[Spaceships] Drive economics

[DaltonS]

Originally Posted by AlexanderHowl

So, if we are using the real life assumptions of the research when comparing magsails to other TL9 drives, they tend to win out for interplanetary passenger travel in realistic settings. A SM+9 spacecraft with 10 magsails could maintain 0.01g thrust out to 75 AU, meaning that it could get to Saturn in 13 weeks. If we assume three armor, one control room, one engine room, one habitat, one hanger bay, and one reactor, that leaves only two cargo holds (300 tons). The spacecraft would likely cost $400M, so it needs to earn $6M a month to break even. Since each leg of the Earth-Saturn run is an average of 13 weeks, that means it needs to charge $80k per ton to break even ($100k per ton to make a profit).

10 magsails on one ship?!? I have trouble imagining one. Those things are huge when deployed. See my table here for dimensions. (The preceding post on that thread has the formulas and source.) I can't imagine how multiple sails would be arranged so they didn't interfere with each other. Two perhaps on opposite sides of the ship but even three would overlap. Numbers and RAW don't tell the whole story; you have to visualize how this would work. The original Roleplayer article that defined them makes for scary reading simply because of the scale involved. (As Douglas Adams said "space is big!") Mind you they would do excellently for low cost interplanetary cargo transport but don't expect express delivery. Interplanetary travel is always time consuming in a hard science setting … that's why we have super-science drives.

Dalton “Hibernation chambers are useful on 'slow boats'” Spence

[Jinumon]

Originally Posted by the-red-scare

In a sense, I guess I’m trying to figure out how (other than GM fiat) to decide which drives failed due to never having a chance to be competitive. And since it isn’t just “more expensive” or “too slow,” how to balance those factors.

Part of the baseline assumption that can be extrapolated from Spaceships 2: Trade Liners and Transports is that standard passage aboard a faster-than-light vessel costs $100 per person per day on board a vessel that operates without expending fuel for jumps. Presumably that figure includes expenses for crew salaries, provisions, financing costs, and depreciation, though based on a ship of what configuration, size, and operating capacity none of us can know for certain. I would use that as a baseline for figuring the cost of the fastest transport available in your setting, based on your own estimations for optimal and realistic ship size, configuration, and operating capacity.

Settling for slower methods may cost some constant multiplier based on the slower speed, at your discretion, though I would suggest considering slower transportation costing more based on the Time-Value of Money. If it takes someone three extra days to get somewhere, that's three extra days they could have been working their job and making a wage, so it'll likely cost about three-days wage (minus their own cost of living) cheaper than the fastest available option.

Of course, many of these variables depend on your own setting and thus your own fiat. How much does it cost to harvest and refine fuel, for example?

In short: $100 per person (or $10 per ton, for cargo) per day, plus expenses for the fastest available method. Consider time value of money when considering slower options, based on the average monthly income for your setting's TL.

Jinumon

[Fred Brackin]

Originally Posted by DaltonS

10 magsails on one ship?!? I have trouble imagining one. Those things are huge when deployed. See my table here for dimensions. (The preceding post on that thread has the formulas and source.) I can't imagine how multiple sails would be arranged so they didn't interfere with each other. ]

Spaceships is not necessarily that literal. 10 slots of most systems can be 10 systems or one 10x system that takes up space in 10 locations on the Hit location chart.

In this case I'd assume one very large magsail.

[Agemegos]

What you need to use here are the economic concepts of "generalised cost", and "behavioural value of time" for passengers or "value of time in transit" for cargo.

I won't go into the derivation. Basically, passengers will choose the travel option that minimises the generalised cost of travel, where the generalised cost is the fare (inclusive of e.g. insurance, taxes, and incidental expenses) plus the travel time times the individual passenger's BVOT. Behavioural values of time ought to be similar to wage rates (after taxes and fringe benefits etc.), but there are complicating factors e.g. when there are deadlines, when working hours are not freely adjustable, etc..

Customers despatching cargo will seek to minimise a generalised cost that is basically the sum of freight (plus insurance, loading, port fees, duties etc.) plus their opportunity cost of capital times the time in transit, plus depreciation (in the case of a perishable cargo). The opportunity cost of capital ought to look a bit like the interest rate, but there are complications in the cases e.g. of restricted access to capital markets, tax deductibility of interest, premiums on interest for e.g. risk….

[David Johnston2]

Honestly if there's one thing GURPS has done for me it is feed my disbelief in playable hard SF space settings.

[AlexanderHowl]

Originally Posted by Fred Brackin

Spaceships is not necessarily that literal. 10 slots of most systems can be 10 systems or one 10x system that takes up space in 10 locations on the Hit location chart.

In this case I'd assume one very large magsail.

Pretty much. Now, this assumes a dynamic magsail that expands and contracts according to the pressure of the solar wind, rather than the static magsail in Spaceships. If you have a static magsail, you are better off diving towards the Sun and using the higher solar wind to achieve phenomenal velocities.

For example, the above spacecraft would average 0.05g of acceleration on a dive to 0.1 AU. The dive would take nearly two weeks, but the spacecraft would reach 320 mps. At that point, it is probably spending the rest of the trip breaking, as it would not want to overshoot its target.

[Jinumon]

Originally Posted by Agemegos

What you need to use here are the economic concepts of "generalised cost", and "behavioural value of time" for passengers or "value of time in transit" for cargo.

I won't go into the derivation. Basically, passengers will choose the travel option that minimises the generalised cost of travel, where the generalised cost is the fare (inclusive of e.g. insurance, taxes, and incidental expenses) plus the travel time times the individual passenger's BVOT. Behavioural values of time ought to be similar to wage rates (after taxes and fringe benefits etc.), but there are complicating factors e.g. when there are deadlines, when working hours are not freely adjustable, etc..

Customers despatching cargo will seek to minimise a generalised cost that is basically the sum of freight (plus insurance, loading, port fees, duties etc.) plus their opportunity cost of capital times the time in transit, plus depreciation (in the case of a perishable cargo). The opportunity cost of capital ought to look a bit like the interest rate, but there are complications in the cases e.g. of restricted access to capital markets, tax deductibility of interest, premiums on interest for e.g. risk….

Considering that 2% is generally considered to be an approximate "ideal rate of inflation," would you consider 3% a solid stand-in for an economy's risk free interest rate?

[Agemegos]

Originally Posted by Jinumon

Considering that 2% is generally considered to be an approximate "ideal rate of inflation," would you consider 3% a solid stand-in for an economy's risk free interest rate?

3% per annum is a reasonable "typical" market real interest rate for a wealthy (i.e. not capital-starved) economy with a well-developed and well-functioning capital market, averaged over the business cycle. But firms sometimes behave as though their opportunity cost of capital were a bit higher, for a variety of reasons. 5% per annum wouldn't be unrealistic. Last time I did an exercise like this I assumed 5% real return.

[AlexanderHowl]

A large company needs to make a 20% profit for the owners to receive a 5% return. Out of that 20%, a quarter should go to charity, a quarter should go to taxes, a quarter should go to reserves, and a quarter should go to dividends. A higher dividend to profit ratio cannot normally be sustained by large companies for long without issues.

While reserves were unfashionable for decades, the pandemic is showing what happens when large companies do not have a year's earnings in reserves. Of course, a large company can instead depend on debt, but that is always risky, as debt usually needs to be paid off. In addition, corporate executives love raiding the reserves for massive stock buybacks and/or massive bonuses for themselves, as they do not care about the sustainability of the large companies they manage, just how much they can rob from them before they get hired by the next bunch of suckers. Large companies with substantial reserves are usually owned and operated by cooperatives, families, or unions.

[DaltonS]

Originally Posted by Fred Brackin

Spaceships is not necessarily that literal. 10 slots of most systems can be 10 systems or one 10x system that takes up space in 10 locations on the Hit location chart.

In this case I'd assume one very large magsail.

Okay, I missed that. But the drive system taking up half the mass of the ship? I suppose it depends on the value of the cargo and how urgently it's needed. When I think of a hard science interplanetary campaign (the kind magsails would be ideal for) I think of long range planning. Interplanetary cargo transport doesn't have to be fast as long as it's regular and reliable. (And cheap, so people would find it easier to pay for.) Express delivery has its place but by its very nature it would have to charge high prices to make a profit. Express boats might be more glamourous but I think "slow boats" would be more profitable in the long run and form the backbone of an interplanetary trading company.

One possibility I just now thought of (which I borrowed from "GURPS Traveller: Far Trader I admit) is the "slow boat" as a LASH liner with vehicle docks holding cargo lighters replacing internal cargo holds so it could transfer cargo more quickly at ports of call. Since with magsails refueling isn't an issue this shortened version of the "LASH Operations" sidebar on page 65 might be useful.

1. A small fleet of replacement lighters and a "bumboat" carrying pilots for the freighter's lighters (plus outgoing passengers and any replacement crew the freighter needs) rendevous with the freighter at a predetermined point.
2. The bumboat docks with the freighter. The pilots head for the lighters they taking out, replacement passengers and crew are exchanged and supplies for the freighter are off-loaded.
3. The outgoing lighters undock from the freighter and the replacement lighters dock.
4. The incoming pilots head to the bumboat and both it and the outing lighters depart.

If the "slow boat" requires fuel, a tanker will accompany the "fleet" and will refuel the freighter while steps 2 and 3 are going on. This might be interesting but would it be economical?

An interstellar super-science campaign is of course completely different and the economics for that would be largely made up anyway.

Dalton “Sudden ideas are bad for my digestion” Spence