Friday, February 27, 2004

Powering a moon base

Yesterday I said I'd start talking about problems with lunar colonisation, and their possible solutions. To start at a completely arbitrary point, how do we power our hypothetical moonbase? Without power, your life support system goes down and you're dead. So quite an important problem, then.

Interestingly, despite quite a lot of Googling last night, I couldn't really find any good suggestions of how to solve this particular issue - lots of complaining about the problem, but no coherent thought about possible solutions.

The primary power source envisaged for a Moon base is solar energy from photovoltaic cells. The Moon doesn't have an atmosphere to get in the way of the Sun's light, so the intensity of the light is pretty much constant for the whole of the lunar day, and more intense than even direct sunlight on Earth. Big advantages for solar power. But then you have to take into account the length of the lunar day.

A lunar day is the same length as a Earth month: 14 Earth days of light, followed by 14 Earth days of darkness. If your base relies solely on solar power, you're in big trouble. This means that if you want to use solar power, you need to couple it with some form of energy storage.

Enough batteries to heat and light a base for a fortnight will weigh tonnes. So batteries aren't much good unless you have a vast launch budget. Neither are flywheels a good prospect: over the course of two weeks, a lot of energy will be lost to friction. Not to mention that a flywheel big enough to store that kind of energy will also weigh tonnes. The most promising technique at the moment seems to be fuel cells: devices that generate electricity directly from a chemical reaction. These would be especially good if they could be made to run in reverse, because they could then be used in a similar fashion to batteries. Even better would be if the fuel from the base crews landing/ascent module was the same as the fuel for the fuel cells: it would considerably simplify storing the fuel. Only one set of tanks needed!

You can tell that my favourite solution for solar power is PV cells with fuel cells. But the ideal solution would be a small nuclear reactor. Although it would weigh a lot, it would be able to power a much larger base than the equivalent mass of PV cells and fuel cells, and would therefore be a much more efficient use of launch capacity. Unfortunately, the political climate is such that you'd never get permission to launch a nuclear reactor for fear of what would happen if something went wrong.

So the base has power, but what form would the base take?

References:* (numerous threads)* (numerous threads)

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