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Orbital Manuevering System/Reaction Control System AC-Motor-Operated Valves
The 64 valves operated by ac motors in the OMS and RCS were modified.

Primary RCS Thrusters
Wiring was wrapped around each of the 38 primary RCS thrust chambers.

Fuel Cell Power Plants
End-cell heaters on each fuel cell power plant were deleted because of potential electrical failures.

Auxiliary Power Units
Improved auxiliary power units are scheduled for delivery in late 1988.

Main Landing Gear
Modifications were made to improve the performance of the main landing gear elements.

Nose Wheel Steering
The system provides positive lateral directional control of the orbiter.

Thermal Protection System
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.

Wing Modification
A weight reduction program was instituted that resulted in a redesign of certain areas of the wing structure.

Midfuselage Modifications
Because of additional detailed analysis of actual flight data modifications were made ensuring positive margins of safety.

General-Purpose Computers
They are half the size, weigh approximately half as much, and require less power to operate.

Inertial Measurement Units
These new IMUs will result in lower program costs.

Crew Escape Systems
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.

Emergency Egress Slide
The emergency egress slide provides orbiter flight crew members with a means for rapid and safe exit through the orbiter.

17-inch 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.

Curator: Kim Dismukes | Responsible NASA Official: John Ira Petty | Updated: 04/07/2002
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