Nuclear rockets could cut cost of Moon base - NUCLEARSPACE MESSAGE BOARD (ACTIVE)

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TOPIC: Nuclear rockets could cut cost of Moon base

10kBq Jaro

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Date: Jun 28, 2007

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http://space.newscientist.com/article/dn12148-nuclear-rockets-could-cut-cost-of-moon-base.html Nuclear rockets could cut cost of Moon base 10:09 28 June 2007 NewScientist.com news service David Shiga Nuclear-powered rockets could save NASA billions of dollars in launch costs for its planned return to the Moon, a top nuclear scientist says. He argues that the higher efficiency of nuclear propulsion would reduce the number of launches needed to build a lunar base.NASA wants to start sending astronauts to the Moon by 2020, with the aim of building a permanent base there. Construction of a lunar base is expected to cost billions of dollars, much of which is due to the high cost of launching hardware from Earth to the Moon.But Steven Howe, director of the Center for Space Nuclear Research (CSNR) at the Idaho National Laboratory in Idaho Falls, US, says the cost could be reduced using more efficient nuclear-powered rockets. Howe presented the results of a recent CSNR study on the topic on Tuesday at the Space Nuclear Conference in Boston, Massachusetts, US. Carried out by university students funded by CSNR, the study examined the potential savings from incorporating nuclear power into NASA's Ares V, the launch vehicle being developed to haul heavy cargo, including parts for a lunar base, to the Moon.Under this scenario, the Ares V would use ordinary chemical rockets to launch into Earth orbit, where it would dock with the Orion crew vehicle that would have launched on a separate Ares I rocket. In NASA's current plans, a second stage on the Ares V would then ignite to send the crew and cargo out of Earth orbit and towards the Moon. But in Howe's scenario, this Earth-departure stage would be nuclear-powered instead.Fewer launchesHowe envisions using a nuclear engine similar to one designed and tested in the 1960s called Nuclear Engine for Rocket Vehicle Application (NERVA). In the NASA-funded NERVA design, hydrogen gas is heated by nuclear reactions in a uranium reactor and expelled to produce thrust.The higher efficiency of such an engine means almost 29 tonnes of cargo could be delivered to the Moon in a single Ares V launch, compared to 21 tonnes with the non-nuclear version. This would allow a 250-tonne lunar base to be constructed with only nine rather than 12 Ares V launches, Howe says.NASA has not said how much each launch would cost, but Howe estimates it at $1.5 billion each. At this price, three fewer launches would save $4.5 billion. Previous work, including a NASA study, have suggested that it would cost only $2.5 to $3 billion to develop the nuclear rocket technology, so even with development costs, the nuclear option could still save NASA billions, Howe says.Safety fearsOnce the technology is developed, it could also be used for missions to Mars and beyond, he says. But getting public support for a nuclear-powered rocket may be difficult. NERVA's exhaust was radioactive, but any new rocket would need to be designed in such a way that no radioactive material it produced would contaminate Earth, Howe says."If you've got to stand up in front of a crowd and say, 'Well, we're spewing radioactivity, but trust us, it's not coming down on you, or it's smaller than what you get [naturally] from space'", the project will not fly, he says.He points out that since the nuclear reactor is not turned on until it reaches space, the radioactive by-products that would present the biggest concern are not produced until the rocket is safely outside of Earth's atmosphere. The raw uranium fuel present before the reactor is turned on has a very low level of radioactivity, he says.Locked awayEven so, the uranium fuel could be encased in tungsten, a metal that has a very high melting temperature, so that even if the rocket exploded during launch or accidentally re-entered Earth's atmosphere, the reactor core would stay intact rather than dispersing uranium into the environment. "That tungsten core comes down as a chunk and you can recover it," he says.Robert Singleterry, who studies radiation safety at NASA's Langley Research Center in Hampton, Virginia, US, says properly designed nuclear rockets would be safe to use. He points out that plutonium-based nuclear power sources used to generate electricity on many previously launched space probes, such as NASA's Cassini mission to Saturn and New Horizons mission to Pluto, are much more radioactive than uranium-based rockets would be.As for crew safety, he says natural radiation from speeding space particles called cosmic rays presents a much bigger hazard than radioactivity from a well-shielded nuclear rocket. "The radiation they get [from cosmic rays] just from being outside the Earth's magnetic field overwhelms what they would get from the rocket," he told New Scientist. -- Edited by 10kBq Jaro at 12:42, 2007-06-28 __________________

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