Gas Phase Interactions in the Shuttle Environment

A quadrupole mass spectrometer was flown on STS-4. A retarding potential grid located in the ion source distinguished between high and low energy ionic and neutral species in the Shuttle environment. The bulk of the neutral water molecules entering the mass spectrometer appear to be thermal. In contrast, a considerable fraction of water ions, which are formed from charged transfer reactions with ambient 0+, have energies greater than thermal. The high energy species are attributed to nonreactive collisions between the thermal water ions and the high energy incoming flux of ambient neutrals. The energy distributions of the ions are affected more by these interactions because of their greater collision cross sections.
Proceedings of the AIAA Shuttle Environment and Operations II Conference Held on 13-15 Nov 85 at Houston, TX., paper no. AIAA-85-6055-CP.