September 17, 2008

NASA Eyes Nuclear Power for Moon Base

Nuclear power could make a comeback beyond Earth if NASA
goes forward with a proposed a fission reactor in its future moon base.

A fission-powered system could generate up to 40 kilowatts
and give any lunar
enough power to supply eight houses on Earth. More importantly,
astronauts will require a reliable and steady energy source on the moon and

"The problem with power on the moon is that, depending
on where you're located, you may have 14 days of darkness," said Lee
Mason, an engineer at NASA's Glenn Research Center in Cleveland, Ohio, who
heads the project. "We think nuclear offers some advantages there in terms
of a continuous power source in sun or darkness."

Engineers envision a nuclear reactor buried
under the surface
of the moon so that lunar soil, known as regolith, can
act as shielding against the reactor's radiation. Power converters would sit
atop a tower jutting above the surface, changing the reactor's heat energy into
electrical energy for astronauts to use.

The tower would also boast two 50-foot (15-meter) panels
made of polymer composite material that could give off excess heat from the
nuclear reactor.

Far-flung robotic missions, such as the Cassini
currently orbiting Saturn, have relied on a different nuclear
technology, Radioisotope Thermoelectric Generators (RTG), which draws on the
energy from the natural decay of radioactive plutonium. Current RTGs produce
roughly 100 watts of electricity, in comparison to tens of thousands of watts
produced by nuclear fission reactors that split uranium atoms.

NASA previously launched just one nuclear reactor into space
in 1965, but the experimental SNAP-10A reactor shut down after just 43 days of
operation. Nuclear power made a brief reappearance in the Jupiter Icy Moons
Orbiter (JIMO) proposal, but the mission was scrapped
in 2005 due to budget constraints.

"JIMO was a little ahead of its time, a very ambitious
program, and it didn't just quite fit in with the budget projections,"
Mason told

Now the moon base proposal offers a new possibility, but
Mason's NASA Glenn team must first decide which power converter engine to use
for any nuclear reactor.

One design, a piston Stirling design from Sunpower Inc., of
Athens, Ohio, uses two back-to-back piston engines that cancel out each other's
mechanical vibration. The second design by Barber Nichols Inc. of Arvada,
Colo., relies on a closed Brayton cycle engine that has a rotary system not
unlike jet turbine engines. Both power converters can produce 12 kilowatts, or
roughly 40 kilowatts in a pack of four.

NASA engineers hope to test the efficiency of power
converters without the nuclear reactor in 2012 or 2013. A non-nuclear reactor
simulator would provide the heat source for the tech demonstration on Earth,
courtesy of NASA's Marshall Space Flight Center in Huntsville, Ala.

The space agency continues to ponder non-nuclear options such
as solar power
for a future lunar base. If NASA does use a nuclear reactor,
it will resemble reactor technology that the U.S. Department of Energy (DOE)
"has operated for many years," said John Warren, executive head of
NASA's Space Power Systems Program in Washington, D.C.

Mason said that the project should finish on schedule if it
continues receiving the $10 million funding shared between NASA and the DOE.

"We would like to design a system that can last eight
years without any maintenance whatsoever," Mason said. "The technology
is there to achieve that."