Monday, August 17, 2009

Lunar Rock Oxygen

I thought that someone would have gotten serious about this a long time ago. Anyway, what is described is simple brute force methods. I sort of prefer a electrolytic system that does give of CO2 first because that is easily passed into a life supporting environment that can actively produce atmospheric oxygen and avoid a need for exotic chemical systems. Life is already there and has all the built in buffers.

In the event, provided we arrive on the moon or anywhere else in some form of efficient manner that supports a long term stay, then cheap power will be our most available raw material. We would have little reason to be there otherwise.

Cheap power can produce any element to hand sooner or later, even if it is a byproduct. Thus elemental oxygen is certainly an option. It also indcates that space exploration will have to wait for cheap light fusion power produced by a devise similar to that of Focus Fusion.

Only a few metals are legitimately concentrated in space, making beneficiation a difficult trick. Cheap power opens the door to lifting material out of the gravity well of Earth or any other natural concentrator tricky as that might be. Once we have cheap power and large enough magnetic bubble craft, mass lifting should be possible to support space construction.

It is also easily forgotten that mineral beneficiation is actually quite dependent on gravity on Earth. Most material that is rich usually has a significant specific gravity allowing some form of mass enrichment as a first simple step. It is only then that we reach for chemicals and energy. -- If humans ever create a lunar base, one of the biggest challenges will be figuring out how to breathe. Transporting oxygen to the moon is extremely expensive, so for the past several years NASA has been looking into other possibilities. One idea is extracting oxygen from moon rock.

Recently, Derek Fray, a materials chemist from the University of Cambridge, and his colleagues have built a reactor that uses oxides in Moon rocks as the cathode in an
electrochemical process to produce oxygen.

The design is based on a process that the researchers invented in 2000 that produces carbon dioxide. In this design, the scientists pass a current between the cathode and an anode made of carbon, with both electrodes sitting in an electrolyte solution of molten calcium chloride, a common salt. The current removes oxygen atoms from the cathode, which are then ionized and dissolve in the molten salt. The negatively charged oxygen is attracted to the carbon anode, where it erodes the anode and produces carbon dioxide.

To produce oxygen rather than
carbon dioxide, the researchers made an unreactive anode using a mixture of calcium titanate and calcium ruthenate instead of the carbon. Because this anode barely erodes, the reaction between the oxygen ions and anode produces oxygen.

Based on experiments with a simulated lunar rock developed by NASA, the researchers calculate that three one-meter-tall reactors could generate one tonne of oxygen per year on the Moon. Each tonne of oxygen would require three tonnes of rock to produce. Fray noted that three reactors would require about 4.5 kilowatts of power, which could be supplied by solar panels or possibly a small
nuclear reactor on the Moon. The researchers are also working with the European Space Agency on developing an even larger reactor that could be operated remotely.

As a recent story in Nature News reports, other researchers are also developing methods for oxygen extraction. For instance, Donald Sadoway at MIT is working on a high-temperature technique called molten salt electrolysis. Here, the Moon rock is molten and acts as the electrolyte itself. Sadoway's reactor could even be built out of the rubble on the Moon's surface called regolith.

NASA and the ESA are strongly encouraging this type of research. In 2008, NASA boosted its $250,000 prize to $1 million for the first team to demonstrate a method to extract five kilograms of
oxygen in eight hours from simulated Moon rock. So far, the prize remains unclaimed.


M. Simon said...

Polywell Fusion is a better bet.

arclein said...

At this point, they are both promising and I am nervously optimistic. They are both able to come close and almost work and both deserve a sustained properly funded development drive.

The charm of focus fusion is that the core decive promises to be compactable which is necessary for space transport. The polywell wants to be bigger to be better.

Hopefully we will soon know more, or know more about how hard it is going to be.