The 1960's Mercury Atlas program employed an on-board emergency detection and automatic abort system called ASIS (Abort Sensing and Implementation System) that monitored precursors of catastrophic missile failure in order to automatically abort the flight if needed. The system design was based upon the knowledge that catastrophic failures of Atlas missiles were endemic. When astronaut John Glenn flew the Friendship 7 spacecraft on Mercury-Atlas-6, February 20,1962, the success rate of the Mercury Atlas was 50%. ASIS was driven by dual imperatives - to protect the astronaut in case of imminent disaster, and to avoid erroneous flight abort of a healthy rocket It monitored only 13 measurements, carefully selected for their broad fault coverage, reliability, and predictability. Fifty years later, Atlas V, as one example of a Commercial Crew launch vehicle, will be safeguarded by the Emergency Detection System (EDS). The Atlas launch vehicle on-board data processing capability is orders of magnitude greater than that of the 1960's, and the Atlas vehicle has flown over 110 times through 28 years since the last failure that would have posed an immediate safety risk to a crewed spacecraft However, the basic security and reliability concerns remain the same. Current NASA human spaceflight experience is primarily with a very different, reusable launch system which has unique failure modes and unique abort modes. As launch services to Low Earth Orbit transition to the next generation, the experience of both expendable and reusable solutions become important contributors to reliable and safe human space launch systems. This paper explores the influence upon the EDS design of 50 years of launch vehicle experience, including Atlas, Delta, Titan and Shuttle. It describes the similarities and differences between the ASIS and EDS solutions, including design drivers, implementation technology, available measurements, and measurement monitoring strategy.
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