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The port and starboard doors are 60 feet long with a combined area of approximately 1,600 square feet. Each door is made up of five segments that are interconnected by circumferential expansion joints. Each door hinges on 13 external hinges (five shear and eight idlers). The lower half of each hinge attaches to the midfuselage sill longeron. The hinges rotate on bearings with dual rotational surfaces. There are five shear hinges and eight floating hinges. The floating hinges allow fore and aft movement of the door panels for thermal expansion.
The forward 30-foot sections of both doors incorporate radiators that can be deployed; they are hinged and latched to the door inner surface in order to reject the excess heat of the Freon-21 coolant loops from both sides of the radiator panels when the doors are open. An electromechanical actuation system on the door unlatches and deploys the radiators when open and latches and stows the radiators when closed.
The payload deployment and retrieval system includes the electromechanical arm that maneuvers a payload from the payload bay of the space shuttle orbiter to its deployment position and then releases it. It can also grapple a free-flying payload, maneuver it to the payload bay of the orbiter and berth it in the orbiter. This arm is referred to as the remote manipulator system (RMS).
The RMS arm is 50 feet 3 inches long and 15 inches in diameter and has six degrees of freedom. It weighs 905 pounds, and the total system weighs 994 pounds.
The RMS has six joints that correspond roughly to the joints of the human arm, with shoulder yaw and pitch joints; an elbow pitch joint; and wrist pitch, yaw and roll joints. The end effector is the unit at the end of the wrist that actually grabs, or grapples, the payload. The two lightweight boom segments are called the upper and lower arms. The upper boom connects the shoulder and elbow joints, and the lower boom connects the elbow and wrist joints. The RMS arm attaches to the orbiter payload bay longeron at the shoulder manipulator positioning mechanism. Power and data connections are located at the shoulder MPM.
The RMS is capable of deploying or retrieving payloads weighing up to 65,000 pounds. The RMS can also retrieve, repair and deploy satellites; provide a mobile extension ladder for extravehicular activity crew members for work stations or foot restraints; and be used as an inspection aid to allow the flight crew members to view the orbiter's or payload's surfaces through a television camera on the RMS.
The basic RMS configuration consists of a manipulator arm; an RMS display and control panel, including rotational and translational hand controllers at the orbiter aft flight deck flight crew station; and a manipulator controller interface unit that interfaces with the orbiter computer.
One flight crew member operates the RMS from the aft flight deck control station, and a second flight crew member usually assists with television camera operations. This allows the RMS operator to view RMS operations through the aft flight deck payload and overhead windows and through the closed-circuit television monitors at the aft flight deck station.
Spar Aerospace Ltd., a Canadian company, designed, developed, tested and built the RMS. CAE Electronics Ltd. in Montreal provides electronic interfaces, servoamplifiers and power conditioners. Dilworth, Secord, Meagher and Assoc. Ltd. in Toronto is responsible for the RMS end effector. Rockwell International's Space Transportation Systems Division designed, developed, tested and built the systems used to attach the RMS to the payload bay of the orbiter.
The inertial upper stage is used with the space shuttle to transport NASA's Tracking and Data Relay satellites to geosynchronous orbit, 22,300 statute miles from Earth. The IUS was also selected by NASA for the Magellan, Galileo and Ulysses planetary missions.
The IUS is a two-stage vehicle weighing approximately 32,500 pounds. Each stage is a solid rocket motor. This design was selected over those with liquid-fueled engines because of its relative simplicity, high reliability, low cost and safety.
The IUS is 17 feet long and 9.5 feet in diameter. It consists of an aft skirt, an aft stage solid rocket motor with 21,400 pounds of propellant generating 45,600 pounds of thrust, an interstage, a forward stage solid rocket motor with 6,000 pounds of propellant generating 18,500 pounds of thrust and using an extendable exit cone, and an equipment support section. The equipment support section contains the avionics that provide guidance, navigation, telemetry, command and data management, reaction control and electrical power. All mission-critical components of the avionics system and thrust vector actuators, reaction control thrusters, motor igniter and pyrotechnic stage separation equipment are redundant to ensure better than 98-percent reliability.
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