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→Post-Challenger abort enhancements: A bit of missing grammar? Revert if necessary.
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After the loss of ''Challenger'' in STS-51-L, numerous abort enhancements were added. With those enhancements, the loss of two SSMEs was now survivable for the crew throughout the entire ascent, and the vehicle could survive and land for large portions of the ascent. The struts attaching the orbiter to the external tank were strengthened to better endure a multiple SSME failure during SRB flight. Loss of three SSMEs was survivable for the crew for most of the ascent, although survival in the event of three failed SSMEs before T+90 seconds was unlikely because of design loads that would be exceeded on the forward orbiter/ET and SRB/ET attach points, and still problematic at any time during SRB flight because of controllability during staging.<ref name = NASACA>{{cite web|title=Contingency Aborts|url=http://www.nasa.gov/centers/johnson/pdf/383441main_contingency_aborts_21007_31007.pdf|website=NASA.gov|access-date=February 1, 2015|archive-date=February 26, 2015|archive-url=https://web.archive.org/web/20150226074439/http://www.nasa.gov/centers/johnson/pdf/383441main_contingency_aborts_21007_31007.pdf|url-status=live}}</ref>
A particularly significant enhancement was bailout capability. Unlike the ejection seat in a fighter plane, the shuttle had an inflight crew escape system<ref>[https://web.archive.org/web/20000817130106/http://spaceflight.nasa.gov/shuttle/reference/shutref/escape/inflight.html spaceflight.nasa.gov]</ref> (ICES). The vehicle was put in a stable glide on autopilot, the hatch was blown, and the crew slid outon a pole to clear the orbiter's left wing. They would then parachute to earth or the sea. While this at first appeared only usable under rare conditions, there were many failure modes where reaching an emergency landing site was not possible yet the vehicle was still intact and under control. Before the ''Challenger'' disaster, this almost happened on [[STS-51-F]], when a single SSME failed at about T+345 seconds. The orbiter in that case was also ''Challenger''. A second SSME almost failed because of a spurious temperature reading; however, the engine shutdown was inhibited by a quick-thinking flight controller. If the second SSME had failed within about 69 seconds of the first, there would have been insufficient energy to cross the Atlantic. Without bailout capability, the entire crew would have been killed. After the loss of ''Challenger'', those types of failures were made survivable. To facilitate high-altitude bailouts, the crew began wearing the [[Launch Entry Suit]] and later the [[Advanced Crew Escape Suit]] during ascent and descent. Before the ''Challenger'' disaster, crews for operational missions wore only fabric flight suits.
Another post-''Challenger'' enhancement was the addition of East Coast/Bermuda abort landings (ECAL/BDA). High-inclination launches (including all [[ISS]] missions) would have been able to reach an emergency runway on the East Coast of North America under certain conditions. Most lower-inclination launches would have landed in Bermuda (although this option was ''not'' available for the very lowest-inclination launches—those to an orbital inclination of 28.5°—which launched due east from KSC and passed far to the south of Bermuda).
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