Ferrying oxygen to the moon might cost $100 million per ton, so researchers have developed a reactor that can extract oxygen from Moon rock:
NASA has been looking for ways to get oxygen from Moon rock for several years. In 2005, as part of its Centennial Challenges programme, the agency offered a US$250,000 prize to the first team to come up with a piece of kit that could extract five kilograms of oxygen in eight hours from some simulated Moon rock. Despite raising the value of the prize pot to $1 million in 2008 with the help of the California Space Authority, the prize remains unclaimed. In addition, the agency’s ongoing In Situ Resource Utilization programme is currently looking at several different technologies for extracting oxygen from Moon rock.Now, Derek Fray, a materials chemist from the University of Cambridge, UK, and his colleagues have come up with a potential solution by modifying an electrochemical process they invented in 2000 to get metals and alloys from metal oxides. The process uses the oxides — also found in Moon rocks — as a cathode, together with an anode made of carbon. To get the current flowing through the system, the electrodes sit in an electrolyte solution of molten calcium chloride (CaCl2), a common salt with a melting point of almost 800 °C.
The current strips the metal oxide pellets of oxygen atoms, which are ionized and dissolve in the molten salt. The negatively charged oxygen ions move through the molten salt to the anode where they give up their extra electrons and react with the carbon to produce carbon dioxide — a process that erodes the anode. Meanwhile, pure metal is formed over at the cathode.
To make the system produce oxygen and not carbon dioxide, Fray had to make an unreactive anode. This was crucial: “without those anodes, it doesn’t work”, says Fray. He discovered that calcium titanate, which is a poor electrical conductor on its own, became a much better conductor when he added some calcium ruthenate to it. This mixture produced an anode that barely erodes at all — after running the reactor for 150 hours, Fray calculated that the anode would wear away by roughly three centimetres a year.
In their tests, Fray and his colleagues used a simulated lunar rock called JSC-1, developed by NASA. Fray anticipates that three reactors, each a metre high, would be enough to generate a tonne of oxygen per year on the Moon. Three tonnes of rock are needed to produce each tonne of oxygen, and in tests the team saw almost 100% recovery of oxygen, he says. Fray presented the results last week at the Congress of the International Union of Pure and Applied Chemistry in Glasgow, UK.
To heat the reactor on the Moon would need just a small amount of power, Fray notes, and the reactor itself can be thermally insulated to lock heat in. “It won’t be a problem,” he says. The three reactors would need about 4.5 kilowatts of power — not much more than that used to heat an immersion heater in a domestic boiler — which could be supplied by solar panels or even a small nuclear reactor placed on the Moon.
(Hat tip to Nyrath.)