Space Power Abstracts 1. SOLAR PHOTOVOLTAIC SYSTEMS & TECHNOLOGY 1-7. Indium Phosphide Solar Cells—Recent Developments and Predicted Performance in Space Irving Weinberg & David J. Brinker NASA Lewis Research Center, Cleveland, OH 44135, USA. The current status of indium phosphide solar cell research, in both the USA and Japan, is reviewed. In the US program, mainly under the aegis of the NASA Lewis Research Center, record high efficiencies of 18.8% were achieved for standard InP homojunction cells while 17% was achieved for cells processed by sputtering indium tin oxide on to indium phosphide. The latter represents a cheaper, simpler processing alternative. Computer modelling predicts efficiencies of over 21% for both flat plate and concentrator InP solar cells. Initial efforts to produce cheaper, lighter weight and stronger cells are focused toward deposition of InP on silicon substrates and include a thin film approach. InP solar cells on board the LIPS III satellite show no degradation after more than one year in orbit. Laboratory experiments and calculations of array specific powers in several space orbits tend to confirm the superior radiation resistance of InP over both silicon and gallium arsenide. In Japan the current emphasis is on production of relatively large area InP cells, mainly for use on a small lunar orbiter. This latter space effort is described together with current efforts aimed at reducing the cost of InP solar cells intended for use in space. (Paper number IAF-ICOSP89-1-7.) 1-10. The Physics of Negatively Biased High Voltage Power Systems in Contact with the Space Environment Daniel E. Hastings & Mengu Cho Department of Aeronautics and Astronautics, 37-441, MIT, Cambridge, MA 02139, USA. Several proposed power systems for use on board space vehicles will involve the use of high voltage elements in contact with the space environment. The term high voltage here will be taken to mean that the voltage on the elements of the order of or greater than the energy for significant secondary emission from any surrounding dielectric surfaces. For materials used in the space environment this is typically a few hundred volts. An example of a power system that will use such voltages in contact with the space environment is a high voltage solar array [1]. In a high voltage solar array the interconnects between the solar cells will be biased positively or negatively depending on location and will interact with the space environment. This interaction can have a harmful effect on the operation of the solar array. We shall investigate the interaction of a negatively biased solar array interconnect with the space plasma. In recent work [1] the electrostatic drag was identified as an important consideration for these solar arrays. The model in Ref. [1] treated the array as a conducting plate and used a very simple model for the electrons. We have extended that model by use of a PIC code for studying the ions and electrons as they hit the surface. With this code we treat the case
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