Fission power for lunar living

11 September 2008

Lunar reactor (NASA) 

A visualisation sees an underground unit with enormous radiators
(Image: NASA)


NASA engineers are actively investigating nuclear fission as a possible source of energy for a lunar outpost and the agency has signed contracts for the first stages of the development of a demonstration system.


The US space agency is currently working with international partners towards the goal of returning people to the Moon and establishing a permanent lunar outpost by 2020. However, the problem of power supply for lunar activities is a thorny one. During the day, solar power is one obvious solution. But lunar nights can last up to 334 hours in some places, and even at the moon's south pole, the sun never rises high. A fission surface power system would be able to produce power steadily even in harsh environments such as the Moon, or even Mars, without relying on sunlight.


Such a system uses the fission of uranium in a reactor to generate heat that is then converted into electricity, and has four primary components: a heat source (the uranium); power conversion; heat rejection and power conditioning; and distribution. Similar steps are employed to generate electricity in a terrestrial nuclear power station, but a nuclear power plant in space would be very different from one on the earth. For a start it would be very much smaller, generating some 40 kW of power - even the smallest civil nuclear reactors today typically have capacities measured in hundreds of megawatts. The nuclear reactor itself could be buried below the lunar surface, and there would be no need for cooling towers - any leftover heat energy would be radiated into space.


NASA's Glenn Center in Cleveland, Ohio has now signed contracts for the design and analysis of two different types of advanced power conversion units, which according to Fission Surface Power Project manager Don Palac will be a key factor in demonstrating the readiness of viable and cost-effective nuclear power options for use on the Moon and Mars.


"Our goal is to build a technology demonstration unit with all the major components of a fission surface power system and conduct non-nuclear, integrated system testing in a ground-based space simulation facility," said Lee Mason, principal investigator for the test at the Glenn Center. The team wants to demonstrate technical readiness early in the next decade, when a decision is expected on the type of power system to be used on the lunar surface.


The two design concepts under investigation both generate a total of 12 kW of power. The first, by Ohio-based Sunpower Inc, uses two opposed piston engines coupled to alternators, while the second, from Barber Nichols Inc of Colorado, will employ a closed Brayton cycle engine with a high speed turbine and compressor coupled to a rotary alternator. After a year-long design and analysis phase, one of the two contractors will be selected to build and test a prototype power conversion unit that will ultimately be incorporated into a non-nuclear demonstration system (with the heat source provided by liquid metal coolant rather than fission) to be ready for test operations around 2012-2013.