美国和俄罗斯是航天领域的“两极”,其载人航天处于世界领先水平。欧洲空间局、中国和日本正成为航天领域迅速崛起的“第三极”。美国为谋求和保持“空间领先”地位,自1958年成立航空航天局以来,实施了一系列载人航天计划。从“水星”计划到“双子星座”计划,再到“阿波罗”计划,先后完成6次登月飞行,把12人送上月球并安全返回地面。上个世纪70年代开始,美国重点实施“天空”实验室和航天飞机两项 The United States and Russia are the “poles” of the aerospace field, with manned spacecraft leading the world. The European Space Agency, China and Japan are becoming the “third poles” of rapid rise in space. To seek and maintain the “space-leading” position, the United States has implemented a series of manned space programs since the establishment of the NASA in 1958. From “Mercury” plan to “Gemini” plan, to “Apollo” plan, has completed 6 lunar flights, 12 people on the moon and safely back to the ground. Since the 1970s, the United States has focused on the implementation of two “sky” laboratories and space shuttles