Spacecraft power beaming and solar cell annealing using high-energy lasers

Abstract

Satellite lifetime is often limited by degradation of the electrical power subsystem--radiation-damaged solar arrays and failed batteries. Being able to beam power from terrestrial sites could alleviate this limitation, extending the lifetime of billions of dollars of satellite assets, as well as providing additional energy for electric propulsion that can be used for stationkeeping and orbital changes. In addition, laboratory research at the Naval Postgraduate School (NPS) has shown the potential to anneal damaged solar cells using lasers. This thesis decribes that research, preliminary work performed lasing a representative solar panel array, and a proposed Maui experiment to demonstrate the relevant concepts by lasing PANSAT, an NPS-built and operated spacecraft. The preliminary work done at Maui involved lasing a PANSAT silicon photovoltaic array using a 975 nm Yb:YAG source at output power levels of 7 W, 14 W and 21 W. These results matched those obtained under near-AM0 conditions atop Mount Haleakala (for the 7 W case) and extrapolated to match predicted output levels. Enough data points were collected at each power level to generate an I-V curve for the panel, identifying the open circuit voltage, short circuit current, and maximum power points. The efficiency of the panel varied from 13.1% (as expected for monochromatic light) at 7 W to 11.3% at 21 W due to uniform heating of the cells. These results represent a "ground truth" baseline from which further research can continue.