Space exploration: How to make moon dust into oxygen
The problem is that such technology works by forming bubbles of oxygen on the surface of electrodes deep within the molten regolith itself. “It is the consistency of, say, honey. It is very, very viscous,” says Dr Burke.
“Those bubbles aren’t going to rise as fast – and may actually be delayed from detaching from the electrodes.”
There could be ways around this. One could be to vibrate the oxygen-making machine device, which might jiggle the bubbles free.
And extra-smooth electrodes might make it easier for the oxygen bubbles to detach. Dr Burke and his colleagues are now working on ideas like this.
Sierra Space’s technology, a carbothermal process, is different. In their case, when oxygen-containing bubbles form in the regolith, they do so freely, rather than on the surface of an electrode. It means there is less chance of them getting stuck, says Mr White.
Stressing the value of oxygen for future lunar expeditions, Dr Burke estimates that, per day, an astronaut would require the amount of oxygen contained in roughly two or three kilograms of regolith, depending on that astronaut’s fitness and activity levels.
However, a lunar base’s life support systems would likely recycle oxygen breathed out by astronauts. If so, it wouldn’t be necessary to process quite as much regolith just to keep the lunar residents alive.
The real use case for oxygen-extracting technologies, adds Dr Burke, is in providing the oxidiser for rocket fuels, which could enable ambitious space exploration.
MIT and Shaan Jagani
Obviously the more resources that can be made on the moon the better.
Sierra Space’s system does require the addition of some carbon, though the firm says it can recycle most of this after each oxygen-producing cycle.
Along with colleagues, Palak Patel, a PhD student at the Massachusetts Institute of Technology, came up with an experimental molten regolith electrolysis system, for extracting oxygen and metal from the lunar soil.
“We’re really looking at it from the standpoint of, ‘Let’s try to minimise the number of resupply missions’,” she says.
When designing their system, Ms Patel and her colleagues addressed the problem described by Dr Burke: that low gravity could impede the detachment of oxygen bubbles that form on electrodes. To counter this, they used a “sonicator”, which blasts the bubbles with sound waves in order to dislodge them.
Ms Patel says that future resource-extracting machines on the moon could derive iron, titanium or lithium from regolith, for example. These materials might help lunar-dwelling astronauts make 3D-printed spare parts for their moon base or replacement components for damaged spacecraft.
The usefulness of lunar regolith does not stop there. Ms Patel notes that, in separate experiments, she has melted simulated regolith into a tough, dark, glass-like material.
She and colleagues worked out how to turn this substance into strong, hollow bricks, which could be useful for building structures on the moon – an imposing black monolith, say. Why not?
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