Fuel for deep space exploration running on empty

May 7, 2009 By SETH BORENSTEIN , AP Science Writer
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(AP) -- 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 U.S. space agency does not have enough 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 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 $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 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 $150 million to resume making it for the 11 pounds 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 doesn't 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.


On the Net:

National Academy of Sciences: http://www.nationalacademies.org/

©2009 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.

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5 / 5 (2) May 07, 2009
Is this the target market for NKs new export drive I wonder?
not rated yet May 07, 2009
Hahaha viv. I like the last line of the article. Pretty sure terrorists are going to create a space program so they can go out and pirate our plutonium.
5 / 5 (1) May 07, 2009
"Pretty sure terrorists are going to create a space program so they can go out and pirate our plutonium."

But they already have, its called the government :D
not rated yet May 07, 2009
Space pirates?!?!?! Hide your children!!! LOL
5 / 5 (1) May 07, 2009
So? Breed some new plutonium. Or buy it from one of the newer nuclear powers- Israel, Pakistan, India, North Korea, Iran, South Africa,...
not rated yet May 08, 2009
Haha! I can see it now. The United States will offer such a huge bounty on plutonium 238 that no criminal organization would fathom being stupid enough to waste it on an attack of any sort.
not rated yet May 08, 2009
My first thought matched GrayMouser's.

Then I stopped to consider. Wait. An engine can't run on more than one radioactive element? Can't run on more than one isotope?

This rings completely false...but if I'm wrong, someone with nuclear expertise correct me.

What I guess, a guess mind you, is that someone is looking for an excuse to restart plutonium processing.
not rated yet May 08, 2009
switch to dilithium.
not rated yet May 08, 2009
"switch to dilithium"

I didn't know there was a way to get energy from dilithium. Can you give a link or explain what reaction produces energy from it?
not rated yet May 08, 2009
I think he means that as a joke to do with Star Trek.
Buying it from new nuclear powers sounds good, they can't use it in nukes then!
not rated yet May 10, 2009
There is a lot of plutonium in spent nuclear reactor fuel stored around the country. I can be extracted from it. In fact, Europeans are doing this now and using the fuel to run second generation reactors.
5 / 5 (1) May 10, 2009
After reading up on Pu-238 and 239, it sounds to me like 238 is a more exotic and difficult to make isotope than 239.

It has a shorter half-life (87.7 years compared to 24,110 years for 239.) It gives off lots of Alpha particles, which induce a flow of electrons in the batteries, but doesn't require much shielding (paper-thin shielding is sufficient.) This might be beneficial as it is less likely to cause problems with the spacecraft's electronics.

Pu-239 is used both for weapons and power plants, but not in nuclear batteries, so no help there.

Perhaps there are other designs they could use that wouldn't require Pu-238, but I think it ends up being similar to the oil scenario: oil is just an ideal fuel for small vehicles, it packs so much energy. Pu-238 simply fits the bill for making small, simple, powerful and trouble-free batteries for far-flung space missions.

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