Verification testing of the superfluid helium on-orbit transfer (SHOOT) experiment

Abstract

The Superfluid Helium On-Orbit Transfer (SHOOT) project is a secondary shuttle crossbay payload which flew on the STS-57/Endeavour mission. It was designed to develop and demonstrate the technologies required to resupply liquid helium containers in space, and to develop new technologies that may be used in other future space cryogenic systems. The SHOOT payload consists of two superfluid helium Dewars with helium management cryostats connected by a transfer line, and six avionics boxes for valve and heater control, temperature, pressure and fluid position monitoring and data processing and telemetry. The cryostats contain numerous specialized helium management components; including high and low flow phase separators, liquid/vapour discriminators, flowmeters, liquid level detectors, cryogenic mechanical valves and cryogenic relief valves and burst discs, and two varieties of fluid acquisition systems. To prepare the SHOOT payload for launch a series of functional, structural, thermal and reliability tests were conducted at every level of hardware assembly, from materials tests to system level thermal, structural and functional performance tests. We present here the verification tests and analyses developed and completed at each level of assembly. We discuss the trade-offs considered for, and the success (or failure) of, models and analyses to predict performance results. Finally, we present some lessons learned of potential interest to future cryogenic missions, whether on the Space Shuttle or on expendable launch vehicles.