Interstellar travel - why travel so fast ?

[Patrick Degan]

In some cases, you can broadly predict the rate of future technical advances (Moore's Law), or at least predict that advances will be made (as someone building steam engines in, say, 1830 might).

Right now it would make sense for us to wait, because even if we decided to pour the entire planetary GDP into building an interstellar probe, there's too much we don't know about building long-lived spacecraft. Working on other interplanetary projects first would almost certainly pay off enough to justify waiting until we actually know we can build objects with century-scale lifespans and operate them in space.

Questions of advances in drive technology depend on too many variables; nothing is certain, so it would be absurd to apply bz's argument in every imaginable situation and argue that it ALWAYS makes sense to wait. However, it would be equally absurd to pretend that it NEVER makes sense to wait, which is what it sounds like you're doing. One thing that bz's argument is right about, for instance, is that it makes no sense to use a drive design we know is highly unreliable or inadequate until we've at least tried to improve on it.

Do the job that's in front of you with the tools you have on hand, but don't take on jobs you know you can't do, or can't do cost-effectively, at the cost of wasting effort you could use to improve on your tools.

Oh, I'm not saying that we should attempt an interstellar voyage with what we've got now. Nobody says that.

[Simon_Jester]

Yes, but as much to the point, there's going to be a window after the time where we can say "Hey, we could conceivably send a probe to Alpha Centauri," but early enough in the development of our space program that waiting a few years to work out the bugs of the technology is still worthwhile.

So the optimal launch date ends up being a compromise between doing the job ASAP and refining the tools to get the best result.