the other one

faces toward it, so the satellite always has the earth in view. As the satellite spins, the eye that is turned toward the earth sweeps over a narrow strip on the ground. Infra-red rays coming up from the strip are reflected by a mirror onto an infra-red*detector. The detector con-verts the light energy it receives into an electrical signal, making the signal strong when the light is strong, and weak when the light is weak. These signals aré fed into a magnetic tape-recorder which makes a tape record’ of them on a 75-foot tape that is % of an inch wide. The tape recorder works only while the satellite is on the






daylight side of the earth. When the satellite enters the

-earth’s shadow (the nighttime side), a small solar bat* tery automatically turns the recorder off. The recorder is working for about 50 minutes out of each 126-minute round trip that it makes around the earth, storing information on the tape at the rate of 0.3 inches per second. When the satellite passes over a Minitrack station, a signal from the ground makes the recorder play back the information it has stored, reading it out through the radio transmitter at a rate of 15 inches of tape per second. On the ground, the information is put on tape again as a permanent record of what the satellite saw. A picture is made from the record in this way. The electrical signals obtained by playing the record are fed ~ into an oscillograph, which produces a line of light on the face of a tube that is like a television picture tube. Each point of this line of light represents part of the strip of ground that was scanned by the satellite’s eye during one sweep. It is bright or faint, matching the brightness or faintness of the light that entered the eye from that part of the ground. Photographing the face of the tube produces a picture of what the satellite saw, strip by strip. To form a picture of a large area, the strips will be mounted side by side. Pictures like this will give scientists new reliable information about how much light is reflected by the continents, and how much

is reflected by the sea. They

will be able to cal-

culate how much of the earth is covered by clouds, and they will see how cloud systems are born, develop, travel around, and die. The Temperature of a Satellite A satellite receives heat from two sources.

It receives |

heat from the sun, and also from the earth. Ihe heat it receives tends to warm it up. At the same time, the — satellite radiates heat, so that it loses héat to space, and— the loss of heat tends to cool it off. The cooling-off

process balances the warming process, so that the aver- 1 age temperature of the satellite remains steady. How-





Se «




ever, only the average temperature is steady, while the actual temperature changes from hour to hour. It goes up in the daytime, when the satellite is bathed in sunlight so that it receives more heat than it loses. It goes down again at night, when it loses more heat than it gains. The instruments ina satellite are insulated to protect them against these changes in temperature. In the moon rocket Lunik, there were no changes in temperature in the instrument case, because it was airconditioned. The instruments were sealed in a spherical container that was filled with gas. The instruments generated heat as they worked, and the heat was absorbed by the gas. But a ventilator kept the gas circulating, so that the heat was transferred from the instruments to the shell of the case. The shell, acting as a radiator, lost the heat to space. In this way, a steady temperature of 68 degrees Fahrenheit was maintained in the instrument case. The Temperature of the Upper Air

The strength of the infra-red rays that a satellite receives from the earth is a clue to the temperature of the upper air. As the rays move upward from the ground, they pass through layer after layer of air. Each layer they pass through changes the strength of the rays by a small amount, depending on the temperature of the ‘Jayer. When the satellite is 200 miles above the ground, ‘it receives rays that have passed through only 200 miles of air. When the satellite is 210 miles above the ground, it receives rays that have passed through 210 miles of air. The extra change in the strength of the rays caused by the last ten miles of air through which they pass is a clue to the temperature of the air in that ten-mile layer 200 miles above the ground. Since the height of Vanguard

II ranges




to 2,087

miles, it

will be possible to measure the temperature, layer by layer, between these two levels. Analysis of the first ‘temperature measurements made by earth satellites and ‘rockets shows that the temperature of the upper air,

a like its density, is higher ‘tha seloteld ee monnrt ae would be. An interesting paradox has also appeared. The * upper air above some cold regions of the earth is” warmer than the upper air above warmer regions. For example, at a height of 125 miles above the ground, the air above Churchill, in Northern Manitoba, Canada, has a temperature of about 4,000 degrees Fahrenheit. At the same height, the air above White Sands, New Mexico, has a temperature of only 2,000 degrees Fahrenheit. The air is so hot high up above Churchill because it is’ ‘warmed up by large numbers of charged particles that strike the air there. They are guided into this region near the earth’s magnetic north pole, by the earth’s magnetic

field. This process is explained in Chapter VII.

3'| 4




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Electricity in the Air Crowds of Electrons

_ The sunlight streaming into the earth’s atmosphere in the daytime contains X-rays and ultra-violet rays. When these high-energy rays collide with atoms in the upper air, they

ionize them by knocking electrons out of them. As a result of these collisions the outermost layer of the earth’s

atmosphere, the ionosphere, contains crowds of free electrons and electrically charged ions. One of the goals of the study of the upper air is to find out how many of these charged particles are there, and where they are concentrated in the greatest numbers. Some of this information had already been obtained by observations made from the

‘ground. The earth satellites have added to and checked this information by making on-the-spot observations as they move among the crowds of electrons and ions in the air. -

Radio Echoes


ae been has air the in ions and electrons of The crowding

measured from the ground by means of radio echoes, Ra-

io waves of different wave lengths are broadcasted from Pitre






_ the ground, and are beamed pitas ear into See iono‘sphere. Some of these waves pass right through and ess

cape into space. Others bounce back from the ionosphere and are _ mgoticing scientists electrons

detected by a radio receiver on the ground. By — which waves come back and which do not, the © get a clue to the density or crowding of the in the air. A layer of air will reflect radio waves

ef a particular wave length only if the electrons in the

_ Jayer are crowded enough to act as a wall that bounces them back. The echo is also a clue to how high this layer —

_ is above the ground. The higher the layer is, the longer

it takes for the radio waves toe reach it from the ground — and then return as an echo. The instrument used for © these ground observations of electron crowding in the ‘ ionosphere is called an ionosonde. It is a combination radio — transmitter and receiver that sends out a series of radio — pulses of different wave lengths, and picks up those that — come back. The pulses that are received are used to produce a line on the face of a tube like a television picture tube. Each wave length that comes back shows up as a spot on this line. The height of the spot on the tube shows how long it took to come

back, and se indicates

the height of the layer of electrons from which it was reflected.

- The ionosonde has shown that the electrons are not spread out evenly in the ionosphere, but are concentrated in distinct layers. The lowest layer is called the D layer. The higher layers are called the E, the F,, and the F, layers. The higher the layer, the more the electrons are crowded in it. The E layer is between 60 and 90 miles above the: ground. During the daytime, when it is being

bombarded by sunlight, the density of electrons in it is about 120,000 electrons per cubic centimeter. The F, __ layer is between 90 and 150 miles up, and has a daytime electron density of about 220,000 electrons’per cubic ea

centimeter.’ The F, layer, located more. than 150 miles© _ above the ground, has 450,000 electrons per cubic centi_ meter. Above the F, layer is the region called the exosphere, where the earth’s atmosphere merges with Ol

ie dane sioske ae were: any artificial ee

- -






littie was known about the electron density in the exosphere, because the ionosphere under it was like a screen — behind which it was hidden. But the earth satellites have penetrated this screen to give us a more complete picture of how charged particles are spread out in the upper air. Catching Electrons

There are several methods by which an earth satellite or a rocket can measure the crowding of the electrons in the air. One way is to scoop up samples of the electrons as the satellite moves along. The instrument that does the scooping, an ion trap, works like a flypaper for charged particles. Flypaper is covered with a sticky substance so that flies that land on it get caught. The more crowded the flies are around the flypaper, the more of them will get caught. The electron catcher on an earth satellite has a voltage applied to it. The voltage holds electrons that strike the exposed surface of the instrument, and makes them move through the instrument in an electric current. The more crowded the electrons are near the instrument, the more of them strike it and get caught, and the stronger the electric current becomes. Sputnik III was equipped with an ion trap and made the first measurements of electron density above the level in the F, layer where the electrons are most crowded. The results of these Sputnik measurements are included in the chart on page 104. In addition to counting negatively charged electrons, Sputnik III also captured, identified, and counted ions - with a positive charge. For this purpose it carried a mass spectrometer, which identifies ions by weighing them as they move across a magnetic field.* Similar measurements

were also made at lower altitudes by American and Russian sounding rockets. The measurements show that in the E layer of the ionosphere, most of the positive ions are either nitric oxide or molecular oxygen (two, atoms of

oxygen joined together in a single molecule). At higher

in A description of how a mass spectrometer works is given

_ The Tools of Science. (See footnote page.) = B sa ~

2 4, ~

Pe ites, there are> Jess Tae jek of thes ap ions, and more and more ions of atomic oxygen (conta fe ing only one atom per molecule). Atomic oxygen is the _principal ion found between 150 and 600 miles above the Conia Atomic nitrogen is also found in amounts that vary with the height. %


Changing the Tone j If an automobile honks its horn as it passes you, the tone of the horn is not the same as it would sound if. _ the automobile were standing still. It sounds higher when the automobile is approaching you, and it sounds lower. after the automobile has passed and is moving away. The change in tone is caused by the motion of the automobile. An earth satellite also has a honking horn. Its horn is its” radio transmitter. The “tone” of the transmitter is not a sound. It is a train of radio waves detected by receivers on the ground. The “tone” of the waves depends on their frequency, or the number of waves received in a second. The frequency is affected by the motion of the satellite in_ the same way that the tone of a honking horn is affecte

by the motion of an automobile. It is higher when th satellite is approaching, and it is lower when the satellite

is moving away. x


To see why the motion of a satellite has this effect on

ber that are received on the ground i in one seconllIf tk Satellite is moving away from the oe

- each

esit moves still

the next |

ae >




101 Position of first and second

pulses if satellite were standing sti!)

Position of first and second

pulses if satellite moves towards the observes



Position of

first and second pulses if satellite moves away from she observer

number that are received on the ground in one second.

The change in tone when the satellite passes over a

receiving station is a clue to the electron density in the

air. The train of waves from the satellite’s transmitter reaches the receiving station after traveling several bhundred miles through the air. It passes through crowds of

electrons on the way. The electrons alter the speed of the wave, and the change in speed also has am effect on the






tone. By comparing the tone that is actually received with — - the tone that would have been received if the train of waves traveled through a vacuum instead of through crowds of electrons, it is possible to figure out how crowded the electrons are in the air. Twisting the Waves

Another method for measuring electron density, used in both American and Russian sounding rockets, is to send broadcasts from the rocket to the ground through two different radio transmitters, operating at different frequencies. A radio wave is a vibration of electrical and magnetic forces. When the train of waves from each transmitter leaves the antenna of the rocket, the vibrations are

in a definite direction. On the way down to the ground, the waves plow through crowds of electrons. The effect that these electrons have on the wave depends on its frequency. The frequency of one transmitter is chosen so



high that the wave passes through the crowds of electrons — undisturbed, The other lower frequency is chosen so that | the electrons do influence the wave as it passes among them. They give the wave a twist, changing the direction — of its electrical and magnetic vibrations, The effect is pic- —




tured roughly in the diagram on page 102. The undisturbed waves are shown as though they were drawn on a flat sheet of paper reaching down to the ground. When the waves are turned by the electrons, they look as though they were drawn on a twisted piece of paper, spiraling down like a corkscrew. By comparing the undisturbed high-frequency waves with the twisted low-frequency waves, it is possible to calculate how much twisting took — place. The amount of twisting is a clue to the density of the electrons in the air layers that the waves pass through. If the twisting caused by a trip through 200 miles of air is compared with the twisting caused by a trip through 300 miles of air when the rocket is at a higher level, the difference shows how many electrons are crowded between the 200-mile and 300-mile level. Whistlers

Another source of information about the crowding of electrons in the upper air is the study of whistlers. Whistlers are low-frequency electromagnetic waves that are caused by lightning flashes. They travel up through the air to the exosphere, where because of the low density of the ions there, they move back and forth between the northern and southern hemispheres under the influence of the earth’s magnetism. They are being observed by two chains of stations running north and south along the coasts of North America. Measurements of electron density made from the study of whistlers are included in the chart on page 104. The chart shows the latest information, obtained from all sources, on the density of electrons in the air during the summer time at middle latitudes, at heights to about 60,000 miles above ranging from about 60 miles the ground. The chart shows that in the D layer of the ion~ osphere, the electron density goes up to about 1,000 per cubic centimeter. In the E layer, it ranges from-1,000 to ever 100,000 per cubic centimeter. In the F layer, the density increases with altitude at first to a maximum of

over a million electrons per cubic centimeter and then be-

_ gins to decrease with altitude at higher levels. At a height Wn

miles Height in










5s =

Electron density in electrons per cubic centimetre

Variation of electron density with altitude

of 60,000 miles, far out in the exosphere, the density is

down to 100 electrons per cubic centimeter. Particles from the Sur

~ Most formed X-rays these,

of the charged particles in the ionosphere from atoms of the air that have been struck or ultra-violet rays from the sun. In addition there are other charged particles that are

are by to not formed in the air, but enter the air from the outside. Some come crashing in at high speed from the sun, which is — ninety-threa million miles away. The face of the sun is a scene of great activity. Giant storms, which we see as sunspots, whirl about in the hot — surface gases. Solar flares shoot up like fountains. In the — course of this activity, streams of electrons and protons —

sometimes shoot out from the surface of the sun and speed j



off into space. Those that are headed toward the earth are guided into the earth’s atmosphere by the earth’s mag- — netic field, and announce their arrival with a brilliant dis-

_ play of colored lights in the sky, the aurora borealis in the northern hemisphere, and the aurora australis in the southern hemisphere. At the same time they stir up magnetic storms which interfere with radio broadcasts and the operation of power lines. When the aurora lights are seen in the sky, the earth’s

atmosphere is behaving like a giant neon lamp. In a neon lamp a stream of electrons races through a tube that is filled with gas. The electrons collide with atoms of the gas and “excite” them. Then the excited atoms send out light, making the gas in the lamp glow. An aurora display of lights is caused in the same way. The electrons and protons that speed into the earth’s atmosphere from the sun collide with atoms of the upper air, and “excite” them. Then the excited atoms radiate light. The flashes of light sweep across the sky like searchlight beams. They fade and brighten, and hop about like spotlights following © dancers on a stage.

The description above of how auroras are caused was

originally built up out of a mixture of fact and theory.

It was an observed fact that the sun shoots streams of matter out into space. It was also an observed fact that _ after a solar flare there are often brilliant auroral displays _ in the sky. That the earth’s magnetic field plays a part in guiding the particles that come from the sun to the ' northern and southern regions where auroras are seen _ was a theory. This theory is now fully confirmed by new

_ facts gathered by the earth satellites and the moon rocket

' space probes. The new facts and the conclusions to which - they have led are summarized in the next chapter, which ~ deals with the earth’s magnetic field. ~%2


There is another type of sky light similar to the aurora, but which is present in the sky all the time. It is called _ airglow. During the daytime it is covered up and hidden _

Pa) S



; oes


/ the bright daylight. At night it is toofaintto be

_ by the naked eye, but it can be detected by sensitive


struments. Part of it consists of green and red light radiated by excited oxygen atoms. It also includes yellow light —7

ao sent out by sodium atoms, and infra-red light sent out —— by the hydroxyl molecule (made up of one atom of hydrogen joined to one atom of oxygen.) Airglow originates Abte

- between 60 and 120 miles above the ground. Before 1958,

ys not much was known about the cause of this “permanent waa& aurora.” It is now thought that it may be caused by an — overflow into the air of charged particles from the great —

radiation belts around the earth. These belts were dis- —

covered by the earth satellites and the Pioneer _ probes. (See page 103.)

space ; ;


Cosmic Rays

While the electrons and protons that pour into the| earth’s atmosphere from the sun travel ninety-three million | miles to reach it, there are other charged particles that come

from an even greater distance. The earth is bom-

barded daily by charged particles called cosmic rays, that come from outside the solar system. Although we call them rays, they are not forms of electromagnetic radiation. _ They are actually the nuclei of atoms that have been

stripped of all their outer electrons. Magnetic forces in

space push them along to give them a very high speed.




magnetic field in a large ring around the earth. He estimated that the ring must be about twenty thousand miles from the center of the earth. In this ring the movements of the charged particles would be a giant electric current. This current would be surrounded by _

its own



of force.


lines of force,

_ reaching down to the surface of the earth, would be part _ of the magnetism that influences compass needles on the ' earth. The earth satellites and the moon rockets have proved that Stérmer’s prediction was correct. There is a ring of charged particles in almost exactly the position that was predicted. There is also another one, closer to

_ the earth, about two thousand miles above the ground. _ These two rings or belts of charged particles are now _ known as the Van Allen radiation belts, after the American scientist who planned the satellite experiments that discovered them. 7 %

_ Gathering the Evidence

_ The first clue that these radiation belts might exist

_ was found in 1953 when some rockoons were fired into

es sia



the air near


The instruments

in the —

~ rockoon showed that there was an unusually large amount —


of radiation 30 miles above the ground. This finding was confirmed by Sputnik IlI, which followed an orbit


that took it repeatedly into the northern regions where

auroras are frequently seen. Whenever it came into the z auroral zone, its instruments on board showed a sharp - jncrease in the number of X-rays in the satellite. These 4

X-rays came from the shell of the satellite when it was ; bombarded from the outside by fast-moving electrons. Sputnik III also carried an instrument for counting these electrons directly. A phosphor screen covered by aluminum foil was mounted on the outside of the satellite. Every time an electron passed through the foil and struck the screen, it caused a flash of light on the screen. A photomultiplier counted these flashes of light as they


5 5

— © ¢ ;

took place.

The most important evidence about the radiation rings —

came from the Explorer satellites and the Pioneer space }

probes. On Explorers I and III, the particle counter — showed very high levels of radiation at altitudes of 600 miles. In some places, the instrument began counting — so fast that it jammed. An instrument designed to take a higher count without jamming was placed on Explorer ~ IV. The measurements made by Explorer IV gave a i - detailed mapping of the lowest levels of the radiation

belt. The






right —

through the heart of the belt, rounded out the picture — by mapping the outer regions as well. They showed that —

there are two radiation zones, one within the other. The — Jocation of these rings of charged particles is shown in— _ the drawing on page 115. The inner ring is like a dough- © — nut surrounding the earth. The charged particles in it

> —~-,

are most crowded in that part of the ring that is about — two thousand miles from the earth. The most crowded© part of the outer ring extends from about eight thousand © to thirteen thousand miles from the earth (twelve thousand to seventeen thousand miles from the center

earth). In these crowded regions, particlesstr we:






counter at the rate of 40,000 particles per square centimeter per second. _ Jumping from Pole to Pole

From known facts about electricity and magnetism, physicists have calculated how the particles in these rings

Van Allen belts ofcharged particles (corpuscular radiation)

are probably moving. Each particle, when it is captured by the earth’s magnetic field, begins to spiral around a - Tine of force, so that it follows a corkscrew path toward one of the poles. As it approaches the pole, the particle is slowed down as if it were pressing against a spring, -and the coils of its spiral path become more tightly


Finally, it begins to spiral the other way and

moves toward the opposite pole. In this way the particle keeps bouncing back and forth between the north and south poles. At the same time, its path drifts slowly ‘around the earth, moving from west to east if the particle ‘is an electron, and going from east to west if the particle -is positively charged.


of this drift, there is a

slow-moving electric current going round and round in

"each of the two rings.


_ As the particles spiral in toward the poles, they come closer to the ground. It is these low particles that were

‘detected by Sputnik III and by the rockoons fired from ‘Newfoundland. When the particles speed through the air Se:

sey » ££

around the poles, they collide with the eis ofair _ and cause the flashes of light of the aurora. The collisions — in the air make the particles lose energy. After several _ trips back and forth between the poles, they fall into the air. As a result, the two rings are constantly losing their particles to the air. But a fresh supply keeps streaming into the rings from the sun, and perhaps from other sources, Some physicists think that the leakage of particles from the rings into the air may be the cause of the mysterious airglow described on pages 105-6.

The Source of the Rings The fact that there are two rings instead of one has presented scientists with a new puzzle. If there were only one ring, it would be likely, as Stérmer thought, that the particles in it come from the sun. But the presence of the inner ring complicates the problem. It seems unlikely that particles coming from the sun would pass through the outer ring, then bypass the space between the rings, to settle in the inner ring. Some American and Russian scientists have suggested that it is more likely



ches RS Si Saad sh







from that the particles in the inner ring actually come up from down g comin of d instea the earth’s atmosphere, atmosthe into crash rays cosmic When es. higher altitud neutrons. phere, they smash large atoms, releasing some

and proThese neutrons then decay to form electrons of source the be may s proton and ons tons. These electr strong ed supply for the inner ring, This theory receiv can expersupport from the results of an interesting Ameri ment, perexperi this In Argus. iment known as Project atomic three 1958, ber Septem and formed in August above the miles 300 of height a at ed explod were bombs large numbers South Atlantic Ocean. The explosions put er IV, as it Explor air. upper the of charged particles into the movedetect to able was earth, the moved about and forth back ments of these charges. They did bounce they did and poles, the n along the lines of force betwee lines The cted. predi y theor cal physi - drift east or west, as explothe where place the gh throu d passe of force that the equator, sions took place, after arching out over ern heminorth the in re returned to the earth’s atmosphe particles the Here ds. Islan s sphere, near the Azore North magnetic

willis pole


By LN South» magnetic


nS wore



released by the explosions caused ‘auroras as the the

predicted. This experiment showed that charged particles

- originating in the air can be trapped by the earth’s mag-—


- netic field to become part of the lower radiation belt that — a surrounds the earth. _ Analysis of the observations of the Argus particles, made by Explorer IV and by sounding rockets fired from

_ the ground, will give detailed information about the shape and strength of the earth’s magnetic field.

_ Space Flight Hazard The presence of the two Van Allen rings of charged - particles around




the earth will have to be taken into

account when plans are made for sending manned rocket _

ships into interplanetary space. Exposure to excessive radiation can cause serious illness and death. Amounts of radiation are expressed in units called a roentgen. The— largest radiation dosage a human being can safely absorb is 5 roentgens per year. An unshielded person pass- — ing through the Van Allen rings would be exposed to from 10 to 100 roentgens an hour. To avoid the danger

that this high level of radiation represents, rocket ships — will have to be built with effective shields against radi—

ation, or they will have to avoid passing through the —

rings altogether. They can bypass the rings by taking offfrom the earth in the far north or the far south, near the poles, so that, instead of crossing the doughnut-shaped—

tings, they pass right through the hole of the doughnut. — Electric Currents in the Air In March

1949, measurements


in an Aerobee

rocket fired near Peru proved that there are electric cur- — _ rents in the atmosphere itself. In these currents, the elec-_

trical particles of the ionosphere flow in broad sheets at

height of sixty miles above the ground. These electri a currents, like those in the Van Allen rings, are rounded by magnetic lines of force that reach

the ground and influence compass needles, = ce be



Noe Sat


SeutEy, Beene Saag

et Cie


e ee ee


es me




Why the Earth Is a Magnet

One of the big problems in the study of the earth’s magnetism is to find out why the earth behaves like a magnet at all. A theory which seems to offer a satisfactory explanation uses the electromagnet as a model, The magnetic field that surrounds an electromagnet is caused by a flow of electric current. It is believed that the earth’s magnetism is also caused by a flow of electric current. But more than one current is involved. There are electric currents inside the earth, and electric currents outside the earth in the space surrounding it. The magnetic fields developed by these currents combine to form the magnetism of the earth. The electric currents inside the earth are located in its core. The core of the earth is a ball of iron and nickel at the center of the earth, and half as wide as the earth itself. The inner part of the ball is solid and the outer part is liquid. Electric currents, related in some way to the rotation of the earth, seem to flow in the outer part of this ball in closed loops. The flow of electric current makes ‘the core an electromagnet whose magnetic field reaches out to the surface of the earth. The electric currents outside the earth seem to be concentrated in two places. One place is inside the atmosphere, in the ionosphere, where there are many charged particles. Every wind in the ionosphere, by moving the particles around, creates an electric current. The other place is in the Van Allen rings, lying entirely outside the atmosphere. The currents in the Van Allen rings and the ionosphere make them giant electromagnets, whose magnetic fields reach down to the surface of the earth. Inside vs. Outside

At the surface of the earth our measuring instruments detect the combined effects of the magnetic fields reaching out from inside the earth and the fields reaching down

_ from outside the earth. The fields are mixed, so we cannot

_ source. However, it becomes oer


eae the¥

fields if we also make measurements of the magnetic field

at places high above the ground. Some of the earth satel- — lites are equipped with a magnetometer, an instrument ~

that can make these measurements. By taking the magne- © tometer up into the air, a satellite takes it farther away from the core of the earth, where the magnetic field that — comes from the currents in the core is weaker than it is on © _ the ground. At the same time, it takes the magnetometer —

closer to the currents outside the earth, where the magnetic fields they make are stronger. Comparing the upper air measurements with ground measurements will show _ what part of the earth’s magnetism comes from the inside and what part comes from the outside. a The satellites will also make it possible to distinguish — between the magnetism that comes from the sheet currents in the ionosphere and the magnetism that comes from the ~ currents in the Van Allen rings. On the ground, we are looking up at both the sheet currents in the air and the

Van Allen rings that are outside the air. The satellites, —

however, rise higher than the sheet currents. So they look down at the sheet currents while looking up at the Van ~ Allen rings. This difference in viewpoint between the © ground and asatellite will make it possible to separate

the effects of the two magnetic fields. When magnetic — storms occur at the time of solar flares, the measurements— made by the satellites will help us find out which currents —

above the earth have the greatest share in causing them. Magnetic Water

The strength of a magnetic field at any place is meas-

_ ured by seeing how hard it pulls on a small magnet held — at that place. The magnetometer on an earth satellite uses — ~ not just one small magnet, but millions of them. They are —

invisible magnets hidden in ordinary water. Water contains atoms of hydrogen, and the nucleus of each hydrogen at is a proton. The proton is spinning like a top, so its el charge is mayne all the time. The movement C

makes the spinning

oie a tiny magnet. When *

water is held in the earth’s magnetic field, the magnet- Ee

ism of the field pulls on the spinning protons the way it pulls on a navigator’s compass. The magnetometer on an — e _ ie earth satellite measures the strength of this pull. rere a Here is how the magnetometer works: Water in a bottle . is surrounded by a coil of copper wire. An electric current is passed through the coil, converting it into an electro- — magnet. The electromagnet pulls on the tiny proton mag-

_ _ 2 _

nets in the water, and lines them all up so that the axis. around which a proton spins is at right angles to the lines _ of force in the earth’s magnetic field. Then the current in the coil is turned off. When the current stops flowing, the

magnetism of the coil dies out, and so it stops holding the _

protons in its grip. When the protons are let go, they are free to move under the pull of the earth’s magnetic field. _ They begin to wobble around the lines of force the way _ a spinning top wobbles when it leans over. This wobbling _ motion is called precession. The stronger the magnetic — _ force that is pulling on them, the faster the spinning pro_ tons wobble. The earth’s magnetic field pulls hard enough _ to make them go around about two thousand times a sec-

si ond. Since each proton isalittle magnet, it is surrounded

__by its own magnetic lines of force. As the protons wobble, | ‘ these magnetic lines of force swing around with them, and

move across the wire in the copper coil. This movement of Eine lines of force causes an electric current of changing

_ strength to flow through the coil. With each turn of the _ protons as they precess, the changes in the current are recated. If the protons swing around the lines of force of the earth’s field two thousand times a second, the current ‘swings back and forth two thousand times a second. The frequency of the current is a measure of the strength of the i earth’s magnetic field. It is recorded in the memory device - built into the earth satellite. This process of measurement is repeated many times as the satellite travels around in its rbit, so that the strength of the earth’s field may be meas-

at allparts of the orbit. The magnetometer that works s way is called a proton free-precession magnetom- —

se AL


Ri a pieraes es AE 122



A Magnetic Brake

A satellite like Vanguard II is spinning when it is re- © leased into its orbit. We saw in Chapter III that the spin of the satellite helps the scientists gather important-information about the density of the upper air. It is important not to allow anything to interfere with that spin. The

earth’s magnetic field is one of the things that can interfere with the spinning of the satellite, by acting as a brake. As the satellite spins, it cuts across the lines of force of the earth’s magnetic field. If any of the metal parts in the — satellite should form closed loops, this movement across the lines of force would start electric currents in the loops. — The electric currents would convert the loops into electromagnets, and the earth’s magnetic field, pulling on these — electromagnets, would slow down the spinning of the — satellite. To prevent this braking effect from being serious, it is necessary to design the satellite so that it does not — have metal loops through which a current can flow easily. This is done by building up metal parts out of thin strips — or laminations of metal instead of single solid pieces. The — laminations chop up any path that an electric current might — take, and so prevent the currents from becoming strong i enough to interfere with the satellite’s spin.

Re ii a iN

sa : re o ;ae. y


Next S teps in. § pace More Satellites

The study of the upper air and the space above it has only just begun. The many earth satellites and several space probes already successfully launched will soon be followed by others. They will gather on-the-spot information about conditions we were able to observe before only from a distance, or were not able to observe at all. In the

United States, the exploration of space is being planned and conducted by two separate government agencies. The National Aeronautics and Space Administration is in charge of all nonmilitary space activities. The Advanced Research Project Agency of the Department of Defense plans and carries out those projects that are of direct military importance. Here are some of the areas they will study in the immediate future: The Atmosphere. More information will be gathered about the pressure, density, and temperature of the upper _ air, to see how they change with latitude, altitude, time of the day, and season of the year. Air movements will be charted and studied for clues to the weather down below. The Ionosphere. More and more accurate counts will

_ be made of the density of charged particles at different levels in the air and over different regions of the earth.


SEEING THE EARTH FROM SPACE The particles will be weighed to identify them. Their effect — . on space vehicles will be closely studied. Fields of Force. There are three important fields of force that surround the earth, an electric field, a magnetic 124

field, and a gravitational field. The electric field will be ©

studied by the exploration of electric currents in the air. The shape of the magnetic field will be traced far out into space. The gravitational field, revealed by the way the satellites themselves move, will give more clues to the shape and structure of the earth.

| —

; e Astronomy. Rockets and satellites will observe the sun — and the stars from above the earth’s atmosphere. Special —

attention will be paid to patches of ultra-violet light first ’


discovered during the IGY.

While some of the satellites will be merely flying re-

search laboratories, gathering information, others will have — ; more direct practical purposes:

Weather satellites will study the cloud cover, heat bal- — ance of the earth, and air movements, to help make ©


weather forecasts.

Navigation satellites will provide a foolproof all-weather —

system by which ships and planes can locate their positions :

anywhere on the earth. When clouds hide the sun or the ;

stars from the navigator’s sextant, he will be able to fix his ship’s position from the radio signals he receives from a satellite in a high stable orbit whose position is accu-—

rately known.

Communications satellites. Atlas showed that it is possible for an earth satellite to relay messages from the | ground. At the present time, to send a radio broadcast out over a great distance around the earth, it is necessary — to bounce it off the ionosphere. But sometimes the ionosphere develops “holes,” and the radio signals fade out. | Television programs cannot be bounced off the ionosphere, — because the high-frequency waves of television. broadcasts pass right ‘through the ionosphere, instead of being reflected down again. If there are several satellites alof equipped as relay stations, they can perform regularly the service that the ionosphere performs irregularly for radi

pr broadcasts, and can extend this service to television 1 +a +


oc! the imorid without seiecienenes ms m

; storms.


radio waves (such as Echo I, the inflated aldininieets balloon). Instead, they will be like the Atlas satellite and _ carry a “repeater” capable of rebroadcasting messages. we it receives. The radio equipment will be capable of handling up to 600 messages at once, and thus be economically A ~ competitive with the submarine cables now used. The post a _ offices and telecommunication firms in Britain, America . and France are busy working on such equipment. Here— are two of the new styles to come, each for a special —

-‘purpose: "yd es Inflatable balloon. The balloon will be blown up after it is in orbit. By exposing a larger surface to the air, it will be slowed down more effectively by the drag effect of the air, and so will give more accurate information


about air density. Paddle-wheeled satellite. The paddles will look like 3

_ the vanes of a windmill. They will contain solar batteries

_that convert sunlight into electrical energy. The large sur- — _ face of the paddles will catch a lot of sunlight, so that a _

igh level of power can be maintained for operating the

nstruments and radios of the satellite.

moon is 240,000 miles away from the ante ‘Oat ape a been taken 1 : peeeceenon stories, it.




distance that is so great. For this reason, trying to do -something that is considered impossible is often described as “reaching for the moon.” But this expression has now lost its old meaning. Mechta and Pioneer IV show that reaching for the moon can be organized as a practical undertaking. Both of these rockets passed the moon and

went beyond it. They didn’t come close enough to the moon to be held by its gravitation field. There are three things that may happen to a rocket that comes close enough to the moon. It may circle the moon

; makes that path a and then return to the earth, following a figure eight. It may be permanently captured by the moon, and remain as a moon satellite, a moon of the moon. Or it may actually land on the surface of the moon. Lunik II and III have done the first and the third of these things. Especially important was the feat of Lunik H, which made a “hard” landing (or impact) on the moon. bepee 8S The next important task in this field of space research is a “soft” landing of a probe on the moon, so that its instru- ments survive the landing and can continue to transmit ?— information back to the earth.


The Other Side of the Moon

; 3 |


The moon revolves around the earth in an orbit that is

about half a million miles wide. It makes a complete —£ round trip in about a month. As it revolves around the ~ earth, it also spins on its axis. Its spinning is in step with

its motion around the earth, so that one side of the moon always faces toward the earth. As a result, no one on © earth has ever seen the other side of the moon. Lunik ITI, -

which passed behind the moon, gave us our first chance to learn about the other side. The pictures it sent back show that the other side of the moon is, as we expected, not very different from the side we always see, It appears to have the: same kind of broad plains, pockmarked with craters inside rings of tall mountains.



ing Venus’ Veil

ee aS

_ After succeeding in getting rockets to land on and ¢ a4 = circle C the moon, the next venture into space was to send ~ _a rocket to one of the planets. This is far more difficult© S q _than the shot at the moon, because much greater distances—se gare involved. A small error in direction or speed of the— _ rocket at launching time becomes a large error after the _ rocket has traveled a great distance, and may mean missdi _ing the target. The time when a rocket will be fired toward — ya planet has to be chosen carefully, to take advantage of é


_the relative motion of the earth and the planet. Calcula_ tions show that the shortest time it would take for a rocket

_ to reach the planet Venus is 146 days. A trip to Mars © would take 260 days. A trip to Jupiter would take two and three-fourths years. . The Russian rocket fired from a sputnik on a journey - to Venus on February 12, 1961, was scheduled to reach _the planet is about 100 days. This shorter journey time * was made possible by a greater expenditure of fuel. It car- — ried additional fuel to enable corrections to be made to its orbit, and weighed 1,420 pounds.


Since Venus can be reached more quickly than any

other planet, Venus was the first planet to which a rocket ras sent. Venus is completely covered by a veil of clouds.

A rocket that lands on Venus equipped with television

cameras that broadcast their observations back to earth ill give us our first view of what lies under the clouds. To keep the measuring instruments and radio transmitters of the rocket working for over 100 days requires a ee sting supply of power. One of the purposes of some of the early satellites was ) develop such a power source for use in a rocket to ‘enus. On the way to Venus, the rocket broadcasted back formation about the conditions it found in interplanetary _ se. It could measure the magnetic field in space, count— particles, weigh them, measure their speed, etc. information will a of value in PcanIng: the first





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3 ’ Rockets with Passengers The rockets launched into space so far have not been spaceships in the true sense of the word. They have carried scientific instruments, and experimental animals like a dog or a monkey. But they have not carried human ~ passengers into distant space. Before any human beings 3 will be sent into space in rockets to the moon or planets, we have to be sure that they can come back safely. A safe return depends on our success in solving some difficult — problems, described in the paragraphs below. Until we crack these problems, mankind, facing the ocean of space that surrounds our earth, is like the timid man at the sea-

shore. By sending out unmanned satellites and space probes, we are dipping our toes into the ocean of space, to see how “cold” it is. Only after our instruments aboard the satellites and rockets assure us that we may “come on in, the water is fine,” will we gather up enough courage to take the plunge ourselves.


Climbing into Trouble

Man is an animal whose natural habitat is above the ground, but under the blanket of atmosphere that surrounds the earth. In this location, the air gives us the © oxygen we need to breathe to keep alive. The air presses — down on us with a force of fifteen pounds per square inch, This pressure has called forth a balancing pressure in the © fluids that are in our bodies. Our comfort and our lives © depend on maintaining this balance. The air also serves as a shield, protecting us from the dangerous rays and particles that rain in on the earth. It burns up the meteors that speed into the atmosphere like bullets, and it absorbs the ultra-violet rays that pour in from the sun..When cosmic rays come crashing in from space, it slows them down enough to make them harmless. When we venture off the ground, out of the denser part of the atmosphere, and out ~ into space, we are throwing off the blanket that protects us. As we climb to greater and greater heights above the ie&




ground, we climb into more and more troubles. At a height of ten miles, the air is already so thin that it cannot

give us enough oxygen to keep us alive. If we overcome this trouble, we run into a new one at a height of thirteen miles. Here the air pressure is so low that our body fluids — would begin to boil. If we manage to survive this difficulty, it will only be to be pierced by cosmic rays at a height of twenty-four miles and be broiled by ultra-violet rays at a height of twenty-seven miles. If we succeed in reaching a height of one hundred miles, we face the danger of collisions with meteors. At higher levels we will be menaced by the radiation in the Van Allen rings. When we give up the protection that the atmosphere gives us against these troubles, we can survive only if we substitute some other form of protection to take its place. We will need oxygen tanks and oxygen masks to make it possible for us to breathe. We will need pressurized cabins to balance the pressure in our body fluids. But the cabins may leak, so we will need pressurized spacesuits, too. We will need special windows in the spaceships to filter out the harmful ultra-violet rays. We will need shields to protect us from cosmic rays. The body of the ship will have to be designed so that it plugs up automatically any holes that are made if it is punctured by collisions with meteors. Oxygen for Long Flights

For a very short trip, a spaceship could take its oxygen supply along in tanks. For a long trip, a pre-packaged supply of oxygen would weigh so much that it would not be practical to take it along. On long journeys, ships would have to carry a small oxygen supply that is renewable. A renewable oxygen supply can be developed by using the _ principle employed in a balanced aquarium. In a balanced - aquarium, water containing fish and green plants is held

in a completely closed tank. The fish breathe oxygen that they remove from the water by means of their pills. They exhale carbon dioxide into the water. The plants, with ‘the help of sunlight, absorb the carbon dioxide, use the carbon

it for growth, and release the oxygen in it back into the in a

Rtaiee. In this way the oxygen nee if t

Be iauily renewed. To use this principle i in ‘spaceships, is planned to take along plants that will absorb the carbon — _ dioxide exhaled by the ship’s passengers and will release q oxygen. The United States Air Force is now testing many — _ types of plants to see which are the most efficient oxygen— _ producers. In a recent experiment at the School of Avia- s

tion Medicine, located at Randolph Air Force Base in—

- Texas, four mice were sealed into a small chamber for| _ three weeks. The air they exhaled was pumped throustels water filled with algae, the tiny green plants found in pond q

scum. The oxygen released by the algae kept the mice

alive throughout the three-week period. It is likely that — ' some type of algae will be used to renew the oxygen. 4 supply aboard the spaceships of the future. Too Many G’s


Merely taking off in a rocket ship would subject the— _ human body to an unusual strain. The rocket ship has to— start from rest and build up a high speed in a short time. ‘While the ship is accelerating, or increasing its speed, the_ body will feel a force tugging it back. The faster it accelerates, the stronger this force will be. Because this force resembles the pull of gravity, it is measured by compar it with the gravity of the earth. A pull that is as strong as _ the gravity of the earth is called one g. Stronger pulls will _ be measured by many g’s. When a person is subjected to too many g’s, he experiences pain, has difficulty in breath- — ing, and may become unconscious. Studies are now belt made to find out how many g’s a person can safely take,~ and what position he should be in to reduce the strain on * his body. Experiments by an Italian scientist suggest that£ oh gatmay be desirable for the passengers in a spaceship to float in water at take-off. The buoyancy of, the water - counteracts‘the effect of the take-off acceleration. e experiments, conducted on oe showed that an animal


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Not Enough G’s

The problem of too many g’s exists when a rocket ship speeds up at take-off, and when it slows down for a landing. It ceases to exist when the rocket ship coasts. But then a new problem comes up, the problem of having no g’s at all. We are accustomed to life on the earth, where everything is affected by the pull of gravity, and falls if it is not ~ held up. We count on this to happen in our everyday activities. When we drink water from a glass, we expect the water to fall down our throats, while our throats stand

stil. But in a spaceship that is coasting, this would not happen. While the water would fall, our bodies would be falling with it. Since we would keep up with the falling water, it would be as though the water did not fall at all, _ but merely floated in space. Under these conditions, a simple activity like drinking a glass of water would become a complicated chore. Space travelers would have to be trained in new ways of eating, drinking and moving during the period of coasting or free fall. Laika’s Experience At the school of aviation medicine in Texas, and in similar institutions in other parts of the world, scientists try to reproduce in specially constructed chambers the conditions that may exist in a spaceship in flight. Volun- - teers are subjected to these conditions to find out how they

affect the human body and mind, There are additional

clues to what space travelers may expect in the information radioed down from Sputnik II, the satellite that carried the dog Laika. The measuring instruments attached to Laika showed that at take-off, her heart began pumping at three times the normal rate. But it returned to normal _ when the satellite began coasting in its orbit. Analysis of the changes in Laika’s pulse rate, breathing rate, and blood

"pressure shows that she was not harmed by either the high

- Jevel of g’s during the period of acceleration, or the abg’s during the period of coasting, Commander ‘ ‘sence of :

6Shepard’s , * wa


| ges

experience was almost identical.




KEY TO SYMBOLS: ~ CR —Cosmic rays

SR —Solar radiation (ultra-violet andX-rays) GO—Gravity zero (weightlessness) R —Respiration € —Cardiac activity B —Blood pressure


Medical and biological data sent by Sputnik Il Reproduced from USSR Illustrate 7

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Coming Back

The most important problem to solve in space travel is that of coming back. Returning to the earth means entering the earth’s atmosphere at high speed. Unless the spaceship can be slowed down as it enters the denser layers of air, it will burn up as meteors do, and as the first earth satellites did. Plans now being developed for bringing a spaceship safely back to the ground rely chiefly on two devices. Spaceships will be equipped with both retro-rockets and parachutes. The retro-rockets will be fired when the ship first begins to fall into the atmosphere. As the ship falls, the retro-rockets will push upward, slowing down the rate of fall. Then, when the ship enters the denser lower layers of air, the parachutes will open. The air resistance against the large surface of the parachutes will keep the speed of descent low enough for a safe landing. So far the exact method by which Major Gagarin returned has not been revealed, but Commander Shepard’s Mercury capsule came down by parachute.

The problem of bringing a rocket’s pay load safely back to the ground is being approached in another way by the scientists and engineers who are developing interconti- _ nental missiles for the armed services. Such missiles are — _ designed to deliver a bomb halfway around the world. The bomb would be housed in the nose cone of a rocket. The socket would be fired to a height of several hundred miles above the ground, where it would coast outside the atmosphere. Then the nose cone, after separating from the rocket, would fall on the target thousands of miles away. _ The engineers of the Army and Navy have succeeded in making a nose cone that can return to the ground without burning up. The surface of the cone becomes as hot as - 5,000

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degrees Fahrenheit


it falls through the air.

But the skin of the cone is designed to peel away quickly as it is heated, so that the heat never reaches the interior. o 2 .

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_. Space Monkeys

-_-In June 1959, the United States armed services used such a cone to carry the first space travelers who left the © in the© earth’s atmosphere and came back. The passengers

cone were two monkeys, named Able and Baker. AJupiter rocket fired from Cape Canaveral raised them 360 |


miles above the ground. The nose cone was dropped 1,700 — miles away. It fell into the sea, and was picked up by a q Navy tug that was waiting for it.

Able and Baker rode into space strapped to beds that

were shaped to fit their bodies. They were subjected to 15 | g’s of force at take-off, and as much as 38 g’s when the

nose cone fell. Electrical instruments attached to their

bodies measured their breathing rate, temperature and heart beat, and radioed the measurements down to the © ground. They came back from the ride alive, apparently — unharmed by their experience. Able died later when she ~ was operated on to remove the electrodes in her skin. Baker, however, is still well, and will be watched closely to see if there are any delayed aftereffects. ag

Project Mercury

In Roman mythology, Mercury was the name of the winged messenger of the gods. This name has been bor-

rowed for the title of the American project for putting - manned satellite into orbit. The plans of Project Mercu

call for putting a man into space for up to twenty-four —

‘hours in a space capsule, after the successful ballistic flight of May 5, 1961. The capsule will be a truncated cone with~ ‘a short cylinder attached, giving it a shape resembling that of a television picture tube. (See the photograph on page

8.) The occupant of the capsule will lie on his back on

a couch during take-off, to reduce the strain of the g’s On

his body. Fhe capsule will be boosted into the air by an jnter-continental ballistic missile rocket. If anything goes wrong in the launching of the rocket, it will be possible the spaceman in the capsule to escape. Firing a ro

the cylinder at the top of the capsule will *

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capsule from the larger rocket. Then retro-rockets and parachutes will control its return to the ground. If nothing goes wrong, the capsule will separate from the rocket at an altitude between 100 and 150 miles, drop the escape _ system, and go into orbit. The capsule will be guided into orbit by the firing of retro-rockets in its base. On the first capsule flight, after two or three trips around the earth, the retro-rockets and then two parachutes will cushion its fall to the ground. The man who will ride in the first Project Mercury space capsule will be ‘one of seven test pilots who have already been selected. All had to pass rigorous physical and mental tests to be sure that they are physically fit for this daring undertaking. The launching will not take place until many trials of the rockets, the control instruments, and the landing gear show that they work properly. Space Platforms

When the era of space travel begins, the first space flights will be in one-passenger ships like the Project Mercury capsule. As ships are improved, they will carry more passengers for longer periods of time. After that, they may _ be ready to participate in the next big step into space, the construction of a permanent space platform. A space plat_ form would be a large man-made satellite placed far enough away from the earth so that it would be entirely outside the atmosphere. Since it would not be slowed down

__ by the drag of the air, it would circle the earth indefinitely. It could serve as a permanent astronomical observatory,

and perhaps even as a launching platform for spaceships. Imaginative engineers and artists have sketched what they think the space platforms of the future may look like.

Before the twentieth century is over, there will be real

platforms like them sailing across the sky.

_ A Space Timetable ye


It is impossible to predict exactly when each new step

into space will take place. But engineers and scientists .

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. 136





engaged in the development of rockets and satellites have - made some rough estimates, based on their knowledge of how long it takes to design, develop, and test new rockets, control instruments, and power supplies. An approximate timetable looks like this: 1962-2 Additional manned space capsules will be put into orbit. 1967 A permanent space platform will be built from parts carried into orbit on rocket ships. The crew of the platform will be rotated at regular intervals. 1968 Project Apollo: Three men will circumnavigate the moon. 1973. A manned spaceship will land on the moon. Twenty years ago, a timetable like this would have been pure fantasy. Today it is a serious forecast of events

: ~ © ~

to come. Indeed, since the achievements of astronauts in 1961 there are some who would shorten these dates


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