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Man has always dreamed of escape from earth to other parts of the universe. In recent years he has achieved the technological knowledge and the skills necessary to take the first steps in this venture. Earth-orbital flight has been achieved by the manned spacecraft of the United States and the Soviet Union and by the numerous unmanned satellites that have been launched.
Flight to the moon was achieved with outstanding success on July 20, 1969, when men landed on the moon for the first time, in the historic Apollo 11 mission. This flight was preceded by many unmanned probes that landed on the moon or orbited around the moon, sending back invaluable information by radio and television.
A notable feat was accomplished in 1970 when the unmanned Soviet probe Luna 16 landed on the moon, collected samples (as the Apollo astronauts had done), and returned to earth with the samples. Interplanetary flight has been achieved in numerous unmanned nights- the U.S. Mariner flights to Mars, Venus, and Mercury, the Soviet Mars and Venera flights to Mars and Venus, the U.S. Pioneer 10 and 11 flights past Jupiter, and the U.S. Vikings to Mars. Manned space travel was initiated with the Apollo moon flights, and astronauts have lived for months in earth-orbiting space stations. A manned flight to Mars may take place before the end of the century.
A successful spaceflight program requires the combined efforts of many specialists. Scientists engage in research to improve methods of flight control, propulsion, navigation, life support, communication, and the many other operations of space flight. From the data supplied by the scientists, engineers design improved spacecraft, launch vehicles, and all the equipment they contain. Other men build the vehicles and all their associated ground equipment. Applied mathematicians and programmers, with the aid of electronic computers, perform the enormously complex calculations necessary to determine the correct paths for spacecraft to travel. Technicians assemble the launch vehicles on the launch pads and launch them in accordance with the computers' calculations. Communications and tracking experts, in stations around the world, check constantly the position and communications of spacecraft. Finally, of course, there are the central figures of the enterprise, the astronauts themselves.
Complex motives - political, military, commercial, scientific, and adventuristic - drive both the proponents and the opponents of space flight. President Kennedy suggested this complexity in his reply to the early critics of the Apollo program in September 1962 when he said:
"The exploration of space will go ahead, whether we join it or not, and it is one of the great adventures of all time, and no nation which expects to be the leader of other nations can expect to stay behind in this race for space...."
Scientific motives include exploring space itself, the earth, the moon, the other planets—all the bodies and actions of our solar system. Space near the earth has been extensively explored with unmanned instrument-carrying satellites, and the physics of space in the vicinity of the earth is now fairly well understood. Other space-probe studies have shown that even so-called empty space contains a small amount of matter, including meteoroids, together with solar winds, magnetic fields, and various kinds of radiation. As yet, however, very little is known about the moon, and even less about the planets and asteroids. One of the most interesting aspects of space exploration is the search for extraterrestrial life. At present it is not known if life exists elsewhere in the universe, although it seems likely that it may. Evidence from the Apollo manned lunar nights virtually rules out the possibility that life exists now or has existed in the past on the moon.
Military uses of space flight include the use of communications satellites that make possible round-the-clock, all-weather communication, free from the usual radio jamming, with military units throughout the world; of navigation satellites, by means of which ships and aircraft can obtain precise knowledge of their positions; of weather satellites; and of reconnaissance satellites. Such orbiting satellites can make for more effective execution of military strategy than would otherwise be possible. In addition, the Soviet Union has tested a nuclear-bombardment weapon system called the fractional-orbit bombardment system that could eventually be stored for long times in orbit or in deep space.
The possible commercial uses of space are in many respects similar to the military uses. Communications satellites relay messages, television programs, or other information more efficiently than transoceanic cables. Weather satellites are now in regular use for the monitoring and prediction of weather conditions throughout the world, and navigation satellites are used by ships as well as by aircraft. Satellites have begun to prove useful in making surveys of such resources as water and timber, in showing the condition of crops, in showing pollution in water and in the air, and in revealing mineral lodes.