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NASA pitching nuclear power for probes

By
IRENE BROWN, UPI Science News

CAPE CANAVERAL, Fla., Feb. 15 (UPI) -- The U.S. government wants to restart research on nuclear propulsion systems for space probes and buy radioactive plutonium generators to power the robots for long-duration missions where the sun doesn't shine.

"It's been a long time since you could say the N-word in Washington," said NASA's space sciences chief Ed Weiler. "But this is the right thing to do."

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For 40 years, NASA has been exploring the solar system in the same manner: catapulting a space probe off the ground with a burst of chemical rocketry and then watching it coast, often for years and years, to the targeted planet. Occasionally, the probes pick up a little speed by steering themselves close to a passing planet and bouncing off its gravitational energy.

With nuclear propulsion, even the farthest corners of the solar system, such as Pluto, which has never been explored, will be within reach, say scientists who have been pushing for a new research and development initiative for years.

NASA has no plans to use nuclear systems to propel probes off the launch pad. Rather, the nuclear reactors, which like nuclear power plants on Earth would use enriched uranium, would not be started up until they were in orbit.

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"We're not talking about new Star Trek technology," Weiler said. "We're looking at a research program where the No. 1 priority will be to design these systems for safety. They will be safe no matter what happens on the launch pad."

NASA's last major effort to develop nuclear propulsion was in the 1960s, however small technology development projects have been ongoing at several of the agency's field centers. Alabama's Marshall Space Flight Center, for example, has been working on a reactor that for test purposes does not use nuclear materials.

President Bush's 2003 budget requests $125.5 million for NASA's Nuclear Systems Initiative, which also includes purchasing electrical generators powered by radioactive plutonium from the U.S. Department of Energy. NASA has used these systems, which are called radioisotope thermoelectric generators, or RTGs, in dozens of spacecraft, including Galileo, which is in orbit around Jupiter, and Cassini, en route to Saturn.

The agency currently has one RTG in its inventory, Weiler said.

Unlike solar-powered systems, RTGs are not dependent on how much sunlight falls on the spacecraft. RTGs, which convert heat from decaying radioactive plutonium into electrical energy, also are impervious to dust and other inclement conditions on a planet's surface and can greatly extend the amount of time a probe can remain operational.

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The successful 1997 Mars Pathfinder mission, which was solar-powered, lasted less than three months. If the lander and rover had been outfitted with RTGs, the mission likely would have lasted years, said NASA's Mars exploration program head Jim Garvin.

Until the Department of Energy restarts its own plutonium production lines, the government plans to buy the material from the Russians, said Earl Wahlquist, associate director for the agency's Space and Defense Power Systems.

NASA plans to delay launch of its 2007 Mars rover for two years to allow time for engineers to switch the probe from solar to nuclear-powered electrical systems.

Nuclear powered rockets, however, remain decades away.

"We welcome the proposal to develop nuclear power and propulsion technology to make the entire solar system more accessible with much shorter flight-times and more powerful investigations at the planets," said Wesley Huntress, president of the California-based Planetary Society. "These developments will revolutionize space exploration in the same way that the Navy was revolutionized by nuclear power."

Even before Congress has begun debating NASA's nuclear revival, the proposal has raised concerns of military implications of space nuclear systems.

"The distinction between civilian and military is being rubbed out," said Bruce Gagnon, coordinator of a Florida-based advocacy group called the Global Network Against Weapons and Nuclear Power in Space. "The nuclear rocket that's being developed is going to have military implications."

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NASA officials disagree and point out the need for space nuclear systems is based purely on the laws of physics.

"The sun ceases to be much of a useful power source beyond Jupiter," said Weiler. "That's not really the way to explore the solar system."

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