Molten lunar regolith heats up space colonization dreams

Human settlement of the Moon made a little easier, maybe?

A study proposes that the Moon's dusty topsoil, also known as regolith, can produce thermal energy.

The paper [PDF], which was written by researchers at the University of Waterloo, Canada, discusses the practical problems of settling or even building a base on the Moon. The key problem is getting necessary supplies to the Moon, which is hostile to life and doesn't have the same kind of resources as Earth.

Hauling materials to the Moon would be both slow and expensive as the trip takes roughly three days. The scale of lunar operations to establish a settlement or a base would be unprecedented. Using as many local resources as possible is ideal, leading to many studies concerning in situ resource utilization (ISRU).

The Waterloo researchers suggest that while the Moon doesn't have everything we need, the lunar topsoil is composed of just the right chemicals to be quite useful for lots of applications. Lunar regolith is composed largely of oxides, chemicals that include oxygen and another element bonded together, among other stuff. Those oxides include iron oxide, aluminum oxide, and silicon oxide.

While there are many methods for processing regolith, most involve heating the lunar soil up to 1,600 degrees Celsius, using electrolysis, or both.

The study took particular interest in molten regolith electrolysis, which involves heating up the regolith to 1,600°C and then applying electricity to force a chemical reaction separating the metals and oxygen. The main improvement proposed by the researchers is progressively increasing the voltage, which allows different materials to be extracted, starting with potassium at the lowest voltage through calcium at the highest.

This method does require a combustion chamber. It's highly efficient in terms of resources, we're told, but requires lots of power to keep the heat up, especially if extra time is spent on the progressive voltage technique.

Of course, there isn't an infinite amount of regolith on the Moon, but it's unlikely we're going to run out any time soon. "As far as the amount of regolith goes, there is an abundance of fine lunar regolith on the surface, about 5 to 15 meters thick, depending on the geographic location on the Moon," researcher Connor MacRobbie told The Register.

"Underneath this layer of finer particles is larger rocks and a bedrock of basaltic material, which is largely the same material makeup as the outer surface, but has not been broken down due to the shielding of the top layers," he said. "This could be excavated and refined to get more of the fine material that is useful in a lot of our applications."

While the basic process of collecting and mining regolith won't be anything too different from mining on Earth, MacRobbie anticipates some hurdles. "Dealing with the zero gravity effects will be the largest challenge. Transporting and refining the material in zero gravity will take a lot of advanced engineering," he explained, referring to the Moon's low-gravity nature.

"On top of this, dust and particle mitigation in equipment is a problem that will need to be addressed."

The myriad applications of regolith

Since regolith is about 45 percent oxygen, according to the study, it will be a key source of breathable air, something that obviously doesn't exist on the Moon since it has no atmosphere. Plus, it can be combined with hydrogen to form water, another basic but crucial resource for human life.

Oxygen can also be used with fuel, for both a lunar settlement or base as well as for the rockets that will presumably play a key role in a hypothetical lunar society.

Metals found in regolith like iron and aluminum will also find uses, such as building materials and even in rocket fuel, which often uses aluminum as an additive. Although heating up these metals to mold them will be challenging without a large source of energy, the study expects solar panels to do most of the heavy lifting when it comes to power generation.

Conveniently, regoliths' biggest component is silicon, a key material for glass and ceramics, with the former being useful for solar panel production and repair, and the latter for semiconductors and even floor tiling.

Plus regolith can also be ignited and hit high temperatures. This is the same technique used for welding railway tracks together, as the study points out, and could conceivably be used for other things that require lots of heat.

A similar study also found that regolith could be melted right on the surface of the Moon to make roads, landing pads, and other smooth surfaces.

While using regolith doesn't solve everything that could go wrong with establishing a presence on the Moon, it certainly makes it seem more feasible than before. However, if regolith is the future for humans on the Moon, it'll have to be handled carefully since it is theorized to be harmful to humans, tools, and electronics due to how reactive and sharp its particles are. ®

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