tim (02/12/83)
Gleamed from Electronic Engineering Times. Monday, Jan. 31, 1983. Lockheed Begins Testing Solar Array Wing for Space Shuttle Sunnyvale, Ca. - Lockheed Missiles & Space Co. here has started testing a solar array wing for the space shuttle that is said to yield more power per cubic inch of solar payload than anything previously flown. The Solar Array Flight Experiment (SAFE) will occupy 614.25 cu ft. (13.5 ft. X 3.5 in X 13 in.) in the shuttles's payload bay and will unfurl to dimensions of 13.5 ft. high x 105 ft. long x 0.0023 in. thick. When fully operational, the solar wing will provide 12.5 kW. "That is about three times the power per cubic inch of space than any solar power system that has flown," said Gary Turner, Lockheed project manager. One of the reasons for the jump in watts per cubic foot is an innovation that helped to reduce the assemble cost, according to Turner. This was the use of Kapton plastic as the basic mounting structure, rather than the conventional rigid honeycomb-type structure usually made of aluminum. "Because we used this material for the structure, we were able to build the cicuitry right into the Kapton sub- strate. In a way, we've married printed-circuit technology and solar technology. This Kapton membrane is -.0023 in. thick. It acts as sort of a membrane, which, pulled taut, becomes a pretty stable structure," said Turner. Lockheed is building the solar wing for NASA's Marshall Space Flight Center. The array is being developed to power the shuttle's stay in space beyond the spacecraft's present 14-day duration. However, according to Turner, "Arrays like this will ultimately be a power source for a space station or space lab, or for something like a space-based manufac- turing operation." The $5.5 million contract for the solar wing was given to Lockheed in 1975. Delivery to Cape Canaveral in Florida is scheduled for the December. However, said Turner, the wing will be ready to ship in March. SAFE is to be tested on the 14th space shuttle mission, presently scheduled for May 6, 1984. The solar wing will carry only two panels of the silicon-crystal cells on that flight, rather than the wing's capacity of 85 panels. The power output will be about 150 W. When the 14th space shuttle mission goes up, a new type of solar cell will be tested. The cell, in addition to the Kapton substrate, has significantly contributed to the solar wing's power/volume ratio. The cell, known as the "wraparound contact cell," was developed for the solar wing. With the wraparound cell, both the negative and positive contacts are located on the back of the cell. The negative contact is wrapped around the cell to its back. Doing it this way presents a number of advantages," said Turner. "It allows more surface area of the system to be exposed to the sun. The equivialent of 5 percent more square footage is gained. Next, doing it this way allows use of highly automated printed-circuit techniques for assembly. As a result, the assembly cost has been reduced by a factor of two." The cells, developed by Applied Solar Energy Corp, in City of Industry, Ca., have a 13 percent conversion effi- ciency. The whole purpose to the approach, said Turner, was to reduce the volume in the shuttle's payload bay needed for the power array. "The thing that is precious in the payload bay is volume. Almost all payloads run out of volume before weight, so a premium was placed on packaging efficiency," he said.