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Comment by dbcooper | Hacker News Reader

There’s no carbon on the moon. Unless you can harvest large numbers of comets, habitation at scale is impossible.

I'm guessing that a small number of carbon-bearing asteroids could easily support a fairly large population. Asteroids contain a lot of material.

http://www.philipmetzger.com/blog/type-of-asteroid-to-mine-p...

But then, why are you moving them to the Moon?

For use by the people who will live there? It'd be easier than building a habitat on or in the asteroid, although that will likely happen at some point as well.

It’s far easier to live in asteroids than the moon. The energy cost of moving them is enormous, and you can develop them without paying the cost of the moons gravity well.

That may be the case. However, for tourism (which will probably be important for a lunar economy), travel time will be a major consideration. The moon wins hands down on that aspect.

Also, I imagine there will be a space elevator on the moon which reduces the gravity cost substantially. I believe it is possible to build one with today's technology (unlike on Earth).

Space elevators on the Moon are 100% possible with Kevlar and steel. The additional advantage to a space elevator is that at a point you get past escape velocity. This means if you let go you would escape the Moon without any propellant and have a free return. This can be capitalized on every month to have a large amount of supplies shipped from the Moon to Earth with half of their fuel cost paid by electricity instead of rockets.

If you are going to move an asteroid, you can get it on a much better position than the Moon.

About the space elevator, anything you can imagine on the Moon would be easier on an asteroid.

Except for moon tourism.

One does not need carbon on the moon to make the moon profitable.

1) No guarantee people would be required on site. 2) If people are required on site you tightly control the carbon cycle, this is the same thing that occurs on earth, just that the earth is doing this on a scale many orders of magnitude larger.

Stupid question. Is carbon only mandatory if you want long term sustainable agriculture? Or is it necessary for something else?

Presumably you'd CO2 to feed plants, so the plants could produce oxygen for breathing purposes. You'd also need carbon to create organic (aka carbon based) food. At a minimum, carbon will part of any system that includes people. A sustainable system would need some way to recycle carbon.

All the carbon on the moon would absolutely be recycled, much like it is on Earth.

So even if you have to ship all of it there, it's only a one time cost.

We are carbon based life forms, our being alive is just a fancy way of taking carbon in a solid form (food) and turning it in to CO2 for plants. So you either ship food and O2 to the moon and CO2 back to Earth, or you build up a supply and start the cycle there.

Presumably if you are running some sort of hotel, you ship enough O2 and food to cover your guests travel and stay. Then only ship back what they need to stay alive on the ride home. Eventually you build up a large enough supply that you don't have to ship as much, reducing costs.

The whole thing is made out of aluminum! It's low-g. We don't need steel.

Expensive, not impossible.

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