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A Tribble's Guide to Space:
How to Get to Space and What to Do When You are There
Alan C. Tribble

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COPYRIGHT NOTICE: Published by Princeton University Press and copyrighted, © 2000, by Princeton University Press. All rights reserved. No part of this book may be reproduced in any form by any electronic or mechanical means (including photocopying, recording, or information storage and retrieval) without permission in writing from the publisher, except for reading and browsing via the World Wide Web. Users are not permitted to mount this file on any network servers. Follow links for Class Use and other Permissions. For more information, send e-mail to

Chapter 1


Space. The Final Frontier.

When Buzz Lightyear heads for space, he sets a course to infinity and beyond. Fortunately for you and me, space is not that far away, and our travel plans don't have to be quite as ambitious to get us there.

    Planet Earth has a radius of about 4000 miles. Let's imagine a sphere that encircles the Earth at a height of 50 miles above sea level. We'll call the region between the ground and the 50-mile altitude the Earth's atmosphere. Everything beyond 50 miles we'll call space. This means that space is closer than you think. If you're sitting in Chicago, you are actually closer to space than to Milwaukee, Wisconsin; and New York City is closer to space than to Philadelphia. There is really nothing magical about a 50-mile altitude. The transition from the Earth's atmosphere to space is not abrupt, so a rocket ship that travels through it would notice little difference as it passed from 49 miles to 51 miles. In the end, though, we need a reference point. Fifty miles is well above the altitude of Mount Everest, which is 5.5 miles high, or above cruising airliners that are 6 or 7 miles high. But it is also below the altitude of most orbiting spacecraft, so this artificial boundary is good enough.

    Flight enthusiasts use terms such as the troposphere, stratosphere, mesosphere, and so forth to describe the various layers of the Earth's atmosphere. Likewise, we give different areas of space different names. The region between about 50 and 500-miles altitude is called Low Earth Orbit, or simply LEO. The upper boundary to LEO, like the 50-mile boundary to space, is rather artificial, but easy to remember because it is ten times the height of the lower boundary. Today, LEO is about as far as most of the spacecraft launched from Earth ever get. It is here where we find the largest payloads, like the Space Shuttle and the International Space Station.

    Of course, a few spacecraft need to go higher and make it into what we call High Earth Orbit (HEO), the region between 500 miles and about 50,000 miles (which is about 12.5 Earth radii). Within this region lies a very special altitude at about 22,370 miles. Spacecraft placed here circle the Earth with the same speed at which the Earth rotates, making them appear to remain stationary above the Earth's surface. This is called the synchronous orbit, or more specifically geosynchronous or simply GEO. GEO is a very popular orbit for many spacecraft, especially for communications spacecraft that send and receive signals from specific points on the Earth's surface, and for spy satellites whose mission is to record what's going on at some specific location.

    Above HEO, physicists have noticed some significant changes in the local environment. Most notably, above this point the Sun's magnetic field is stronger than the Earth's, causing the Sun, and not the Earth, to control what little atmosphere can be detected. Furthermore, once spacecraft get this far away from Earth, they rarely stay in orbit but move on to other parts of the solar system. Consequently, above HEO lies interplanetary space. Unless we choose to go into orbit around another planet, we would remain in interplanetary space until we are well past the orbit of Pluto. Relative to the size of our Earth, interplanetary space is vast. The distance to Pluto, the outermost planet, is over 3.6 billion miles, a distance so great that it takes light from the Sun over five hours to reach it.

    The ancient Greeks were the first to try to determine the size of the solar system using simple geometry. Aristarchus, Eratothenes, and Hipparchus all made various estimates of the Earth-Sun distance. Although their original measurements were too small, they showed clearly that the solar system was hundreds of times larger than the Earth itself. The great distances between planets had been appreciated for centuries, but Galileo Galilei, over three hundred years ago, was the first to see firsthand just how large interplanetary space is. With his new invention, the telescope, he even saw that Jupiter had its own moons circling it. As the years passed and observations of the moons of Jupiter continued, observers developed the ability to predict when the moons would emerge from behind the great planet.

    These early astronomers noticed, however, that sometimes their predictions were off. The moons of Jupiter would appear several minutes early, or they would appear several minutes late. They finally deduced that the appearance of the moons occurred later than expected whenever the Earth and Jupiter were on opposite sides of the Sun (fig. 1). The predictions were accurate, but the early astronomers did not realize that it takes light several minutes to travel the great distances involved. When the Earth and Jupiter were on the same side of the Sun, the light would arrive early; when they were on opposite sides of the Sun, the light would arrive late. Olaus Roemer, a Danish astronomer, was the first to realize that this delay was due to the finite amount of time it takes light to cross these great interplanetary distances. He used this insight in 1675 to make the first crude measurement of the speed of light, 186,000 miles per second.

    As we start to explore beyond our own solar system, somewhere past Pluto we will expect to find a point where the Sun's magnetic field has weakened so much that the small magnetic field in the interstellar medium becomes stronger. This point will mark the beginning of interstellar space. As big as interplanetary space is, it is still dwarfed by the distances to the stars. The first estimates of these distances were made using parallax measurements. Parallax is an easy concept to understand. Hold your thumb up in front of your face. Close your left eye and look at your thumb relative to the background with your right eye. Now close your right eye, open the left, and note how your thumb "appears" to have moved relative to the background. That shift is called a parallax. Parallax measurements of the stars are made by allowing the Earth to take the place of your eyes, and a close-by star to take the place of your thumb. We simply take a picture of the star in question from the Earth, then wait six months and take another picture when the Earth is on the opposite side of the Sun (fig. 2). By comparing pictures taken when the Earth is in two different locations, we can determine the parallax to some of the stars closest to the Earth. F. W. Bessel, a German astronomer, first succeeded doing this in 1838 and found that the stars were over a million million miles away, a distance so great that it takes light from other stars years, or centuries, to reach us. This realization opened up the size of the Universe immensely.

    As we continue our outward exploration, we will pass other star systems with planets of their own, but we will eventually come to the edge of our own Milky Way galaxy and move into intergalactic space. Even if we make it this far, we still have a long way to go. The Andromeda galaxy, for example, is over 10 billion billion miles away, and it takes light over 2 million years to reach us from this great distance. Because of these huge distances and our limited history of sending machines into space, the Universe is still too large for us to explore in person (fig. 3).

    Humans have dreamed of exploring space for countless centuries. According to Greek mythology, the first two men to become airborne were Daedalus and his son, Icarus, two prisoners on the island of Crete. Impatient while waiting for King Minos to pardon them, Daedalus fabricated two pairs of wings by gluing feathers to a wooden frame with wax. With their wings attached, father and son were soon airborne. Daedalus warned his teenage son not to fly too near the Sun lest its heat melt the wax, but the young Icarus became so absorbed in his new ability to fly that he did not heed his father's words. He flew too near the Sun, the wax melted, his feathers fell off, and he dropped into the sea, to his untimely death.

    For the next several centuries, wings preoccupied the imaginations of those who wished to fly like the birds. Then, in 1766, Henry Cavendish discovered what he called "inflammable air"—hydrogen—and showed that it was much lighter than the surrounding atmosphere. Knowledge of this new discovery inspired French paper manufacturer Joseph Montgolfier to begin experimenting with lighter-than-air machines. In 1782, with his brother Etienne, he succeeded in flying small unmanned paper and cloth balloons filled with hot air. By November 21, 1783, they were ready to try a manned flight in a large balloon made of cotton and paper, coated with alum as a means of fireproofing. Cords sewn into the fabric carried a wicker gallery at the base. In between was a large brazier that contained a fire that could be fed with straw. Unsurprisingly, the Montgolfier brothers were reluctant to fly in a paper balloon with a roaring fire inside of it, so they arranged for others to serve as pilots: the Marquis D'Arlandes and Pilatre de Rozier. Although the balloon burned in a few places, it survived long enough to give the men a twenty-five-minute flight over the rooftops of Paris. They reached a height of 3000 feet before landing in a park outside the city. Over two hundred years later, on March 20, 1999, Bertrand Piccard and Brian Jones became the first aviators to circle the globe nonstop in a hot-air balloon. Their trip lasted 19 days, 1 hour, and 49 minutes.

    As nice as balloons were for getting an aerial view of things, they left you completely at the mercy of the local winds. Balloonists learned to control their altitude, but they could travel only in the direction in which the wind was blowing. Birds, on the other hand, could fly hither and yon as they pleased. Consequently, it was only a matter of time before interest in flying shifted back to winged machines. By the end of the twentieth century, many people had successfully piloted winged gliders, but, lacking a power source, they too were at the whim of the winds.

    Two brothers from Ohio, Orville and Wilbur Wright, decided to become serious "students of the flying problem," as they liked to call themselves. Approaching the problem in a scientific manner, the brothers realized that in order to develop a functioning airplane they would have to solve three problems: (1) lift, provided by the wings; (2) power, provided by an engine; and (3) control. After experimenting with wing shapes (to generate lift), propeller shapes (to power the airplane), and different ways of twisting the wings (to control the direction of flight), the brothers were ready for a test. On December 17, 1903, at Kitty Hawk, North Carolina, they succeeded in proving the concept of powered flight with a 200-foot sprint lasting a mere fifteen seconds. But by 1910, they were flying for more than 20 miles at a time and remained airborne for over an hour and a half. In 1947, less than forty years later, Chuck Yeager was already able to fly his Bell X-1 aircraft faster than the speed of sound. Try as they might, however, airplanes could not fly more than a few miles high because the air at those altitudes is too thin, essentially leaving nothing for the plane to fly through. To get to space, it was clear what was needed: a means of generating lift without relying on wings or the air pushing up underneath them.

    In 1865, Jules Verne had proposed that we get to the Moon by shooting people out of a large cannon. George Melies, the writer, director, and actor of the earliest science fiction film of all time, Le voyage dans la lune (1902), chose this method of travel as well. However, it was rockets, which could carry their own fuel and burn it continuously along their journey, that were destined to carry men into space. The Chinese had already been using rockets as early as the second century B.C., primarily for entertainment in the form of fireworks (fig. 4). Over the next two thousand years or so, rockets eventually worked their way into use as a means of warfare as well. "The rockets' red glare" was already noted by Sir Francis Scott Key during the War of 1812 and was immortalized in his poem, "The Star Spangled Banner."

    As with most technological developments, the greatest advances have occurred in the past one hundred years. Near the dawn of the twentieth century, a Russian schoolteacher, Konstantin Tsiolkovsky, showed that a rocket—powered by liquid fuel—was the only practical way to get out of the atmosphere and into space. In 1919, an American student named Robert Goddard proposed that a rocket could be flown to the Moon. The public rapidly dubbed him an eccentric. But their reaction did not stop him from building and launching the first liquid-fueled rocket from his aunt's farm in March 1926. It reached the amazing height of 150 feet.

    Because of the reaction to his 1919 paper, Goddard religiously avoided publicity for the rest of his life. He even refused to aid the American Interplanetary Society's attempts to publicize his work. Members of the society visited Germany in 1931 and made contact with the German Rocket Society, whose membership included Hermann Oberth, the author of The Rocket into Interplanetary Space (1923). A German teenager named Wernher von Braun had read the book in 1925, and he was so intrigued by it that he had strapped some rockets onto his little red wagon and propelled it through the streets of his hometown before the fireworks exploded and the annoyed villagers summoned his parents. Von Braun had joined Oberth by 1930 in trying to develop functioning rockets, and the visiting Americans were very impressed with what they saw. Still, they were unable to stir up sufficient interest at home to get a research program up and running. The Germans did not have this problem and were flying liquid-propellant rockets by 1934. By 1942, yon Braun was leading the German rocket program and stayed at its helm during the remaining war years.

    The most famous of the German rocket designs was the vengeance weapon number two, or V-2 (fig. 5), the first long-range ballistic missile, capable of flying from Germany to England. Germany was so protective of this secret that Hitler ordered the execution of von Braun and his team in the closing days of the war. However, von Braun's brother managed to contact the American forces, who quickly took custody of the team just before the German SS could enforce Hitler's orders. General Dwight D. Eisenhower, aware of the rocket's potential for warfare, allowed the German team to continue with a final series of tests after the war. A Russian colonel, Sergei Korolev, was allowed to observe the last few tests flights. Ten years later, Korolev would be head of the Soviets' rocket program.

    In 1946 von Braun's team was transported to White Sands, New Mexico, in the American desert, where it continued its experimentation in rocket design. In 1950 the team moved to Huntsville, Alabama, and eventually became part of NASA. Finally, in 1957, a rocket was developed that could carry a payload into space. Unfortunately for von Braun and his colleagues, this feat was accomplished by the Soviet Union, which launched the first satellite, Sputnik, on October 4, 1957.

    By 1958, only a year later, von Braun and his team were ready to launch the first U.S. satellite, Explorer 1. The group also played an integral part in launching America's first astronaut, Alan Shepard, into space in 1961. Unlike the shy Goddard, von Braun was able to survive the world war and continue his research largely due to his outgoing nature. On his desk, von Braun kept a plaque that advised: "Late to bed. Early to rise. Work like hell, and advertise!" Homer Hickam's recent novel, Rocket Boys, and the screen adaptation, October Sky, clearly indicate how popular von Braun was in the United States in the late 1950s.

    Besides the glamour associated with the "rocket scientists" who were busy developing rockets, there was the challenge of keeping a crew member alive once the rocket was out in space. The balloonists had known about this problem for many years. When researchers suffocated or froze to death in the bitter cold during the early balloon flights, it quickly became obvious that some means of protecting the crew must be found. This had been achieved by November 1935, when the altitude record of 73,395 feet was set by two U.S. Army "aeronauts" in a balloon made of rubberized fabric.

    By the late 1950s, high-altitude balloon flights were conducted under program names such as the air force's 'Man-High" or the navy's "Strato-Lab." When Joe Kittenger bailed out of his open gondola as part of the Man-High project at an altitude of over 100,000 feet, his first reaction was to think that something had gone terribly wrong. In normal parachute jumps, you feel the force of the wind buffeting you relentlessly, but he felt nothing. He described the feeling as "like being suspended in space." For a fraction of a second, he wondered if the scientists had made a mistake in their calculations and he had actually flown high enough to be above the Earth's gravitational pull. However, when he rolled onto his back he saw the balloon rapidly disappearing above him as he fell toward Earth. After only a few seconds, the atmospheric density increased enough so that he could feel the wind rush by him. In May 1961, the Strato-Lab V balloon conducted a test of the Mercury space suits by carrying two men to an altitude of 115,000 feet in an open gondola. That altitude is above 99 percent of the Earth's atmosphere. Balloon tests such as these, and aircraft test programs such as the X-15, sometimes lay claim to having sent the first astronauts into "space" by flying high enough to see the curvature of the Earth.

    As valid as those claims may be, the glory went to an entirely different group of people. The United States selected its first astronauts in 1959. At about the same time, the Soviet Union selected its first cosmonauts. The selection process was classified at the time, so little was known about the candidates until the "winners" were announced to the public. The original Mercury astronauts were chosen from a pool of five hundred candidates, all of whom were military pilots. The original selection criteria were quite brief: experience in flying jet aircraft, preferably as a test pilot; an engineering background; and a height of less than 5 feet 11 inches. The height requirement was an acknowledgment of the fact that real estate on a spacecraft is very expensive, and smaller astronauts, who can fit into smaller spacecraft, help reduce the cost. As shown in the movie The Right Stuff, a rather sophisticated series of tests eventually reduced the pool down to the final seven (fig. 6). Half a world away, the original cosmonauts were military test pilots as well.

    The Soviet pilot Yuri Gagarin won the honors as the first man in space after a one-orbit flight in April 1961. Unknown to the public at the time, Gagarin actually bailed out of his capsule before it landed, parachuting the last two miles back down. His arrival on Earth was witnessed by an old woman who asked, "Have you come from outer space?" He replied, "Yes. Would you believe it, I certainly have." Then, to calm her fears, he quickly added, "But don't be alarmed, I'm a Soviet." Ironically, Gagarin was killed in a plane crash in 1968.

    In order to keep up with the Soviets, several Americans flew into space in quick succession. Alan Shepard became the first American in space after a brief fifteen-minute suborbital flight in May 1961. John Glenn (fig. 7) became the first American to orbit the Earth in 1962. His great popularity with the public may have made it difficult for NASA to consider sending him back into space again. He left NASA in 1965 to pursue a business career and then was elected to the Senate from his home state of Ohio in 1974. Thirty-six years after his first mission, he returned to space in 1998, the oldest person ever to do so, on the Shuttle. In 1999, NASA renamed its research facility in Ohio, formerly the Lewis Research Center, the Glenn Research Center.

    After President Kennedy challenged the nation to "put a man on the Moon and return him safely to Earth," it was obvious that more than seven astronauts would be needed. The second group of nine astronauts, referred to as the "new nine," was selected in September 1962 and included Neil Armstrong and Jim Lovell.

    Jim Lovell (fig. 8) began his space-flight career with a record-setting fourteen-day trip in Gemini 7. (That's fourteen days confined to one chair, with another astronaut, Frank Borman, sitting only 2 feet away.) He flew again on Gemini 12, then was part of the first crew to visit the Moon on Apollo 8. While he and his colleagues Borman and Bill Anders orbited the Moon on Christmas Eve 1968, television viewers across the United States watched as the astronauts read from the Bible's Book of Genesis. Later, Lovell was the commander of Apollo 13 on a return flight to the Moon, but an explosion turned the "routine" flight into one of the most heroic rescue missions ever recorded. Twenty-five years later, director Ron Howard immortalized the event in one of the most detailed movies of the Apollo program ever made, entitled simply Apollo 13.

    Another famous astronaut, Nell Armstrong (fig. 9), flew on Gemini 8 in 1966 and was the first man to walk on the Moon as part of Apollo 11 in July 1969. As he did so, he uttered the memorable, "That's one small step for man, one giant leap for mankind."

    The third group of fourteen pilot astronauts, selected in October 1963, included Apollo 11 Lunar Module pilot Buzz Aldrin and Apollo 11 Command Module pilot Michael Collins. Aldrin seemed destined for spaceflight from the beginning. His mother's name was Marion Moon, and his father was a student of rocket pioneer Robert Goddard. He earned a doctorate in astronautics from the Massachusetts Institute of Technology, where he devised rendezvous techniques used on virtually all NASA missions. After walking in space on Gemini 12, he and Neil Armstrong drew the largest worldwide television audience ever during the historic Apollo 11 event. Interestingly, all of the Apollo 11 photographs of an astronaut on the Moon are of Aldrin. Armstrong carried the only camera and never got in the picture himself, except as a reflection in Aldrin's helmet (plate 1).

    As the Gemini program neared completion, a group of six scientist-astronauts was chosen in 1965, including Harrison Schmitt, the only scientist to walk on the Moon. This was followed by nineteen additional pilot-astronauts in 1966 and eleven more scientist-astronauts in 1967. With the Apollo program's days clearly numbered, the final selection of the decade was a group of seven astronauts selected for the Air Force Manned Orbiting Laboratory. Among these was Major Robert Lawrence, Jr., the first black man selected for astronaut training. He was killed on December 7, 1967, in the crash of his F-104 fighter during a training exercise. Although he never flew the magical 50 miles up to earn his astronaut wings, his name was added to the astronauts' memorial at Kennedy Space Center thirty years after his death in official recognition of his astronaut status. After the air force canceled the Manned Orbiting Laboratory program in 1969, the remaining men in the program joined the NASA astronaut corps.


Copyright © 2000 PRINCETON UNIVERSITY PRESS. All rights reserved.

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