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The Low Pressure Gas Effects On The Potency Of An Electron Beam On Ceramic Fabric Materials For Space WeldingThis investigation was undertaken to evaluate if molten metal or electron beam impingement could damage or burn through the fabric of the astronauts Extravehicular Mobility Unit (EMU) during electron beam welding exercises performed in space. An 8 kilovolt electron beam with a current in the neighborhood of 100 milliamps from the Ukrainian space welding "Universal Hand Tool" burned holes in Nextel AF-62 ceramic cloth designed to withstand temperatures up to 1427 C. The burnthrough time was on the order of 8 seconds at standoff distances between UHT and cloth ranging from 6 to 24 inches. At both closer (2") and farther (48") standoff distances the potency of the beam against the cloth declined and the burnthrough time went up significantly. Prior to the test it had been expected that the beam would lay down a static charge on the cloth and be deflected without damaging the cloth. The burnthrough is thought to be an effect of partial transmission of beam power by a stream of positive ions generated by the high voltage electron beam from contaminant gas in the "vacuum" chamber. A rough quantitative theoretical computation appears to substantiate this possibility.
Document ID
20020022355
Document Type
Preprint (Draft being sent to journal)
Authors
Nunes, Arthur C., Jr. (NASA Marshall Space Flight Center Huntsville, AL United States)
Fragomeni, James M. (Ohio Univ. Athens, OH United States)
Munafo, Paul M.
Date Acquired
August 20, 2013
Publication Date
January 1, 2001
Subject Category
Man/System Technology and Life Support
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.