(I wanted to belatedly move this discussion out of the scheduling thread)
There are a lot of factors to consider when deciding as an MC how interstellar trade actually works in your campaign. There should be interstellar trade in considerable volume. But it is not as straightforward as it seems, imho. The conditions of interstellar trade are quite different than maritime trade, even if you assume that gravitic technology makes surface to orbit transits no more costly than trains or trucks delivering to a maritime port.
Maritime trade is measured in TEUs. A TEU is 1360 cubic feet. A Traveller displacement ton is very close to 500 cubic feet. Trying to compare ships and cargo by tonnage is just impossible, because Traveller doesn't use mass/weight anywhere in starships, its all volume. A Galika class megafreighter is 50,000 TEUs (twice the capacity of any maritime ship in use today). And its also a midsized cruise liner in terms of passenger capacity.
The question is not whether that much trade exists. It does. The question is how often it makes sense to ship it that way.
The Port of Honolulu seems like a reasonable proxy for a pop 6 world and it handles about 1 million TEU a year, scattered over about 4000 ships (3/4 are inter-island domestic shipping, though). The largest freighter it handles is about 10,000 dtons of cargo space. There's no way Galika makes sense for a pop 6 planet unless you imagine trade is one big ship a month and just locale trade the rest of the month. That is as possible trade concept that could work.
The United Kingdom is a pop 7 region (though it cheats a bit by having some cross channel trucking trade
). It handles about 10 million TEU a year, but its scattered over a number of ports, the largest of which (Felixstowe) handles a bit under 4 million TEUs a year. Now you could have a Galika engage in round trip trade (ie visit once a month) without it absorbing the entirety of the planet's trade. The planet would still be structured to be utterly dependent on that one ship not breaking down.
Once you get to the hi pop planets, you could see sustaining that kind of ship trade in terms of the volume involved.
You still have infrastructure problems. You have to have a A or B starport, because ships that size are not gonna land on the planet. So your space port complex will have to be ENORMOUS so you can take in this ship, unload its cargo, transship to the feeder ships that will take down to the surface or out to the secondary locations in the system. You have to either have that much warehousing on your space station or the ability to directly ship to the cargo barges moving it elsewhere.
Twenty smaller freighters (10k) would be more expensive on the shipping side, but dramatically cheaper on the starport infrastructure side of things. And they would be able to run to smaller worlds profitably, as well as making those planets less dependent on a single ship arrival.
You could also replace the Galika with a large jump ship that carries a lot of smaller freighters that can spread around the star system and land at downports. Again, making infrastructure at the planet vastly easier.
What works for interstellar trade in your game is going to depend on the assumptions you make about how big your spaceports are, how many secondary settlements exist in your star systems, and what kind of domestic trade and production your planets have compared to what's profitable to import. There's a pretty wide variety of viable solutions given the relative lack of hard data provided by an entirely fictional universe.
There are a lot of factors to consider when deciding as an MC how interstellar trade actually works in your campaign. There should be interstellar trade in considerable volume. But it is not as straightforward as it seems, imho. The conditions of interstellar trade are quite different than maritime trade, even if you assume that gravitic technology makes surface to orbit transits no more costly than trains or trucks delivering to a maritime port.
Maritime trade is measured in TEUs. A TEU is 1360 cubic feet. A Traveller displacement ton is very close to 500 cubic feet. Trying to compare ships and cargo by tonnage is just impossible, because Traveller doesn't use mass/weight anywhere in starships, its all volume. A Galika class megafreighter is 50,000 TEUs (twice the capacity of any maritime ship in use today). And its also a midsized cruise liner in terms of passenger capacity.
The question is not whether that much trade exists. It does. The question is how often it makes sense to ship it that way.
The Port of Honolulu seems like a reasonable proxy for a pop 6 world and it handles about 1 million TEU a year, scattered over about 4000 ships (3/4 are inter-island domestic shipping, though). The largest freighter it handles is about 10,000 dtons of cargo space. There's no way Galika makes sense for a pop 6 planet unless you imagine trade is one big ship a month and just locale trade the rest of the month. That is as possible trade concept that could work.
The United Kingdom is a pop 7 region (though it cheats a bit by having some cross channel trucking trade
). It handles about 10 million TEU a year, but its scattered over a number of ports, the largest of which (Felixstowe) handles a bit under 4 million TEUs a year. Now you could have a Galika engage in round trip trade (ie visit once a month) without it absorbing the entirety of the planet's trade. The planet would still be structured to be utterly dependent on that one ship not breaking down.Once you get to the hi pop planets, you could see sustaining that kind of ship trade in terms of the volume involved.
You still have infrastructure problems. You have to have a A or B starport, because ships that size are not gonna land on the planet. So your space port complex will have to be ENORMOUS so you can take in this ship, unload its cargo, transship to the feeder ships that will take down to the surface or out to the secondary locations in the system. You have to either have that much warehousing on your space station or the ability to directly ship to the cargo barges moving it elsewhere.
Twenty smaller freighters (10k) would be more expensive on the shipping side, but dramatically cheaper on the starport infrastructure side of things. And they would be able to run to smaller worlds profitably, as well as making those planets less dependent on a single ship arrival.
You could also replace the Galika with a large jump ship that carries a lot of smaller freighters that can spread around the star system and land at downports. Again, making infrastructure at the planet vastly easier.
What works for interstellar trade in your game is going to depend on the assumptions you make about how big your spaceports are, how many secondary settlements exist in your star systems, and what kind of domestic trade and production your planets have compared to what's profitable to import. There's a pretty wide variety of viable solutions given the relative lack of hard data provided by an entirely fictional universe.
