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4 Right: The fir~....~.. f Six hundred million people an earthling ..~....~er ..................... ~ r. r ~ ~ ~ , celestial body are rim.. in nearly one-tlit. :1 at the world . S ..,~.,,~,,,,.,., ,, ,.,., ~ ~ ~' . ~.population watched on . . ~ ~lSlOn In JU. .y lamp as an earthling first set foot onto another celestial body. With that step, human conscious- ness leaped a quarter million miles into space, expanding mankind's vision to a degree unequalled since Columbus's voyage to the New World. "The astronauts didn't just go to the moon," said one observer. "All our minds went to the moon." Looking back from the moon, people saw white wispy clouds and blue sparkling water covering a planet framed by immense ~1 darkness. Earth appeared as a highly integrated unit, not just a collection of I isolated oceans and continents. And it was strikingly obvious how small, fragile, and beautiful our planet really is, a precious oasis in the vastness of space. The Apollo program sent nine spacecraft to the moon from 1968 to 1972, landing a dozen astronauts at six different sites. The rocks and scientific information they brought ~ ~ I - ~ In - ena back revealed that the moon was formed at I the same time and of the same elements as earth but that it lacks water, atmosphere, and life. The astronauts also left instruments to gather data on ground tremors and other phenomena. A laser reflector left by Apollo 11 astronauts is still being used to measure the earth-to-moon distance and study the movement of continents. The feat of landing men on the moon and returning them safely home ranks the Apollo project with the Egyptian pyramids, the Panama Canal, and the Manhattan Project as outstanding engineering achieve- ments of all time. It stands alone for the advances in size and sophistication it made over prior technology. Apollo required a E N G ~ N E E R ~ N G A N ~ T ~ E A ~ VA N C E M E N ~ O F H ~ M ~ N W E ~ FA R E

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rocket 15 times more powerful, a navigation I system far more reliable, a unique lunar landing craft, and improved space suits capable of withstanding a very hostile environment. In addition, the program demanded a novel, comprehensive manage- ment system to ensure that thousands of government and industrial organizations worked together well enough so that millions of parts would arrive where they should on schedule and would fit and function properly. The Saturn/Apollo system was com- posed of an Apollo spacecraft, a lunar lander, 1 M O O N L A N ~ I N G I Apollo ~ 7 is readied for a nighttime launch toward the moon, peeking out from the clouds beyond. The spacecraft carried the first scientist to the moon and was the only one launched at night in the Apollo series.

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and a three-stage Saturn V rocket, which I launched them toward the moon. Once in lunar orbit, the spacecraft released the two- stage lander, which carried two of the three astronauts to the surface. The lander's ascent stage later returned them to the spacecraft and was abandoned. lust before they reentered the atmosphere, the astronauts jettisoned the large service unit that supplied An Apollo ~ ~ astronaut unpacks a scientific experiment to measure ground tremors on the moon. The small laser reflector, on the ground behind the astronaut, is still being used for laser measurements of the distance between the earth and moon. 6 power, water, and oxygen and returned to earth in the small command capsule of the spacecraft. Buildings shook and the ground trem- bled when a Saturn V rocket roared skyward with the first trio of astronauts heading for lunar orbit in December 1968. The rocket developed roughly enough thrust to hurl a small house into earth orbit. Thirty-six stories tall and weighing as much as a good-sized Navy destroyer, the Saturn/Apollo vehicle used the biggest, most powerful rocket ever built. The first stage of the three-stage Saturn V dwarfed the largest rockets of its day. An Atlas ballistic missile, for instance, produced I 360,000 pounds of thrust. The first-stage engines of the Saturn V, however, each produced 1.5 million pounds, and there were five. Together they burned 3 tons of kerosene and liquid oxygen per second. Building reliability into such monstrous engines was a monumental challenge. Yet, all 12 Saturn V rockets launched in the Apollo series suc- ceeded. To fuel the second and third stages, engineers chose liquid hydrogen, which gave 40 percent more thrust per pound of fuel burned than kerosene. The second stage was a cluster of five engines, while the third had just one. But unlike those in lower stages, the third-stage engine had to be restartable in order to push the spacecraft toward the moon after coasting an hour and a half in earth orbit. Building a rocket of such size and design required many new and advanced engineer- ing techniques. The field of fracture mechan- ics, for example, advanced greatly in answer- ing questions raised during construction of the second-stage fuel tank, which was 65 feet long, 33 feet in diameter, and held liquid hydrogen at -423 degrees F. The aluminum tank was pieced together with literally miles I of welds, which could contain a few tiny cracks. But how big could the cracks be before they began to weaken the tank? By analyzing aluminum with similar cracks, engineers calculated the amount of pressure the metal could stand before cracks of various sizes begin to grow and thus become dangerous. To ensure its safety, they tested each second-stage tank by loading it with liquid hydrogen at a pressure 5 percent higher than the maximum required for flight. If cracks did not grow at that pressure, they would not grow at the lower pressure during flight. The Apollo flights would have been impossible without inertial navigation, I which was developed in the 1950s and was just being installed in the early 1960s on aircraft, submarines, and ballistic missiles. Radio navigation from earth was impractical during the final minutes of a landing approach to the moon. The time radio signals take to travel that distance is too long for the immediate reactions needed to land a craft safely. Radio navigation was also useless for flights behind the moon because it requires line-of-sight transmission from earth. ~ N G I N E E R I ~ G ~ N ~T ~ E ~ D VA N C E M E N ~O ~H U M A N W E ~ FA R E ~

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~. l Apollo's navigation the rocket, spacecraft, and lunar lander each had a separate system included gyroscopes and accelerometers, which sensed change In direction and speed. They were combined in single subsystems, called inertial measure- ment units, or IMUs, which measured movement along, as well as off, the desired course due to rocket thrust or atmospheric resistance. When leaving or approaching the earth or moon, IMUs were critical for making quick guidance decisions. Gravitational influences of the earth and moon were calculated before flight and added to onboard guidance computers. This informa- tion and the IMU data permitted control systems to keep the craft almost exactly on course. During the flight, astronauts used a sextant in calculating midcourse corrections. In practice, however, ground radar stations usually performed this time-consuming task and radioed up commands to correct deviations. The two-stage lander that ferried astronauts to the lunar surface was the first manned vehicle designed to fly solely in space. Its structure could be extremely lightweight, since the moon's gravity is only one-sixth that of earth. And aerodynamics did not need to be considered, since there is no air on the moon. The lander was essential- ly built inside out. Its thin aluminum pres- surized cabin was inside, wiring and tubing surrounded that, and a patchwork of black or golden ~nsulahng materials covered the outside. These materials absorbed or reflect- ed light, depending on whether that part of the lander needed protection from cold or heat. Its four spiderlike legs with wide foot pads could keep the lander upright, whether it touched down on a slope, in deep dust, or under any of 500 other combinations of terrain and landing conditions anticipated by the engineers. ! One of the most critical parts of the lander was the small ascent engine. Once the astronauts landed, they were completely dependent on this engine to return them to the mother ship. There was no backup. The basic portion of the flight engine had been briefly test-fired on earth. Its fuel system, however, had not previously been exposed to the highly corrosive propellants for fear of weakening its seals and corroding its valves. So engineers ground-tested ascent-eng~ne prototypes for every failure they could The five first-stage engines of the mighty Saturn V rocket lift Apollo ~ ~ off the launch pad anal start the spacecraft toward the moon. Astronauts are in the conical command capsule atop the rocket. Just below the capsule is the cylindrical service unit. Below that, the lunar lander is packed in another cylinder just above the rocket's third stage. - M O O N L A N D I N G 7

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required more than 450 persons in the launch I control center and nearly 7,000 others on 9 ships, in 54 aircraft, and at stations around I the world. At its peak, 400,000 people were working on Apollo at three major space centers and 20,000 contractor sites. The people who managed Apollo pioneered techniques that remain the model for operating a massive, well-run engineering program. In 1961 NASA estimated that the project would cost $20 billion and would put a man on the moon before 1970. The space agency actually spent $25.4 billion for all the Apollo flights. And two Apollo 11 astronauts stepped onto the moon on July 20, 1969. On the planning and control side of the program, the Apollo managers created a monitoring system that gave them enough information to ensure that the millions of pieces for the project were coming together at I the right time and place, in the right engi neering configuration, and for the right price. To do this, they identified a few hundred critical milestones such as "rocket first stage complete" or "stage shipped to Cape Kennedy" for each program area. Once a month, contractors reported their progress to the three NASA centers, who reported to the _ Apollo managers. The managers, in turn, identified projects that were falling The lunar lander, seen from imagine that might happen in flight. None behind-most of them did-and devised the Apollo ~ ~ spacecraft, ~ did. solutions to bring them back on schedule. heads for a landing on the Astronauts who walked on the moon For instance when a tragic fire killed three moon. The descent stage, , with outstretched legs and wore a three-piece space suit and backpack astronauts during a ground test of their protruding rocket nozzle, will of life-support equipment for up to four spacecraft, managers swiftly reviewed the remain on the moon when the hours outside the lander. The ensemble safety of nearly the entire Saturn/Apollo upper ascent stage brings the weighed q.90 pounds on earth but only a system, redesigned the spacecraft and space mother ship sixth of that on the moon. The first piece was suit, and brought the program back on a cooling undergarment of knitted nylon- schedule in little more than a year. spandex with a network of plastic tubes Right: Dressed in a three- filled with water circulating from the piece space suit, an Apollo T ~backpack. The next piece was the basic suit, a astronaut climbs down a leg rubber_cOated nylon bladder sandwiched ~ of the lunar lander and hops I s - __ onto the hard, dusty surface between a cloth lining and a nylon cover to of the moon. His life~support shape the suit. The third piece was a protec back pack carried enough live outer garment of 17 layers, including 6 oxygen for, a 4-hour tour layers of Beta cloth. This is a fireproof fabric outside the lander of fiberglass threads coated with Teflon to _ prevent itching. The outfit was completed by ~ --~'':._. I a helmet, boots, gloves, and the backpack, _ ~ . . TIC which also carried a radio and antenna. _- ~/~ The Apollo program was probably the ~ .` :~ most complex and ambitious engineering . . If- ~ I_ project ever attempted. A moon flight , ~ 3 ! E N G ~ N E E R ~ N G A N D T H E h ~ VA N C E M E N T O F H U M A N W E L FA R E _ ~_ .

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On the technical side, the great challenge was to create a management system that would ensure the precise interface among millions of pieces the Saturn V alone had 6 million manufactured by thousands of contractors. Careful records were kept of specifications for all the parts and the interfaces between them. This documenta- tion was especially valuable when, for instance, during the unmanned second Apollo flight, the first-stage engines began to flicker, a piece of an aluminum panel fell off, and two second-stage engines quit early. By comparing flight instrument data with the documentation, engineers were able to find the problems, simulate them on the ground, and correct them with enough confidence to go ahead with the next flight the first with astronauts aboard. astronauts traveled over the lunar surface in a motorized rover to gather rocks and conduct scientific experiments. Apollo 17, the last of the program, carried the first scientist a geologist to the moon in December 1972. Since the inception of the Apollo program, nearly all the known planets in our solar system and many of their moons have I been visited by unmanned spacecraft. Between them, the United States and the Soviet Union have sent automated probes to Earth's two neighbors, Mars and Venus, as well as to Mercury, the planet nearest the sun. U.S. probes have journeyed to all the other planets except Pluto. The most cele- brated unmanned spacecraft, Voyager 2, left Earth in 1977, rendezvoused with [upiter in 1979 and then with Saturn, Uranus, and finally Neptune in 1989. Yet, it was man's . _ hi _ - _y! ~ ;7_- ~ ~ I Apollo Is astronauts explore the moon in a lunar rover, which was packed aboard the lander and unfolded on the lunar surface. It carried the astronauts 1 7.5 miles during three exploratory tours and helped them collect 170 pounds of moon rocks for the return to earth. The first two moon flights Apollo 8 and 10 put astronauts into lunar orbit; Apollo 11 and 12 put them on the moon. An exploding oxygen tank in the service unit crippled Apollo 13, whose astronauts took temporary shelter in the lunar lander during the emergency return to earth. Apollo 14 went smoothly. During the next three missions, landing on the moon that truly captured the world's imagination, an engineering achieve- ment that has extended the human domain far beyond the boundaries of earth. MOON LANDING I The earth, like a sparkling jewel against black velvet, rises above a barren lunar landscape to greet the Apollo ~ ~ astronauts 240,000 miles out in space. 9