Space nuke boffin: NASA Moonbase needs nuclear rockets

Could face stiff opposition from granola tendency

One of America'a top nukes-in-space boffins says it's time to consider nuclear-powered rockets again. He reckons atomic boosters could cut the cost of NASA's upcoming Moonbase plan.

Stephen Howe is director of the Centre for Space Nuclear Research, a division of America's Idaho National Laboratory (INL), and he was speaking at Tuesday's Space Nuclear Conference in Boston. INL already makes nuclear systems for use in space: it is "becoming a single source for radioisotope thermal generators (RTGs)."

RTGs are essentially nuclear batteries, able to supply electricity for many years without going flat. They are used in deep-space probes which will travel far from the sun, and so can't use solar panels to get their juice. RTGs are also required for "national security missions," generally taken to mean military/spook satellites.

But Howe reckons that there's more to nukes in space than just providing electricity. He says that nuclear power should be used for propulsion, too. According to an article in New Scientist, his plan is to update a 1960s design called Nuclear Engine for Rocket Vehicle Application (NERVA) to carry payloads from Earth orbit to the Moon.

NERVA-type rockets use a fission reactor to heat up hydrogen and blast it out of the thrust nozzle at extremely high speed, faster than can be achieved by normal chemical-powered boosters. This allows a nuclear-driven spacecraft to achieve more with a given amount of liquid fuel, or "reaction mass." The NERVA test programme had its problems - not least the fact that the reactor tended to come apart and fire itself out of the exhaust - and was terminated in 1972 during NASA budget cuts.

Howe and his team reckon that the greater efficiency of nuclear drive would allow each Moon shot to carry an additional eight tons of payload, which would mean fewer launches being needed. He thinks the savings from a lower number of launches would more than offset the cost of updating the original NERVA design, perhaps yielding overall savings of as much as $2bn.

One of the reasons the original NERVA was never used was that the hydrogen reaction mass became radioactive as it passed through the reactor. This would still be true for Howe's proposed new design, but in the case of the Moonshot plan the nuclear rocket would only be fired outside the Earth's atmosphere, so there would be no ecological or health risks. Space is full of natural cosmic radiation anyway, so it wouldn't be meaningful to suggest that radioactive rocket exhaust was polluting it.

That said, the nuclear rocket's uranium core would be a hazard before it was ever fired, and it might be involved in a catastrophic explosion while being lifted to orbit by a normal rocket. But Howe reckons it could be encased in tungsten, which is extremely strong and doesn't melt even under high temperatures. In the event of a disaster, it would come down as a single chunk and be recovered safely.

In the end, it's fair to say that if the human race is ever going to develop space transport in a serious way we will need to develop something more powerful than chemical rockets to do it with. That means some form of nuclear-powered rocket, unless we're willing to accept that that it will always take months, years or decades to move between planets in the solar system. Anyone who sees the human race ever achieving a spacefaring civilisation should probably be in favour of nuclear-propelled spaceships.

That doesn't necessarily mean approval of NERVA-type designs, of course: there are other things on offer. But it's noticeable that most of the more technically rigorous sci-fi authors and other future visionaries have simply assumed that - barring antigravity or something - nuclear rockets would have to come into widespread use, or there could never be any real travel in space.

But space-loving techheads have a big public-relations hill to climb here. Many people are violently opposed to nuclear technology at any time, and its use in space seems to arouse especially virulent opposition - for all that it's been going on for decades without any apocalypse. RTG-type power packages have flown on dozens of exploration missions - most notably the Cassini probe to Saturn and the New Horizons mission to Pluto.

Nuke-fear protesters rallied against Cassini's launch, and even panicked about its subsequent close passby to Earth in order to gain a gravitational "slingshot" assist two years later. It's as well they didn't live in the USSR back in the old days; they'd have probably died of fright if they knew what was going on there.

The Soviets, bless them, sent up spy satellites equipped not just with mere RTGs but actual nuclear reactors*. It's generally believed that several of these reactors were involved in explosions and accidental re-entries to the Earth's atmosphere. (And yet we're all still here - though anti-nuke people would contend that millions fewer people would have died of cancer if the Russians hadn't done all that terrible stuff.)

All in all, the odds of Howe getting his nuke-rocket plan built into NASA's Moonbase programme seem slim, and the dreams of science fiction will remain just that for the foreseeable future.

The New Scientist report is here

*Though the plutonium preferred for RTGs is usually seen as nastier than uranium reactor fuel. Howe's NERVA-type rockets would use the nicer uranium.

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