Of Reactors and Regolith
The other need--the capacity to process and use indigenous resources--centers on one central challenge. The fact is that propellant mass is an exorbitant portion of the total mass of any launch. When a mission has to return to Earth--for example, like the bedeviled Mars Sample Return mission--it has to haul all the propellant required for the return trip with it. There are no gas stations on Mars. And that propellant is not only taking up valuable space that could have gone to useful scientific payload, but also forcing the total propellant requirements to spiral up and up and up in the very definition of a "vicious cycle," because all that return-trip propellant needs still more propellant at launch in order to accelerate it to escape velocity. The problem is nothing short of gruesome. By the time we're dealing with the masses involved with a meaningful manned expedition, the propellant requirements become plain cruel.
But suppose there actually was a gas station on Mars? Thanks to the carbon dioxide in the atmosphere and the various compounds that we know are present in the regolith (it isn't actually soil because, so far as we know, it doesn't have any organic material in it), there are a variety of chemical reactions at our disposal that, given a few tons of hydrogen feedstock and our plentiful supply of electrical power, would allow us to produce all sorts of useful things. Oxygen, for example, and water--and especially methane, which makes a fair rocket fuel. A nuclear-powered robotic plant, sent out ahead of the manned mission, could produce all the propellant--fuel and oxidizer--required for the trip home. The fancy word for this is "In-Situ Resource Utilization." Put simply, if there aren't any gas stations on Mars right now, then we ought to build a few.
Naturally it isn't completely as easy as all that. Stein Sture of the University of Colorado in Boulder points out that facilities on Earth that handle granular materials are significantly trickier and more prone to mechanical problems than facilities working with simple liquids and solids. We just don't have that good of a handle on how granular materials behave. For Martian regolith, there are many, many things we don't know--about its consistency, cohesion, and so on. We just haven't acquired the data we need. But work is ongoing, and that Mars Science Laboratory will concern itself with just such questions. In the end, we
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