Liquid Hydrogen Zero‐Boiloff Testing and Analysis for Long‐Term Orbital Storage Available to Purchase

Advancement of cryocooler and passive insulation technologies in recent years has improved the prospects for zero‐boiloff (ZBO) storage of cryogenic fluids. The ZBO concept involves the use of a cryocooler/radiator system to balance storage system incoming and extracted energy such that zero boiloff (no venting) occurs. A large‐scale demonstration of the ZBO concept was conducted using the Marshall Space Flight Center (MSFC) multipurpose hydrogen test bed (MHTB) along with a commercial cryocooler unit. The liquid hydrogen (LH₂) was withdrawn from the tank, passed through the cryocooler heat exchanger, and then the chilled liquid was sprayed back into the tank through a spray bar. The spray bar recirculation system was designed to provide destratification independent of ullage and liquid positions in a zero‐gravity environment. The insulated MHTB tank, combined with the vacuum chamber conditions, enabled orbital storage simulation. ZBO was demonstrated for fill levels of 95%, 50%, and 25%. At each fill level, a steady‐state boiloff test was performed prior to operating the cryocooler to establish the baseline heat leak. Control system logic based on real‐time thermal data and ullage pressure response was implemented to automatically provide a constant tank pressure. A comparison of test data and analytical results is presented in this paper.