[Space/Spaceships] Getting the velocity/Delta V I want with the tech I want

[Johnny1A.2]

Originally Posted by malloyd

Actually spaceships on a freight run 4 years long probably should meet the second of those, since there's no good reason to have any crew at all.

And the freight *better* be high value for its weight. Even at perfect efficiency, getting your ship up to 300 mps and back down uses energy thtn has never been cheaper than on the order of $1000 per pound. So if you can't charge $1000 per pound for it, your freight run is a money loser even if the other operating costs are zero and cargo (and ships!) are free at the point of origin.

It's next to impossible to make interstellar trade make sense in a realistic setting, since any civilization that can actually build a starship is going to be able to make anything at home more cheaply than they could ship it back. Even if they have to assemble it atom by atom. And you can send the atomic scale blueprint without a starship.

That's a bit of a non sequiter, because the ability to build fast STL starships doesn't automatically imply the ability to assemble anything you want atom by atom. Just because you have the energy doesn't mean you have the means to apply it to whatever you want. It's a bit like saying that the ability to build an Apollo moonship implies the ability to synthesize a steak from scratch.

It's true that shipping bulk ore or the like doesn't make sense over interstellar distances, but that doesn't mean that nothing could possibly be worth shipping.