An experiment developed by the
Naval Research Laboratory (NRL) recently flew aboard the space
shuttle Columbia, STS-87. The Sodium Sulfur Battery Experiment
(NaSBE) was designed, built and tested at NRL's Naval Center
for Space Technology under the sponsorship and request of the
Air Force's Phillips Laboratory in Albuquerque, New Mexico.
Sodium sulfur (NaS) cells use
molten sulfur and sodium electrodes with a solid ceramic electrolyte
which conducts sodium ions. To operate, NaS cells must be heated
to 350 degrees Celsius (662 degree F) to melt the sodium and
sulfur and to increase the mobility of sodium ions through the
electrolyte.
Scientists are testing the sodium
sulfur battery cells' performance for possible future use in
powering satellites. NaS battery cells have three times greater
energy than the specific energy of nickel hydrogen (NiH2) batteries
that are currently used to power satellites. "Thus for the
same amount of energy storage, a NaS battery weighs 60% less
than an equivalent NiH2 battery," explains NRL's Mr. Chris
Garner, one of the principal investigators for the experiment.
The NaS batteries offer a potential savings of money, since a
lighter payload costs less to launch. And because the NaS batteries
weigh less, they would also allow more payloads to be carried
on each satellite.
The experiment launched four
40 ampere-hour cells, built by Eagle Picher in Joplin, Missouri.
The cells were launched charged and at ambient temperature. On
orbit, the cells were heated to 350 degrees Celsius. The cells
were then discharged and charged in different regimes that simulated
the operation of the batteries in geosynchronous and low earth
orbit satellites. On the final test of the experiment, the cells
were discharged to different states of charge and then cooled
down to ambient temperature. Once they are returned to earth,
the NaS cells will be subjected to a destructive physical analysis
to study how the cells performed in zero gravity.
Experiment operations were conducted
from the NASA Goddard Space Flight Center Payload Operation and
Control Center. On orbit, the NaS cell performed as well or better
than their performance on Earth. All phases of the experiment
were successful, and the experiment was returned to NRL on December
23.
The U.S. Naval Research Laboratory is the Navy's full-spectrum corporate laboratory, conducting a broadly based multidisciplinary program of scientific research and advanced technological development. The Laboratory, with a total complement of nearly 2,500 personnel, is located in southwest Washington, D.C., with other major sites at the Stennis Space Center, Miss., and Monterey, Calif. NRL has served the Navy and the nation for over 85 years and continues to meet the complex technological challenges of today's world. For more information, visit the NRL homepage or join the conversation on Twitter, Facebook, and YouTube.
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