Corona and Breakdown Voltage in Helium-Oxygen Atmospheres

Helium-oxygen mixtures are being considered for use in low-pressure (3.5 to 7.5 psia) compartments of manned spacecraft. Electrical wires, cabling, and components will be required to operate in these low-pressure compartments. During extra-vehicular maneuvers the pressure could decrease to that of space vacuum. During the depressurization and pressurization periods, corona and voltage breakdown will be a significant problem. This paper provides corona and voltage-breakdown data for electrical system components operating in these possible spacecraft environments. The breakdown voltage in pure helium, pure oxygen, and helium-oxygen mixtures is presented as measured between 5-cm-diameter parallel plates at various pressures and spacings at a frequency of 400 Hz and a temperature of 23°C. In addition, the corona onset voltages of twisted and spaced-parallel Teflon-insulated wires and wired connector contacts are presented.