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

[johndallman]

Originally Posted by flyingwombat

Four years isn't all that long. I believe that is how long it took for ships to go from Spain to the Philippines and back.

Those were carrying goods (such as spices) that were both lightweight and extremely valuable, rather than more general trade. Also, sailing ships were a technology that was quite economical to run, didn't have to carry their propulsive energy with them and provided a very low standard of living for their crews. Spaceships don't usually meet those criteria.

[David Johnston2]

Originally Posted by scc

OK, I'm working on a so far hard Sci-fi setting and I've got two planets that are 400 AU apart, +/- 44 AU. Now according to my math that means that at a velocity of ~300 mps it will take a ship 4 years to move between the two planets.

My problem is that I want there to be somewhat regular trade between them (In fact one's supposed to be settled from the other).

The logical thing to do is to either dispense with the apes in cans or use FTL.

[Flyndaran]

Originally Posted by David Johnston2

The logical thing to do is to either dispense with the apes in cans or use FTL.

A.I. ships means background color not center stage gaming. And FTL obviously breaks OP's attempt at hard science fiction.

[jacobmuller]

If it's any help, TL's aren't set in stone - unless you're seeking to publish a generic article, ie getting paid by SJG. Even then, RAW covers you having different TLs for different technologies. Basically, if the drive you want doesn't work at the settings baseline TL, use a better one.

I wanted an FTL and subwarp that didn't work well with spaceships; realistic TL10 systems actually made more sense. However, strict adherence to the spaceships stats also didn't fit. So I have a hyperdrive and a realistic sublight but the sublight stats are from TL11.

[malloyd]

Originally Posted by johndallman

Those were carrying goods (such as spices) that were both lightweight and extremely valuable, rather than more general trade. Also, sailing ships were a technology that was quite economical to run, didn't have to carry their propulsive energy with them and provided a very low standard of living for their crews. Spaceships don't usually meet those criteria.

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.

[malloyd]

Originally Posted by Anthony

Any meaningful fraction of 300 kps will vaporize any conceivable TL 9 ship, as they basically turn the kinetic energy of your ship into heat, and 300 kps is 45 gigajoules per kilogram, which is likely somewhere upwards of 1,000 times the energy required to turn the ship into an expanding cloud of vapor.

It's a bit worse than that, since 300 mps is in miles/second - 486 km/s. You hit with 1 kT equivalent per 80 pounds of ship.

[Anthony]

Originally Posted by Flyndaran

A.I. ships means background color not center stage gaming.

Who needs AI ships? This is firmly TL 8 stuff, we routinely manage comparable stuff with interplanetary probes.

[Flyndaran]

Originally Posted by Anthony

Who needs AI ships? This is firmly TL 8 stuff, we routinely manage comparable stuff with interplanetary probes.

With quite a few mistakes that might not have happened with on board A.I. Not to mention the expense of having such a tense paid ground control.

But I meant as in no humans on board makes the whole trade background color.

[Anthony]

Originally Posted by Flyndaran

But I meant as in no humans on board makes the whole trade background color.

Is there any reason to think it's not intended to be background color?

The other problem is that realistically, it's hard to think of much in the way of goods that justify expending several hundred gigajoules per kilogram, there's really not much that you can't synthesize for less. Other than information, which doesn't need a ship at all to trade.

[Flyndaran]

Checking the original post, you are right that I made an assumption. OP never wrote that they intended for it to be center stage.