A former nuclear weapons site in Aiken County has an little-heralded tie to a space probe that completed a historic flyby of Pluto earlier this month.
Savannah River Site’s (SRS) HB Line and H Canyon facilities processed and produced plutonium (Pu)-238 oxide used to power NASA’s New Horizons space probe. The craft seized headlines the past two weeks as it provided NASA with the first-ever close-up views of the icy dwarf planet.
SRS spokesman D.T. Townsend told South Carolina Radio Network that the former weapons site has been providing fuel to NASA for years. “In addition to the New Horizons probe we’ve got three Mars missions and nine planetary missions that have all used this power system.”
In all he said over 27 space missions have used the power sources from the site. ”We here at the Savannah River Site have been using the H Canyon facilities for many years for a variety of missions and goals.”
SRS restarted the Pu-238 Oxide Line to produce the oxide for NASA’s Cassini space mission in 1991. Cassini was built to explore the Saturn system. Because this unmanned mission would take many years and needed to travel a long way, NASA needed a long-lasting, compact and incredibly reliable power source. To solve that problem, plutonium inside three Radioisotope Thermoelectric Generators (RTGs) was used. RTGs take the heat from the radioactive decay of Pu-238 and convert it into electricity. The RTG used for New Horizons currently produces about 200 Watts of electrical power.
The same type RTG used in Cassini was used to power New Horizons. RTGs are rugged and reliable, with no moving parts to wear out or break, making an RTG what the Energy Department considers the perfect power source for the spacecraft’s 9.5 year, 3-billion-mile journey to Pluto.
Both Cassini and New Horizons have completed their primary missions, but they are still functional. Cassini will continue to survey Saturn’s rings and New Horizons will continue to probe into deep space for many years to come.
Pu-238 Radioisotope Heater Units (RHUs) also use plutonium from SRS. RHUs do not produce electricity; they are only used as a heat source. Mars Rovers Spirit and Opportunity are solar powered, but use RHUs to keep axle grease from freezing.