A Mass-Spectrometer System for Detecting Gas Leaks

The Hydrogen Umbilical Mass Spectrometer (HUMS) consists of an integrated sample delivery system, a commercial mass-spectrometer- based gas analyzer, and a set of calibration gas mixtures traceable to NIST (National Institute for Standards and Technology). The system, except for the calibration gas mixtures and the remote operator display, fits into a standard 24-in. wide, 6-ft high, 36-in. deep (0.61 by 1.83 by 0.91 m, respectively) equipment rack and is powered by 120-Vac, 30-A, 60-Hz source. It was designed to perform leak detection and measurement of cryogenic propellants (oxygen and hydrogen) from a remote location during shuttle-launch countdown. It is used specifically to sample the background gas surrounding the 17-in. (0.43-m) Orbiter-ET disconnect, looking for leakage of gaseous hydrogen. The capability to monitor shuttle purge gases and cryogenic hydrogen fill and drain line T-0 disconnect helium purge gas is incorporated into the shuttle installation on each Mobile Launch Platform (MLP).