According to an article in Nature, fission power is back on NASA‘s agenda thanks to its inclusion in a list of technology priorities for the space agency in a report by the National Research Council.
Space-based fission or nuclear power, should it be achieved, would have profound implications for space exploration and the settlement of other worlds. Propulsion methods using nuclear power would greatly reduce the time a space craft would take to reach other worlds, such as Mars. Nuclear power plants would greatly expand the amount of energy available for future space settlers.
NERVA
Nuclear thermal rockets, which use a nuclear reactor to heat propellant, is not a new technology. NASA produced a number of test engines in the 1960s under the Nuclear Engine for Rocket Vehicle Application program, designed to create a nuclear rocket engine for manned missions to Mars. According to The Encyclopedia of Science, the NERVA program achieved 4,500 megawatts of thermal power, 5,500 degrees of exhaust temperature, 250,000 pounds of thrust, a specific impulse of 850 seconds and 90 minutes of burn time. Despite the technological success of the program, NERVA was canceled by President Richard Nixon in 1973.
Modern Nuclear Thermal Rockets
Though the success of NERVA was impressive, it did not achieve the performance theoretically possible for a nuclear thermal rocket. A recent interview in Next Big Future with Tabitha Smith, who is affiliated with a private company that is exploring nuclear rockets, General Propulsion Sciences, suggests a nuclear stage attached either to a Space X Falcon Heavy or more suitably a Space Launch System vehicle could cut trip times to Mars in half.
Nuclear Electric Rockets
Another application for nuclear power for space propulsion would be to power an ion or plasma rocket with a nuclear reactor. A concept along these lines was explored in Project Prometheus, which envisioned a nuclear powered ion vehicle that would have explored each of the major moons of Jupiter. The project was canceled in 2003 due to budget reasons.
Ad Astra, a private company developing a plasma rocket called VASIMR, has a concept for a nuclear-powered version of its engine called VF-200M-N, The concepts involves a crewed Mars ship propelled by four VASIMR engines powered by 50 megawatt nuclear power plants. The company claims that such a ship would be able to reach Mars in two months, thanks to the superior specific impulse of its engines.
Space-Based Nuclear Power
The U.S. and the former Soviet Union have experimented with space qualified nuclear power plants. According to the World Nuclear Association, the U.S. flew a 45 kilowatt nuclear reactor that produced 650 watts of power in 1965. Russia has flown numerous nuclear-powered satellites, particularly under the Topaz program. But these power plants produced kilowatts of power. The technological leap to create a space qualified reactor in the megawatt range, which would be needed to make nuclear electric propulsion practical, would be considerable. But nuclear power would free NASA and other space organizations from reliance on lower energy solar power systems, fuel cells, and RTGs which use the decay of plutonium to power space probes to the Outer Planets.
Mark R. Whittington is the author of Children of Apollo and The Last Moonwalker. He has written on space subjects for a variety of periodicals, including The Houston Chronicle, The Washington Post, USA Today, the L.A. Times, and The Weekly Standard.
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