阿波罗-联盟测试计划
Though the final Skylab mission became known for the incident, it was also known for the large amount of work that was accomplished in the long mission. Skylab orbited for six more years before its orbit decayed in 1979 due to higher-than-anticipated solar activity. The next U.S. spaceflight was the Apollo–Soyuz Test Project conducted in July 1975, and after a human spaceflight gap, the first Space Shuttle orbital flight STS-1 in April 1981.