Launch escape system

A launch escape system is a crew safety system connected to a space capsule, used to quickly separate the capsule from its launch vehicle rocket in case of a launch abort emergency, such as an impending explosion. Such systems are usually of two types:

The system is typically controlled by a combination of automatic rocket failure detection, and a manual backup for the crew commander's use.

Escape systems have not proven to be practical for more complex spacecraft designs such as the Space Shuttle, mainly because most crew members cannot be seated next to escape hatches.

The idea of using a rocket to remove the capsule from a space vehicle was developed by Maxime Faget in 1958. The system, using the tower on the top of the space capsule to house rockets, was first used on a test of the Project Mercury capsule in March 1959. Historically, LESes were used on American Mercury and Apollo spacecraft. Both designs used a solid-fuel rocket motor. The Mercury LES was built by the Grand Central Rocket Company in Redlands, California (which later became the Lockheed Propulsion Company). Apollo used a design that had many similarities to the Mercury system. Launch Escape Systems continue to be used on the Russian Soyuz and Chinese Shenzhou programme spacecraft. The SpaceX-designed Dragon V2 uses a liquid fueled launch abort system integrated to the capsule to minimize spacecraft costs.

The LES may be used while the launch vehicle is still on the launch pad, or during its ascent.

The Soviet Vostok and American Gemini spacecraft both made use of ejection seats. The European Space Agency's Hermes and the Soviet Buran spaceplanes would also have made use of them if they had ever flown with crews. As shown by Soyuz T-10a, an LES must be able to carry a crew compartment from the launch pad to a height sufficient for its parachutes to open. Consequently, they must make use of large, powerful (and heavy) solid rockets. The Soyuz launch escape system is called CAC or SAS, from the Russian/transliterated Russian Система Аварийного Спасения or Sistema Avariynogo Spaseniya, meaning emergency rescue system.

...
Wikipedia