Engineering topics
Publications and source records attributed to Stella, P..
A technology review committee from NASA, the U.S. Department of Energy (DOE), and the Air Force Research Lab, was formed to assess solar cell and array technologies required for future NASA science missions.
Recent advances in space cell technology have produced substantial increases in Air Mass zero efficiency. Since these cells have been developed primarily for Earth orbiting missions, little is known of their behavior at distances far from the sun.
In October, 1998, the first of the NASA New Millenium Spacecraft, DS1, was successfully launched into space. The objectives for this spacecraft are to test advanced technologies that can reduce the cost or risk of the future missions.
The RAINBOW multi band gap system represents a unique combination of solar cells, concentrators and beam splitters. RAINBOW is a flexible system which can readily expand as new high efficiency components are developed.
Most spacecraft are powered by nuclear sources. Now, on smaller, low-cost missions, photovoltaic arrays are being planned. Because they may be exposed to high temperatures and radiation when exploring the inner planets, cell materials and array structures must be able to perform at high incidence angles.
Two solar array designs developed for the Advanced Photovoltaic Solar Array program are described. The goal of the program is to develop solar arrays with higher mass specific power and power density and good robustness. The specific design requirements are: a beginning-of-life value of 130 W/kg, and end-of-life goals of 105 W/kg and 110 W/sq m. The two array-wing designs consisted of a single blanket. The differences in the blanket material (25 micron-thick Kapton versus 50 micron-thick carbon-loaded Kapton), solar cells (100 micron-thick wrap around versus 50 micron-thick 2 x 4 cm planar contact cells), and performance objectives (proposed industry requirements versus mission objectives) of the two designs are examined.
This paper describes the current status of the JPL high performance solar array development program. Recent progress in solar cell, blanket and structure technologies is described. Future plans for integrating this work are discussed. The impact of the Mariner Mark II mission set on the future direction taken by this development program is assessed.
The NASA-OAST high performance solar array program is described. The rationale for this effort, its objectives and strategy, as well as progress made during the past 5 years, are discussed. It is shown that welded, ultrathin silicon solar cell array blankets are on the verge of technical readiness. It is argued that the most reasonable approach to achieving more significant performance improvements (to about 300 W/kg) involves the development of a higher efficiency (16-18 percent AM0) solar cell and a lightweight, efficient structure.
Photovoltaic development projects applicable to space power are identified. When appropriate, the type of NASA support that would be necessary to implement these technologies for space use is indicated. It is conducted that the relatively small market and divergent operational requirements for space power are mainly responsible for the limited transfer of terrestrial technology to space applications. Information on the factors which control the cost and type of technology is provided. Terrestrial modules using semiconductor materials are investigated.
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The electron-beam technique for evaporating a dielectric material onto solar cells is investigated. A process has been developed which will provide a highly transparent, low stress, 2 mil thick cover capable of withstanding conventional space type qualification tests including humidity, thermal shock, and thermal cycling. The covers have demonstrated the ability to withstand 10 to the 15th power 1 MeV electrons and UV irradiation with minor darkening. Investigation of the cell AR coating has produced a space qualifiable titanium oxide coating which will give an additional 6% current output over similar silicon oxide coated cells when covered by glass.