Effects of outgassed products from spacecraft materials on the insulating strength of the space vacuum

The authors describe investigations into the nature of outgassed products from spacecraft materials and the electrical breakdown characteristics of the resulting contaminated vacuum regions. The materials studied for their outgassing characteristics were G-10 polyethylene, TFE Teflon, Plexiglass, and Mylar. The major outgassed products from the materials studied were H₂O, H₂, O₂, CO₂, and N₂ . The outgassing products raise the local pressure in the vicinity of the spacecraft materials, resulting in a pressure gradient with higher pressures near the material surface and lower pressures away from the spacecraft. The high pressures resulting from the contaminating gas lower the breakdown voltage and reduce the ability of the region to support high electrical-field stresses. The breakdown characteristics (Paschen curve) measured for the outgassed mixtures from the materials are predictable and representative of typical air breakdown characteristics at very low pressures