The space age dawned with the launching of Sputnik 1 by the Union of Soviet Socialist Republics on Oct. 4, 1957. Since that event many thousands of spacecraft have been placed into Earth orbit, and numerous probes have been launched on lunar, planetary, and cometary missions. Most of these craft were launched by the United States and the USSR, with the Soviets accounting for more than 50% of all the successful launches. Although the early years of the space age were characterized as a "space race" between the United States and the USSR, other nations quickly began developing their own domestic programs. Such activities soon transcended national boundaries. While the programs of a number of individual nations are described below, many nations do their most advanced work in alliance with other nations. DEVELOPMENT OF NATIONAL SPACE PROGRAMS Since the early 1950s, scientists and engineers in both the USSR and the United States had been planning for the flight of an artificial satellite in connection with the International Geophysical Year, or IGY, which ran from July 1957 through December 1958. During this period an intensive and coordinated effort was made throughout the world to obtain data on a great variety of natural phenomena.
On July 29, 1955, President Dwight D. Eisenhower approved the launching of a small Earth-circling satellite as part of the U.S. participation in the IGY. Four days later the Soviets made a similar announcement in the Moscow press. In actuality, the IGY represented a suitable occasion for both nations to launch artificial satellites, since they had already been vigorously pursuing missile programs that created the requisite technology. At the time of the Eisenhower approval, for example, the U.S. Army, Navy, and Air Force each had a current proposal for putting up the first satellite. The one finally approvedÑthe Naval Research Laboratory's Vanguard proposalÑinvolved upgrading two existing sounding rockets, the Viking and the Aerobee, and the construction of a few solid-propellant rockets, creating a three-stage launcher.