Getting everything into orbit is only the first part in a long journey. For the next one, we’ll have to look at interstellar transport.
I’m modelling the freighter after the Zhongguang (SS8:20). Nicknamed the Atlas class for now, it’s an SM+11 (30,000 ton) spacecraft and looks like this:
|||Light Alloy Armour|
|[2-6]||Cargo Hold (1500t each)|
|||Light Alloy Armour|
|[2-5]||Cargo Hold (1500t each)|
|||Fuson Reactor (de-rated, 1PP)|
|[core]||Smaller Systems (Control Room, Habitat, Hangar [300t])|
|||Light Alloy Armour|
|[2-5]||Fuel Tank (4500t, 30km/s total)|
|||Water Fusion Torch (1.5g)|
SM+11, 30,000 tons, unstreamlined, 13,500t tons cargo
12 workspaces; high automation ($9M) reduces that to 1 workspace Crew is 4x bridge crew, 3x technicians, 4x cargo masters Control Room: 10 stations
1 workspace (with high automation)
Crew is 4x bridge crew (one of two people for orbital manoeuvres, two others for watch), 3x technicians (1 per shift of 8h), and 4x cargo masters.
Cabins are 15x luxury, 1x sickbay including an automed, 1x robofac ($1k per hour), 2x office (one cargo office, one accounting office), 130t storage (for spare parts, food, etc).
Top air speed is 300km/h (not that you’d ever survive going into atmosphere)
Comm/Sensor is 9, Complexity C9. It would have ten control stations, but we’ll reduce that to 8 (mostly because it reduces our cost to a flat $681M).
All in all, this might well be an average freighter. Sure, the cabin situation is extremely comfortable - eleven crew and fifteen luxury cabins - but this just ensures the crew doesn’t spend that much time on leave, and would in principle allow you to take a few extra passengers. And replacing them with bunk rooms would add less than one-half of a percent in cargo capacity.
An Atlas (like Traveller’s liners) operates on a fixed route. We’ll start over any planet which has something to trade, which is usually going to be an inhabited one. In low orbit, the Atlas is going to be fuelled and loaded by several shuttles. If the planet doesn’t have that much space presence, it might be loaded by directly by the shuttles (75 flights are necessary to completely load it), otherwise the cargo might have been brought into orbit by the space elevator.
Once loaded, the Atlas is going to cast off, burning once to increase apoapsis to jump distance. For Earth, that’s 64 000 km orbital radius, and our Atlas will have to spend 5km/s and have to wait for eight hours for the jump. The jump will then deposit it above its first target world - and here, somewhat annoyed by the additional calculations needed because spacecraft don’t end up in a stable orbit, I’ll change the FTL system to emerge in such a stable orbit.
Again, the jump causes the Atlas to emerge 64 000 km above its first waystation, where the process is repeated - another 5 km/s total are spent for transfer and to achieve the parking orbit, where the Atlas will spend another eight hours recharging the FTL drive. During that recharging, cargo might also be transferred - just because it’s not a habitable planet doesn’t mean there aren’t any people living in the system. That’s fairly small-scale, though. What the Atlas does, though, is take on additional fuel. That one jump cost about 1/3rd of its fuel reserves, meaning that about 1500t of water is transferred.
This kind of operation (jump-park and recharge-jump) is repeated about five times between each of the main stations of the Atlas. Finally, it will park over an inhabited and populated planet, where a large part of the cargo might be exchanged before it continues its travels.
Changes to FTL mechanism
To simplify math, all FTL jump will depost the spacecraft into a stable orbit.
As with the interface cost, we’ll look at both variable and fixed costs.
Fuel/Provision Fuel is about 1500t per day, or 7500t per travel between interesting systems. We have already assumed that fuel costs $20 per ton over inhabited systems at least; assuming the same price at the waystations, it will cost $150,000 per travel between interesting system.
Regular Maintenance Contrary to shuttles, this is actually done by on-board technicians (with robotic support) and therefore is arguably fixed cost.
Provisions Even luxury provisions would be $10k per 500 person-days, or less than $14k per month. It really doesn’t make a difference.
Purchasing Cost This is $831M. Let’s again say this is written off over 12 years at 8% (matching SS2:27), which makes it roughly 1% per month, i.e. $8.31M per month.
Docking/Berthing Fees These are $2/ton for the first week, or $60k. I’ll assume that’s about $50k spent for fees over the main world (despite the Atlas only remaining in orbit for eight hours) which mostly covers traffic management cost and the arguably significant costs of either coordinating massive numbers of shuttle flights (surging) or in-orbit storage of cargo. Remember - you only have eight hours to load and unload your whole cargo, every hour you waste costs you more than ten thousand dollars.
Crew Salaries Total crew is 4 bridge crew, 3 technicians, and 4 cargo masters. SS2:28 classifies the captain of such a large craft as Rank 3, first officer as Rank 2, and most officers and senior enlisted as Rank 1. I’ll assume there’s one Rank 3, one Rank 2, and everybody else is (as a compensation for the long travel times) Rank 1. That makes a total of $184.8k per month, or about $50k per travel between interesting system.
Insurance Insurance is about 0.1% of the total value (i.e. $831K) per month. Cargo insurance will again be covered by the cargo owner.
Annual Maintenance Again, we don’t have numbers for that. Using Traveller Far Trader’s 0.1% of the purchasing price per year in spare parts (this is regular maintenance), plus another 0.1% for annual maintenance gives us $831k per year, or about $70k per month ($17.5k per main-system travel).
In total, this gives us variable costs of $150k between main systems, and fixed costs of about $9.5M per month, which is about $2.375M of fixed costs between main systems, for 13 500t of cargo - or about $190 per ton, most of which is fixed cost. Clearly, though, it’s more probable that the purchasing cost is instead written off over a longer time period. 40 years, instead of the 12 years above, would reduce the monthly payment to less than half a percent, or about $3.5M and therefore the total cost to about $1.2M per main systems, or about $100 per ton.
In a recession, this might be decreased to less than $30 or so, simply to cover operating expenses.
Next time, we’ll look at passenger transport and what kind of cargo one can transport economically.