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.