The in-flight crew escape
system is provided for use only when the orbiter is in controlled
gliding flight and unable to reach a runway. This would normally
lead to ditching. The crew escape system provides the flight crew
with an alternative to water ditching or to landing on terrain other
than a landing site. The probability of the flight crew surviving
a ditching is very small.
The hardware changes required to the orbiters would enable the
flight crew to equalize the pressurized crew compartment with the
outside pressure via a depressurization valve opened by pyrotechnics
in the crew compartment aft bulkhead that would be manually activated
by a flight crew member in the middeck of the crew compartment;
pyrotechnically jettison the crew ingress/egress side hatch in the
middeck of the crew compartment; and bail out from the middeck of
the orbiter through the ingress/egress side hatch opening after
manually deploying the escape pole through, outside and down from
the side hatch opening. One by one, each crew member attaches a
lanyard hook assembly, which surrounds the deployed escape pole,
to his parachute harness and egresses through the side hatch opening.
Attached to the escape pole, the crew member slides down the pole
and off the end. The escape pole provides a trajectory that takes
the crew members below the orbiter's left wing.
Changes were also made in the
software of the orbiter's general-purpose
computers. The software changes were required for the primary avionics
software system and the backup flight system for transatlantic-landing
and glide-return-to-launch-site aborts. The changes provide the
orbiter with an automatic-mode input by the flight crew through
keyboards on the commander's and/or pilot's panel C3, which provides
the orbiter with an automatic stable flight for crew bailout.
Note that the side hatch
jettison feature could be used in a landing emergency.