July-August 1983:Spacelab preparations

While Shuttle Orbiter Challenger has been grabbing the headlines, the first orbital ship. Columbia, has been quietly undergoing modifications to convert it from a flying test bed and prepare it for the important Spacelab mission this autumn.

Columbia is being modified at the Kennedy Space Center in Bay 2 of the Orbiter Processing Facility. In general terms, the changes will enable Columbia to carry Spacelab and accommodate the six-man crew. Other systems have been upgraded for added reliability and extended lifetimes. An airlock and tunnel adapter so that astronauts and payload scientists can go back and forth between the Columbia and the Spacelab has been added. Oxygen lines will be routed from Columbia to the workshop where it will be mixed with the Spacelab's own nitrogen system to provide a breathable atmosphere.

Columbia's fifth flight (STS-5 in November 1982) carried the first four-man crew. The pilots' ejection seats, which have not been removed, limit the amount of room up on the flight deck so two more seats have been installed down on the mid-deck. They are of the same type of airliner-type chairs used on STS-5 for passengers, and are standard equipment on Columbia's sister ship. Challenger.

Since there are more people on board, a number of the modifications are to provide the crew with the comforts of home. A kitchen was installed in the mid-deck to serve as an eating and food storage area. A large rack of development flight instrumentation was removed to make room for the modern space kitchen. A personal hygiene station was also added in the area.

Since the crew will work and sleep in 12-hour shifts, three bunk beds were installed on the other side of the mid-deck with sleeping bag restraints. Three hammock-type sleeping bags were also included. More people means more equipment, so additional permanent lockers and compartments were added, many of them under the mid-deck floor. Changes were made to provide adequate breathing air for the larger crew and portable oxygen systems were installed for the added crewmen.

To handle the additional Spacelab power requirements and to provide an abundant supply of liquid reactants which can be converted into breathing air for the crew, several major changes were made to the power reactant storage and distribution (PRSD) system. The three standard two sub-stack fuel cells, which provide electrical power, were replaced with fuel cells that have three sub-stacks, thus increasing the available voltage margin. The number of cryogenic storage tanks, which hold and supply the super cold reactants to the fuel cells, is being increased from three to five sets. All five of the oxygen tanks are new, designed for added durability and reliability over the 100-mission lifetime of Columbia.

Some of the other modifications include: a new set of stronger main landing gear wheels, plus a modified set of brakes; between 400 to 600 payload bay insulation blankets were replaced with blankets made of a stronger, more heat resistant material and the heat-rejecting radiators inside the cargo doors were replaced with new diffuse coated radiators for reduced glare and better heat-rejecting capability. Other items include some 100 electronic "black boxes," the reinforced carbon-carbon panels on the leading edge of the two wings and several antennae. The carbon-carbon panels are going back to their manufacturer for treatment to increase their resistance to oxidation and increase their mission life. Many of the "black box" changes are to upgrade Columbia's instrumentation systems and because of the removal of the development flight instrumentation.

Substantial rewiring added about 100 more measurements previously undertaken by the development instrumentation to the Orbiter's Operational Instrumentation System. A text and graphics unit was added to allow black and white facsimiles to be sent to the Orbiter from the ground. The unit will also receive digital data from the Ku-band signal processor and supply the crew with a hard copy of the processed data.

Three of Columbia's tactical air navigation (TACAN) units, used as an external navigation aid during reentry, were replaced with upgraded units, and the four quadrant S-band antennae were replaced with new antennae to communicate with the Tracking and Data Relay Satellite. The S-band system, which has a larger beam width compared to the narrow pencil beam of the Ku-band system, will be used to lock on to the Tracking and Data Relay Satellite. Once the S-band signal is acquired, the Ku-band signal can be turned on. A new Ku-band antenna will be used specifically for transmitting Spacelab information down to the ground via the TDRS satellites.

Columbia's engine subsystems also received a thorough going-over. The twin Orbital Maneuvering System pods and the forward Reaction Control System were removed and processed in the Hypergolic Maintenance Facility. The three main engines are being overhauled for use on the fourth Orbiter, Atlantis. These engines, which operated at 100 per cent of rated thrust on Columbia, will be modified and retested to certify them for operation at 109 per cent aboard Atlantis. Columbia has a brand new set of main engines and additional leak detection development was added in the engine compartment. While in the Orbiter Processing Facility technicians removed and densified more of the thermal tiles that have not previously undergone the strengthening process. About 2,400 tiles, all on the belly area, were treated.

Spacelab will be installed in early August and tests conducted to verify proper operation of the integrated vehicle. Columbia is scheduled for a late August to early September move to the Vehicle Assembly Building for mating with its boosters and External Tank.