Manned Spacecraft

Since rockets first became capable of reaching space in the late 1950s, much debate has focused on the relative merits of crewed versus uncrewed space travel. Some experts have argued that scientists can learn almost all they want to know about the solar system and outer space by using uncrewed, mechanized space probes. Such probes can be designed to carry out most of the operations normally performed by humans at much less cost and with little or no risk to human life. The enormous cost and complexity of crewed space flight—mandated by the tons of foolproof equipment needed to keep human beings alive in the utterly hostile space environment and to return them alive to the Earth—is, these critics say, not justified by the modest additional benefits obtained by including human beings in a space vehicle. Other experts insist that there is no substitute in space exploration for human intelligence. Only human beings can deal with the unexpected.

To this debate about scientific efficacy have been several nonscientific elements, political and romantic. One is the emotional appeal of traveling in space, an appeal long promulgated by science fiction. Many people argue that it is human destiny to transcend the "cradle" of Earth and to colonize the planets or even the stars (which are many orders of magnitude harder to reach). For example, NASA planners are taking seriously the Mars exploration proposals of U.S. engineer Robert Zubrin (1956–), who argues that the psychological benefits of colonizing Mars would justify the high cost; U.S. society, Zubrin argues, can be reinvigorated by becoming a "frontier society" again, as during the opening of the American West. Another nonscientific motive for the exploration of space is, as mentioned above, national interest. This motive lessened for the U.S. and Soviet Union after the U.S. landed on the Moon—by far the most spectacular goal within practical reach—but did not fade completely from the political scene. Even the cash-poor Russian Federation has maintained its space program, lest it suffer the humiliation of ceding space entirely to the U.S. Furthermore, China now proclaims that it is on the verge of putting astronauts into orbit in late 2003. Although China will be using Soviet Salyut-style capsules from the 1960s, the boost to China's international prestige will be substantial.

In the 2000s, however, much of the public captivation of space exploration has dissipated. Facing budgetary constraints and a weaker world economy, the world's two space powers have begun to reassess the relative position of crewed versus uncrewed travel in some of their space programs. The loss of the space shuttle Columbia on February 1, 2003, has further spurred debate in the U.S. over whether crewed space exploration is cost-effective compared to the mechanized alternative.

There is, in fact, no debate about whether mechanized space probes such as Voyager, Pathfinder, Galileo, and Magellan produce more scientific knowledge per dollar than crewed space missions; what is at stake, ultimately, is intangible and nonquantifiable. Is it, as critics of crewed space travel argue, folly to spend trillions of dollars to put a few hundred human beings into space. Or is it, as crewed-space-flight advocates argue, folly not to make the human race a "multi-planet species" while we can, with colony populations on at least the Moon and Mars, thus no longer dependent on the fate of the Earth for its long-term survival?