航天员返回地面离不开“保护伞”。这道伞就是飞船进入大气层以后用于减速的降落伞。神舟飞船上的降落伞是世界上正在使用的降落伞中最大的一种。 如果说飞船发射时需要加速的话,那么飞船返回时则需要减速。当飞船启动返回程序,3吨重的返回舱下降到距地面15千米时,它所受到的气动阻力近似于它所受的重力,下降速度由超音速减到到亚音速,并稳定在200米/秒左右,这时再减速就要靠降落伞了。 Astronauts to return to the ground is inseparable from the “umbrella.” This parachute is the parachute used to slow down the spacecraft after entering the atmosphere. Parachutes on the Shenzhou spacecraft are the largest of the parachutes in use in the world. If you need to speed up the spacecraft launch, then the spacecraft needs to slow down when returning. When the spacecraft starts the return procedure and the 3-tonne return capsule drops 15 km from the ground, it receives a similar aerodynamic drag as its gravitational force, decreasing its speed from supersonic to subsonic and stabilizing at 200 M / s or so, then slow down to rely on the parachute.