We now know the cost - but what kind of cargo are we transporting? And how does a passenger’s life look like? Let’s start with the humble-ish cargo!
Recall that transporting a ton of cargo into orbit costs between $100 and $200 to transport between main systems, and $25 to transport it into orbit. I’ll assume we can accept a markup of up to 10% to the price through transport costs.
I’ll refer to the gigantic table on SS2:37 for this. Note that I’ll purposely only mention a few of the prices to avoid copying the book outright.
Now, let’s look at the few categories:
Don’t bother transporting
Those are goods you can’t even ship to orbit for that price. They are most food-related things (grain, fruits), worthless things (scrap) and some raw materials (wood, chemicals). For all of these, you’ll not sell them anywhere.
Admittedly, that makes sense for the food (there might be a small market supplying outposts, but those should mostly be preprocessed rations) and scrap/chemicals. For wood, it depends on environmental characteristics (maybe trees don’t grow on some planets?), but for my personal assumptions, it makes sense.
Strictly local trade
These are goods you can transport, but you’ll lose money if it’s more than a few jumps. These are a bit higher-quality industrial materials (ceramics, glass, light metals, polymers, industrial metals, mechanical parts), consumer goods (literal consumer goods, textiles, liquor) and other food stuff (fish/meat, spices, livestock).
All of those can be transported for five main systems. Straddling the border to the next category would be surface vehicles, farm machinery and software. The former two are produced goods (though of low value-density), while software… really? Even assuming you can’t duplicate them and have to ship something like DVDs (not even hard drives), you should easily get 200 DVDs per kilo including packaging, meaning a value density of a few million dollars per ton. I’ll just ignore them.
Other than that, it looks fine. Industrial materials (which can be shipped for at most two main systems, excluding mechanical parts) mean that mining outposts can be economically viable, and consumer good shipping also makes sense to me.
You can transport these between twenty and fifty systems. They are mostly finished goods (survival equipment, ammo, weapons), electronic parts, or a few last raw materials (special minerals, radioactives). All of these make sense to me. There’s also artworks, which I’ll take to mean an average price for physical artworks.
Really long-distance trading
All of these are transportable over more than 100 main systems (or almost two years of constant travel!).
These are finished, high-value goods (environment suits, computers, scientific equipment, pharmaceuticals), high-tech (nanotech, bio-tech), large high-tech goods (robots, aircraft), and heavy metals, whatever those are.
There’s also the absolute outlier, which are gems at $10M per ton. You can transport those for about 5000 jumps (or almost 60 years). I’m assuming those are natural gems, industrial ones being subsumed under special minerals/crystals.
So, in summary, we’ll probably see three main types of trading:
Raw Material Transports Those are strictly transporting things between producers and consumers. They transport mostly raw materials and some food. That kind of cargo will almost never change spacecraft, and freighters like that are probably carrying a certain cargo almost exclusively.
Product Transports Those transport more expensive finished goods between different systems, motivated by either economy of scale or perceived quality (Made on Alpha Centauri!). They will regularly change spacecraft, and are probably mounted in containers to facilitate easy loading and unloading. They therefore share their transports with the next category,
High-value Transports Those are the most expensive finished goods. A special case are probably gems, as you could hire a whole Atlas for four jumps for the price of one ton of gems.
As an interesting observation, somewhere in the Long-distance trading category does the cargo become more expensive than the Atlas. And for one Atlas-load of gems, you could buy 160 new Atlas.
For passengers we actually need to change the Atlas. Instead of nine cargo holds, we’ll install nine habitats, for a total of 1,800 cabin-equivalents. And now we have another issue with Spaceships: Where usually, we only have to fill twenty systems, with this habitat configuration, we have to fill those 1,800 cabins, i.e. make 1,800 choices. That’s clearly annoying - it would be far faster, in my opinion, to have prebuilt passenger modules available: one for luxury passengers, one for troop transport, etc.
Lacking that, we can still look at SS2:43 to check out different passenger types. There are three: Luxury, First-Class and Economy. There’s also Hibernation-class, but we don’t have any hibernation pods right now, so they’re out. Instead, we’ll introduce the Slum-Class (which probably won’t be named that by the shipping line PR).
Luxury Class passengers need one luxury cabin per passenger, at least one attendant per two luxury passengers, one establishment per ten cabins, and at least one open space. This means we convert one of the components into open spaces. For every ten cabins (20 cabin-equivalent spaces [CES]), we also need one establishment (2 CES) and five attendants. We’ll assume there are three workers per establishment, meaning eight total, for four cabins for the employees. In total, we end up at 28 CES for ten passengers. Filling one of the available habitats, that’s 7 of these units, plus four other rooms (sickbay, minifac, …?). In total, we can transport 560 passengers with the Atlas-L.
First Class passengers expect their own cabin, one attendant per five cabins, and one establishment per 100 cabins. Each 100 cabins (100 CES) therefore needs one establishment (2 CES) and 20 workers (in another 10 CES). In total, we can fit 16 of these blocks into the Atlas-F, for 1,600 passengers.
Economy-Class passengers don’t expect anything but shared cabins, one attendant per 20 people, and one establishment per 1,000 passengers. This means we can build them as 250 double-occupation cabins (250 CES), 50 attendants (in another 25 CES) plus one establishment (2 CES). We can fit about 3,200 people in there.
Slum-Class passengers are even worse off. They’re packed in bunk-rooms, don’t have any establishments, and only the minimum number of attendants necessary (I’m assuming one per 40 passengers). That means 250 bunkrooms (250 CES), and 50 attendants (25 CES). That way, you can cram in 6,500 people (and still have twelve CES leftover for what might be optimistically called a “sickbay”). Conditions, I should mention, are probably quite bad: You either share a cabin with three other people with no privacy but the bunk curtain, or share a larger space with many such cabins. Shared bath and toilet facilities, not much walking space (if it even has spin gravity). For a description of how it might look like, check out The Expanse’s Babylon’s Ashes: From the inside, it looked like the inside of a giant garbage can except that it was divided into twelve decks, fifty people to a deck. The only privacy to be had was thin curtains in the shower stalls, and people only ever seemed to use the head when uniformed crew members were around. […] He selected a bunk, just a crash couch with a little storage under it and a tiny entertainment screen on the bulkhead next to it […]. (p. 82)
In addition, there’s food, which comes to eight tons per main-system travel for bunk habitats, less for the others. We can easily put that in the core cargo section. Cost is a flat $20 or $200 per main-system travel per person for normal and luxury food respectively.
All passengers have to pay the operating cost for the whole spacecraft. This is about $1.5M per travel between main system excluding stewards and food.
For Luxury passengers, the cost increases by another $400k for stewards. Per passenger, that’s $3.4k ($3.6k including food) per main-system voyage.
For First-Class passengers, the cost for stewards is $450k for stewards, a total of $1.2k ($1.4k for luxury food, $1.25k for normal food) per main-system travel.
Lastly, for Economy-Class passengers, we add another $230k for stewards, for a total of $560 including food per main-system travel.
For Slum-Class passengers, the total cost is the same as for Economy, but divided over double the passenger numbers. Ergo, that’s $290 including food.
In summary, luxury passengers pay almost triple compared to first-class, and economy-class less than half. This actually meshes quite nicely with the numbers given in SS2:42 (3:1:0.5).
Edit 2017-01-02 Added missing Slum-Class description and cost, following a comment by ericthered. I was sure I’d written that…