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MinibearRex comments on [Link] Space Stasis: What the strange persistence of rockets can teach us about innovation - Less Wrong
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You are correct in saying that the technology isn't here yet. I do think, though, that the Hero of Alexander claim is a bit hyperbolic. I would be surprised if we had inches of the necessary construction material, but I think part of the reason why it seems so far away is that there isn't a major, concerted effort to do it yet. I'd say it sounds about as far off as the proposal to go to the moon did, before the US had even achieved earth orbit. Or perhaps, as far fetched as the theoretical scheme that the matter in the nucleus of atoms could be converted into energy, creating an incredibly powerful explosive did, before there was a major push for that. A space elevator is a theoretical idea at present, but when there is the funding and the effort behind a technological development, it can happen faster than we typically think. I'm definitely not expecting a space elevator within the decade. But I'd be surprised if it wasn't possible in my lifetime.
Both had, a decade or three beforehand, the basic technology proven. What is the difference in kind, and not degree, between putting a man in orbit and putting him onto the moon? Once you've gotten all the way to a reactor pile which can go critical, you've done most of the hard work.
If we could manufacture a few meters of space elevator material, that'd be one thing, and I might accept an argument that 'with a Manhattan project equivalent, we could build a space elevator in a decade or two'. If you can manufacture a few meters, then you can do it again and again and scale your processes up. But we can't even manufacture inches, putting us closer to the Curies or Roentgens of space elevator than the Fermis or Oppenheimers.
I think you are looking at the wrong problem. Assume that you can easily turn coal into bucktube material suitable for building an elevator. Now, compute how many tons of the stuff you will need. And then, how many tons of chemical rocket fuel will be required to lift all that material up to GEO.
Oh, we may build an elevator some day. But I doubt that the material for building it will come from the Earth's surface.
Assuming von Neumann machines doesn't do much to strengthen the argument 'we could build a space elevator relatively soon if we really wanted to'. If anything, it weakens it...
By "von Neumann machines", I usually understand stored program computers. You are apparently talking about some kind of self-reproducing (nanotech?) robots. Assuming that such things exist doesn't change the rocket fuel requirements for building an elevator, but they might help to build the rocket-fuel refineries. So, I don't see how this assumption weakens the argument.
FYI.
Oh, I assumed your last comment meant that the material would be coming from the moon and/or asteroid belt, and usually people aren't proposing sending humans out there to mine them but von Neumann machines.
Ok, so we send a pair of robots to an asteroid and let nature take its course ...
And then a few generations later we have thousands of robots heading back to earth to build an elevator for us. Yeah, that might work. And it might be cheap. But it probably won't be particularly quick. Maybe 40 - 100 years from first arrival of robots at asteroid, I'd guess. I still don't see how the argument is weakened by the existence of robots, but I agree it is left pretty weak.
No, it's weakened by a variant of the conjunction fallacy, as it were. If you previously argued 'A ~> C' but have now changed your argument to 'A & B ~> C', then probablistically C has gotten less likely.
So one originally starts off arguing 'we may have elevators soon, since when we can create miles of nanotubes, then we can create space elevators quickly', and changes it to 'we may have elevators soon, since when we can create miles of nanotubes and we have also finally developed space robots to go synthesize it in orbit for us, then we can can create space elevators quickly'.
You have narrowed the possible routes to creating a space elevator by ruling out routes that don't involve von Neumann machines; that ought to reduce our probability.
Ah! I've got it now. The assumption that bots are available doesn't weaken the case for an early elevator. The assumption that bots are necessary does weaken the case.
I don't know why it took me so long to pick up on that. Sorry.
No problem. I wasn't sure I was being fair in inferring that the bots were necessary. If they aren't necessary, then by the same exact logic, our probability ought to go up - 'A v B ~> C' is stronger than 'A ~> C'. (The more independent pathways to a result, the more likely one will work within a certain time span.)