If humanity is ever to spread out into the Solar System, we're going to need to find a way to put fuel into rockets somewhere other than the cozy confines of a launchpad on Earth. One option for that is in low-Earth orbit, which has the advantage of being located very close to said launch pads. But it has the considerable disadvantage of requiring a lot of energy to escape Earth's gravity—it takes a lot of fuel to put substantially less fuel into orbit.
One alternative is to produce fuel on the Moon. We know there is hydrogen and oxygen present, and the Moon's gravity is far easier to overcome, meaning more of what we produce there can be used to send things deeper into the Solar System. But there is a tradeoff: any fuel production infrastructure will likely need to be built on Earth and sent to the Moon.
How much infrastructure is that going to involve? A study released today by PNAS evaluates the energy costs of producing oxygen on the Moon, and finds that they're substantial: about 24 kWh per kilogram. This doesn't sound bad until you start considering how many kilograms we're going to eventually need.
Original Article Published at Arstechnica
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