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Old 08-08-2019, 05:58 PM
k9bfriender is offline
Join Date: Jul 2013
Posts: 11,339
Originally Posted by Sam Stone View Post
All of which had to be imported to the space colony, since it was built from nothing. And if any of it is sold, it has to be re-imported. The point is that there are no natural resources at a space colony to exploit. Unlike the moon, where there is essentially unlimited iron, aluminum, titanium, magnesium, silicon, oxygen, and water. These can be turned into rocket fuels (Aluminum-Oxygen, hydrolox, etc) and launched to low Earth orbit or lunar orbit for a fraction of the energy, and therefore could be highly profitable.
Where do you think taht we would be building these things, just in the depths of space? You'd be building them on or near asteroids, and that is where you would be getting resources.
What is there on a space station that could generate enough profit to pay for its own maintenance and whatever the people need to import to stay alive and be happy? Maybe in a couple of hundred years there will be lots of things - maybe we'll treat them like cruise ships and they'll be filled with tourists. But they HAVE to have a reason for existing, measured in economic terms, or there is no reason to build them.
What is there on the planet that does this? People make their own economies. In the short term, manufacturing satellites and other space structures that we are currently spending thousands of dollars a kilogram to get up there. If it's worth that much to put it up there, if you can find a cheaper way to build it up there, then you have cornered the market.

Once you have a critical mass, the economy comes from people buying and selling things to other people.
Maybe zero-g manufracturing will be a thing. Maybe we'll make a bunch of discoveries of goods that are highly desirable but can only be made in zero-g. Maybe we'll start building orbital manufacturing facilities in a decade after a huge discovery like that. But if we did, that would be even more reason to go to the moon, because we'll need a lot of mass in orbit and it's extremely expensive to send it from Earth.
Right, but I'm not talking about sending it from the Earth, I'm talking about getting it from the rock that you are sitting on.

Maybe. But we are so far from being able to hollow out asteroids and build bases in them that by the time we do that the economy will likely be so different that we don't know what we'll need and want at that time. Maybe we'll have automated facilities and mass drivers shooting huge quantities of mass into lunar orbit, where robotic 3D printing robots spin it into huge floating complexes essentially for free.
You don't need to "hollow out" an asteroid. Most asteroids are going to have the consistency of Mica at best. Unless quite a bit changes, then we will need goods and services, the same as we have always needed.
That's why I'm not too interested in talking about what a space colony might look like in hundreds of years. No one knows. No one knows what our needs will be then, what our tech will look like, how wealthy we are, or a host of other things that we need to know to be able to even remotely predict what the future of space will be like.
Looking out that far can be fun, but I agree, we are talking more near term here. That doesn't change anything. Asteroids are still easier to get to, and from, than the moon.
If you're writing a science fiction story, all of this is fair game, and they are all good ideas. But if we are talking about things that should affect NASA policy now, or trying to debate where we should be investing our resources to make effective use of space, that stuff is all completely irrelevant. We have to start with economics, with what is do-able now, and with feasible plans to get there from here. That's what I'm talking about. Practical plans, not speculation about a distant future that is probably no more accurate than random guesses. If you had asked people in 1800 how people will live in 2020, do you think any of them would have been even remotely close?
Find a way to make crude metals out of asteroids, and use that as trusses in satellites, saving hundreds of millions a year in launch costs. Work your way up from there.

The basis of the rocket equation is the fact that rockets work by throwing mass out the back. So every mass you want to manipulate requires another mass to be accelerated to do it. If you want to do it quickly, it can require many multiples of the mass you want to manipulate. But even if you do it slowly, you still need extra mass to do it.
Right, but when we are talking about hohmann transfer orbits, we are talking about pretty tiny amounts of delta-v, probably more than an order of magnitude less than what is needed to get off the moon, much less the Earth.