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.