In manned spaceflight, there will always be an element of risk to a rocket launch, despite improvements in operations and reliability. Capable Launch Escape Systems (LES) are used to safely extract the crew from a malfunctioning or exploding launch vehicle on the pad or in flight Historically, there have been several examples of launch escape systems employed should a safety situation arise. Starting with the Mercury program and progressing to the latest Chinese Shenzhou or United States Orion spacecraft, tractor type launch escape architecture has been consistently selected. Now, a new wave of commercial launch vehicles is in development to safely take crew to low Earth orbit. These designs are considering pusher or even side-mounted configurations with the goal of reducing launch weight, minimizing complexity, providing additional thrust if not used for crew escape, and enabling potential reuse. This paper examines the basic architecture of pusher, tractor and side-mounted launch escape systems from a systems engineering perspective, using a 15 foot (4.6 meter) diameter generic crew capsule. High level requirements, architecture, and an operations analysis are first examined. Trade spaces in weight, performance, relative cost and safety for each LES are investigated, based on a low Earth orbit mission to the International Space Station. A significant driver in the design involves the launch pad abort scenario and this is studied in the context of Launch Escape System sizing. Finally, potential benefits for secondary use of the launch escape systems such as orbital boost (ascent assist) are examined and discussed.
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