Accession Number : ADA140666

Title :   Charging and Discharging of Spacecraft Thermal Control Dielectrics.

Descriptive Note : Technical rept.,


Personal Author(s) : Riddel,J D ; Kitterer,B D ; Passenheim,B C ; Vahldieck,J P ; van Lint,V A J

PDF Url : ADA140666

Report Date : 01 Aug 1982

Pagination or Media Count : 184

Abstract : Dielectric spacecraft thermal control materials: Mylar (polyethylene terephthalate), Kapton (polyimide), Teflon (PTFE) and glass second surface mirrors (optical solar reflectors) and solar cell cover glass (fused silica) were exposed to monoenergetic electron beams ranging in energy from 5 to 31 keV and current densities from approx. 0.1 to approx. 100 nA/sq cm, at room temperature, in a vacuum of less than 6 x 10 to the minus 6th power torr. The charging characteristics, (which depend on conductivity, backscatter and secondary emission) have been documented. Conductivity was inferred from slow charge leakage measurements. Numerous spontaneous discharge transient events have been recorded with segmented electrodes under the dielectrics, and a blow-off collector around the dielectric to determine the nature of the discharge (flashover, blow-off, punch-through) and the discharge propagation velocity. This provides direct (Kapton, Teflon, Mylar) whereas others apparently propagate faster then 2 x 10 to the 8th power cm/s (Glass and Mylar). A variety of discharge patterns were observed under very similar charging conditions.

Descriptors :   *Dielectrics, *Electrical conductivity, *Space charge, Glass, Materials, Solar cells, Polyethylene terephthalate, Polyimide resins, Fluoropolymers, Polyethylene plastics, Mirrors, Fused silica, Spacecraft, Electric charge, Electric discharges, Electron beams, Exposure(General)

Subject Categories : Ceramics, Refractories and Glass
      Electricity and Magnetism
      Unmanned Spacecraft

Distribution Statement : APPROVED FOR PUBLIC RELEASE