gandalf@pro-canaveral.cts.com (Ken Hollis) (09/28/90)
Greetings and Salutations: Reference: >From: wargo@odin.ucsd.edu (Dave Wargo) >Subject: A question and a thought about hydrogen leaks. > >The friday KCS Shuttle status reports: > > STS-35 - COLUMBIA (OV 102) - PAD 39-A > Workers gained access to the aft compartment yesterday and > have begun preliminary inspections. Technicians are continuing to > remove foam from around valves, actuators and areas of the recir- > culation pump package to allow further inspections and tests. > >The question I have is what is the foam doing there? Is it to deaden the >noise? >If it needs to be there why not develop a foam that reacts to concentrations >of hydrogen (turns a different color) so that it would make detecting leaks a >little easier. >Just a thought. >Dave The foam is insulation installed at places on the LH2 feedline where Vaccuum jacketed lines are unable to be installed. The nominal line for the LH2 system consists of two metal lines (one inside another) with the space in between the lines vacuumed down to less than 1000 microns of mercury pressure. On places like the prevalve, or the recirculation system where actual valves are installed, instead of attempting to make a vacuum jacket around these parts, foam insulation is installed. There are also places, like the detent covers, that come in direct contact with LH2, and would produce liquid nitrogen in the aft if not insulated (as the aft is purged with pure GN2 during loading). As to why a different foam is not produced for color differentiation when reacting with H2, there are always small amounts of H2 in the aft during loading, and this would eventually turn all of the foam another color. The foam is also protected with an aluminum tape (LT80) on top, to protect the foam (Polyeurathane (SP?)). Ken Hollis