Manuevering System/Reaction Control System AC-Motor-Operated Valves
The 64 valves operated by ac motors in the OMS and RCS were modified.
Wiring was wrapped around each of the 38 primary RCS thrust chambers.
Cell Power Plants
End-cell heaters on each fuel cell power plant were deleted because
of potential electrical failures.
Improved auxiliary power units are scheduled for delivery in late
Modifications were made to improve the performance of the main landing
The system provides positive lateral directional control of the
The low-temperature thermal protection system tiles on Columbia's
midbody, payload bay doors and vertical tail were replaced with
advanced flexible reusable surface insulation blankets.
A weight reduction program was instituted that resulted in a redesign
of certain areas of the wing structure.
Because of additional detailed analysis of actual flight data modifications
were made ensuring positive margins of safety.
They are half the size, weigh approximately half as much, and require
less power to operate.
These new IMUs will result in lower program costs.
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.
The emergency egress
slide provides orbiter flight crew members with a means for rapid
and safe exit through the orbiter.
Orbiter/External Tank Disconnects
Each mated pair of 17-inch disconnects contains two flapper valves:
one on the orbiter side and one on the external tank side.