Space travel

[JRDelirious]

@Kinthalis

Sadly, we’re still mostly the angry, hateful, spiteful, covetous and greedy hairless apes that we’ve always been.

Until that changes, the global effort required for interstellar travel is probably not going to happen. Too busy trying to figure out better ways of killing each other.

That one’s easy. Detect aliens. Decide we need to kill THEM and get busy finding out a way to get to them before they get to us.

[SamuelA]

@Darren_Garrison

. So to accelerate the ISS at .00167 Gs would take around 4.2 gigawatts of electricity. That’s 3 and a half Delorians worth, and more than the biggest nuclear power station in the US.

tl;dr: Probably no need to hold your breath.

(Disclaimer, I acknowledge that I could have utterly screwed up my math at some point along the way.)

Because you didn’t consider energy density, just absolute numbers, your analysis is terrible.

The key number is the energy density required, in kilowatts/kilogram. By your numbers, it would be 10 kilowatts/kilogram - and you obviously don’t want the entire ship to be a reactor + turbogenerators. For the far more near term VASIMR to mars in 30 days mission, you would need 1 kilowatt/kilogram, which is also considered to be extreme and not achievable with current engineering.

So you happen to be correct, but only by luck. If we had a power source that had the needed energy density (it would need to be about 30 kilowatts/kilogram so only 1/3 of the ship is energy production), the fact that the ISS is too small for a generation ship is totally irrelevant. You would just scale the whole design up to the size you need.

[Darren_Garrison]

@SamuelA

So you happen to be correct, but only by luck.

So I’m correct, but you still have to try to tell me how I’m wrong. You know what? I’m putting you on ignore right now. I suggest that you do the same for me. Otherwise, we are both going to end up getting warnings issued to us sooner or later.

[Trinopus]

@SamuelA

Because you didn’t consider energy density, just absolute numbers, your analysis is terrible. . . .

He’s right, and you’re wrong. Energy density was in his calculation: he talked about the energy needed to move the ISS. That gives both elements of the equation: the mass, and the energy. Voila, the density.

Also, energy density is implicit in the technology. Hydrogen and Liquid Oxygen are, intrinsically, of a certain level of e.d., and nuclear fission is of a higher level. Fusion would be higher yet. If we can go to total conversion, we get the highest possible.

All of these are numbers can can happily throw around on a back-of-the-envelope fashion. We don’t need (and don’t want) serious engineering proposals here.

Space travel is obviously possible – we’ve sent probes out of the solar system entirely. We want to make it better, and there are no real reasons we can’t.

That said, I agree with RTFirefly that robots will do the exploring for quite some time to come.

(I also agree, very sadly, with JRDelirious that good old xenophobia would be a great stimulus to our investment in space travel.)

[SamuelA]

@Trinopus

He’s right, and you’re wrong. Energy density was in his calculation: he talked about the energy needed to move the ISS. That gives both elements of the equation: the mass, and the energy. Voila, the density.

No, you’re also wrong. He just posits as given that 4 gigawatts is ridiculous and doesn’t even bother to see what it would take. As it happens, you can get 4 gigawatts - or 16 gigawatts thermal quite easily in a few thousand kilograms. That’s what a NERVA rocket engine ends up being. The problem, of course, is you can’t shed any mass for a century, and it’s really hard to cool an engine like that by radiation, so the actual total mass does end up being a lot.