5 - Up We Go: Space Travel
As long as we can investigate the planets only from the surface of the Earth, we are limited in what we can find out. No matter how we analyze the light and the radio waves that reach us, there must be so much we miss.
If only we could get closer. If only we could get away from our Earth-prison.
Actually, such a dream doesn't date only from the time of modern astronomy. Men have always longed to free themselves from being bound to the Earth's surface. This is not just to get a better view of the heavens; it is to gain freedom. Surely almost every child at one time or another, watching a bird fly, has wished that he, too, had wings and could swoop through the air.
A famous Greek myth tells of a man who flew. The man was Daedalus, a clever inventor of legend, who was imprisoned on a small island near Crete. He had no boat, so in order to escape from the island he fashioned wings.
He constructed a light framework and stuck feathers to it with wax. By flapping these wings, he could rise in the air and fly. He made another pair for his son, Icarus, and together they flew away.
Daedalus escaped to Sicily. Icarus, however, in the joy of flying, soared too high and the heat of the sun melted the wax that held the feathers of his wings. He fell to his death.
Of course, wings alone, no matter how feathered and birdlike, can't make you fly. What counts are the muscles that flap them fast enough and manoeuvre them properly, so as to use the air as a cushion. Human muscles are simply not strong enough to raise the weight of the human body into the air simply by flapping wings.
When man finally did lift off the surface of the Earth, it was not by flapping but by floating. In 1783, two French brothers, Joseph Michel Montgolfier and Jacques Etienne Montgolfier, filled a large linen bag with hot air. Hot air is lighter than the same quantity of cold air (that is, hot air is less dense), so it floats on cold air as wood floats on water. The hot air rose, carrying the bag with it, and drifted for a mile and a half.
Soon larger bags were filled with hydrogen, which is far less dense than hot air. Such bags, or "balloons" could not only lift themselves, but also gondolas carrying human beings.
There was a ballooning craze in the first part of the nineteenth century. For the first time men rose miles high into the air.
Of course, such balloons were at the mercy of the wind. To make it possible for a balloon to go in some particular direction, even against the wind, a motor and a propeller would have to be placed on board. This was first done successfully by a German inventor, Count Ferdinand von Zeppelin, in 1900.
Such "dirigible balloons" eventually carried hundreds of people over wide oceans, but they were terribly fragile. Storms destroyed them. The future of air travel lay elsewhere.
After all must things be lighter than air to be lifted by it? Leaves and pieces of paper are denser than air; if still, they will not float. A brisk wind will, however, set them whirling through the air. If a heavier-than-air object has flat surfaces and if it moves fast enough, those flat surfaces will ride the air and lift the object high.
Towards the end of the nineteenth century there was a glider craze. Light objects, with broad, flat wings, could ride the wind like kites and could carry men with them.
But gliders, like the original balloons, were at the mercy of the wind. Could one place an engine upon them? In 1903, the American brothers, Wilbur Wright and Orville Wright, placed a motor and propeller on a glider of their own design. The propeller pulled the glider through the air quickly enough to raise it into the air and allow it to fly without wind or even against wind. That first power-glider remained in flight for almost a minute.
Thus, the third year of the twentieth century saw the construction of the first "heavier-than-air" flying machine; or, as we call it now, "aeroplane."
Aeroplanes have improved and developed until now they are capable of carrying a hundred or more people in luxurious surroundings for thousands of miles at speeds of many hundreds of miles an hour.
Balloons and aeroplanes both float on air. The difference is that balloons will float even if motionless, while aeroplanes must travel with great speed in order to ride on moving currents of air.
Neither balloons nor aeroplanes could rise off the ground if there were no air.
The air gets thinner as one moves higher above the surface of the Earth. Eventually, it gets so thin that neither balloons nor planes will get enough support to move higher. Twenty miles above the Earth's surface represents a reasonable limit.
Even twenty miles rise can be very useful to astronomers. At that height, something like 99 percent of the atmosphere is below the balloon or plane. The trace of air left above can scarcely obscure the heavens in any way, and this is important.
For instance, to reach us here at the low-lying surface of the Earth, the sun's radiation must travel through the twenty miles of thick atmosphere that would lie under a high-flying balloon. The visible light reaches us scarcely diminished, but ultraviolet light and infrared light are mostly absorbed and can't be studied. If sunlight were observed from a height of twenty miles, the ultraviolet and infrared could be studied as carefully as we have studied visible light in the past.
For this reason, photographs have been made of the sun from the gondolas of large balloons, and the sunlight has been carefully analyzed from that height.
As another example, the light reflected to us by Venus shows certain regions of absorption which indicate that light has passed through layers of water vapour molecules on its way to our eyes. Does that mean there is water vapour in Venus's atmosphere and that its clouds are made up of water droplets or ice particles?
Or is it just the water vapour in our own atmosphere?
If the light from Venus were studied from a high balloon, there would be no problem. The balloon would be above the water vapour content of Earth's atmosphere. Any sign of water vapour in the light absorption would have to be caused by water in Venus's atmosphere.
In 1959, light from Venus was studied by an American astronomer, John Strong, from a high-flying balloon. He did indeed detect small quantities of water vapour but, unfortunately, that did not end the problem. Similar studies in highflying aeroplanes in 1967 have failed to detect water, so there is still a dispute as to whether Venus's atmosphere contains water vapour or not.
But planes and balloons don't represent complete freedom. They lift man from the surface of the Earth but not more than twenty miles high. Man is still a prisoner of the atmosphere.
Is there any way of rising beyond the atmosphere? There might be if one weren't forced to depend on floating. There must be some way of lifting an object that could work in a vacuum as well as in air.
One way would be to shoot an object upwards out of a giant cannon. Cannonballs may be made to go high in the air this way. The faster they are sent shooting out of the muzzle, the higher they go.
As they go higher and higher, Earth's gravitational force grows slightly weaker so that they go a little higher than one might expect. If they are sent up fast enough, by the time they lose half their speed they are up where Earth's gravity is only half its strength. Though the objects continue to lose speed, so does Earth's gravity continue to lose strength. If the cannonball goes fast enough, Earth's gravity can never bring it to a halt, let alone cause it to start falling back to Earth.
An object which is shot upwards at such a velocity that it never returns is said to have been fired at "escape velocity." For Earth, escape velocity is 7 miles per second, or 25,200 miles an hour. If a large hollow object with people inside could be fired upward at 7 miles per second (or more), it would rise and rise and continue to rise. If it were aimed correctly, it would rise to the moon.
In 1865, the French science fiction writer Jules Verne wrote From the Earth to the Moon, a novel describing how a group of men are hurled to the moon in this fashion.
Unfortunately, the method, while correct in theory, is not practical. Not only would it require an enormous cannon that is not likely ever to be built, but if a spaceship were fired out of a cannon in this way, the sudden increase of speed (or "acceleration") would kill every person on board in a moment.
Another method, though, is to make use of the "law of action and reaction," which was first announced by Isaac Newton in 1687. This law explains that if a portion of a body is thrown off in one direction, the rest of the body must move in the opposite direction.
Imagine yourself sitting on a smooth aluminium platter resting on a sheet of smooth ice. With you are a bunch of heavy steel balls. If you threw one of the balls away with all your might, the platter carrying you and the rest of the balls would start sliding in the opposite direction. Throw a second ball after the first and the platter will move more quickly. Keep it up, and if you have enough balls you will end by skimming along the ice quite rapidly.
In 1891, an eccentric German inventor, Hermann Ganswindt, suggested a trip beyond the atmosphere by using this method. (He was the first man to try to design a spaceship along scientific principles.) Instead of throwing steel balls by hand, he imagined a ship that would fire them out to the rear by dynamite explosions.
If enough steel balls were hurled backwards with enough speed and in sufficient quantity, the ship would reach escape velocity. It would then travel away from the Earth indefinitely. The important difference between this and a cannon is that the speed would be built up slowly over a long period in Ganswindt's ship, where it would build up all at once before the ship left the muzzle in Verne's cannon. Acceleration would not be murderous in Ganswindt's ship.
But why fire out heavy objects? If a ship fired out a jet of gas from the rear, that could do the job, too, provided the gas were fired out quickly enough.
The advantage of gas over solids is that gas can be made to shoot out in a continuous stream. The ship would gain speed smoothly instead of in a series of jerks and it would do so more efficiently.
We can actually watch a gas jet do the work of moving an object. Suppose you fill a toy balloon with air, hold it up and let the air escape. The air, rushing out in one direction, will cause the balloon to move in the other.
For such action and reaction to take place, air does not have to surround the moving object. In fact, air gets in the way. When escaping air moves a balloon, the balloon's motion is slowed by the resistance of the air all about it. The balloon is pushed this way and that by air currents. Action and reaction would work best in a vacuum where nothing would interfere with motion.
Actually, the spherical shape of a balloon is bad for rapid motion. To allow for rapid motion through air with least interference, you need an object that is narrow and streamlined. Then, too, you want as much gas in it as possible so that it will come out with great speed and in large quantities. One way of packing an object with much gas is to pack it with a solid that can be easily and quickly turned into a gas.
Suppose you take a narrow cylinder, coming to a pointed end on one side and open at the other. Fill it with gunpowder, close the open end lightly, and push a fuse through into the gunpowder. Once the fuse is lit, the gunpowder will quickly catch fire and form large quantities of gas. A hot jet of these gases will push out of this "rocket," which will move rapidly in the opposite direction. Small rockets shot into the air in this way can be very impressive.
Large rockets of this same sort might easily be used as a war weapon. By sending burning rockets into a city, buildings could be set afire, ammunition could start exploding, and people could be panicked. For a while in the nineteenth century such rockets were indeed used in warfare. They were used in the War of 1812 between the United States and Great Britain. The Star-Spangled Banner, our national anthem, written during that war, speaks of "the rockets' red glare."
Rockets faded out as a war weapon because cannonballs could be fired more accurately from cannon and would do more damage.
However, rockets remain more practical for reaching great heights than cannon. A cannon must fire off all its gunpowder before the cannonball comes out of the muzzle. After that the cannonball can only slow down. A rocket rises up while the gunpowder is still burning, and it carries the gunpowder upwards along with itself. As it rises, it therefore goes faster and faster as more and more of the gunpowder burns.
In order for the ordinary rocket to work, however, it must be surrounded by air while the gunpowder is burning, for the gunpowder won't burn in the absence of air. This means that such a rocket can accelerate only inside the atmosphere.
Acceleration inside the atmosphere is important for many purposes, to be sure. The rocket principle can be applied to aeroplanes very neatly.
At first, aeroplanes were sped through the air by means of a propeller. The propeller was the weak point of the plane. Its tips had to move through the air much more quickly than the plane itself did. There was a limit to how quickly propellers could be whirled and that helped set a limit to how quickly planes could fly.
Suppose, though, that you fed kerosene into a rocket arrangement, had it burn, and sent the gases out through the rear. The plane would then be driven forwards without a propeller. At high speeds, such a "jet plane" is much more efficient than a propeller plane. Indeed, a jet plane can easily reach speeds a propeller plane could never achieve.
The jet plane was developed during World War II as a war weapon. In 1952, it made its first appearance in commercial aviation and travel by jet is now very common. Jet planes can easily go faster than the speed of sound, which is 750 miles an hour, or 0.2 miles a second.
If a jet plane built up enough speed and reached escape velocity, it could leave the atmosphere altogether and enter space. It would need no further jet blasts to continue onward indefinitely.
This is not practical, though. The jet that drives the plane is kept going by fuel burning in air drawn in from the surrounding atmosphere. This means that the jet only works where the atmosphere is fairly dense. All the acceleration must take place in this dense atmosphere, where air resistance is so high it would waste fuel and would heat up the ship dangerously.
It would be much better if the jet plane could reach the upper atmosphere at low speeds, avoiding too much resistance and heating. Then up there, where the atmosphere is too thin to be any trouble, the real job of acceleration could take place. Unfortunately, up there the atmosphere is too thin to keep the kerosene burning.
A spaceship must, therefore, carry its own supply of air (or, better, oxygen) along with the fuel. Then, once the spaceship got into the upper atmosphere, it could mix its stored fuel with its stored oxygen, burn the mixture, and accelerate to escape velocity without trouble.
A self-educated Russian schoolteacher, Konstantin Eduardovich Tsiolkovsky, was the first to make this clear. In 1898, he wrote a long article in which he described a spaceship that would be powered by a rocket exhaust. It was published, finally, in 1903, the same year in which the aeroplane was invented. It was the first description of the kind of spaceship that eventually came into use.
The real breakthrough, however, came in the United States, through the work of an American rocket engineer, Robert Hutchings Goddard.
As a boy, he was fascinated by science fiction. In 1899, he read War of the Worlds by Herbert George Wells, a thrilling adventure in which Martians invade Earth and almost conquer it. With that began Goddard's lifelong dream of penetrating outer space. By 1901, he was writing essays on the possibility of space travel.
Both Goddard and Tsiolkovsky saw that the older rockets were unsuitable. When gunpowder was used, its burning could not easily be controlled and it did not produce a fast enough exhaust anyway. Both men felt that what was really needed was a liquid fuel. This could be pumped into a chamber where it could be burned. The pumping could be started or stopped, made to go fast or slow. The exhaust could thus be controlled.
Tsiolkovsky was content merely to theorize, but Goddard went further. He began to design actual rocket engines. In 1914, he obtained two patents for inventions to be used in such engines. In 1919, he finally published a small book (only sixty-nine pages) on the subject.
Now he was ready to build small rocket engines and see how they worked. In 1923, he tested an engine in which a stored supply of kerosene and a stored supply of liquid oxygen were contained. The two liquids were pumped into the burning chamber where they were mixed and ignited. The engine worked well and the next step, Goddard decided, was to send a liquid-fuel rocket upwards.
He was teaching at Clark University in Worcester at this time, and he performed his experiments on an aunt's farm in Auburn, Massachusetts.
There, on March 16, 1926, he made ready to fire his rocket. His wife took a picture of him standing next to it. It was a cold day and there was snow on the ground. Goddard, wearing overcoat and boots, was standing next to what seemed a child's jungle gym. At the top of the structure was a small rocket, four feet long and six inches thick.
There were no reporters present and no one was interested in what he was doing. That was too bad, for what was about to happen was one of the news stories of the century, if only the world had known. The first liquid-fuel rocket was about to rise into the air.
Goddard ignited it and the rocket rose 184 feet into the air, reaching a speed of 60 miles an hour. This wasn't much, but it showed that Goddard's rocket engine worked. It was only necessary to build improved rockets on a larger scale.
Goddard managed to get a few thousand dollars from the Smithsonian Institution and continued his work. In July 1929, he sent up a larger rocket, which went faster and higher than the first. More important, it carried a barometer and a thermometer, along with a small camera to photograph their readings. This was the first instrument-carrying rocket.
Unfortunately, Goddard now ran into trouble. News had leaked out that he was trying to reach the moon and many people began to laugh at him. The New York Times printed an editorial telling him his science was all wrong. (Actually, the editorial writer was quite foolish, for he didn't even understand the law of action and reaction, thinking that air was necessary for its working-yet he dared lecture an expert like Goddard.)
When one of Goddard's rockets made a loud noise while being launched, policemen and firemen were called and he was ordered to conduct no more rocket experiments in Massachusetts.
But Charles Augustus Lindbergh, the famous aviator, had heard of Goddard's experiments and he used his influence to get the rocket engineer some financial help. Goddard built a new rocket-launching site in New Mexico, where he could experiment without disturbing anybody.
Here he built larger rockets and developed many of the ideas now used in all rockets. He showed how to build a combustion chamber of the proper shape and how to keep its walls cool. He showed how the rocket could be steered and how it could be kept on a straight course.
He also worked out and patented the notion of multi-stage rockets. A two-stage rocket, for instance, consists of a small rocket built on a large one. The large one burns its fuel and carries itself and the small rocket up into the upper atmosphere. Then the large rocket, empty of fuel, breaks loose and drops away, while the small rocket goes into action.
High up where the air is too thin to interfere, the small rocket's fuel blasts off. It is already moving upwards at considerable speed thanks to the action of the large rocket, and now its own engine makes it go higher still.
The small rocket moves a lot higher and faster than the whole rocket would have moved if it were all one piece.
In the early 1930s, Goddard finally fired rockets that reached speeds faster than sound and rose a mile and a half into the air. The American government was never really interested in this work while Goddard was alive, but years after his death, it had to pay a million dollars for the use of two hundred of his patents. Work on rockets would have come to a dead halt otherwise.
Interest in rocket experiments was particularly great in Germany. In 1923, a book on space travel was published in that country by Hermann Oberth, who was born in a region that is now part of Rumania. By 1927, a "Society for Space Travel" had been founded in Germany. Its young and enthusiastic members began to plan rocket experiments. Similar societies were formed in other countries but the German society was by far the most successful.
Among the members of the German society were two young men, Willy Ley and Wernher von Braun, each destined for great fame. They threw themselves into rocket-building and in the next couple of years some eighty-five rockets were fired. One reached an altitude of nearly a mile.
Goddard was doing even better, but he was a lone wolf, ignored by the United States. The German rocket engineers were soon receiving government support. When Adolf Hitler came to power in Germany in 1933, he began to think of the new rockets as a possible war weapon.
In 1936, a secret experimental station was built at Peenemunde, on the Baltic seacoast of Germany. There, by 1938, rockets capable of flying eleven miles were built. Such rockets might be expensive just at first, but they flew by themselves and required no human pilots. They could be aimed quite accurately and they went so quickly they couldn't even be detected, let alone stopped.
The first rocket-driven "missile" was fired in 1942 and by 1944, Wernher von Braun's group put these missiles into action. They were the famous V-2 rockets. (The V stood for vergeltung, meaning "vengeance.")
In all, 4,300 V-2 rockets were fired during World War II and of these, 1,230 hit London. Von Braun's missiles killed 2,511 Englishmen and seriously wounded 5,869 others. Luckily for the world, the V-2 came too late. Hitler had lost the war and the V-2 couldn't reverse that decision.
Goddard lived just long enough to see this awful triumph of the rocket. He died on August 10, 1945.
One thing the V-2 rocket did was to rouse the interest of Germany's adversaries, the United States and the Soviet Union. Immediately after the war, both made efforts to capture Germany's rocket experts. The United States got most of them, including Wernher von Braun. (Willy Ley had left Germany for the United States long before-as soon as Hitler came to power.)
Both nations then worked hard to build missiles. By the 1950s the old V-2 was a piddling affair compared to the monsters that were coming into existence. Both the Soviet Union and the United States developed "Inter-Continental Ballistic Missiles" (ICBMs). These could travel for thousands of miles and land accurately on target.
Both nations could strike any place on Earth, now, with missiles based on their own territory. These missiles could carry hydrogen bombs. A new world war would be more terrible than had ever been imagined. In the space of half an hour, hundreds of millions of people could die, and civilization might be destroyed.
But rockets were not used only for war weapons. Some were sent up into the heavens in order that new knowledge might be brought back. Soon after the war, captured V-2 missiles were used by the United States to carry instruments into the upper atmosphere. One reached a height of 114 miles, five times as high as any plane or balloon could reach.
In 1949, the United States put a small American rocket on top of a V-2. When the V-2 had reached its maximum height, the small rocket took off and reached a height of 240 miles.
Another way of accomplishing the same purpose was to send a balloon as high into the atmosphere as possible and then to launch a small rocket from it. The air would be too thin to interfere and such a "rockoon" combination could reach great heights with very little expense. A leader in this work was the American physicist James Alfred Van Allen.
Such high-flying rockets brought back useful information about the nature of the upper atmosphere. They described the temperature, density, winds, gases, and ions of the upper atmosphere and recorded how all of these changed from time to time.
But such rockets only stayed in the upper air a short period of time and could only gather information concerning the portion immediately about it. What was wanted was a rocket that could stay up for a long time.
Suppose a rocket were sent up at a velocity less than escape, and was steered so as to travel parallel to the surface of the Earth. Since it could be travelling at less than escape velocity, it would fall towards the Earth. The surface of the Earth, however, is curved. The surface curves away from the rocket as the rocket falls while moving forwards.
If the speed of the rocket is just right, then it will travel so far parallel to the Earth's surface while it is falling a mile that the Earth's surface will have curved away one mile. In that case the rocket will never actually fall to Earth, but will circle it forever. The rocket will be "in orbit" about the Earth; it will become a "man-made satellite" of our planet.
If the speed and direction of the rocket is just right, it will go about the Earth in a perfect circle. Otherwise it will circle the Earth in an ellipse. This ellipse can be quite oval, sort of long and flattened. The satellite could come quite close to the surface of the Earth on one side of its orbit and be quite far away at the other.
Although, in theory, such a satellite should stay in space forever, part or all of its orbit might be within 100 or 150 miles of the Earth's surface. In that case, the very thin air of the upper atmosphere will produce enough resistance to consume the satellite's energy of motion very slowly. The satellite will spiral lower and lower and eventually penetrate the thick atmosphere and burn up.
Rocket experts began thinking of possible satellites in connection with a huge international study of our planet planned for 1957 and 1958 (the "International Geophysical Year" or IGY). Perhaps the launching of a satellite could be made part of the IGY. On July 29, 1955, the American government officially announced the attempt would be made.
The Soviet Union then announced that it would also make such an attempt, but most Americans paid no attention. Those that did thought the Soviets were just playing "copy-cat" and that only the United States had the ability to perform such a difficult rocket feat.
The Soviet Union therefore surprised the whole world (and particularly the United States) when, on October 4, 1957, they launched the first successful satellite. This was meant to celebrate the hundredth anniversary of the birth of Tsiolkovsky (which had taken place on September 17). They called it "Sputnik," meaning "satellite," a name that Tsiolkovsky himself had used to describe such man-made objects in orbit.
The United States was soon launching satellites of its own. On January 31, 1958, the first successful American satellite, Explorer I, was launched. In the years that followed, hundreds of satellites were launched by each nation.
These satellites turned out to have a great many practical uses. For instance, some were designed to take many thousands of photographs of the Earth. Such photographs would show the cloud pattern over large areas. Scientists would learn more about the way in which air circulated and clouds formed. They could watch the birth and development of hurricanes. They could predict weather more accurately.
The first satellite intended for such a weather-watch was launched on April 1, 1960. It was called TIROS (standing for "Television and Infra-Red Observation Satellite) and it proved to be a great success. Soon, the sight of the Earth as seen from hundreds of miles in the air grew to be common.
Eight such satellites were launched altogether and then a more advanced type of satellite, "Nimbus," was launched on August 28, 1964.
Satellites can also be used for communications. Ordinary radio waves bounce off the charged particles in the ionosphere. That makes it possible to send radio messages around the world. Short radio waves, like those used in television, go right through the ionosphere. However, if they could be made to strike a satellite outside the Earth's atmosphere, they could be reflected back to another part of the Earth.
This was first pointed out in 1945 by Arthur C. Clarke, a young Englishman who was to become one of the best science fiction writers in the world. Another science fiction enthusiast, the American engineer John Robinson Pierce, who worked at the Bell Telephone Laboratories, endeavored to bring this idea to reality.
On August 12, 1960, Echo I, made possible by work at Bell Telephone, was launched. It carried a collapsed plastic balloon which was inflated, once it was in space, into a huge sphere that was as tall as a ten-story building. Radio waves striking it were reflected, and messages could be sent from continent to continent in this way.
Messages reflected from Echo I were very weak by the time they were received, of course. On July 10, 1962, Telstar I was launched. It did more than receive messages; it amplified them once received and made them stronger. Then it sent the strengthened signals back to Earth. This meant that American television sets could now easily receive pictures live from Europe and vice versa.
These early "communications satellites" were close to the Earth and travelled rapidly around it. They could only be used to transmit messages across the Atlantic when they happened to be in the right spot above the Atlantic.
If a satellite is sent higher and higher, it takes longer and longer to travel about the Earth. If it is about 22,300 miles above the Earth's surface, it takes twenty-four hours to circle the Earth, or just the time it takes the planet to turn on its axis. The satellite moves in time with the planet and is always over a particular spot on the surface. Clarke had suggested satellites of this kind.
This was achieved with full success on August 19, 1964, when Syncom III was launched. It was placed over the Pacific Ocean just in time to make it possible to broadcast the Olympic Games, live, from Tokyo to the United States.
Satellites can also be used to help determine the shape of the Earth. The Earth is not a perfect sphere. Because it turns, a centrifugal effect tends to lift its matter upwards against gravity. (If you attach a heavy object firmly to a cord and whirl it rapidly round your head, you will feel it pull away from your hand.)
The Earth turns most rapidly in the equatorial regions. Its matter lifts up highest there. The Earth has an "equatorial bulge," therefore, that is thirteen miles high at the equator.
On March 17, 1958, Vanguard I was launched. It was a tiny thing, only the second satellite the United States had placed in orbit, and all it carried was a small radio sending out a steady signal. Its motion could be followed by that signal, and that was sufficient to be useful.
Vanguard I had an orbit that was at an angle to the equator. In part of its orbit it was north of the equatorial bulge and in the other part it was south. The bulge had a special gravitational effect on the tiny satellite and altered its orbit in a way that scientists could easily calculate.
Scientists expected that the bulge would have the same effect on the satellite whether it was to the north or the south. That turned out not to be so. The part of the bulge south of the equator turned out to be a little higher than the part north.
Indeed, by studying the orbit of Vanguard I and later satellites very carefully, scientists could determine all kinds of bulges and hollows in the Earth's surface, even though these were only a few dozen feet high or low.
By knowing the Earth's shape more exactly than ever before, it became possible to make maps with greater accuracy. It turned out that some islands were a mile or more away from where the old maps had showed them to be. For the first time, the distance between London and New York could be worked out to within a few feet.
What's more, ships could locate their own positions on the ocean with new accuracy, by observing satellites.
Nor was it only knowledge of the Earth itself that was the product of satellite work. Those portions of space through which the satellites travelled could be studied in detail for the first time. Ordinary telescopes could see nothing there, but did that mean that nothing was really there? What about cosmic ray particles?
Explorer I, America's first satellite, carried special devices to record cosmic ray and other electrically charged particles. Its orbit was elliptical enough to bring it as close to 217 miles to Earth's surface in one part of its orbit and take it out to 1,155 miles in the opposite part. It could record charged particles at all heights between.
Up to a height of 500 miles, the number of particles recorded per minute was about as expected, and increased slowly as the height increased. Above 500 miles, however, the number of detected particles dropped suddenly, sometimes all the way to zero.
Scientists wondered if it might not be that the instrument was out of order. But then a later satellite sent back the same kind of records.
James A. Van Allen, in charge of these experiments, thought the trouble might be that there were so many charged particles that they were "blinding" the instruments. On July 26, 1958, Explorer IV was launched. Its instruments were designed to handle very high quantities of particles and now things were different.
Around the Earth, there proved to be regions that were enormously rich in charged particles. These were sent out by the sun (the "Solar wind") and were trapped by the Earth's magnetic field. These particle-rich regions were called "Van Allen belts."
The belts came closest to the Earth near the magnetic poles in the polar regions. There the charged particles leaked into the atmosphere and produced the beautiful shifting colours of the aurora (or "Northern Lights").
At first, it was thought these belts were perfectly even, all around the Earth. Further satellite studies showed that the solar wind struck the Van Allen belts and flattened them on the sun-side. The solar wind then veered to either side, circled the Earth and passed on beyond. The Van Allen belts on the night-side of the planet were drawn out almost as though they were a comet tail.
The lopside area inside the solar wind and circling the Earth is now called the "magnetosphere." No one suspected its existence until the age of satellites had opened.
But satellites need not be restricted to the neighbourhood of the Earth. If they are made to go at velocities that are a little faster they can reach the moon. They can escape from Earth altogether and take up orbits about the sun as "manmade planets."
The first successful "Lunar probe," that is, the first satellite to pass near the moon, was sent up by the Soviet Union on January 2, 1959. It was "Lunik I." It was the first man-made object to take up an orbit about the sun, and within two months, the United States had duplicated the feat.
On September 12, 1959, the Soviets sent up Lunik II and it was aimed so accurately that it hit the moon. For the first time in history a man-made object rested on the surface of another world.
Then, a month later, the Soviet satellite Lunik III slipped beyond the moon and pointed a television camera at the side we never see from Earth. (The moon always faces the same side toward us.)
Lunik III changed the photographs into radio signals that could be transmitted to Earth and changed back into photographs. They were fuzzy and of poor quality, but they showed something interesting.
The side of the moon we see is covered with craters but there are also large flat "maria" (or "seas") which are dark in colour and have hardly any craters. It is the maria that make the dim splotches on the face of the moon that cause some people to imagine they see the "man in the moon" there.
On the other side of the moon, though, as revealed by Lunik III, there are hardly any maria and no sizable ones at all. A number of satellites since Lunik III, both American and Russian, have made similar photographs of far better quality, and this is borne out. There are no maria to speak of on the other side of the moon.
Astronomers don't know why.
Lunar probes also reported on conditions in the neighbourhood of the moon. It was found that the moon did not behave like a magnet and did not have any Van Allen belts of its own.
This was not surprising, really. In order for a heavenly object to behave like a magnet and collect belts of charged particles, it should have a core of melted iron and it should turn rapidly. The turning sets up swirls of liquid in the melted iron and these swirls are what cause the planet to act like a magnet.
The moon is too small to have a melted iron core, and even if it had one, it rotated on its axis too slowly (once in twenty seven days) to set up important swirls.
Such observations could be made in greater detail by satellites sent into the neighbourhood of the moon, and then manoeuvred (by tiny bursts of rocket fuel set off by radio message from Earth) into orbit about the moon. This is a most delicate feat but by 1966, both the Soviet Union and the United States had worked out their rocket techniques so well that they could do it.
The Soviet Union's "Luna 10" took up an orbit about the moon after having been launched on March 31, 1966. The United States satellite, "Lunar Orbiter 1" was launched on August 10, 1966, and was the first of several like it.
The Lunar Orbiters took pictures of various portions of the moon's surface. Some of them were from an angle so that the rolling hilly nature could be seen clearly. Such photographs looked just like a desolate desert might seem on Earth. It was hard to believe they were taken of another world, a quarter of a million miles out in space.
Even more startling, perhaps, were pictures taken, past the curve of the moon's surface, of the Earth. There was our own planet, seen as a thick "crescent Earth," from a distance of a quarter of a million miles.
From the orbits of the satellites circling the moon, astronomers were able to figure out the exact location of the centre of the moon. Combining that with studies of radar echoes, as described in the previous chapter, they found they could calculate the diameter of the moon down to a fraction of a mile. Pictures of the moon from probes and orbiters that flew by and around the body might be startling but they were usually taken from a considerable distance. What about really close photographs?
The United States planned a whole series of probes designed to strike the moon and take photos on their way down. These satellites were called "Rangers." Ranger I through Ranger V were test satellites that were not sent to the moon. Finally, on January 30, 1964, Ranger VI was launched and headed for the moon. The aiming was very good and it hit the moon only twenty miles from target-but the television cameras failed.
A half-year later, on July 28, 1964, Ranger VII was shot into the sky and this time everything worked perfectly. Photographs were taken, right down to the very moment of impact, and the portion of the moon in view of the cameras was seen with greater detail than had ever before been possible.
Some astronomers had thought that the moon might be covered by a thick layer of fine dust, and they searched the Ranger photographs for some sign of that. Most astronomers felt that no dust showed up, but the matter wasn't settled.
What was needed was a "soft landing." Until 1966, all the probes that had reached the moon's surface had made a "hard landing," hitting with such force that they had been destroyed. If a satellite fired rockets downward just before landing, however, its speed of fall would be slowed up and it might then come down gently enough to allow its instruments to keep working. This would be a soft landing.
Both the Soviet Union and the United States tried for a soft landing and both succeeded. On January 31, 1966, the Soviet probe, Luna 9, was launched and succeeded in landing softly on February 3. It took the first pictures of the moon from its surface.
On May 30, 1966, the Americans launched Surveyor I, which landed softly on the Moon by June 2 and which took additional photographs. These and other such successful attempts seem to have made it quite clear by now that the moon's surface is rather like the Earth's. No signs of any dust layer have been detected. One of the later Surveyors even dug up a shovelful of moon soil on signal from Earth and a television camera scanning that soil showed it to be a rather usual soil. Another surveyor carried through a delicate analysis of Lunar soil in 1967 and showed it to resemble earthly basalt.
What about heavenly bodies farther than the moon? The next nearest bodies of importance are Venus and Mars, and both the Soviet Union and the United States have attempted to send out "planetary probes" in the direction of these two bodies.
So far, the Soviet Union has been plagued with bad luck in this respect. One of the "Venus probes," named "Venus 3," actually landed on the planet on March 1, 1966, but the feat was a disappointing one, for the probe's instruments had failed and no information was sent back.
A more successful Venus probe was the American "Mariner 11"
It was launched on August 27, 1962, and travelled through space for four months to make its rendezvous with Venus. The probe skimmed by within 21,000 miles of Venus on December 14, 1962. At that time, it was thirty-five million miles from Earth but successfully returned the information it gathered. It was a wonderful example of good aim and clever communications.
Mariner 11 was able to study the space in the neighbourhood of Venus. It found that Venus was not a magnet and did not have any Van Allen belts. To be sure, Venus was large enough (almost as large as the Earth) to have a melted iron core. However, it turned on its axis even more slowly than the moon, so it set up no swirls in that core.
The most exciting thing that Mariner II did was to scan the surface of Venus for microwaves. Astronomers had received microwaves from Venus in such quantity that they had decided the surface of the planet must be exceedingly hot.
This was such a surprising fact, though, that they were eager to have the microwaves studied at close range. Mariner 11 did this little job and the earlier findings were confirmed. Venus did indeed seem to be very hot.
On October 19, 1967, an even more sophisticated American probe, Mariner 5, flew past Venus. At the same time, a Soviet probe, Venus 4, landed on the planet and this time sent back information. Venus's high temperature was confirmed and its atmosphere, much thicker than Earth's, seemed almost entirely carbon dioxide.
Spectacular rocket successes were also carried through in connection with Mars.
On November 28, 1964, "Mariner IV" was launched in the direction of Mars. Mars is the more distant of the two planets and the journey took eight months. On July 15, 1965, Mariner IV edged past Mars at a distance of little more than 6,000 miles. The information gathered by the probe had to be relayed back to Earth over a distance of nearly 150 million miles.
Mariner IV investigated the space near Mars in a number of ways. It reported on the concentration of dust and particles, the strength of the solar wind, and on the magnetic nature of the planet. It quickly turned out that Mars, like the moon, was too small to have much of a melted iron core. It was no magnet and had no Van Allen belts.
Mariner IV was able to check on the density of the atmosphere of Mars and this turned out to be only one-tenth of what astronomers had thought.
This was important. Astronomers had long suspected there might possibly be life on Mars. By this, they didn't mean the kind of intelligent, canal-building life that Percival Lowell had speculated about (as described in the previous chapter). Astronomers didn't accept that, but they thought it just barely possible that very simple forms of plant life might exist.
The reason for considering this possibility was that Mars has a climate that does not completely eliminate the chance of life. It is colder than Earth and the air is thinner and there is no oxygen and very little water. Still, some very simple forms of Earth life could be made to live under conditions that were similar to those that astronomers thought existed on Mars. If there were Martian life, it would be especially adapted to Martian conditions, and it would get along even better than Earth life would.
Besides, there actually seemed to be signs of life on Mars. Mars had ice caps just as the Earth had, though the Martian ice caps were much smaller. Its axis was tipped so that the northern hemisphere had spring and summer when the southern hemisphere had autumn and winter, and vice versa, just as was true on Earth.
As seen through the telescope, Mars had reddish areas that might be desert, and dark areas that might, just possibly, be a sign of plant life. When spring came to one of the hemispheres, the ice cap on that side would begin to melt and the dark areas would grow darker and larger, almost as though plant life were flourishing because water from the ice caps was soaking into the soil.
But that notion seemed less likely thanks to the unexpected thinness of the Martian atmosphere. It was only 1/100 as dense as Earth's instead of 1/10 as had been thought, and that seemed to make the possibility of life a poorer one.
Of course, it might have been that the Martian atmosphere was thicker ages ago and that more water had been present then. Life would have started and might then have slowly adapted itself as conditions grew ever harder.
Arguing against this was the most astonishing feat of Mariner IV. These were the photographs it took of Mar's surface and then transmitted to Earth. Mariner II might have taken pictures of Venus but all it would have got would have been unbroken, featureless clouds. Mars, however, had very few clouds, if any, and its surface lay exposed.
Twenty-one photographs were taken. They were of poor quality and not at all clear but they showed the Martian surface in far greater detail than it had ever been seen from Earth.
When the pictures were received on Earth, there was instant astonishment. It turned out that the surface of Mars was riddled with craters, just like those on the moon. These were craters that had never been seen through the telescope because Mars was so far away and because its atmosphere, thin as it was, blurred the fine detail on the surface.
But there they were now. More than seventy craters were counted on the various photographs and one of them was seventy-five miles across. Astronomers, such as Fred Whipple of Harvard, and Tombaugh, the discoverer of Pluto, had predicted there might be craters on Mars, but few seemed to take such speculations seriously. Now they had to.
The existence of craters makes it seem that not only is the air thin now, but it may have been very thin through all of Mars's history. There may have been very little water, too. Only in that way could the craters have survived. Otherwise, the action of air and water would have smoothed them down.
The chances for life on Mars looked considerably worse than they had looked before, but not all astronomers were disheartened. It was pointed out that satellites much closer to Earth than Mariner IV had been to Mars could see no signs of life on Earth. A still closer look is required.
A number of projects are being considered whereby a Mars probe might make a soft landing on Mars. It would carry an instrument that would test for possible life on Mars. A sticky string might be cast out into Martian soil, then pulled back into the craft. Perhaps some Martian bacteria or one-celled plants might stick to the string. If the string were then placed in certain chemicals, the living cells might bring about changes in those chemicals and information about the changes could be transmitted back to Earth.
That, however, is for the future.
More spectacular still than soft landings on the moon and probes passing by Venus and Mars is the notion of sending men into space!
No matter how many instruments we send to the moon and how much information they gather, they could not possibly excite the world as much as would the landing of men upon another world.
But can men survive the rocket takeoff into space? They will have to undergo strong accelerations. They will feel as though they were being pressed down by weights of hundreds of pounds.
Then, once they are in space, with the rocket engines turned off, they will be in "free fall." They will be falling constantly even though they never hit the Earth and they will feel no weight in consequence. They will feel weightless all the time they are in orbit.
What's more, there is the question of radiation out in space. How dangerous are the solar wind and the Van Allen belts? From the very beginning, the satellite program was geared to such questions both in the Soviet Union and the United States. The second satellite sent up, the Soviet Union's Sputnik Il, launched on November 3, 1957, carried a dog. The dog survived the takeoff and the weightlessness and lived until it was painlessly poisoned. There was no way of bringing it back to Earth, however.
Later, as techniques improved, both nations sent all sorts of animals into orbit-mice, dogs, even chimpanzees-and brought them back. They also began to train men for trips into space. In the United States, these men were called "astronauts"; in the Soviet Union, they were called "cosmonauts."
The first step was merely to put the men into orbit about the Earth. In orbit, the men could be brought back after only a few hours in space. They would also stay beneath the possibly dangerous Van Allen belts.
The United States took elaborate precautions to make sure the men would be brought back safely. They set up a worldwide network of observers and planned to have the satellites make landings in the ocean with navy ships standing by.
The Soviet Union worked more secretly and without seeking the cooperation of other nations. This made tracking harder for them. They also planned for the return of the satellite, by parachute, to a land surface, which also made things harder.
Even so, the Soviet Union got men into space first. On April 12, 1961, the Soviet cosmonaut Yuri Gagarin was launched in the spaceship Vostok I. It was shot into orbit, travelled once around the Earth in 108 minutes. and was brought safely back to Earth.
On August 6, 1961, less than four months later, the feat was repeated. Another Soviet cosmonaut, Gherman Titov, was launched in Vostok II. He remained in space through seventeen orbits, which kept him weightless for over twentyfive hours before being returned to Earth.
Then, on February 20, 1962, the United States put its first man into orbit. This was John Herschel Glenn, Jr., who made three orbits in just under five hours and was brought back safely.
In the years that have passed since those first manned launchings, both nations have put more men in orbit for longer and longer periods. The Soviet Union, on June 14,
1963, launched Valery F. Bykovsky, who stayed in space five days, circling the Earth eighty-one times before coming down.
While he was still in orbit, Valentina V. Tereshkova was launched on June 16, 1963. She was the first woman in space. She has since married and had a child, so the experience seems to have done her no harm.
The American-manned space program took up speed as President John Fitzgerald Kennedy called for an American on the moon by 1970. The first few American launchings were in Mercury capsules, little one-man jobs, nine feet high and six feet wide, weighing one and a half tons. In 1965, more ambitious capsules were put in use for the "Gemini" project. This is the Latin word for "twins" and it is used because the new craft was to carry two men.
The Gemini craft was twice as large and twice as heavy as the Mercury. To put a Mercury into orbit required 360,000 pounds of thrust; the Gemini required 530,000 pounds.
On August 21, 1965, a Gemini capsule carrying L. Gordon Cooper and Charles Conrad stayed in orbit for eight days for a new endurance record. The Russians retained another, though, for on October 12, 1964, a Soviet spacecraft was launched with a crew of three. In 1968, a three-man American craft, the Apollo-7 remained in orbit eleven days.
Both the Soviet Union and the United States now had rockets with sufficient power to send men to the moon. The United States had the Saturn V rocket which, with 7,600,000 pounds of thrust, was capable of launching a 45 ton object into space. Sheer power, however, was not enough, complex manoeuvres also had to be learnt; manoeuvres such as ships moving into lunar orbit, smaller ships leaving larger ones and descending to the moon and returning. Astronauts had to learn to rendezvous; that is, to bring one ship into contact with another. They also had to learn how to leave their ship, if necessary, and manoeuvre in space, clad in a space-suit, powered by a hand-rocket, and linked to the ship by a lifeline.
On March 18, 1965, during the course of a two-man Soviet space flight, the cosmonaut Aleksei A. Leonov stepped out of his capsule and became the first man in history to take a "spacewalk." On June 3, 1965, an American astronaut, Edward H. White, duplicated the feat.
In 1966, the United States was suddenly alone in the field. For some unexplained reason, Soviet manned flights ceased, though they continued to launch many unmanned satellites. America's Gemini Project continued in high gear as several dramatic and successful rendezvous were carried through.
The manned flights had not been without their problems. Some rendezvous attempts had had to be abandoned. One flight had had to make a premature landing because of malfunctioning controls. Nevertheless, no lives had been lost in the American programme, and none (despite rumours to the contrary) in the Soviet programme either as 1967 opened.
The next step on the American side was the Apollo program, in which capsules containing three men were to be launched into space.
Then came disaster. On January 27, 1967, three astronauts, including White, who had been the first American to walk in space, were ground-testing the Apollo capsule in preparation for the first flight, scheduled for only a few weeks later. A fire started, somehow, and in a matter of a couple of minutes, all three were dead.
A long delay was at once necessary. The United States, to save on weight, had been using a simple oxygen atmosphere in its space capsules. This meant that if a fire did start, it would burn much more quickly and ferociously than if there were ordinary air in the capsule.
Soviet capsules, which were larger and heavier (since the Russians used larger rockets), used ordinary air, which required bulkier equipment but was safer. Naturally, public pressure began to rise for the Americans to use ordinary air, too.
This meant new equipment, new designs, new precautions. It seemed that no new manned flights would be launched by Americans in 1967.
Nor could the Soviets find much cheer in their own programme. Not long after the American disaster, in April 1967, they launched a manned capsule, their first in nearly two years. After a troubled flight, a landing was attempted and it failed. The cosmonaut, Vladimir M. Komarov, died in the crash and the Soviets found they would have to go slow, too.
Both nations continued to move forward with determination, however. In 1968, the Soviet Union sent several unmanned probes to the moon, had them circle the moon several times, then return to Earth, where they were recovered safely.
The United States then performed an even more spectacular feat. In December 1968, the probe, Apollo 8, duplicated the Soviet manoeuvre, but with three men aboard-Frank Borman, James Lovell, and William Anders. They left on December 21 and spent Christmas Eve, circling the moon ten times at a height of less than 70 miles. They arrived safely back on Earth on December 27.
With the success of Apollo 8, the United States began its final preparations for landing men on the Moon. First, however, they had to test the Lunar Module, which would land men on the Moon, and practise the rendezvous between the Lunar Module and the Command Module, which would return the men safely to Earth.
On March 3, 1969, astronauts James McDivitt, Russell Schweickart and David Scott, in Apollo 9, were launched into Earth orbit. Once out in space, McDivitt and Schweickart climbed into the Lunar Module at the back of the final stage of Apollo 9. They separated from Apollo 9 and moved into a different orbit. After a series of orbital manoeuvres, McDivitt and Schweickart rendezvoused with Scott in the Command Module, docked, and climbed back into the Command Module.
The stage was now set for the final dress rehearsal for the Moon landing. In May, 1969, Apollo 10 was launched. On board were Eugene Cernan, Tom Stafford and John Young. On this mission, as Apollo 10 circled the Moon, Stafford and Cernan took the Lunar Module to within 9 miles of the lunar surface. The astronauts also gathered information about the Moon's surface and gravity; information essential for a successful Moon landing.
All was now ready for the United States to put the first man on the Moon. The men chosen for the mission were Edwin Aldrin, Neil Armstrong and Michael Collins. Apollo 11, the heaviest spaceship ever launched-6,484,280 lb.-blasted off on July 16, 1969 (E.D.T.). After an uneventful voyage, Armstrong and Aldrin climbed into the Lung Module, and, leaving Collins behind in the Command Service Module, at 4.20 p.m. on Sunday, July 20 (E.D.T.) touched down on the surface of the Moon.
Then, watched by over 600,000,000 television viewers, Neil Armstrong, soon followed by Edwin Aldrin, climbed down from the Lunar Module on to the lunar surface. One of man's oldest and greatest dreams had become reality.
Of this event Wernher von Braun, the father of the United States space effort, said that this was the most historical moment in the Earth's history since the first creature crawled out of the sea on to dry land.
It seems very likely that the horizons which have been opened by Man's landing on the Moon will be further extended by landings on Mars before the twentieth century is done and this may lead to developments that will make the twenty-first century even more exciting and astonishing than the one in which we now live.
From: Twentieth Century Discovery by Isaac Azimov