A Lunar Nuclear Reactor
- From: as <assidd73@xxxxxxxxx>
- Date: Mon, 7 Sep 2009 21:24:48 -0700 (PDT)
miniturisation of nuclear reactors will be good news for many
applications here on earth.
-------------------------
http://www.technolo gyreview. com/energy/ 23247/
A Lunar Nuclear Reactor
Monday, August 17, 2009
Researchers at NASA and the Department of Energy recently tested key
technologies for developing a nuclear fission reactor that could power
a human outpost on the moon or Mars. The tests prove that the agencies
could build a "safe, reliable, and efficient" system by 2020, the year
NASA plans to return humans to the moon.
A fission reactor works by splitting atoms and releasing energy in the
form of heat, which is converted into electricity. The idea for using
nuclear power in space dates back to the late 1950s, when they were
considered for providing propulsion through Project Orion. In the
1960s a series of compact, experimental space nuclear reactors were
developed by NASA under the Systems Nuclear Auxiliary Power program.
But public safety concerns and an international treaty banning nuclear
weapons in space stopped development.
Now nuclear power is being considered for lunar and Mars missions
because, unlike alternatives such as solar power, it can provide
constant energy, a necessity for human life-support systems,
recharging rovers, and mining for resources. Solar power systems would
also require the use of energy storage devices like batteries or fuel
cells, adding unwanted mass to the system. Solar power is further
limited because the moon is dark for up to 14 days at a time and has
deep craters that can obscure the sun. Mars is farther away from the
sun than either the Earth or the moon, so less solar power can be
harvested there.
The new nuclear power system is part of a NASA project started in
2006, called Fission Surface Power, that is examining small reactors
designed for use on other planets. While nuclear power remains
controversial, the researchers say that the reactor would be designed
to be completely safe and would be buried a safe distance from the
astronauts to shield them from any radiation it would generate.
The recent tests examined technologies that would see a nuclear
reactor coupled with a Stirling engine capable of producing 40
kilowatts of energy--enough to power a future lunar or Mars outpost.
"We are not building a system that needs hundreds of gigawatts of
power like those that produce electricity for our cities," says Don
Palac, the project manager at NASA Glenn Research Center in Cleveland,
OH. The system needs to be cheap, safe, and robust and "our recent
tests demonstrated that we can successfully build that," says Palac.
To generate electricity, the researchers used a liquid metal to
transfer the heat from the reactor to the Stirling engine, which uses
gas pressure to convert heat into the energy needed to generate
electricity. For the tests, the researchers used a non-nuclear heat
source. The liquid metal was a sodium potassium mixture that has been
used in the past to transfer heat from a reactor to a generator, says
Palac, but this is the first time this mixture has been used with a
Stirling engine.
"They are very efficient and robust, and we believe [it] can last for
eight years unattended," says Lee Mason, the principal investigator of
the project at Glenn. The system performed better than expected, Palac
says, generating 2.3 kilowatts of power at a steady pace.
The researchers also developed a lightweight radiator panel to cool
the system and dissipate the heat from the reactor. The prototype
panel is approximately six feet by nine feet--one-twentieth the size
required for a full-scale system. Heat from a water-cooling system is
circulated to the radiator where it dissipates.
The researchers tested the radiator panel in a vacuum chamber at Glenn
that replicates the lack of atmosphere and the extreme temperatures on
the moon--from over 100 degrees Celsius during the day to below 100
degrees Celsius at night. The panel dissipated six kilowatts of
energy, more than expected--a "very successfully test," says Palac. On
the moon, the panel must also survive the dusty environment cause by
the regolith.
Lastly, the researchers tested the performance of the Stirling
alternator in a radiation environment at Sandia National Laboratories
in Albuquerque, NM. The objective was to test the performance of the
motor, ensuring that the materials would not degrade. The alternator
was subjected to 20 times the amount of radiation it would expect to
see in its lifetime and survived without any significant problems.
Mason says that the tests are very important in showing the
feasibility of the system and that the next step is for the
researchers to conduct a full system demonstration, by combining a non-
nuclear reactor simulator with the Stirling engine and radiator panel.
He says that these tests should be completed in 2014.
The researchers are also working on the power transmission and
electronics of the system. "A lunar base needs lots of power for
things like computers, life support, and to heat up rocks to get out
resources like oxygen and hydrogen," says Ross Radel, a senior member
of the technical staff and part of the advanced nuclear concepts group
at Sandia. His group is working on the systems dynamic analysis, a
computer model that predicts how the reactor will perform during
testing. "Nuclear is a stepping stone to move further out into manned
space exploration, " says Radel.
"It is a fascinating project and the only possible method of providing
power for a manned trip to Mars," says Daniel Hollenbach, a researcher
in the nuclear science and technology division at Oak Ridge National
Laboratory, who was not involved in the project.
Mason says that nuclear fission is one of a number of concepts being
tested as a power source for human missions to the moon and Mars, and
if selected, he says the technology could be deployed by 2020.
.
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