Launch escape system

A Launch Escape System (LES) is a small top-mounted rocket connected to the crew module of a rocket and used to quickly separate and launch the crew module away from the rest of the rocket in the case of an emergency. Since the escape rockets are above the crew module, the LES typically used three (for the Mercury spacecraft), or four (for the Apollo spacecraft) separate engines which are each pointed down and away from the crew module to prevent the LES from firing its engines directly at the crew module. The LES is used in situations where there is an imminent threat to the crew, such as an impending explosion.

As the Gemini spacecraft was initially designed with the possibility of a runway landing under a paraglider, it was fitted with ejection seats, which served as an escape system.

The Space Shuttle was initially fitted with ejection seats for the initial "shakedown" flights, but these were removed once the vehicle was deemed operational. Following the Challenger disaster, all surviving orbiters were fitted to allow for crew evacuation through the main hatch, though this can only be used when the shuttle is in a controlled glide.