High Speed Compressor for Subcooling Propellants

The most promising propellant subcooling systems for LH2 require compression systems that involve development of significant head. The inlet pressure for these systems is typically on the order of 1.4 psia with a discharge pressure requirement above atmospheric pressure. In the past this has required multiple stages of compression by machines operating at high speeds on ball bearings. The bearing life in these machines was at most a few hundred hours. While this is feasible to use for a proof of concept test system, it is not acceptable for the H2 compressors in application at the launch pad. It is desired to replace these grease-packed ball bearings with foil bearings to greatly increase compressor life. Additionally higher speed can eliminate several stages thus reducing complexity and cost of the system. If this technology proves feasible it could finally make densified LH2 propellant a reality for future launch and space applications.