см. включать и выключать ; см. тж. вводить в действие ; вступать в работу
I switched on the retro-rocket unit, and the spacecraft obediently left the orbit and started moving towards the Earth.
The impulses from the radar of the "active" spacecraft were sent to computers which in turn issued the necessary signals that switched on the appropriate engines.
…the propulsion system was fired to inject the spaceship into towards-Earth trajectory.