Under a National Aeronautics and Space Administration (NASA) Phase II Small Business Innovative Research (SBIR) Grant, Barber-Nichols designed, built and tested a cryogenic compressor capable of densifying liquid hydrogen. Cryogenic propellant densification improves rocket specific impulse (ISP) by allowing a greater mass of cryogenic propellant to be loaded into a given tank volume and if the densification system results in a sub-cooled liquid, the pump suction performance margin is also improved.
Centrifugal hydrogen densification compressors demand high shaft speed due to the high head requirements. Previous centrifugal densification compressors relied upon grease packed ball bearing which has limited compressor shaft speed and operating life. The newly developed technology uses liquid hydrogen propellant directly injected into foil bearings. The foil bearings support a high-speed permanent magnet motor driving two stages of compression.
The unit was tested at Innovative Engineering Services in Murietta, California using cryogenic hydrogen liquid and gas. Shaft speed of 35,000 rpm was obtained with the compressor pulling from a 1000 gallon liquid tank and expelling the hydrogen gas to the atmosphere.