NASA is running out of nuclear fuel needed for its deep space
exploration.
The end of the Cold War's nuclear weapons
buildup means that the US space agency does not have enough plutonium for future
faraway space probes - except for a few missions already scheduled - according
to a new study released Thursday by the National Academy of
Sciences.
Deep space probes beyond Jupiter can't use solar
power because they're too far from the sun. So they rely on a certain type of
plutonium, plutonium-238. It powers these spacecraft with the heat of its
natural decay. But plutonium-238 isn't found in nature; it's a byproduct of
nuclear weaponry.
The United States stopped making it
about 20 years ago and NASA has been relying on the Russians. But now the
Russian supply is running dry because they stopped making it,
too.
The Department of Energy announced on Thursday that
it will restart its program to make plutonium-238. Spokeswoman Jen Stutsman said
the agency has proposed US$30 million in next year's budget for preliminary
design and engineering. The National Academy's study shows why it is needed, she
said.
"If you don't have this material, we're just not
going to do" deep space missions, said Johns Hopkins University senior scientist
Ralph McNutt, who has had experiments aboard several of NASA's deep space
missions.
So far only NASA undertakes these missions, so
the shortage limits the world's look at deep space, added Doug Allen, a
satellite power expert and member of the National Academy's study
panel.
By law, only the Department of Energy can make the
plutonium. Last year then-NASA administrator Michael Griffin wrote to
then-Energy Secretary Samuel Bodman saying the agency needed more
plutonium.
The National Academy report says it would cost
the Energy Department at least US$150 million to resume making it for the 5kg a
year that NASA needs for its space probes.
Without that
material "a lot of things will be shut down and they will stay shut down for a
long time", McNutt said.
Upcoming NASA missions using
plutonium include the overbudget and delayed Mars Science Laboratory, set to
launch in 2011, and a mission to tour the solar system's outer planets scheduled
for launch in 2020.
The last two missions to use plutonium
were the New Horizons probe headed for Pluto and the Cassini space probe that is
circling Saturn.
Plutonium-powered probes last a long
time. The twin Voyager spacecraft headed beyond our solar system and launched in
1977 are expected to keep working until about 2020, McNutt
said.
Solar power is preferable to plutonium because it is
cheaper and has fewer safety concerns, McNutt and Allen said. But solar power
just does not work in the darkest areas of space, including deep craters of the
moon.
Some have protested past nuclear-powered missions,
such as Cassini, worrying about potential
accidents.
AP