If you have FTL travel but no FTL communication then the primary job of space freighters will be to deliver stacks of space telegrams.
But this all comes down to technology which underpins the economics. How much does it cost to move a metric ton of material off a planet, then across light years, then land it on another planet, and sell it?
You need dirt cheap antigravity and dirt cheap superluminal travel to make this work. If you posit both things then ramshackle tramp freighters IN SPACE become a possibility. Otherwise it just can’t work.
Every solar system worth visiting will have approximately the same resources, in about the same ratios; so there is little reason to transport physical materials (mined materials) from system to system (unless monopoles are a thing; these may be so rare that they occur in very few systems, typically one per system or less, so you’d better be very good at detecting and catching them).
What a new colony won’t have is information, advanced technology, and skills. You can transmit information from system to system, but that basically makes it free (unless you encrypt it), since anyone in the receiving system could pick up the transmission, and rebroadcast it. Note that even a very tight, hi-frequency laser beam would spread out to cover whole planets as interstellar distances. So you could expect to send any information that you want to keep secret, including encryption keys, via physical spacecraft.
The sort of data that you might prefer to send as physical databases could include the designs for robots and artificial intelligent agents, fabricators, digitised DNA and perhaps even digitised human minds, if such a thing were possible. You could send the entire Library of Congress in a small package, assuming that data technology continues to progress the way it has in the past. If skills and training can be somehow recorded and digitised, you could send them too; allowing the colonists (or their robot servants) to become experts in a variety of fields.
None of these things require a large freighter - even the monopole would only be tiny, and would need some some kind of retaining magnetic field that might not be very bulky. The idea of vast interstellar freighters seems very unlikely to me.
I saw an article that speculated on how you’d pay the crew on an interstellar near-light-speed trip. Do you pay them based on the number of years they’re away from Earth, or based on the much shorter duration of time as experienced on the ship? And how do you compensate someone for being away from their families for decades, so they never see the children grow up? Perhaps that’s why some of the Star Trek shows have whole families on board the ships.
I think probably industry will be moved to other planets. There is an uninhabited planet, which has Earth-like gravity and atmosphere. Why not shift all your polluting and dirty factory there?
Darren Garrison’s link points out that going really, really fast would require crazy amounts of fuel, so that an economical speed would be something like 20% of the speed of light, which does not lead to a “much shorter” duration of time experienced on the ship. Even if fuel were magically not an issue and you could accelerate at 1g indefinitely, your trip still takes years, which rather rules out hauling food and tourists.
Why have crewed ships? We’re automating car driving right now, we can probably do the same for interstellar freighters.
Of course that ruins the plot of all the tramp freighters epics, but what can you do? Sorry guys, your tramp cargo ship has just been undercut by computers.
That’s not necessary. Even today we have secure key exchange protocols that allow secure encrypted communication between two parties, even if the two parties have never met nor exchanged anything over a secure channel. This is what allows you to send your credit card number to Amazon without worrying that someone might intercept it. It does require a two way communication to initiate the conversation, so if communication is limited to light speed, it will take a while to get the conversation started.
Somewhat related: the novel Downbelow Station describes a human spacefaring civilisation where the colonies (mostly large space stations, with a few planets) do depend on trade with each other, but Earth has mostly lost interest in trading with them and returned to its usual infighting. There are commercial freighters that run between the colonies, operated by family companies. There is FTL travel, but it was not yet available when the colonies were first established. (I’m not giving much away, this is all described in the prologue.)
A Deepness in the Sky by Vernor Vinge is based on a human interstellar trading culture in a pure STL setting. The most notable effect is that human planetary cultures rise and fall, with great predictability, and your best marketable commodity may be basic technologies you have carted around for centuries but your recently-fallen customer culture may need at this moment.
The Qeng Ho culture may be sublight space peddlers, but they’re also Humanity’s cultural backup system. And fairly profitable at it.
And virtually all trade is conducted in a fashion akin to the Age of Sail. With sparse exceptions, there is almost no exploration of what actual interstellar exploration or colonization would be like, and most science fiction (especially film and television depictions) posits a level of technology development that is absurdly retarded in most practical aspects save for the few narrative conceits that make it convenient for storytelling, e.g. faster-than-light travel and communication, matter transmitters, universal translation systems, et cetera, and then almost never explore the implications of those technologies.
There is no credible reason that interstellar trade would or could exist without some absurdly cheap and rapid means of transfer. The energy and time required to execute the trade of goods would render it prohibitive and uncertain; how could you assume profit on trade of a cargo of Applied Phlebotinum for some Liquid Metal Unobtainium if some technological innovation make make either or both unnecessary or useless in the intervening period? A civilization with the capacity for interstellar travel would also most likely have the means to construct complex structural materials and computational or biological technologies from raw elements, which begs the need for material trading even on an interplanetary scale, other than perhaps for scarce raw materials, and the entire question begs of by what means or need a profit could be made by a post-scarcity society. The only plausible trade between stars would be intellectual property of some form, and even that would be limited in the case of speed of light or slower transmission just by virtue of relevance after been transmitted years or decades previous.
There are also limitations to the distance such messages could be practically transmitted; microwave or laser transmission might be sufficient for the local neighborhood but it requires substantially more power and receiving area (and lower bandwidth) for distant star systems; microwave frequncy transmission becomes impractical at any plausible level of transmission power at somewhere around 300 light years, and visible laser out to about 1000 ly or so, albeit with low modulation or polarization bandwidth due to quantum effects. Coherent X-ray frequency messages could be transmitted over longer distances but because of quantum noise would have a very low bandwidth.
Two highly speculative means of communication over longer interstellar distances would be controlled emission of neutrinos or gravitational waves, both of which pass through normal matter and are essentially unaffected by other radiation. However, we have no path to making either of these practicable systems of communications; neutrino emission is result of beta decay, which is stochastic, and the generation of focused high frequency gravitational waves would require some kind of precise control of high gravitational gradients or topological flaws in space, e.g. an artificial cosmic string. Both would be limited in tranmission speed (gravity at the speed of light, neutrinos slightly slower) and would undoubtedly require the generation and control of enormous energies which are vastly beyond anything we can imagine today.
In terms of securing communication, you’d have to assume purely asynchronous protocols (no handshake or other response), and therefore would have to have some previously agreed upon security protocol and keyset, as well as some sophisticated means of error detection and correction lest the message that the recipient has been awaiting for decades or centuries is rendered unusable by corruption in critical areas of the transmission. As noted above, at some point it may just be quicker and more effective, if not necessarily faster, to send a physical messenger; but again, with slower than light travel what information is sent may be rendered moot by technological innovations or social changes by the time it is received.
Poul Anderson has a collected of works involving Interstellar Spice and Liquors. With FTL, trade is much like it is on a planet, whether a new liquor made on Antares III or the latest Earth built hover car taken to Antares III.
In the pesky real universe, I agree that interstellar trade would be limited to information.
Thanks to you and Dewey Finn for referencing this classic paper by a witty genius.
“This paper, then, is a serious analysis of a ridiculous subject, which is of course the opposite of what is usual in economics.”
Information could be sent at a higher bandwidth using relay satellites. A few hundred of them between us and Alpha Centauri could do the trick. Which leads to another answer to the OP:
Relay satellites!
Send out a big mothership loaded with a bunch of them and have it drop one off here and there along the way.
Note that you don’t have to slow the satellites down at all. As they move forward, just send new ones up from the source. And at the other end as they approach the destination they can be nabbed and examined like a time capsule.
Okay, okay, so there’s probably several better ways of distributing them.
Unless the scenario includes very cheap interstellar travel, then nothing much made from metal or synthesisable chemicals such as plastic is worth shipping, no matter how complex, it’s going to be cheaper to manufacture closer to the market, using local materials.
Unless the technology exists to replicate them, then the things that can’t be made from scratch locally such as living organisms could have a high initial value (and then the market tails off quickly once a breeding population is established)
And after that, it comes down to ‘naturally-occurring stuff that doesn’t naturally occur everywhere’ - so… I dunno - exotic stuff like gemstones that only form in certain planetary conditions that not every solar system has, or biological materials analogous to timber, ivory, etc - but even then, is it worth hauling it across interstellar distances?
And all planetary ecologies look like a single state on Earth, or even a single county. Ice planets, jungle planets, desert planets and farm planets drive me bonkers.
I vote for art, number 1, since even perfect reproductions of an artwork are not that artwork, and food. Subtle differences in ingredients can make big differences in food.
However, since there will probably be 3D food printers by then, that might not work either.
