Braking thruster
The braking thruster was a type of thruster used to brake a starship's speed. If the ship's crew was incapacitated somehow, these thrusters could fire automatically. 

In 1986, after traveling successfully to this year, the 's braking thrusters fired as it approached Earth. Later, in 2286, after another successful time travel, these thrusters fired again as the ship approached Earth. ()

While on board the Retellian escape pod approaching the surface of a planet,  told Kaitaama that he was sure the braking thrusters would fire. ()

Propulsion technology