In 1975, an attempted docking between a U.S. Apollo spacecraft and a Soviet Soyuz went wrong, resulting in an orbital collision killing everyone aboard both vessels.
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The tragedy dealt the U.S. space program a blow from which it would never recover. In the aftermath, those who had been arguing that putting humans into space was a dangerous and pointless stunt would prevail in Washington, leading, among other things, to the abandonment of the ongoing Space Shuttle program, launched by President Nixon soon after the first moon landings. A single shuttle, named the Enterprise thanks to a lobbying campaign by fans of the television series Star Trek, would be built and would fly cross-country on the back of a cargo jetliner, but it would never go into space. The U.S. would continue to send unmanned probes into space, but with decreasing frequency as public interest in the space program waned.
Apollo-Suyuz Tragedy by Eric LippsThe Soviets would continue to send men into space for years, but the increasing fragility of their economy and political system would lead them, too, to abandon manned spaceflight by the early 1980s. Buran, the proposed Soviet version of the Space Shuttle, would never make it off the drawing boards.
In the 1990s, Japan and China would reignite the space race with their own first successful manned orbital launches. By then, however, the Soviet Union would have collapsed and its successor, the Commonwealth of Independent States, would be far too preoccupied with fending off complete economic collapse to think of resuming its own program. As for the United States, while a vocal minority continued to call for a resumption of manned spaceflight, most space scientists favored automated missions as faster, cheaper and better. "Cheaper" was without doubt the most important priority: year after year, NASA would face either stagnant or declining budgets, forcing the elimination of one program after another. Some space advocates insisted that private enterprise would step in - someday - and open a new Space Age far beyond what the government-run space program had achieved, but efforts in that direction have been slow to progress. If anything, advances in cable and fiber-optic transmission threaten to undermine one of the few remaining justifications even for unmanned orbital launches, the lofting of communications satellites. Only the space efforts of the military and intelligence establishments have so far remained vigorous, as there is presently no substitute for the observation satellites they maintain in low Earth orbit.