Zero Boil Off Storage of Liquid Hydrogen Using a Linear-Drive Pulse Tube Cooler

Future NASA missions will involve transportation and/or storage of liquid hydrogen tanks for use as propellant. If no precautions are taken substantial amounts of liquid may be lost by evaporation due to inevitable parasitic heat loads well before cryogen utilization. Cryocoolers may intercept parasitics, thereby, achieving zero boil off (ZBO) of the cryogen. ZBO is necessary if the mission design requires a small tank volume or if the mission duration is sufficiently long. A linear-drive 20K pulse tube cooler is an ideal choice for this application. By virtue of the absence of cold moving parts the PTC is inherently more reliable and induces less vibration at the cold tip than the alternative coolers including the competitive Stirling cooler. Consequently, the PTC is becoming the cryogenic cooler of choice on-board spacecraft.