Mining the moon
With the space race back on, engineers are considering the potential of using lunar resources to fuel further exploration of the solar system. Jon Excell reports
When, in July 1969, Neil Armstrong stepped onto the surface of the Moon, anything seemed possible. The wildest imaginings of science fiction writers had been made fact. The rest of the solar system beckoned. And few would have predicted that manned lunar exploration would stutter to a halt a few years later.
Finally, after a decades long hiatus, a lunar renaissance looks to be underway. A host of probes and orbiters are scheduled for launch and manned missions are expected to follow. Both the US and Russia have stated their intentions to put men back on the Moon by 2025, while Europe, India, China and Japan are also mulling over the options.
And while a trip to the Moon is still a potent political symbol, today’s motivations for getting there are more varied than they were last time around.
For a start, with the few samples returned by the nine manned lunar missions outliving their usefulness many years ago, there is unfinished scientific business. But beyond this, the Moon is increasingly seen as in important staging post to the further exploration of the solar system; its low gravity making lift-off a far less energy-intensive process than it is on Earth.
To do all of this will require a long-term manned presence on the Moon, and indeed both the US and Russia are also planning manned lunar bases. The problem is that with current technology it’s simply not possible to take enough food, water and fuel to last for much longer than a few days.
That is why a loose-knit alliance of space scientists and members of the mining community are increasingly considering the development of so-called In Situ Resource Utilisation (ISRU) techniques that will enable the next generation of astronauts to make use of their destination’s raw materials.
Some pretty bold claims have been made about mineral resources on the Moon, but according to Birkbeck College planetary scientist Dr Ian Crawford the first challenge is finding out exactly what is up there.
’There’s a certain amount of jumping the gun in some quarters about lunar resources,’ said Crawford. ’The truth of the matter is we haven’t actually yet explored the Moon enough to know whether there is anything economically useful there or not.’
With the six Apollo landings and three Russian landings all bringing back samples from the same general area on the near side close to the equator we still have a great deal to find out. ’Most of the Moon is pretty much unexplored with the exception of what can be seen by remote sensing from orbital instruments,’ added Crawford, who is also project lead on MoonLite, a UK plan to create a network of sensors on the Moon by firing projectiles into its surface (The Engineer June 2008).
One of the most useful resources that is thought to be present on the Moon is the water ice that scientists believe may exist in the shadowed craters at the lunar poles.
Deposited by comets, water ice, if present in large enough quantities, could provide many of the materials essential for a long stay in space, explained Crawford. ’If you’ve got ice, you’ve got a supply of water that is useful in itself and it is electrolysable into hydrogen and oxygen — your two main rocket propellants of choice.’ So far, evidence of ice deposits is based on the rather sketchy data acquired from an instrument flown around the Moon on the lunar prospector spacecraft in the late 1990s. But Crawford is hopeful that NASA’sLunar Reconnaissance Orbiter (LRO), which is scheduled for launch this June and able to detect smaller quantities of ice, will provide a clearer picture.
Another lunar resource that is often spoken about is Helium 3 (He-3), a non-radioactive isotope of helium that some have suggested could even be mined on the Moon and brought back to Earth to power future fusion reactors. Crawford is sceptical. ’We know He-3 is present in the lunar regolith because it has been extracted from the Apollo samples, but it is present in the Apollo samples in such small amounts — of the order of 10 parts per billion — that the amount you would need to make a significant difference for nuclear energy production on earth would mean strip mining thousands of square kilometres of lunar surface.’ But He-3 could have potential for powering future spacecraft propulsion systems. ’In the context of future space nuclear power systems where you’d require much more modest quantities, then, assuming a He-3 reactor is ever made to work, He-3 might be less unrealistic.’
But even if there is no ice and He-3 turns out to be a dead end, the moon still has plenty to offer, and numerous scientists have devised methods for extracting both hydrogen and oxygen from the lunar regolith itself.
Of particular promise is a technique that was originally developed by UK firm British Titanium for extracting titanium from ilmenite, a titanium iron-oxide mineral that occurs in some lunar lavas. In the process of extracting titanium, oxygen is also produced and, according to Crawford, the company is now investigating the potential of the technique for producing oxygen on the moon.
Metals such as titanium and aluminium could also be a useful lunar resource for future astronauts.
Carole McLemore, project lead for NASA’s ISRU programme, is currently looking at different methods of extracting aluminium and titanium from lunar rock for use in fabrication processes on the Moon. According to McLemore, NASA’s vision is that astronauts will be able to use rapid-manufacturing techniques in order to produce components and tools from lunar metals.
But while NASA is looking at a range of extraction techniques and instruments that might be used on the moon, its activity is being mirrored by unlikely allies in the mining industry.
Prof Greg Baiden is Canadian Research Chair in robotics and mine automation at Laurentian University.
A veteran of the Canadian mining industry, Baiden is currently working on the development of teleoperated mining robots for use in extreme environments.
His techniques harness the latest breakthroughs in telecommunications and robotics technology and are primarily of interest for mining deep beneath the sea. But his work has also attracted the interest of the Canadian space agency, for whom he is currently sketching out plans illustrating how future lunar mining facilities might work. ’Today we mine the 30 per cent of the planet that is above the water surface,’ he said, ’and we’re likely to go and mine underwater as we start to run out of surface resources. Running robots underwater is allied in technology to what might happen on the Moon.’
And despite some analogies with mining on the earth, Baiden warned that the low gravity on the Moon — one-sixth of that on earth — will present some severe engineering challenges. ’A lot of the density separation techniques used on earth rely on gravity and would have to be rethought,’ he added. ’Low gravity would also have a bearing on the size and scale of mining equipment. For instance, drilling on earth is almost always a function of gravity: for example, you need a machine that weighs a few tonnes to get the force you need to drill a hole, then if you move to the Moon, the mass you need goes up by six times, which means the weight goes up by six times and the cost to get it there goes up.’
Intriguingly, while large-scale commercial mining of the Moon is unlikely to be economical, Baiden believes there may be a strong case for using mining equipment to build and excavate an underground lunar base. ’I think there’s going to be very significant investigation in terms of radiation exposure, micrometeorite exposure, and temperature extremes that are going to force a very significant look at building an underground habitat as opposed to a launched habitat,’ he said.
Such suggestions may sound far-fetched, but Baiden claimed space scientists are increasingly interested in what the mining industry has to say. ’Mining people have a lot to contribute to the space programme, and I think that the space programmes are starting to recognise that. I went to a recent NASA conference, and the general impression I walked away with was that everybody was trying to do their best to figure out how to get into orbit and get to another planet, but not many people have given a lot of thought to what we’d do once we get there.’