Description: The Civil Space Technology Initiative High-Capacity-Power Environmental Interactions Program has made great progress in defining and evaluating the interactions of the SP-100 power system with its expected ambient environments. The NASCAP/LEO and POLAR computer codes demonstrated that local electric fields at the user interface module are high. Therefore, particular attention must be paid to geometries and materials in this region to prevent arcing at conductor-insulator junctions in low Earth orbit. NASCAP/LEO and EPSAT computer models revealed that SP-100 payloads float about 100 V negative of the LEO plasma. In addition, ground tests and modeling done for the Space Station Freedom Electrical Grounding Tiger Team found that dielectric coatings often break down at such voltages in a plasma. Thus, surface coatings for SP-100 payloads should be carefully selected. Sputtering may also be a concern for long-duration missions in LEO at these voltages. Much work has been done on a sputtering model to evaluate surface material loss rates on SP-100 payloads. In ground plasma chamber tests of cables and cable insulators at SP-100 voltages, parasitic power losses due to the plasma current collected from possible pinholes or coating defects were quantified and shown to be small. Modeling revealed that the power loss from currents to other surfaces is also small. The atomic oxygen durability of SP-100 materials and coatings continues to be investigated in ground tests. In the upcoming Evaluation of Oxygen Interaction with Materials (EOIM-3) Shuttle flight experiment, a host of SP-100 materials will be evaluated for atomic oxygen durability in LEO. Finally, an evaluation of the interactions of the SP-100 power system with lunar and planetary environments has started. At a workshop on chemical and electrical interactions on Mars recently held at the NASA Lewis Research Center, many of primary interactions were identified.
Date: January 1, 1993
Creator: Ferguson, D. C.
Partner: UNT Libraries Government Documents Department