- WASHINGTON -- NASA is considering
the use of nuclear-powered spacecraft in the future to explore Mars - an
idea certain to ignite a firestorm of protest on Earth, SPACE.com has learned.
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- No such spacecraft would be launched to Mars anytime
soon.
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- Probes targeted for launching in 2001 or 2003 still would
carry conventional solar panels or wings that would draw their power from
sunlight.
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- A Primer on Radioactive Space Exploration
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- The United States and Russia have used dozens of nuclear-powered
spacecraft in orbit around Earth and in deep space for more than 40 years.
<link
Want to Learn More?
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- But the plan to use nuclear power at Mars, as was done
with the 1970s-era <link
Viking mission, is "not off the table," said Ed Weiler, NASA's
associate administrator for space science. "For better or worse, Mars
is a faraway planet and using these things makes a lot of sense when you're
trying to build a robust program there."
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- Both the <link
Galileo and <http://www.space.com/space/cassini.html Cassini deep space
missions had nuclear power packs known as radioisotope thermoelectric generators
(RTG's) on board. These were needed to provide electrical power in the
far reaches of the solar system where sunlight is minimal.
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- Dan McCleese, Chief Scientist of the Mars Exploration
Directorate at NASA's Jet Propulsion Laboratory said that the space agency
is encouraging Mars planners to look again at using RTGs on Mars.
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- The idea is gaining momentum as NASA puts the final touches
on its new multi-year, <link
$1.5 billion program to explore Mars. The revamping of the Mars program
follows last year's losses of the Mars Climate Orbiter and the Mars Polar
Lander.
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- An independent panel led by former Lockheed Martin executive
Thomas Young is studying those failures and is to issue its report on March
15. NASA plans to reveal its restructured plans for Mars the same day.
The agency is expected to announce:
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- * It has canceled a lander spacecraft for 2001 and will
instead send one in 2003 that lacks a robotic rover but includes new communications
gear to help ground controllers better monitor the lander. The added gear
would allow NASA to maintain contact with the spacecraft during its descent
to the surface and avoid a repeat of Polar Lander, which vanished without
a peep on the way down. * It will fly an orbiting spacecraft in 2001 as
planned but it will have improved technology that was not aboard the doomed
Climate Orbiter. * A mission to return a sample of the Martian soil to
Earth is still a key scientific goal but NASA will not be held to a specific
time on when it might fly. The mission, which had originally called for
separate launches in 2003 and 2005, will still include European participation
and will be launched on a French <link
Ariane rocket. * The primary scientific goals at Mars are to search
for evidence of past life and investigate the planet's climate and resources.
The thread that connects all of those is water and future missions to Mars
will strive to find out where the water was on the surface, where it is
now and what it did during the transition.
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- "Let's be bold and say it up front," Weiler
said in an interview Thursday. "We're looking for two things. Is there
life and can we live on Mars and colonize it. As for the missions, we will
fly them when we have a good chance of success. I am not going to sign
on the dotted line for any mission unless it stands a good chance of succeeding."
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- One way to build a more robust exploration of Mars is
through nuclear-powered spacecraft. "I,m not saying we're going to
use radioactive power sources in the near term," Weiler said. "Something
like that takes years to get approvedBut people forget that the reason
Viking lasted so long on the surface of Mars was because it had one of
these."
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- The Viking 1 and 2 landers were launched in 1975 and
arrived at Mars in 1976. Viking 1 lasted until November 1982 and Viking
2 stopped transmitting in April 1980. The solar-powered Polar Lander, by
comparison, was designed to last just 90 days, the same lifespan as that
of Mars Pathfinder in 1997.
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- NASA has flown a total of 25 missions with radioactive
power packs since the 1960s.
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- NASA last sent radioactive material, Plutonium-238, to
Mars in 1997. The rover Sojourner carried three radioisotope heater units.
Each of the units -- about the size of a C-cell battery -- contained a
0.1-ounce (2.6 grams) of the isotope to keep the vehicle's electronics
warm.
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- As program managers see it, radioactive power would only
be needed for spacecraft that land on the surface and any rovers that those
craft might carry. Any decision to outfit such landers with nuclear power
would have to be made by the White House and would need to be coordinated
with such agencies as the Department of Energy and the Environmental Protection
Agency.
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- "NASA doesn't make a decision by itself to fly nuclear
material," Weiler said. "There's a long list of requirements
and quite a list of agencies that are involved. It takes years to fly those
types of missions."
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- One reason it takes so long is because such missions
tend to touch off protracted legal battles. Anti-nuclear protesters filed
suit in federal court to stop both the 1989 launch of the Galileo probe
to Jupiter and the 1997 launch of Cassini to Saturn, arguing the missions
put Americans at risk from radiation exposure in the event of a launch
accident.
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- "We'll be very much on top of it and organizing
to stop it," said Bruce Gagnon, of the Global Network Against Weapons
and Nuclear Power in Space in Gainesville, Fla. "Our concern goes
beyond launch problems. It's also the health and safety of workers who
have to produce this material. What NASA has in mind is a massive infusion
of nuclear material in the space program"
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- Gagnon was among those filing a federal suit to stop
the Galileo and Cassini launches and said his ground might do the same
with nuclear-powered Mars missions.
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- In the case of Mars, nuclear power on a spacecraft "solves
the problem of what happens at night," said Carl Pilcher, NASA chief
of solar system exploration. "At night you get to stay warm. You need
a power system for the heaters in order to keep the lander alive. It's
thermal cycling, going from warm in the day to cold at night, that kills
you at Mars."
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