A Gas-Bearing Compressor System for Space station Airlock Gas Recovery

AiResearch has investigated the application of high-speed turbocompressor technology to the space station airlock gas recovery system. Design studies have shown that multi stage centrifugal compressors can complete the airlock evacuation cycle in half the time and at one-third the weight of traditional positive-displacement vacuum equipment.

The key elements of this technology are the self-acting gas bearing and the permanent magnet motor. The compliant foil bearing uses the lip speed of the rotor to pump the surrounding air into the lubricating film. The bearings are free of potential contaminates to the station air as no other lubrication is needed. The permanent magnet brushless dc motor allows the compressor to operate at the high rotational speeds needed for efficient aerodynamics. To provide a simple control method the motor operates at constant torque during the airlock evacuation cycle. As the air is evacuated and the density decreases, the compressor accelerates, operating at steadily higher pressure ratios.

The two-stage compressor is capable of evacuating a 215 cu ft airlock to 0.90 psia in 7.0 min, consuming 1030 kj of energy. With the power electronics, shutoff valve, aftercoolers and supporting structure, the system weighs 80 lb. A similar two-stage compressor for use in a long-life spacecraft cryocooler system has been under development at AiResearch since October 1985.