To keep people on the ground safe , it 's best to deorbit a spacecraft with a strong burn of propellant , to slow it down at the right time .
为确保地面上人的安全，最好的方法是以一个强大的推进器燃烧来使宇宙飞船脱轨，在正确的时间使其慢下来。
Space tether include mechanical tether and electrodynamic tether and the principles of their deorbit abilities are different .
空间系绳包括导体系绳和非导体系绳，它们在废弃航天器离轨中的原理不同。
However , many space agencies are considering a third option : robot missions that would dock with dead satellites and fire rockets either to boost them into " graveyard " orbits or to deorbit them completely , so they crashed into the sea .
