I just read the Kindle free sample of a space opera. It was set on a space freighter. It did not hold my interest and I will not be buying the book.
I could write better than this. (As I often claim.)
So anyway if Humanity was alone in the universe, and had say 100 inhabited planets, what could possibly justify being hauled around in freighters?
People do not count.
Surely the industrialized planets would be hauling factories, machine tools and manufactured goods to the less-developed places. But what could they haul on the reverse trip to pay for the fancy, expensive stuff headed out?
There are only so many raw materials, only so many chemicals. Almost any craft made on one planet could be made on another. Do you really want a chess set hand-carved Somethingwood for Alpha-Beta-6?
Assuming fairly cheap and quick FTL I would say cutting edge tech, art & craft items, exotic foods, livestock semen and ovas, possibly mail and media depending on if the ships are faster than communications. Also could be smallish shipments of very valuable goods going for rare elements and metals where the high tech planet is fairly depleted.
Let me noodle on it. A freighter would be a great place for a space opera. Slowly moving from one backwater to another, cutting sharp deals only to get out of town before the sheriff catches up with them. Shady characters, smuggled goods, all sorts of stuff.
It would probably depend on what sort of magic propulsion technology the civilization had. If we are stuck with the light speed limit and propulsion methods that will realistically be a fraction of even that then the only thing I see is people and colonies, with supplies and machinery to get them started and viable. I suppose you could have some unique materials or crafted items that are only possible on a certain planet or star system that could be transported, but it’s hard to see how a ship that would take a decade or two to get from one star system to another could make a viable go at hauling cargo. It gets even worse when we are talking about 100 star systems that are probably a couple hundred light years apart in total.
I’d also have to say that by that point in our technological journey it seems reasonable that we will have things like nano-tech fabrication, so what you’d really be trading are plans at light speed (even there you’d have a really long time lag between systems).
If the OP is interested in a fairly long YouTube video, this is one by Isaac Arthur on interplanetary trade. I believe he’s planning to do one on interstellar trade in January as well, so be interesting to get his take on that.
Krugman does leave open the analysis of what happens when the worlds are not in the same inertial reference frame. Can someone post a link to where that case is worked out? (I assume it’s been worked out since 1978; if not, we could do it from scratch.)
It depends on the exact scenario. How fast can the ships go (and is this a FTL universe)? Do the 100 inhabited planets have breathable air and do plants grow there, or are the people living in domes? These questions all make a big difference to the feasibility and desire to ship goods.
If we have a way out of a gravity well (e.g. space elevator, or just shipping between space stations), then the cost goes down considerably. It will be much cheaper to “slide-over” a hunk of gold than to try to mine it.
I think the logic of the destination needing to supply something for the return trip to make it worthwhile is flawed.
Let’s say scientists decide to build a space station near to Wellcool III, to study it. We ship the pieces of the station there, and ship nothing back. There is no need to set up a production plant making, I dunno, pogs, on the space station, for selling back to earth.
Later we sell tourist trips. Still no need to ship anything back to make it worthwhile (apart from the tourists themselves), but now Wellcool III has some industry of its own as people are paying for (the equivalent of) rooms to rent, and buying trinkets (which could be made anywhere, but tourists want to buy the one made locally).
Finally, there is some export industry, not necessarily because there are things that can’t be made elsewhere, but because that happens to be where some people live who are making stuff.
This has got to be the weirdest simulpost I’ve seen.
The OP’s question exposes the crumbling pillar on which all sf is based: analogies to Earth history and customs. All space battles are based on WWII movies. All off-planet colonies are based on western movies. All systems of government are based on Duck Soup.
The Future caught up with science fiction and hit it hard. It can never be the same as it was in the days of colossal ignorance and blind optimism.
Information might be worth hauling as freight. Sure, you can send it on radio waves, but the data rate is going to be atrocious for interstellar transmission. You can mitigate that by building bigger and bigger antennas, and pumping more and more power into them, but at some point that’s going to catch up with the cost of a ship.
Information seems a likelier exchange in interstellar trade than anything physical – but it doesn’t require freighters. It can be broadcast by whatever signal you’re sending. Send the aliens plans for something to be manufactured (using additive technology, 3-D printing, computer-controlled machinery, or a bunch of guys with a machine shop) using local materials. Much faster and cheaper. Once biological tinkering is on par, you can send genetic code instead of transporting ova and semen and samples. And you can check to see if any serious compatibility problems exist – no need to worry about contamination.
One of my favorite stories about such trade is one of Larry Niven’s Draco’s Tavern stories where ambassadors from Earth visit a planet and, apparently as a matter or routine, have samples taken. From this, the aliens – revealed to be horrible, human-eating creatures – grow portions of human bodies. Arms, legs, whole headless bodies, which they then eat. But they pay royalties, so there’s trade involved. They grow the body parts on their planet, using local raw materials, so there’s no need to haul around all that meat. The terrible man-eating aliens really do exist, but they’re very civilized and don’t kill anybody, and we derive a tidy profit from it. (The ambassadors are warned that if they don’t accept the royalty agreements, there will still be "bootleg’ copies of them that will be raised and sold, so they might as well accept the money).