Does Interstellar Trade Make Sense For Realistic Science Fiction?

[AlexanderHowl]

Of course, this is assuming that reactionless drives are realistic (GURPS reactionless drive violate the law of conservation energy around 6 mps because the energy produced by the reactors is less than the energy gained by the spacecraft). If you have to depend on non-superscience reaction drives (plus FTL), then the economics shifts dramatically.

[trooper6]

Originally Posted by mlangsdorf

And from a game design perspective, if you're playing a game about merchant traders, you can't handwave this stuff. Players get annoyed if they buy a trade ship and engage in good faith transactions and discover that there is literally no way for them to make a profit because the GM didn't do the math right.

(ninja'd by acrosome)

I ran a GURPS Traveller Interstellar Wars free trader campaign using the trade stats in that book (that the numbers from Spaceships are based off of), and it worked fine.

[Johnny1A.2]

Originally Posted by lwcamp

Not to mention that many of the accidents are due to inexperienced young people doing impulsive stuff. As you get older and wiser and more seasoned and experienced (but remain in excellent health) you can expect to be at less risk for accident.

Luke

All true.

Still, I don't know that we can safely assume that with such long lifespans, other motives/lack of motives might kick in. The average suicide/violence rate might decline through the first 2 or 3 centuries of life, then tick up in the fourth century for reasons we couldn't even guess at, because we have no experience with such life spans.

Certainly I would not fault an SF writer who posited such a thing.
Multi-century lifespans are terra incognita.

[Johnny1A.2]

Originally Posted by David Johnston2

Actually interstellar travel doesn't make sense. "Realistic" universes would make interstellar travel so expensive and slow that nobody would do it. A realistic science fiction setting is one in which space travel is almost entirely automated and restricted to the solar system.

No, that's a realistic SF setting for a given set of assumptions, in this case that our current understanding of physics, chemistry, economics, and engineering plausibility are reasonably complete and accurate. But that still an assumption. Setting that as the 'realistic' default is no different than a SF story written in 1850 asserting that stories about time dilation are unrealistic because time is constant, or that stories assuming a time billions of years before the present on Earth are unrealistic because the Sun cannot have been in existence that long, for lack of any realistic energy source.

'Realistic' is a moving target.

[Ulzgoroth]

Originally Posted by Johnny1A.2

All true.

Still, I don't know that we can safely assume that with such long lifespans, other motives/lack of motives might kick in. The average suicide/violence rate might decline through the first 2 or 3 centuries of life, then tick up in the fourth century for reasons we couldn't even guess at, because we have no experience with such life spans.

Certainly I would not fault an SF writer who posited such a thing.
Multi-century lifespans are terra incognita.

I probably would fault them quite a lot for such a thing unless they sold it particularly well. But for Doylist reasons, not Watsonian ones.

[RyanW]

Originally Posted by Ulzgoroth

Because there are a number of benefits to loading the cargo into a ship only once, on the ground, and with the powerful reactionless drives on the TL11^ vessels, hauling the hyperdrive up and down the gravity well isn't really so much effort.

Assume it takes two days to travel to and from the hyperdrive boundary (the OP's numbers). Say a typical run is eight days at FTL. Let's say it takes a further day to load and unload ship.

• The interface craft can complete their runs every four days. The interstellar craft can complete theirs every nine. Assuming each type of ship has the same capacity, a fleet of 13 ships can average a shipload of cargo every day.
• A dual-purpose craft can complete a run in 11 days. That represents about an 18% increase in throughhout assuming ships of the same capacity.

The key question then becomes: Does adding both hyperdrive and landing capability to every ship increase cost and/or reduce cargo capacity enough to eat up that 18%? That depends heavily on the tech assumptions and what passes for a "default" freighter.

The above assumes shipping that operates on a relatively fixed timetable. For the classic space opera cowboy freighter pilot that picks up cargos as they show up destined for wherever they happen to be going, you'll need to be more flexible. But that's where the line about drug cartel go-fast boats comes in, which incidentally was exactly what the Millennium Falcon was.

[Ulzgoroth]

Originally Posted by RyanW

Assume it takes two days to travel to and from the hyperdrive boundary (the OP's numbers). Say a typical run is eight days at FTL. Let's say it takes a further day to load and unload ship.

• The interface craft can complete their runs every four days. The interstellar craft can complete theirs every nine. Assuming each type of ship has the same capacity, a fleet of 13 ships can average a shipload of cargo every day.
• A dual-purpose craft can complete a run in 11 days. That represents about an 18% increase in throughhout assuming ships of the same capacity.

The key question then becomes: Does adding both hyperdrive and landing capability to every ship increase cost and/or reduce cargo capacity enough to eat up that 18%? That depends heavily on the tech assumptions and what passes for a "default" freighter.

The above assumes shipping that operates on a relatively fixed timetable. For the classic space opera cowboy freighter pilot that picks up cargos as they show up destined for wherever they happen to be going, you'll need to be more flexible. But that's where the line about drug cartel go-fast boats comes in, which incidentally was exactly what the Millennium Falcon was.

There are two kinds of context here - the one where we're looking at, for instance, the freighter for SS2 that the OP did (or its less-adventurous sibling), and the one where we're looking at a wide range of possible technological paradigms.

In the former, landing capability adds no cost for a typical freighter because the basic thruster is a 2G reactionless type. You'd need to be really cutting to the bone to build a freighter that can't fly its way across the solar system, land, and launch back to space in that context, though it's not inconceivable.

In the latter, it's obviously too broad to be able to make any strict statements. You could very plausibly have as many as three separate types of ship involved - an interface shuttle covering surface-to-orbit, an STL freighter (or cargo tug) that hauls cargo from orbit to the FTL point, and a jump carrier which is solely responsible for the interstellar step and may not even be capable of significant insystem flight.

[David Johnston2]

Originally Posted by Johnny1A.2

No, that's a realistic SF setting for a given set of assumptions, in this case that our current understanding of physics, chemistry, economics, and engineering plausibility are reasonably complete and accurate. .

We can skip the chemistry, economics and engineering. Physics is enough to cover it. And certainly if we assume that we can travel effectively instantaneously for free over interstellar distances interstellar trade makes just as much sense as international trade. But at that point "realistic" stops being a meaningful concept.

[Ulzgoroth]

Originally Posted by David Johnston2

We can skip the chemistry, economics and engineering. Physics is enough to cover it. And certainly if we assume that we can travel effectively instantaneously for free over interstellar distances interstellar trade makes just as much sense as international trade. But at that point "realistic" stops being a meaningful concept.

Not so.

It's trivial to have unrealistic economics in fiction that doesn't overtly fail to have realistic physics, and conversely one can have realistic economics within a framework that violates known physics.

[David Johnston2]

Originally Posted by Ulzgoroth

Not so.

It's trivial to have unrealistic economics in fiction that doesn't overtly fail to have realistic physics,

It doesn't matter because no matter how unrealistic your economics are, trade between point A and point B requires something to go between point A and point B and you can't do that without unrealistic physics.