It is the policy of the United States that activities in space should be devoted to peaceful purposes for the benefit of all mankind.

—National Aeronautics and Space Agency Act of 1958

Once it became obvious that space exploration was an achievable reality, it became a national priority for rich and powerful countries. Following World War II there were only two superpowers in the world—the United States and the Union of Soviet Socialist Republics, and they considered each other enemies.

Both superpowers had military, scientific, and political reasons to pursue space travel. Outer space was a potential battlefield and provided an opportunity to spy on enemies on the other side of the world. Scientists, however, valued space travel for another reason. They wanted to gather data from space to help them unravel the mysteries of the universe. From a political standpoint, a successful space program was a source of national pride, a symbol of national superiority. This motivation above all others drove the earliest decades of space exploration.

The Soviet Union's space program was under the control of the military. In contrast, the United States split its space program into two parts. The U.S. military was given control over space projects related to national defense. A new civilian agency called the National Aeronautics and Space Administration (NASA) was formed in 1958 to oversee peaceful space programs.

Throughout its history NASA has been associated with spectacular feats and horrific disasters in space exploration. It has received great praise for its successes and harsh criticism for its failures. Space travel is an expensive enterprise. As a government agency NASA is bound by federal budget constraints. This budget rises and falls according to the political climate. American presidents set space goals, but the U.S. Congress sets NASA's budget.

In 1961 President John F. Kennedy charged NASA with the monumental task of putting a man on the Moon before the end of the decade. Congress allocated billions of dollars to NASA and this goal was accomplished. Later presidents also set grand goals for the agency, but none of these were realized. Every major endeavor went over budget and fell behind schedule. The public seemed to lose interest in space travel. Congress lacked the political motivation to increase NASA's funding. In 1965 NASA's budget comprised nearly 4% of the federal budget. By 1974 this percentage was less than 1%. It has remained near this level for more than thirty years. (See Figure 2.1.)

Since the 1980s NASA's reputation has suffered. Between 1986 and 2003 the agency experienced a string of failures. Two spacecraft sent to Mars were lost. A space telescope was launched into space with a faulty mirror. Worst of all, two catastrophic disasters killed fourteen astronauts. Critics complained that NASA had become overconfident, too bureaucratic, and had lost its technological edge.

In 2004 and 2005 NASA got a huge boost in prestige with the success of its robotic missions to Mars and Saturn. This was accompanied by a declaration from President George W. Bush that NASA should set bold new goals to send crewed missions to the Moon and Mars. It remains to be seen whether Congress will fund these enterprises and whether NASA will be able to overcome the many obstacles in its path to space.