约翰·格伦,首次乘坐宇宙飞船进入太空的时代,应追溯到1962年。那个年代,宇航员在进行医学实验时,必须耐受住夹带直肠体温计的痛苦,并要通过离心机的超重训练。只有经受过这类考验的人才有参与选拔的资格。早先宇宙飞船的密封舱容积窄小,刚刚能够将宇航员塞进去。那时,能使宇航员安全生还就是发射宇宙飞 John Glenn, the first time to take spacecraft into space, dates back to 1962. In that era, when astronauts were conducting medical experiments, they had to endure the pain of having a rectal thermometer attached to them, and they had to pass the overweight training of a centrifuge. Only those who have undergone such tests are eligible to participate in the selection. The space capsule of the earlier spacecraft was small and was able to contain astronauts. At that time, astronauts could be made safe by launching spacecraft.