Small Scroll Pump for Cryogenic Liquids

Launch Vehicle – Load Responsive Multi-Layer Insulation (LV-LRMLI) could provide a high performance thermal insulation for Launch Vehicles with an integrated lightweight vacuum shell, able to withstand aerodynamic forces during launch, and substantially reducing cryopropellant boil-off. LV-LRMLI could provide benefit to NASA with increased launch vehicle mission capabilities such as longer duration cryogenic powered missions, longer coast times for orbital transitions, higher payload capacity to GSO, enhancements to the workhorse Atlas V and Delta IV launch vehicle families, applicability to upcoming cryogenic upper stage designs such as Advanced Common Evolved Stage and Space Launch System. A small, cryogenic scroll pump would have several NASA cryopropellant applications. It would enable efficient, low boil off or zero boil off cryogenic systems by circulating cryogenic helium gas from a cryocooler to broad area thermal shields surrounding the tanks. This would eliminate the need for high efficiency heat exchangers that are required with ambient temperature circulator pumps. The pump would also enable thermodynamic vent systems in which cryopropellants are dropped in pressure and temperature and heat exchanged with liquid pumped in a circulation loop with the tank. NASA Marshall has done considerable work with such systems involving spray bar tank heat exchanger and destratifiers.

United Launch Alliance (ULA) is currently developing an integrated fluid system (IVF) to recover and use boil off hydrogen and oxygen from its Centaur upper launch vehicle. An enabling component of this system would be a positive displacement cryogenic pump. The cold propellant gases would be pumped to a pressure of approximately 200 PSI and stored in tanks for use as reaction control system fuel or tank pressurization. The small size and pressure capability of the scroll pump would be well suited for this application. A strong demand exists for small cryogenic pumps for use in liquid hydrogen fueled aircraft. The Boeing Company and AeroViroment, Inc. have developed and flown hydrogen fueled, unmanned aircraft as reconnaissance platforms. Typically, these aircraft fuel systems require the hydrogen to be delivered at a pressure of 90 PSIG, currently this done by making the operating pressure of the tanks at minimum of 90 PSIG. This results in tanks that can operate with a safety margin above this pressure. If the tanks could operate at a lower pressure, such as 30 PSIG, the tank walls could be thinner and lighter. The estimated weight savings of a pumped system for the Boeing Phantom Eye hydrogen fueled aircraft is over 400 pounds per aircraft. The scroll pump would be an important discriminator in aircraft performance. More »