Oxygen-from-Moon-dirt passes vomit comet test

American boffins say they have developed a viable process for making oxygen out of moon dirt, which could allow humans to live for long periods in lunar bases. The new tech has been tried out under the equivalent of the moon's one-sixth-G gravity aboard NASA's famous "vomit comet" low-gee simulator plane.

A long-term moonbase, which is still officially part of NASA's plans for the coming decades - though the whole US manned space programme is seriously imperilled by lack of funds - would surely require a means of producing oxygen locally. Astronauts need the precious gas to breathe, of course, but the need to refuel rockets on the Moon is perhaps even more critical. If all the fuel to be used on the Moon-to-Earth return trips must first be hauled up from Earth to Moon - requiring the burning of huge amounts more rocket juice to do so - the vast majority of the programme's budget and activity will be eaten up simply moving propellants through space.

A sustained moonbase programme would still be hugely expensive with lunar fuel production, but not nearly as much so: and a source of rocket fuel on the Moon could in time make the further exploration of the solar system much more economical as well. Fuel for voyages to Mars or the asteroids, rather than having to be hauled up through Earth's heavy gravity, could be fired up relatively easily and cheaply from the lunar refineries.

So the human race - assuming it would like to explore personally beyond its home planet* - would like to have rocketfuel refineries on the Moon. With current chemical rockets, the mainstream spaceflight technology, this also means oxygen. So how to make oxygen out of Moon dirt?

Well, according to boffins at Case Western Reserve uni in Ohio, the way ahead is to scoop up moon dust (probably using a robotic digger machine) and dump it into a hopper. Metal oxide particles of the correct size would be sifted from the dirt and heated with hydrogen at 1000°C, so breaking out the oxygen and attaching it to hydrogen to form water, which could then be used to produce oxygen easily via electrolysis.

The tricky part is the sifting, a process well understood in Earthly gravity but less so under the reduced lunar field. Hence the Case Western brains have been taking their prototype refinery feed machines on flight in NASA's "vomit comet", a aeroplane which zooms upward and then enters a controlled dive to provide either weightlessness inside its cabin or - as in this case - an environment similar to that on the Moon.

"It was as if they were working on the moon, 20 seconds at a time," says Case Western engineering prof David Zeng.

The boffins tried out two different dirt-sorting mechanisms, a "sifter that operates much like a flour sifter" and a jiggling "vibro-table".

"As on Earth, the process[es] worked," report Case Western spokespersons.

Exactly which type of sifter will go into the final oxy-refinery design will depend on further analysis of the results, but it seems clear that a working lunar oxygen factory can practicably be built.

As to how much oxygen such a plant could produce, that would be capped by the amount of power available to run it. Solar power isn't a good option for the Moon in general, owing to the fortnight-long nights, but there are thought to be a few locations on polar crater rims where solar energy could be usefully harvested. NASA's Lunar Reconnaissance Orbiter is even now trying to find any such location that might be accessible by lander (a flat spot to set down on would be required).

The other option is a nuclear reactor - but there are those who would say that once you have powerful nuclear reactors in space you no longer need oxygen rocket-fuel. Much more efficient plasma drives would be an option if large amounts of electricity were available.

It's a knotty debate - and one which may be irrelevant in light of NASA's budget problems. But Julie Kleinheinz, aerospace engineering prof at Case Western and veteran vomit-comet rider, says that the oxy-factory tech will still be of use even if Moonbase plans are scrapped in favour of a straight-to-Mars strategy.

"The technology is useful outside the lunar system," she says. "It's applicable to Mars."

There is known to be actual water ice on Mars, however, so the dirt-refinery tech might not be as applicable there. ®

Bootnotes

*Whether it does or not is beyond the scope of this article. We'll just throw in Arthur C Clarke's famous remark:

If man survives for as long as the least successful of the dinosaurs - those creatures whom we often deride as nature's failures - then we may be certain of this: For all but a vanishing instant near the dawn of history, the word "ship" will mean "spaceship".

(Any comments referring to the 1990s-era UK tabloid bullshit regarding Clarke's sex life will be spiked. It would be nice if we didn't have to tell you that, but experience suggests we do.)