Macroeconomics is a branch of economics dealing with the performance, structure, behavior, and decision-making of an economy as a whole. This includes regional, national, and global economies. Planetary or galactic. Some of it is about supplying services (like spacecraft rental or cargo shipping), some is about manufacturing, some is about resource development (mining), and some is about space commerce and trading.
For our purposes, it is the study of how a solar system or galactic empire's interstellar economony works together as a whole. As opposed to the economy of a solitary tramp freighter merchant with a scratch crew.
World-building SF authors will be interested in such macroeconomic questions as is there an economic MacGuffinite that can start the industrialization of space, and what kind of economic trade wars can spark full-scale shooting wars.
In a near-future non-FTL-starship rocketpunk universe limited to the solar system, the interplanetary economy will have to be created mostly from scratch. Yes, the existing megacorporations of Terra will be the major players, but there is no existing infrastructure. Everything will have to be build from scratch, and it will be about as quiet and law-abiding as the mythical Wild West.
Crewed starflight is going to be expensive, really expensive. All the various proposed methods from slow world ships to faster fusion vessels require huge resources to build and fuel. Even at Apollo levels of funding in the 1960’s, an economy growing at a fast clip of 3% per year is estimated to need about half a millennium of sustained growth to afford the first flights to the stars. It is unlikely that planet Earth can sustain such a sizable economy that is millions of times larger than today’s. The energy use alone would be impossible to manage. The implication is that such a large economy will likely be solar system wide, exploiting the material and energy resources of the system with extensive industrialization.
Economies grow by both productivity improvements and population increases. We are fairly confident that Earth is likely nearing its carrying capacity and certainly cannot increase its population even 10-fold. This implies that such a solar system wide economy will need huge human populations living in space. The vision has been illustrated by countless SciFi stories and perhaps popularized by Gerry O’Neill who suggested that space colonies were the natural home of a space faring species. John Lewis showed that the solar system has immense resources to exploit that could sustain human populations in the trillions.
But now we run into a problem. Even with the most optimistic estimates of reduced launch costs, and assuming people want to go and live off planet probably permanently, the difficulties and resources needed to develop this economy will make the US colonization by Europeans seem like a walk in the park by comparison. No doubt it can be done, but our industrial civilization is little more than a quarter of a millennium old. Can we sustain the sort of growth we have had on Earth for another 500 years, especially when it means leaving behind our home world to achieve it? Does this mean that our hopes of vastly larger economies, richer lives for our descendents and an interstellar future for humans is just a pipe dream, or at best a slow grind that might get us there if we are lucky?
Well, there may be another path to that future. Philip Metzger and colleagues have suggested that such a large economy can be developed. More extraordinary, that such an economy can be built quickly and without huge Earth spending, starting and quickly ending with very modest space launched resources. Their suggestion is that the technologies of AI and 3D printing will drive a robotic economy that will bootstrap itself quickly to industrialize the solar system. Quickly means that in a few decades, the total mass of space industrial assets will be in the millions of tonnes and expanding at rates far in excess of our Earth-based economies.
The authors ask, can we solve the launch cost problem by using mostly self-replicating machines instead? This should remind you of the von Neumann replicating probe concept. Their idea is to launch seed factories of almost self-replicating robots to the Moon. The initial payload is a mere 8 tonnes. The robots will not need to be fully autonomous at this stage as they can be teleoperated from Earth due to the short 2.5 second communication delay. They are not fully self-replicating at this stage as need for microelectronics is best met with shipments from Earth. Almost complete self-replication has already been demonstrated with fabs, and 3D printing promises to extend the power of this approach.
The authors assume that initial replication will neither be fully complete, nor high fidelity. They foresee the need for Earth to ship the microelectronics to the Moon as the task of building fabs is too difficult. In addition, the materials for new robots will be much cruder than the technology earth can currently deliver, so that the next few generations of robots and machinery will be of poorer technology than the initial generation. However the quality of replication will improve with each generation and by generation 4, a mere 8 years after starting, the robot technology will be at the initial level of quality, and the industrial base on the Moon should be large enough to support microelectronics fabs. From then on, replication closure is complete and Earth need ship no further resources to the Moon.
Gen Human/Robotic Interaction Artificial Intelligence Scale of Industry Materials Manufactured Source of Electronics 1.0 Teleoperated and/or locally operated by a human outpost Insect-like Imported, small-scale, limited diversity Gases, water, crude alloys, ceramics, solar cells Import fully integrated machines 2.0 Teleoperated Lizard-like Crude fabrication, inefficient, but greater throughput than 1.0 (Same) Import electronics boxes 2.5 Teleoperated Lizard-like Diversifying processes, especially volatiles and metals Plastics, rubbers, some chemicals Fabricate crude components plus import electronics boxes 3.0 Teleoperated with experiments in autonomy Lizard-like Larger, more complex processing plants Diversify chemicals, simple fabrics, eventually polymers Locally build PC cards, chassis and simple components, but import the chips 4.0 Closely supervised autonomy Mouse-like Large plants for chemicals, fabrics, metals Sandwiched and other advanced material processes Building larger assets such as lithography machines 5.0 Loosely supervised autonomy Mouse-like Labs and factories for electronics and robotics. Shipyards to support main belt. Large scale production Make chips locally. Make bots in situ for export to asteroid belt. 6.0 Nearly full autonomy Monkey-like Large-scale, self-supporting industry, exporting industry to asteroid main belt Makes all necessary materials, increasing sophistication Makes everything locally, increasing sophistication X.0 Autonomous robotics pervasive throughout Solar System enabling human presence Human-like Robust exports/imports through zones of solar system Material factories specialized by zone of the Solar System Electronics factories in various locations
Table 1. The development path for robotic space industrialization. The type of robots and the products created are shown. Each generation takes about 2 years to complete. Within a decade, chip fabrication is initiated. By generation 6, full autonomy is achieved.
Asset Qty. per set Mass minus Electronics (kg) Mass of Electronics (kg) Power (kW) Feedstock Input (kg'hr) Product Output (kg/hr) Power Distrib & Backup 1 2000 ----- ---- ---- ---- Excavators (swarming) 5 70 19 0.30 20 ---- Chem Plant 1 - Gases 1 733 30 5.58 4 1.8 Chem Plant 2 - Solids 1 733 30 5.58 10 1.0 Metals Refinery 1 1019 19 10.00 20 3.15 Solar Cell Manufacturer 1 169 19 0.50 0.3 ---- 3D Printer 1 - Small Parts 4 169 19 5.00 0.5 0.5 3D Printer 2 - Large Parts 4 300 19 5.00 0.5 0.5 Robonaut assemblers 3 135 15 0.40 ---- ---- Total per Set ~7.7 MT
launched to Moon
64.36 kW 20 kg
Table 2. The products and resources needed to bootstrap the industrialization of the Moon with robots. Note the low mass needed to start, a capability already achievable with existing technology. For context, the Apollo Lunar Module had a gross mass of over 15 tonnes on landing.
The authors test their basic model with a number of assumptions. However the conclusions seem robust. Assets double every year, more than an order of magnitude faster than Earth economic growth.
Once robots become sophisticated enough, with sufficient AI and full self-replication, they can leave the Moon and start industrializing the asteroid belt. This could happen a decade after initiation of the project.
With the huge resources that we know to exist, robot industrialization would rapidly, within decades not centuries, create more manufactures by many orders of magnitude than Earth has. Putting this growth in context, after just 50 years of such growth, the assets in space would require 1% of the mass of the asteroid belt, with complete use within the following decade. Most importantly, those manufactures, outside of Earth’s gravity well, require no further costly launches to transmute into useful products in space. O’Neill colonies popped out like automobiles? Trivial. The authors suggest that one piece could be the manufacture of solar power satellites able to supply Earth with cheap, non-polluting power, in quantities suitable for environmental remediation and achieving a high standard of living for Earth’s population.
With such growth, seed factories travel to the stars and continue their operation there, just as von Neumann would predict with his self-replicating probes. Following behind will be humans in starships, with habitats already prepared by their robot emissaries. All this within a century, possibly within the lifetime of a Centauri Dreams reader today.
Is it viable? The authors believe the technology is available today. The use of telerobotics staves off autonomous robots for a decade. In the 4 years since the article was written, AI research has shown remarkable capabilities that might well increase the viability of this aspect of the project. It will certainly need to be ready once the robots leave the Moon to start extracting resources in the asteroid belt and beyond.
The vision of machines doing the work is probably comfortable. It is the fast exponential growth that is perhaps new. From a small factory launched from Earth, we end up with robots exploiting resources that dwarf the current human economy within a lifetime of the reader.
The logic of the model implies something the authors do not explore. Large human populations in space to use the industrial output of the robots in situ will need to be launched from Earth initially. This will remain expensive unless we are envisaging the birthing of humans in space, much as conceived for some approaches to colonizing the stars. Alternatively an emigrant population will need to be highly reproductive to fill the cities the robots have built. How long will that take? Probably far longer, centuries, rather than the decades of robotic expansion.
Another issue is that the authors envisage the robots migrating to the stars and continuing their industrialization there. Will humans have the technology to follow, and if so, will they continue to fall behind the rate at which robots expand? Will the local star systems be full of machines, industriously creating manufactures with only themselves to use them? And what of the development of AI towards AGI, or Artificial General Intelligence? Will that mean that our robots become the inevitable dominant form of agency in the galaxy?
The paper is Metzger, Muscatello, Mueller & Mantovani, “Affordable, Rapid Bootstrapping of the Space Industry and Solar System Civilization,” Journal of Aerospace Engineering Volume 26 Issue 1 (January 2013). Abstract / Preprint.
As I've mentioned so many times you must be sick of it, in the California Gold Rush of 1849, it was not the miners who grew rich, instead it was the merchants who sold supplies to the miners. Once people are traveling in space, there will arise numerous business opportunities to sell things to traveling people.
Please note that none of these are MacGuffinite, they are not economic motivation for the colonization and industrialization of space. But once there are people in space, they become potential customers.
Science fiction authors should note that the presence of these various spacegoing corporations can lead to a very colorful background for their novels. Indeed, the history of how a given corporation got started could be an interesting series of stories. Things are raw and cut-throat on the space frontier, especially when the people starting the company are novices learning the ropes the hard way. Hilarity ensues.
This is more a near-future business. Which means it could be a MacGuffinite precursor.
In the present time the biggest space industry is satellites. These are mostly of the communication variety (telecommunication, radio, television, phone, internet access), but navigation, weather, and crop monitoring are also viable industries. Not to mention all the military spy satellites.
These suckers are hideously expensive to design, build, and launch into orbit. Obviously the longer their effective lifespan, the more the owner can amortised the cost.
What limits the satellite's lifespan? Is it meteorite strikes? No. Is it deterioraization due to space radiation? No. Is it electronic malfunctions? No. Well, what is it? The blasted fuel tanks for the attitude control jets being used up! And the little darlings generally run dry years before anything else on the satellite zaps out.
Gee, it is a shame there exists no company running satellite orbit-side servicing like an outer space Triple-A, filling empty attitude-jet fuel-tanks and repairing malfunctions. They could charge huge fees without being more expensive than launching an entire new replacement satellite.
Sounds like a business opportunity to me.
This was the inspiration for the 1988 MOVERS Orbital Transfer Vehicle study. More recently (2017) the Space Infrastructure Services LLC (SIS) company proposed a similar service, using teloperated drones. Now please understand that their drones can only refuel SIS designed satellites, but they probably consider that to be an advantage.
Remember that once you get to orbit you are halfway to anywhere. So a company offering an affordable way to get your payload and crew into orbit will find their services in high demand. The point is that a laser launch service is likely to be much cheaper than any chemical rocket will ever be. Freeman Dyson is of the opinion that a large country such as the United States should invest in such a service and offer it at a nominal fee, in order to promote interplanetary Prairie Schooners. See below.
Jerry Pournelle foresees that with the availability of a laser launch service coupled with affordable habitat modules could lead to wagon train in space. Details here.
Entrepreneurs could sell habitat module services between Terra and Mars by making a space-going motel into an Aldrin Cycler. Space explorers on a budget would only need enough delta V to get themselves and their payload up to Mars transfer velocity, they could then rent a room and life-support services at Motel 6 km/s. This concept is quite similar to the Wagon Train in Space.
Spacecraft going to a given destination, e.g., Mars, will tend to clump into convoys in order to take advantage of Hohmann transfer windows. Clever operators will have special ships in the group: not to travel to Mars but to do business with the other ships in the group (with an eye to making lots of money).
Things like being an interplanetary 7-Eleven all night convenience store, selling those vital little necessities (that you forgot to pack) at inflated prices.
A fancy restaurant spaceship for when you are truly fed up with eating those nasty freeze-dried rations.
A space-going showboat for outer space riverboat gambling.
An (expensive) health clinic, when you are not sure if that is merely a tummy-ache or actually full-blown appendicitis.
Not to mention a orbital brothel.
Fans of TOS Battlestar Galactica will be reminded of the Rising Star, luxury liner and casino in space.
And the owners of an wagon train in space might want to add a couple of these company-owned modules, to sell stuff to the wagon train riders.
Orbital laser services might be just as lucrative as laser launching services. Owners of cheap laser thermal rockets could rent laser time from Beams-Я-Us. Not to mention spacecoach owners. You could probably even rent the cheap laser thermal rockets for use with the laser time.
For that matter, Beams-Я-Us would probably have their own cargo laser rockets for transport services, making them the interplanetary equivalent of the railroad (The Laser Horse). Even if there is no initial need for such services, a government might create it for political reasons. Even if it is eventually taken over by the military.
A laser railroad could easily become Wagon Train in Space.
Go here for technical details on laser thrust services.
The multi-billion dollar Terran petroleum industry is a model for offering the services of orbital propellant depots. Since propellant is the sine qua non of rockets, owning a network of such depots and the supplying them by in situ resource utilization will be a license to print money.
There is also money to be made on the side by being the interplantary equivalent of a 7-Eleven convenience store attached to a gasoline station. With the same inflated prices.
Rob Davidoff and I worked up a science fiction background where the Martian moon Deimos becomes the water supplier for the entire solar system. We call it Cape Dread.
These are giant spinning bola-like tether propulsion installations. A pod with engines not much stronger than attitude jets can attach itself to one and be precisely catapulted at a destination with many gravities of acceleration. At the destination the pod is caught by a similar installation. All for a fee, of course.
These would work well with interplanetary Prairie Schooners.
Laser Launching is a remarkable inexpensive way to get payload into LEO (aka "Halfway to Anywhere"). Unfortunately it requires lots of money for creating the initial facillity.
Genius Freeman Dyson believes it would be a good investment for a country such as the United States to build a laser-launch site and charge a modest fee to anybody who wanted to boost a payload into orbit. Such as Maw & Paw asteroid mining businesses. This is similar to the political motivation behind the US transcontinental railroad mentioned here.
An affordable space-going version of a Prairie Schooner could be purchased by private individuals, boosted into orbit for a modest fee by laser launch, then another modest fee to an ion-drive tug to join the wagon train to Luna, Mars, or the Asteroid belt. LEO is halfway to anywhere, remember? This would also allow grizzled old asteroid miners to go prospecting in the belt.
For a possible space-going Prairie Schooner, take a look at the Spacecoach concept.
Jerry Pournelle foresees that with the availability of a laser launch service coupled with affordable habitat modules could lead to wagon train in space. Which should bring a bit grin to the face of any science fiction author trying to find a plausible reason to write novels about asteroid miners and homesteaders living in the solar system.
Maw and Paw pioneers/rock-rats/space-entrepreneurs just need the price of a hab module (i.e., Prairie Schooner) and laser boost fees for the overhead of space access. This gets them into LEO. Yes, in theory they can boost their hab module using something like an SpaceX style reusable chemical rocket instead of laser launching, but that is liable to be much more expensive. This entire concept hinges on some method to drive surface-to-orbit cargo cost down to the point where almost anybody can afford them.
In a future where the industrialization of space has advanced even further, hab modules and all the other equipment needed for space homesteading will be manufactured in space (i.e., outside of Terra's gravity well and its expensive 7.6 km/sec delta-V cost). So all Maw and Paw will need are tickets for themselves and any children on a Pan Am Space Clipper passenger shuttle flight into orbit (plus a full bank account). Or steerage-class tickets to ride in the payload bay of a cargo rocket (or laser launch capsule) lying on lumpy shipping crates while wearing space suits. Once in orbit they will purchase a hab module all needed equipment from orbital factories, avoiding the monstrous shipping charge of boosting all that mass from Terra's surface. From a science fiction author's standpoint, this just replaces a huge investment in laser launching with an even huger investment in orbital manufacturing. With a bonus of political tension as the laser launch companies angrily watch their business fall in lockstep with the rise in orbital manufacturing. That will supply the author with some dramatic plots.
Once in orbit with their hab, all Maw and Paw need (besides supplies for their business model) is transport for their hab module, to get it to the asteroid belt or whatever the plan is. Possible business models include asteroid mining, peddler, tinker, cobbler, boomtown store, and camp following. Maw and Paw con artists can try their hand at selling interplanetary snake oil. Or maybe just founding a space settlement. It's American Pioneer days all over again.
So Maw and Paw get to go homesteading among the asteroids, and the science fiction author gets a reasonably bullet-proof justification for a rocketpunk background for their novels. Sounds like a win-win to me.
There are several options to transport Maw and Paw in their hab module to their desired destination.
For an interplanetary Prairie Schooners owned by a Maw-and-Paw company, momentum-energy banks dovetail nicely with laser launch services. It doesn't matter that your tin-can habitat module has the same delta V as a can of underarm deodorant spray. The laser will boost it into orbit and the bola will sling it to the destination. The limits are [a] you can only travel between momentum-energy banks installations and [b] do you have enough money to pay for the bola services? [c] is the acceleration low enough so it won't instantly kill Maw and Paw? Momentum banks for raw cargo will probably accelerate it at levels far above lethal, ones rated for 100% fully healthy Mom and Pop will have to keep under 30 gs for no more than 10 minutes.
They will have orbital tugs for hire, with regularly scheduled service to haul hab modules to various interplanetary destinations. The tugs could probably haul long strings of hab modules at a time like an outer-space train, especially if the tugs had a water-skiing thruster arrangement. Wagon train indeed!
The tug would probably also haul a company emergency module. If one of the hab modules springs a leak or otherwise has an emergency, the company module could rescue them. In exchange for a stiff fee, of course. In the wild west, wagon trains were mostly for mutual assistance, so the inhabitants of the various hab modules would probably want to try and help each other. Only if nobody offers any help would the unlucky Maw and Paw have to mortgage their souls to the company emergency module.
Orbital laser services could rent Maw and Paw a cheap laser thermal rocket engine (with a stiff deposit fee, refundable upon return of the engine). Bolt it to the hab module, set up payment transfers to Beams-Я-Us service department, and you are good to go.
Beams-Я-Us probably also has a Laser Horse or two: the laser equivalent of a choo-choo train. This would operate in the same manner as the Wagon Train Company, substituting a Beams-Я-Us laser thermal orbital tug.
In theory Maw and Paw could use an Aldrin Cycler to transport their prairie schooner. In practice it is more expensive. Remember that Cyclers are just clever ways to avoid the necessity of spending the delta-V expense on your life-support system, instead using the system on the cycler. You still have to spend the delta-V to get Maw and Paw and their payload up to Asteroid Belt Transfer Velocity. But wait, you have to spend it on the life-support system in the hab module, so you ain't saving any money. This only makes sense if you are planning on just transporting your bodies to the belt and purchasing your hab module, supplies, and equipment in the belt. Maw and Paw better check prices on hab modules in cis-Lunar space and compare them to asteroid belt prices before they try this stunt.
If Maw and Paw have lots of money, they might purchase a real spacecraft instead of just a habitat module plus renting transport. A Spacecoach with a Water Wall would do nicely. This would be required if the business model necessitates mobility, e.g, chasing boomtowns or following camps.
But even though they now have no need of transportation services, it might make sense for them to travel along with a Convoy Services flotilla or shadowing a Wagon Train. Just in case Maw or Paw suddenly needs the services of the company emergency module...
Chances are good that most of the transport options noted above may have Convoy Services tagging along, like vultures. Just in case Maw and Paw might suddenly desperately need something, and is willing to shell out for inflated prices. A Wagon Train Company may very well covertly include some of their own convoy services modules in the train, outside of the standard emergency services module. Maw and Paw don't need to know that the Wagon Train tug, emergency module, and all the Convoy Services flotilla all belong to the same company.
After they arrive and start working their homestead it won't be long before Maw and Paw are visited by the peddlers, tinkers, cobblers, and the arrival of the latest catalog from Sears Robot & co. And the snake-oil salesmen of course.
So all the science fiction author has to do is postulate a drastically cheap method of boosting payload from Terra's surface, and in exchange receive justification for an industrialized and colonized solar system background. Plus the option of using the huge library of cowboy-and-westerns literature about pioneers for plot inspirations.
Oh, I'm sure you've seen this trope with media associated with the North American frontier. The peddler / Yankee trader / tinker traveling from pioneer homestead to homestead, selling the little necessities and luxuries.
But as I've mentioned many times before, futurologists and science fiction writers can save themselves tons of work by remembering that everything old is new again. The North American frontier is dead and gone, but roughly the same situation could arise in the future. I'm thinking about mom-and-pop asteroid mining operation and pioneers colonizing interstellar planets.
All three groups advance into wilderness areas with no infrastructure nor shopping malls. All of them need tools and items for survival, and certain luxuries that make life bearable. Any entrepreneur worthy of the title can see this is a business opportunity.
Now, there are differences. Peddlers in North America could travel by foot, carrying their wares on their backs. They could also obtain their wares at a modest cost. This made the trade attractive to beginner businesspeople with strong legs but little starting capital. However, a interplanetary peddler selling things to asteroid miners are going to need a space suit and a space taxi at a minimum (though the latter could indeed be jury rigged out of stuff from the spaceship junkyard). If the peddler is traveling from star colony to star colony they have to have some kind of starship. This raises the bar for entry into the business, but the bar has already been raised for the pioneer star colonists. If they can afford the interstellar transport fee, so can the peddler.
The pioneer people were also eager for any hot-and-juicy gossip the peddler could bring from the last villiage they were at. Interstellar colonists might already know all the news by virtue of their jury-rigged internet.
And of course some peddlers were con artists. That ain't gonna change in the future, not without drastic changes in human personality.
Frontier peddlers in history would often find their stock boxes growing heavier as they sold stuff. This is because many of the pioneers had no money, so they had to pay with crops, food, honey, or other barter. The peddler would lug all this barter back to more civilized regions and sell it. Asteroid peddlers would probably have to be paid in asteroid ore.
Readers who are rich with years will remember the wearisome number of jokes on the topic of the traveling salesman and the farmer's daughter. The "traveling salesman" was a peddler.
Closely related is the profession of Tinker. North American pioneers had very little money, so they could not afford to replace a broken household utensil. The tinker would use low-tech methods with inexpensive or free local materials to make the repair. To fix a hole in a pan, the tinker would make a "tinker's dam" out of clay, mud, or dough. The tinker would then pour some molten solder into the dam, which would solidify and mend the hole. The tinker's dam would be removed and thrown away, since it is literally "not worth a tinker's dam."
So in the future, Asteroid Dan: the Tinker Man would travel to Maw and Paw Kessler asteroid mine to glue together their broken antiquated laser drill. And have to be OK with being paid in fresh asteroid ore instead of cash.
Now, if times get tough (or if you are trying to take advantage of alien technology), a tinker could graduate into becoming a Cobbler.
Maw and Paw Kessler have a problem repairing their broken laser drill due to a lack of money, NOT a lack of technology. The tech is available, assuming you have coin.
If the technology become unavailable, that's when the tinkers will have to become cobblers. A tinker tries to repair broken parts. A cobbler tries to replace a broken part with some locally available equivalent.
For instance: a tinker welds together a cracked gear. A cobbler deals with a sudden absence of automobile gasoline by altering the car to run on methane (compress methane boiled off by stable-dung, and plumb a gas-supply into the induction manifold using scrap tubing and insulated tape).
Why would the technology become unavailable? Many reasons. A sudden zombie apocalypse. The galactic empire descends into the Long Night. Or if you are a combat archeologist trying to fix some million-year old alien paleotechnology, where the alien repair parts also became unavailable a million years ago.
While most of the scams are optimised for urban dwelling victims, many work well in a frontier setting.
Wild west TV shows and movies often feature the classic Medicine Show scam where mountebanks and quacks distract the crowd with entertainers while peddling their worthless miracle elixir cure-alls and snake oils. Change the labels to "alien serums" or "nanotech breakthroughs" and you are good to go.
The old "salting a mine" trick should work perfectly well on gullible asteroid miners.
Colonists facing crop failure in the face of adverse weather are ripe for the ancient Rain making scam.
Trade improves pretty much all economies, so a planetary colony will find their economy enhanced by interplanetary and/or interstellar trade spacecraft.
My question is what happens to such a colony who relies upon off-world trading if the trade is cut off? Is this a minor inconvenience or does it cause a major recession that crashes the entire planetary economy?
That question is above my pay grade, but I suspect that either outcome is plausible enough for an author to utilize it in their novel.
Such interruptions can happen due to trade embargoes, blocades by hostile starfleets, a planetary quarantine imposed to stop the interstellar spread of a planetary pandemic, or by the decline and fall of the galactic empire.
As a side note: if a trade cut-off is an economic disaster, a planetary government will be tempted to cover up any news of a planetary pandemic.
The law of comparative advantage describes how, under free trade, an agent will produce more of and consume less of a good for which they have a comparative advantage.
In an economic model, agents have a comparative advantage over others in producing a particular good if they can produce that good at a lower relative opportunity cost or autarky price, i.e. at a lower relative marginal cost prior to trade. Comparative advantage describes the economic reality of the work gains from trade for individuals, firms, or nations, which arise from differences in their factor endowments or technological progress. (One should not compare the monetary costs of production or even the resource costs (labor needed per unit of output) of production. Instead, one must compare the opportunity costs of producing goods across countries).
David Ricardo developed the classical theory of comparative advantage in 1817 to explain why countries engage in international trade even when one country's workers are more efficient at producing every single good than workers in other countries. He demonstrated that if two countries capable of producing two commodities engage in the free market, then each country will increase its overall consumption by exporting the good for which it has a comparative advantage while importing the other good, provided that there exist differences in labor productivity between both countries. Widely regarded as one of the most powerful yet counter-intuitive insights in economics, Ricardo's theory implies that comparative advantage rather than absolute advantage is responsible for much of international trade.
Classical theory and David Ricardo's formulation
If a foreign country can supply us with a commodity cheaper than we ourselves can make it, better buy it off them with some part of the produce of our own industry employed in a way in which we have some advantage. The general industry of the country, being always in proportion to the capital which employs it, will not thereby be diminished [...] but only left to find out the way in which it can be employed with the greatest advantage.
Writing several decades after Smith in 1808, Robert Torrens articulated a preliminary definition of comparative advantage as the loss from the closing of trade:
[I]f I wish to know the extent of the advantage, which arises to England, from her giving France a hundred pounds of broadcloth, in exchange for a hundred pounds of lace, I take the quantity of lace which she has acquired by this transaction, and compare it with the quantity which she might, at the same expense of labour and capital, have acquired by manufacturing it at home. The lace that remains, beyond what the labour and capital employed on the cloth, might have fabricated at home, is the amount of the advantage which England derives from the exchange.
In 1817, David Ricardo published what has since become known as the theory of comparative advantage in his book On the Principles of Political Economy and Taxation.
In a famous example, Ricardo considers a world economy consisting of two countries, Portugal and England, each producing two goods of identical quality. In Portugal, the a priori more efficient country, it is possible to produce wine and cloth with less labor than it would take to produce the same quantities in England. However, the relative costs or ranking of cost of producing those two goods differ between the countries.
Hours of work necessary to produce one unit ProduceCountry Cloth Wine England 100 120 Portugal 90 80
In this illustration, England could commit 100 hours of labor to produce one unit of cloth, or produce 5/6 units of wine. Meanwhile, in comparison, Portugal could commit 90 hours of labor to produce one unit of cloth, or produce 9/8 units of wine. So, Portugal possesses an absolute advantage in producing cloth due to fewer labor hours, but England has a comparative advantage in producing cloth due to lower opportunity cost.
In other words, if it is cheaper for a country to produce one good relative to a second, then they will have a comparative advantage and an incentive to produce more of that good which is relatively cheaper for them to produce than the other--assuming they have an advantageous opportunity to trade in the marketplace for the other more difficult to produce good. Similarly most anyone should take the opportunity to offer in the marketplace a good which they have a relative advantage in producing.
In the absence of trade, England requires 220 hours of work to both produce and consume one unit each of cloth and wine while Portugal requires 170 hours of work to produce and consume the same quantities. England is more efficient at producing cloth than wine, and Portugal is more efficient at producing wine than cloth. So, if each country specializes in the good for which it has a comparative advantage, then the global production of both goods increases, for England can spend 220 labor hours to produce 2.2 units of cloth while Portugal can spend 170 hours to produce 2.125 units of wine. Moreover, if both countries specialize in the above manner and England trades a unit of its cloth for 5/6 to 9/8 units of Portugal's wine, then both countries can consume at least a unit each of cloth and wine, with 0 to 0.2 units of cloth and 0 to 0.125 units of wine remaining in each respective country to be consumed or exported. Consequently, both England and Portugal can consume more wine and cloth under free trade than in autarky.
The 11 Billion Dollar Bottle of Wine
The Possibilities of Interstellar Trade
This article originally appeared in Ares nr. 12 (Jan 1982), a science fiction/gaming magazine published by SPI. I was a contributing editor at the time. Despite its age, it holds up quite well, I believe.
Given what scientists say about the probability of intelligent life in the galaxy, it seems almost inevitable that, sooner or later, we will come into contact with another technological species. We can expect that the same kind of interrelationships which existed between primitive peoples on our planet will occur between the two species.
There are basically two ways which individuals or groups can interact—peacefully and violently. Peaceful interaction implies voluntary exchange between two groups which benefit both—that is, trade. Violent interaction implies the attempt by one group to coerce the other—that is, war. Much attention has been paid to the second possibility in the gaming field, but only recently has much been paid to the first.
The reason trade exists is that different groups are efficient at doing different things. For example, let us say there are two countries, A and B. A takes 15 man-hours to make a widget, but only 5 to make a thingummy. B takes 5 to make a widget and 15 to make a thingummy. Suppose each country produces as many thingummies as widgets, and each has 100 man-hours to allocate. Each will then produce 5 thingummies and 5 widgets ((5*15) + (5*5) = 75 + 25 = 100 man-hours). If A and B now open trade, each may concentrate on producing the item which it produces more efficiently; A will produce thingummies and B widgets. Since a thingummy costs A 5 man-hours, it can produce 20; similarly, B produces 20 widgets. They trade 10 thingummies for 10 widgets, since each wants as many thingummies as widgets. The final result is that each country has 10 thingummies and 10 widgets and each is twice as well off as before. (Indeed, trade is even in the best interest of both when one party has an efficiency advantage in both products, because trade will allow him to shift production into areas where his efficiency is greater.)
One problem not taken into account in the above analysis is the cost of transportation (and other barrier costs, such as import and export duties) which raise the cost of doing business with another group. Let us say that it takes 5 man-hours to transfer a unit of widgets or thingummies from country A to country B or vice versa. Each country will then have to allocate 10 man-hours to each unit of a good transported to the other country, and 5 to each unit consumed at home. It is still more efficient for A to concentrate on making widgets and B on making thingummies. However, the best A can do is to make 14 widgets (70 man-hours) and transport 6 to B (30 man-hours) while B does the reverse. Each country is still better off engaging in trade than not, but not as well off as they would be if transportation were costless.
This is, of course, an extremely important result for interstellar trade because the costs of transporting anything over interstellar distances is bound to be high, even given some kind of faster-than-light (FTL) drive.
In essence, in order to make trade in a good worthwhile, the cost of creating a good in one location and transporting it to another must be less than the cost of creating it in that distant location. To determine what interstellar trade (if any) is feasible, there are then two questions we must answer, at least in principle: 1.) what are the costs of interstellar transportation, and 2.) what are the costs of production in a highly advanced civilization capable of interstellar trade? Neither question can be easily answered, but we can, at least, make some conjectures.
In the simple analysis above, we assumed that the cost of production or transportation could be measured in "man-hours." For any more sophisticated investigation, this is inappropriate. An hour of a PhD's time is worth considerably more than an hour of an unskilled laborer's time. Furthermore, such things as the relative efficiency of production machinery (and other capital goods) and the cost of resources cannot easily be measured in man-hours. That is the primary reason why money exists—because it is an easy tool to measure relative costs.
Extrapolating costs into the future is difficult or impossible because technology constantly advances—changing both costs and relative costs—population trends are not entirely predictable, and the cost of resources may change dramatically as terrestrial resources become scarcer and extraterrestrial resources begin to be exploited. However, the cost of transportation is dependent on three primary factors: the cost of building and operating transport vessels, time, and energy required for transportation.
The first factor is very difficult to figure, but the second two are easily calculable, at least for sublight travel. Given a particular transportation system, it is possible to calculate the amount of energy needed to move something from point x to point y in a given amount of time. This will be discussed in more detail later.
Ignoring the cost of maintaining and building a transportation system, the amount of energy needed to transport a unit of mass is roughly proportional to the cost of transporting it. Thus, the less energy transportation requires, the more likely trade can occur and the more commodities it is profitable to trade.
Time is also an important factor, because the longer it takes to transport a good, the further in advance an investor must put up his capital before he will see a return. At sublight speeds, interstellar transportation will necessarily require between 10 and 10,000 years for a round trip. In America, there are few companies who are willing to wait even 10 years for an investment to provide a return. Government tends to think in even shorter terms; the insistence of Congress on space programs which produce short-term return and its reluctance to engage in projects that may prove immensely profitable over a period of decades, but costly in the short-term, is an example of this thinking.
Quite apart from this psychological reluctance to think too far ahead is the very real economic cost of delayed return on investment. When determining whether an endeavor will be profitable, an investor must keep "opportunity costs" in mind. If an investor has a choice of two investments, both profitable, and chooses the one which is less profitable, he has, in real terms, lost money; he could have made more by taking the more profitable investment. If one can earn 17% of one's money in a money market fund, and investing in a small game company is likely to produce a profit of 10%, there is no reason to invest in the company.
If, say, an investor can earn 10% of his money per year by investing in his own planet, over a period of ten years he can increase his wealth by 160%. To be profitable, an interstellar trading voyage would have to generate more profit than this. So the high time required for interstellar voyages result in high opportunity costs. (In 100 years, at 10% an investor would have increased his wealth by more than 15,000 times.) High opportunity costs combined with high transportation costs make interstellar trade extremely (though not necessarily prohibitively) expensive.
Energy Costs of Sub-Light Travel
Many different interstellar propulsion systems have been proposed, and the energy required for each is different. Since we want to encourage interstellar trade, it behooves us to make relatively optimistic assumptions. In Ares nr. 1, John Boardman investigated the times and costs in energy entailed in using an anti-matter drive capable of 100 percent conversion of energy into gamma rays, accelerating off reaction from such conversion. It is possible to conceive of even less costly drives—such as a ramscoop which gathers its reaction mass en route—but Boardman's drive is at least theoretically feasible while the ramscoop concept has some real technical problems. The Boardman anti-matter drive can then be taken as the most optimistic drive for sublight transportation.
Boardman derived a formula to determine the mass ratio needed between the initial mass of a ship and the mass of the final payload (see table below) assuming the ship accelerated to a given speed, coasted at that speed, and decelerated to rest at its target. He also derived a figure (5704 megawatt-years) for the amount of energy required to produce a kilogram of anti-matter. Combining these two, we can determine the amount of energy needed to accelerate a ship to a given speed and then decelerate to rest. Evidently, the higher the "coasting" speed, the greater the initial investment and the faster the ship will get to its target.
Historically, the US economy has grown at an average annual rate of 3% (corrected for inflation) over the past 150 years. If we assume that net human growth will continue at the rate of 3% in the future, we can calculate the opportunity cost of tying capital up in an interstellar voyage by assuming an average 3% rate of return were the capital invested at home. Obviously, the longer the voyage, the higher the opportunity cost. Compound interest mounts up very rapidly.
The important point is that the opportunity cost goes down if the maximum velocity of the ship goes up (because the ship gets to its destination and back sooner, so the interest is compounded for fewer years). The initial investment goes up, however as the maximum velocity of the ship goes up (because more energy is required to accelerate it to a higher velocity). Evidently, there is, for a voyage of a given length, a maximum velocity at which the minimum net cost is achieved. Table 1 shows the minimum costs for voyages of several lengths between 5 and 100 light-years.
Table 1: Minimum Cost Journeys Using Anti-Matter Drive Distance Velocity Time Invest
5 .23c 43.9 6,820 2.99 3.66 25,000 10.9 10 .38c 53.4 14,000 6.13 4.85 67,900 29.7 25 .59c 86.0 32,800 14.40 12.70 417,000 183.0 50 .74c 136.9 64,900 28.40 57.20 3,710,000 1,630.0 100 .84c 240.2 120,000 52.60 1,120.00 145,000,000 63,600.0
- Distance: distance in light-years from earth to star.
- Velocity: maximum velocity of ship as percentage of speed of light.
- Time: time for a round trip in years.
- Invest (MY-yrs): initial investment in megawatt-years per kilogram.
- Invest (1981$): initial investment in billions of 1981 US dollars per kilogram.
- OM: opportunity multiple.
- Cost (MY-yrs): total cost in megawatt-years per kilogram.
- Cost (1981$): total cost in billions of 1981 US dollars per kilogram.
Assumptions: The figures in this table are drawn using the following assumptions: Boardman anti-matter drive; refueling at destination; vehicle mass neglected; 100% efficiency drive; acceleration = 9.8 m/sec2; rate of return on investments at home is 3% annually; $.05 in 1981 dollars per kilowatt-hour ($438,000 per megawatt-year).
The cost of the energy needed to move a kilogram of matter at the minimum cost velocity of 0.23 times light-speed to a point 5 light-years away and back is 6,820 megawatt-years, which at average American prices of 5 cents per kilowatt hour works out to about $3 billion in 1981 dollars. When including opportunity costs, the total cost rises to about 25,000 megawatt-years, or about $11 billion. Costs increase rather more than linearly; the total cost of a 100 light-year trip is about $64 trillion dollars (about 20 times the US Gross National Product in 1981).
Actually, $11 billion is not bad when one considers that the Apollo program cost around $10 billion. To look at the energy figures, the initial investment of 6,820 megawatt-years is about 3% of the installed electrical generating capacity of the US as of 1975 — it would take 6 fairly large nuclear plants operating full-blast for a year to produce the antimatter needed for the trip. That is a lot of energy, but it is by no means beyond our capabilities. (Of course, the technology does not exist at the moment, and is likely never to exist at least in the idealized form postulated by Boardman.) This limitation implies that sending miniaturized, robot probes to the nearer stars is well within the realm of feasibility and will, barring nuclear war or some other catastrophic end to human civilization, probably occur sooner or later.
However, the cost is per kilogram, which means that human beings are unlikely ever to go to the stars, given the mass entailed in the life support system necessary to keep a human alive for several decades.
Standards of Living
Eleven billion dollars is a lot of money — or is it? We have postulated that the economy will continue to grow, world-wide (or perhaps I should say solar-system-wide), at a rate of 3% per annum. Many countries have growth-rates higher than this (and quite a few less), so it seems a reasonable presumption — assuming 1.) technology continues to advance, 2.) we begin to exploit the vast resources available in the solar system off earth, and 3.) economic growth does not get choked off by the continued growth of parasitic government at the expense of the productive sector of the economy (the last is the most questionable assumption).
As an example, let us say that the average individual on the earth commands about $1,000 per year (the figure is probably somewhat, but not much, lower, averaged over the earth's population). Figure 1 shows how much money individuals will, on the average, be able to command in the future. Talking of "money" in this context may be confusing; we are talking, actually, about the resources, energy, and goods which an individual commands. The average individual will be able to command $1 billion in about 500 years — which means he will be able to afford the equivalent of a Cray computer and a fleet of space shuttles. He will not be able to hire huge numbers of domestic servants — because the average servant will, after all, make somewhere around $1 billion himself.
Real economic growth comes from technological advances that permit increased productivity. Mechanization, division of labor, computerization, robots, etc., mean that fewer and fewer man-hours are needed to produce a given good, and thus that individuals can be paid more (in terms of goods and services) than they could be paid under less productive arrangements. There may be a limit to this process, but we are nowhere near it; indeed, mechanization of services (as opposed to industries) has only begun to occur with the computer revolution. Economic growth means a greater ability to command goods and services; it does not mean a greater ability to command others.
Some things, however, are not susceptible to growth of this kind. There are only so many Rembrandts; the soil of Burgundy can only support so many grand cru vineyards. If a Rembrandt sells for $1 million today, when the average income is $1000, it will sell for $1 trillion when the average income is $1 billion. (All things being equal.)
Historically, per capita energy consumption has been very closely linked to economic growth. Both have increased in the US at an average rate of around 3%. Consequently, as standards of living increase, the amount of energy which an individual can command increases -- and his ability to contribute to what now seems an incredibly expensive sublight trading mission increases. If an average income of $1 billion does not make everyone able to own a Rembrandt, it does make it much more possible to engage in interstellar trade. If a Rembrandt sells for $1 trillion, spending $11 billion to import the equivalent of a Rembrandt from Alpha Centauri does not sound so bad.
How reasonable is it to expect that per capita incomes will increase a millionfold over the next 500 years or so? Assume that the population increases at a rate of 2% per annum (roughly the current global average). Total energy use will increase at a rate of 5% (3% per capita plus 2% increase in population). Current total world consumption of energy is around 8 x 109 MW-years per year. The sun puts out about 1.28 x 1020 MW; in 500 years at a growth rate of 5%, humanity would consume a little bit more than twice the energy produced by the sun (and the human population would be about 8 x 1013, eighty-thousand billion people). It seems unlikely that we could produce enough energy to provide the equivalent of a second sun for humanity. However, if we assume that the population would level off at 100 billion people, humanity would consume about 5 x 1017 MW, about 1/2% of the sun's output. Thus, if we solve the population problem sometime in the 22nd Century, all will be well and our children will be billionaires.
Assume that this picture is over-optimistic. Assume that the $11 billion/kg is off by a factor of ten, and that a better figure is $100 billion/kg. Even today, such a cost, though huge, could be paid. And barring the collapse of civilization, growth will continue. The relative cost of interstellar trade should decline. Doubtless, it will never be as common as trans-Atlantic traffic is today; nonetheless, it seems feasible.
We said that in order to determine the feasibility of trade in a given good we would have to know 1.) the cost of transportation and 2.) something about the cost of production of the good. The first question we have answered, and the second we can talk about. If the standard of living has increased a millionfold, what this really means is that the cost of goods has decreased a millionfold. If per capita income increases from $1,000 to $1 billion, an individual can command a million times as much energy or resources. Effectively, we are holding the dollar cost of goods constant while increasing the number of dollars available to individuals.
This being so, it is obvious that common resources and products are not going to be worth trading over interstellar distances. Spending 25,000 MY-years to import a kilogram of lead makes no sense. What might be worth importing?
First, perhaps there are extremely valuable resources which cannot easily be produced in our solar system: monopoles, or superheavy metals, perhaps (if such things exist at all). If, however, there are monopoles on Alpha Centauri because the Centaurians can manufacture them, it is likely that it will be more efficient to purchase the techniques from them rather than to import monopoles.
Which brings up the point that manufactured goods of any kind are probably not worth trading, because given the high costs of transportation, selling the manufacturing technology makes more sense than trading in the goods themselves. What does this leave?
This leaves goods the value of which is not transmittable, which cannot be described and reconstructed, but have somehow intrinsic value. A Rembrandt can certainly be described and the Centaurians could certainly print copies of Rembrandt paintings from information we send them, but those copies would not be the originals. Lithographs sell for prices about 5 orders of magnitude less than originals. Originals have intrinsic value; any copy, no matter how perfect, is but a copy.
So one possible category of trade objects is luxury items, not only objets d'art, but such things as exotic wines and liqueurs and the like. (I refuse to believe that any reproduction technology, no matter how sophisticated, can reproduce the bouquet of wine to the complete satisfaction of a wine snob. The future may see the trillion dollar wine.)
The last category of goods it might make sense to trade is genetic information, or something similar. Given sophisticated genetic manipulation techniques, getting the raw material — the genetic codes — of alien species might prove extremely beneficial, especially if the species is very alien in biology. By manipulating such beasties, we might be able to engineer new genetic products that could not be created with the genetic material available on earth. On the other hand, the genetic code is a code; and one day we may be able to read the precise order of amino acids on a strand of DNA, and thus be able to precisely describe a gene to an interested party. There is, naturally, a hell of a lot of information encoded in even the simplest bacterium, and transmitting this much information might be difficult. On the other hand, radio data transmission rates have increased by several orders of magnitude over the last few decades, and it may be that we will be able to transmit instructions for building genes in the future, thus obviating the need for trade in genes.
In summary then, though human civilization is likely to be engaged in interstellar trade, there probably will not be much worth trading, since any society capable of doing so on a major scale can probably produce almost anything it needs at home. Trade in esoteric and extremely rare resources like superheavy metals might be possible; genetic material is another possibility. The most likely trade good would seem to be the relatively frivolous trade in luxuries.
Trade via Radio
There are immense gains to be made from trade with other stars through exchange of information. A space-going civilization is almost certain to have developed technologies which we have not, and vice versa. Exchange of scientific information would also be worthwhile, and surely both our cultures would be enriched by exchange of the artistic masterpieces of our two heritages. Such trade would not require physical transportation of objects, however; a more likely possibility is telecommunication. Getting into radio contact with another civilization would be extremely profitable to both of us, and the cost to operate a large radio transmitter would be immensely less than the cost of operating an interstellar trading vessel.
This kind of trade, however, cannot be built on a direct, bargained exchange. If it takes, say, ten years to send a message and get a response, making a deal would be an effort requiring a lifetime. If making a profitable exchange necessarily requires first coming to an agreement on the terms of that exchange, information will be exchanged at a very slow rate. Instead, it seems likely that both of us will transmit whatever information we think the other might find useful or interesting, transmitting other information as requested. In essence, as Asimov suggests in one of his stories, we will both be talking at once. Whether this kind of exchange can even be termed "trade" in the classical sense is debatable, since there is no agreed exchange of items of value; but it is certainly a voluntary arrangement benefitting both parties. It is also evidently the most cost-effective and simplest way to deal with alien friends.
Trade Faster than the Speed of Light
In this article, I have talked about the possibilities of sublight trade at some length. Trade in FTL vessels may be a more interesting topic, despite the fact that FTL will probably never exist.
The problem is that any FTL drive will necessarily depend on physical principles of which we have not the slightest glimmer at the present time. Consequently, we can not make any assumptions and have no real way of speculating about the costs of such trade or the forms which it will entail. The basic principles, however, remain the same. The lower the cost of transportation of goods, the more trade will go on. One expects that any mechanism for traversing distances measured in light-years is going to be very expensive, even if it involves (or perhaps especially if it involves) somehow transcending Einsteinian mechanics. Consequently, interstellar trade is always likely to be limited. The fact that travel can occur at trans-light speeds means that opportunity costs are much reduced, of course; the cost of building and operating an FTL-drive ship, however, cannot even be guessed at.
Calculating the Cost of Interstellar Trade
The cost C of a round trip is equal to an opportunity multiple (OPm) times the investment required to make the trip. The opportunity multiple arises from the fact that investment could be made at home instead, and is equal to:
OPm = (1 + I%)2T
where T is the time required for one leg of the journey (out or back) and I% is the rate of return possible if the money were invested at home instead of on the interstellar voyage.
Ignoring the cost of building and maintaining a ship (as well as the costs of overhead, employees, etc.), the investment required to send a sublight trading mission using the Boardman anti-matter drive is calculated from:
I = 2 * Rm * P * 5704 MWy/kg
where I is the investment, Rm is the number of kilograms of anti-matter required per kilogram of payload, the factor "2" entering because anti-matter must be purchased at the destination before the return trip (doubling the cost), and 5704MWy/kg is the amount of energy (in megawatt-years, MWy) required to produce a kilogram of anti-matter. For a one-way trip, the value of Rm is:
Rm = ( c + u - 1) c - u
assuming the ship is capable of refueling at its destination, where c is lightspeed (3 x 105 km/sec) and u is the maximum velocity of the ship.
Cost C is then:
C = (1 + 1%)2T * ( c + u - 1 ) * 2 * P * 5704MWy/kg c - u
T, however, is a function of u, the maximum velocity. If we plug an equation for T into the equation for C and assume values for u and I%, we can calculate the cost per kilogram of trade goods. T is calculated from:
T = d + 2 * [ c2 + (1 - u2 )-1/2 * (u - c2 ) ] u g u c2 u
where d is the distance to be travelled and g is the rate of acceleration.
One of the interesting things about the equation for C is that the opportunity multiple decreases as u increases (because the journey takes less time) while the investment increases as u increases (because more anti-matter is required). This implies that there is, for a given set of conditions, some maximum velocity u at which minimum cost is achieved.
Table 1 shows minimum costs for a number of journeys of different lengths.
This section is basically a rough outline of Rick Robinson's Interstellar Trade: A Primer. You'd probably be better off reading the full article but some people want executive summaries. Rick starts with certain assumptions and follows them to various conclusions about the interstellar economy. You can alter some of the assumptions yourself to tweak the economy to suit your science fictional background.
Merchant Starship Costs
Assumption: starships in the interstellar empire are equivalent to present-day jet airliners. They go fast, can carry lots of people and cargo, and are the most advanced technology that can be massed produced.
The ticket prices will not be similar between airliners and starships because FTL interstellar travel will probably take more than a few hours for the trip. Therefore the starships will do fewer trips per year than airliners, so the starship passenger ticket price (and cargo waybill) will have to cover a larger share of the starship's yearly expense.
For comparison purposes we need an airliner's average cost of running, but the corporations are remarkably closed-lipped about that. Using a long series of estimations whose details can be found in Rick's article he concludes that the annual operating cost for an airliner is about $30 million (not counting fuel, landing fees, and taxes). An airliner's purchase price is $100 million so one year's uses costs about one-third of the purchase price.
A cargo jet can carry 50 tons so its purchase price is about $2 million per ton of cargo capacity.
Assumption: starship purchase price will only be about $1 million per ton of cargo capacity instead of $2 million, because starships are orbit-to-orbit, need no landing gear, need no wings, can use lighter structure because they accelerate under 1 g, and we will assume they can carry twice as much cargo per deadweight (inert mass) as a cargo jet.
Assumption: cargo starship operating cost is similar to cargo jet. Therefore it costs $300,000 per ton of cargo capacity per year to run a cargo starship. This ignores taxes, station docking fees, and fuel. Assumption: starship fuel is cheaper than cargo jet JP-4 fuel. Big assumption since JP-4 is about $1.39 per gallon.
(ed note: starships are going to require lots of infrastructure.)
Assumption: the service life of a merchant starship is 30 years. So the starship initial purchase price is about 1/10th of the overall lifetime service cost ($1 million / (30 * $300,000)). Actually it will be closer to 1/5th due to the interest on the purchase loan. With creative maintenance, the service life might be longer than 30 years, see below.
Question: how many cargos can a merchant starship carry in 1 year? That is, assuming a full cargo turnover at each port of call, how many one-way runs can the ship make?
Assumption: a one-way trip takes three months. From departure planet orbit to FTL flight to arrival planet orbit. This is comparable to the Age of Sail.
Assumption: each trip requires one month for servicing, maintenance, selling the cargo, buying new cargo for the next run.
This makes each trip four months from departure to departure, or three cargos per year. This means the ship owner must earn $100,000 of profit per ton of cargo. That is, selling price at destination MINUS purchase price at origin must be $100,000 or more. Therefore if the cargo was available for free at the origin the minimum selling price at destination is $100,000 per ton, or $100 per kilogram. The implication is that only very high value cargo can be profitably shipped interstellar.
Assumption, average of 1/2 of retail price goes to shipping cost. Therefore the minimum price of interstellar imported goods are $200 per kilogram.
The implication is that the only things shipped interstellar would be luxury goods, items with a very high value per weight. Jewelry, spices, fine liquor, designer-label clothing. Maybe some high value per weight industrial goods, such as microchips. Not high mass items such as sports car, not with a $100,000 shipping charge added to the car's price. Bottom line is that you are not going to ship bulk goods like wheat, not at $100,000 per ton you ain't.
Assumption: the Gross Planetary Product (GPP) of a colony planet is $100,000 (about three times that of present day USA). If 2% of citizen income goes to imported luxuries and high-value capital goods, it comes out to $2000 per capita, with $1000 going to shipping cost.
Assumption: Colony planet population is 10 million. Therefore the total shipping cost of imported goods is $10 billion.
Calculating backwards, this implies that 100,000 tons of interstellar cargo arrives at the colony planet annually. The colony must export the same amount or it will run a trade deficit and import prices will rise. This is because if they don't export, the cargo starships cannot find cargoes to transport and sell at the next destination. Starships with empty cargo holds cost nearly as much to run as with full holds. They will have to make up the shortfall somehow, so they will raise the price of what they sell at this planet.
Take simplest model: two planets trading with each other. Each year, 100,000 tons moves in each direction, or 200,000 tons total.
Assumption: average cargo starship carries 1000 tons. This is less than seagoing cargo ships, but more than cargo airplane. This means there has to be 200 annual cargo loadings and unloadings to accommodate 200,000 tons.
Since each ship can make 3 one-way legs per year, then each ship will do three loadings. The implication is that the two planet's combined merchant fleet is between 65 to 70 ships.
Of course if each ship carries more than 1000 tons then fewer ships are needed. If the ships can carry 5000 tons then you would only need 13 or 14 ships. In practice this would not work very well, since the larger the cargo hold, the more difficult it is to find enough cargo on the planet to fill it.A trade network of a dozen colony worlds will support a few dozen to a few hundred cargo ships depending upon cargo hold size.
Airliners carry about four to five passengers per ton of equivalent cargo capacity. However airliner trips are only a few hours. Interstellar passengers cannot live in their seats for three months.
Assumption: Each interstellar passenger berth equals one ton of equivalent cargo capacity. This includes the passenger, their baggage, the berth, apportioned galley/diner space, and food.
The direct result is that the cost of the passenger ticket is the same as the cost of one ton of cargo: $100,000. You are not going to get much tourist traffic, not at those prices. A few rich people and business travellers.
Problem: you must have large scale passenger traffic for the colony network to exist at all. In a word: Colonization.
$100,000 per colonist is prohibitive. Probably several times that for extra stuff like tractors and horses. Even worse, since the new colony will not have any exports, the cargo starship will have not cargo buy for the next trip. So the starship captain will have to charge round-trip prices for a one-way trip. It could total to around $1 million per colonist.
The problem is that our assumptions have made it so that only millionaires can afford the ticket, but millionaires do not want to go live on some jerkwater frontier world. Sending 10,000 colonists to a new world could cost $10 billion, which is a huge amount for private industry or governments to spend, regardless of the potential value of the planet.
Our price schedule has made interstellar colonization unlikely in the first place.
We will have to change some of the assumptions. Lucky for us, there is some room to bring the costs down. We can make the merchant starships cheaper, or make them faster. We shall do both.
Assumption: annual starship service cost is $100,000 per ton of cargo capacity, not $300,000. This is reasonable, since starships are not stressed as much as airliners (at least not orbit-to-orbit starships).
Assumption: starship purchase price is $500,000 per ton of cargo capacity instead of $1 million, since starships are build for long-haul reliability.
With the 30 year service life, the purchase price is now 1/6th of the total lifetime service cost instead of 1/10th. Within interest payments this may be closer to 1/3th.
Assumption: a one-way trip takes 35 days instead of three months. This means the cargo starship can deliver 10 cargoes per year instead of three. Assume 27 days is transit, 8 days is for servicing, maintenance, selling the cargo, and buying new cargo for the next run.
Crunching the numbers, the minimum profit per ton of cargo or passenger ticket is now $10,000 instead of $100,000.
The cost for colonists (provisions and no return cargo) is probably about $100,000 or less. That's more like it. In the reach of the middle class. This price schedule makes interstellar colonization viable.
Note that the same ten-fold cost reduction can be had by making the one-way trip 12 days but keeping the original $300,000 annual cost.
Our colonization-viable starships will also increase interstellar trade. Shipping cost of $10,000 per ton means the threshold cost of imported goods is about $10 per pound. Only $10,000 shipping cost for a sports car. But no bulk cargo, not when oil's shipping cost will be $1500 per barrel. As with all freight the rates will vary. Higher value merchandise will support higher shipping charges. A long-term fixed contract (allowing ship owner to have dependable regular cargoes) will get a lower rate. Standby cargo will get a better rate, if the ship is making a run anyway, it is better to have full cargo holds.
If imports are still only 2% of CPP, the volume of goods will increase ten-fold. The shipping capacity will only have to increase three-fold since starships now deliver three times as much cargo per year. Since shipping costs ten times lower (so a wider range of goods are worth importing) then the import-export sector can expand in total value of goods shipped as well.
Assumption: an inverse square-root rule applies here, so reducing the shipping costs by a factor of 10 will increase spending upon imported goods by a factor of 3.
This means 6% of CPP now goes to imports. High, but not out of reach for a mature trading zone. So a colony of 10 million will have an annual export and import of 3 million tons per year.
Each trade starship can pick up and deliver 10 cargoes per year, so they need a net cargo capacity of 300,000 tons. For a trade network of 12 colonies, the combined merchant marine needs a capacity of some 3.6 million tons. Most ships will still be small (but bigger than jumbo jets) to facilitate filling their cargo holds, but the heaviest-traffic routes will support some bigger ships.
Assumption: say the trade network's merchant fleet is:
|Type of ship||Number|
of one ship
|Total cargo capacity|
|Large||75||20,000 tons||1,500,000 tons|
|Medium||300||5000 tons||1,500,000 tons|
|Small||400||1500 tons||600,000 tons|
If there is no FTL radio, then some of the small freighters will sacrifice cargo capacity for speed (i.e., acceleration), in order to become something like an interstellar FedEx or pony express. The idea is to reduce the normal space transit time. Actually this might be a better job for an unmanned drone, they can take higher acceleration than human beings.
Passenger traffic is only a fraction of total cargo volume (unless there is a colonization effort underway). Freight makes a profit for somebody, passengers are pure expense to whoever pays their ticket. Perhaps passengers are 1% of total volume, makes 360,000 passengers per year. A few routes may support scheduled passenger service (probably in small ships). But most will ride in cargo bays (like railroad sleeping cards), in freighters, or in spare crew quarters.
Ship mass and size
Full load mass and physical size depends upon assumptions about fuel mass ration, fuel bulk, etc.
|Deadweight (inert mass)||1||17%|
Note that total mass is three times the cargo capacity. As you can see, deadweight is the ship proper, structure, engines, anything that is not cargo or propellant.
With this assumption, the big freighters will have a fully loaded mass of 60,000 tons. The largest ships might be twice as big: 120,000 tons.
Our building cost is $500,000 per ton of cargo capacity, the mass assumption makes a building cost equal to $1 million per ton of deadweight. Annual service cost is $100,000 per ton of cargo capacity, the mass assumption makes the annual service cost equal to $200,000 per ton of deadweight. The starship hulls are not cheaper, but they can carry more cargo in proportion to their structural mass.
|Type of ship||Cargo capacity||Purchase price|
|Large||20,000 tons||$20 billion|
|Medium||5000 tons||$2.5 billion|
|Small||1500 tons||$750 million|
At $500,000 per ton of cargo capacity, largest giant freighter cost $20 billion to build, but it it has a cargo capacity of 200 Boeing 747 jets, and accounts for over one percent of whole fleet's cargo capacity all by itself. Small freighter costs $750 million, and has seven time the capacity of 747.
With a 30 year service life, the combined shipbuilding yards of the 12 planet trade network will turn out about 25 ships per year.
Hulls will last longer than 30 years but the equipment wears out and has to be replaced. Ships go back to the yards for an overhaul every decade or so, but eventually the cost of stripping everything and replacing it will exceed the value of the ship. Depending upon overhaul costs the shipyards may make more money on rebuilding than on constructing brand new ships. Some ships will stay in service for many decades. Others will be retained as the futuristic equivalent of naval hulks or the old passenger equipment that railroads use as work trains. Every big commercial space station will have a bunch of these old ships in the outskirts.
If modular design is taken to its limit, "ships" will have no permanent existence. Instead they will be assembled out of modules and pods specifically for each run, much like a railroad train. In that case, a ship's identity is attached to a service, not a physical structure. Example: the Santa Fe "Chief" was identified by a timetable and reputation, not a particular set of locomotive and cars.
The analysis up until now focused on money and economics. Businessmen only care about how long it takes to deliver the cargo and how much transport costs, they could care less about the scientific details of the ship engines. But authors care.
As with everything else, it all depends upon the assumptions. Your assumptions will be different, so feel free to fiddle with these and see what the results are.
Assumption: the time spent in FTL transit is zero (jump drive). For the FTL segment of the transit you can use whatever you want, as long as the details do not affect the analysis. The main thing is that the required time spent in FTL transit will add to the total trip time, and thus the number of cargoes a starship can transport per year.
Assumption: starships use reaction drives for normal space travel.
We know that the mass ratio is 2.0. So the Tsiolkovsky rocket equation tells us that the starship's total delta V will be the propulsion system's exhaust velocity times 0.69 (i.e., ln(2.0) ). Since starships accelerate to half their delta V, coast, then decelerate to a halt, their maximum speed is half their delta V, or exhaust velocity times 0.35 (i.e., ln(2.0) / 2). In practice you would accelerate up to a bit less than half their delta V in order to allow a fuel reserve in case of emergency.
It will be even less if the FTL drive happens to use the same type of fuel that the reaction drive does. Basically part of the fuel mass will have to be considered as cargo, not propellant, which will alter the ship's mass ratio.
|Reaction drive||Exhaust velocity|
|Nuclear powered Ion||~100 km/s|
|Fusion||a few thousand km/s|
|Beam core matter-antimatter||about 100,000 km/s|
( 1/3 c )
We have assumed that the ship spends 27 days in route (with an instantaneous FTL jump), so the outbound and inbound legs are 13.5 days each (1.17 million seconds).
Assumption: the acceleration on each leg is constant. In reality at the same thrust setting the acceleration will increase as the ship's mass goes down due to propellant being expended. The thrust will probably be constantly throttled to maintain a constant acceleration. Makes it easier on the crew and easier on our analysis. The implication is that obviously the average speed will be half the maximum speed (which is half the delta V)
|Reaction drive||Exhaust velocity|
or Early Fusion
|400 km/s||130 km/s||75 million km|
|Advanced Fusion||10,000 km/s||5000 km/s||20 AU|
|c||0.3 c||350 AU|
(x5 Pluto's orbit)
|8 g !!!|
These figures will be lower if time is consumed in FTL flight, maybe be only Terra-Luna distance
Propulsion system's thrust power is thrust times exhaust velocity, then divide by 2. To get the thrust, we know that thrust is ship mass times acceleration. The ship mass goes down as fuel is burnt. As a general rule for ship mass, figure that it only has 2/3rds of a propellant load. That is, multiply the total ship mass by 0.83. So our 120,000 metric ton ship would have a general rule mass of 120,000 * 0.83 = 100,000 metric tons (100,000,000 kilograms).
|Reaction drive||Exhaust velocity|
or Early Fusion
|1.08×107 N||2.16×1012 W|
|Advanced Fusion||10,000,000 m/s|
|4.3×108 N||2.15×1015 W|
|7.65×109 N||1.15×1018 W|
(1 million terawatts)
Where does fuel come from and who does it get into the ship's fuel tanks? Easiest if it is obtained locally at the destination's solar system. The economics of interplanetary transport is same as interstellar (since we did a lot of work making interstellar a cheap as interplanetary).
if fuel from a gas giant at a distance comparable to Terra-Jupiter and round trip is to only take weeks, interplanetary tankers will need speeds of around 1000 km/s. So tankers will be almost as expensive as starships. If tankers use low speed (to make them cheaper), the round trip balloons to a year or more. To service the starship fleet's thirst for fuel, tankers will need to be huge or there will have to be a lot of them. Either way, fuel shipped from gas giants ain't gonna be cheap.
If we forgo interplanetary tankers and instead have starships make extra leg to the local gas giant to refuel, it will cost you more than you will save.
The alternative is shipping fuel up from destination planet. Yes, we know about how surface to orbit is "halfway to anywhere" in terms of delta V cost. But in order to colonize space at all, surface-to-orbit shipping cost will have to be cheap anyway. The industrialization of space will start with using space based resources, but eventually surface-to-orbit will have to be cheap or there is no rocketpunk future. Laser launch, Lofstrom loop, space elevator, something like that.
Assumption: surface-to-orbit shuttle economics are equivalent to current day airliner economics. Round trip to LEO and back is about two hours (not counting loading/unloading). With loading/unloading and maintenance, figure 4 flights a day. Implication is that a round trip passenger ticket is $250 and round trip freight service is $1000/ton (which is +10% added to interstellar transport costs)
Fuel is not round trip, it only goes from surface to orbit, but shuttles have to go orbit to surface in order to get the next load. You will have to streamline the process. High capacity pumps to minimize load/unload times, crew-less shuttle. You might be able to squeeze fuel lift cost to $500/ton. So if starships carry 1.5 tons of fuel per ton of cargo, surface-to-orbit fuel lift costs adds $750/ton to interstellar shipping cost.
So total surface-to-orbit overhead is $1000/ton + $750/ton = $1750/ton or 17.5%. This is an ouch but not a show-stopper.
Back to starships. How big are they?
Present-day maritime tonnage rule: 1 registered ton = ~3 cubic meters.
Assumption: 1 ton = 3 m3 applies to fuel and hull (e.g., crew quarters, engineering spaces, etc) as well as cargo. Therefore, if the absolutely hugest cargo starship in service has a cargo capacity of 40,000 tons (twice that of a large cargo starship), then:
Volume of a sphere is 4/3πr3, so the radius of a sphere is 3√(v/(4/3π)) or
radius = CubeRoot( v / 4.189)
diameter = (CubeRoot( v / 4.189)) * 2
Assumption: a "cigar-shape" for a spacecraft is a six times as long as it is wide, with the proportions indicated in the diagram above. The center body is a cylinder 1 unit in diameter (0.5 units radius) and two units high. The two end caps are cones of 0.5 units radius and 2 units high.
If the monstrous cargo starship is spherical, it would have a diameter of 88 meters. If it is cigar shaped then length = 300 meters and diameter of 50 meters.
A 1500 ton cargo capacity tramp freighter would have a wet mass of 4500 tons and a volume of 13,500 m3. Spherical shape would have a diameter of 30 meters, cigar shaped length = 100 meters long and diameter of 17 meters.
Modular ships dimension would be similar but a bit larger due to being assembled out of component parts.
This is very difficult to estimate.
Since each crew has same berthing requirement as passengers, each crew represents one ton = $100,000/year in lost revenue capacity. Therefore crew will be kept as small as practical.
Operating crew: pilot-navigator and engineer for each watch. Plus life support specialist/medic, cargo-master, and captain. Total of nine. Small ships might squeeze this to four or five. Big ships might double up with assistants and trainees for 20 to 25.
Maintenance technicians will be needed. Ships are en route for a month or so at a time. Unlike aircraft, maintenance can't all be done during layovers. Time is money, you do not want to hold off departure because station tech has not finished some routine servicing. So techs will be carried to do maintenance during the flight. Assume (conservatively) 1 tech embarked per $100 million in construction cost (i.e., stuff to be maintained). So small ships will have a maintenance crew of seven or eight (total crew of ten or twelve). Largest ships in service might have total crews up to 250. Scut work (swabbing decks and peeling potatoes) will be done by junior crew. As has been the case since time began.
Hotel Staff: passenger-carrying ships will need crew for hotel-type services (stewards, chefs, etc.), but not if passengers are colonists (fend for yourselves, steerage scum!). Coach class could make do with one for every 10 passengers. First class would have one for every 2 or 3 passengers (and the ticket price would reflect this). If a typical ship has 1 percent of cargo given over to passengers, the required hotel staff could increase the crew by about a third. Naturally the hotel staff will be looked down upon by the operating and tech crew members. On a passenger ship the hotel staff will vastly outnumber the rest of the crew by some 30 to 1.
Orbital high ports
These are primarily starship ports and service bases, though they may have other functions.
With our current assumptions, at a given time 3/4ths of the ships are en route, the rest are in port. So at the stations of the dozen colony worlds there will be docked about 15 cargo ships. One or two would be large cargo ships. A cargo ship will arrive and depart about three times a day.
Orbit-to-surface traffic is heavy. If each shuttle can carry the load of a 747 jet, about 100 arrive and depart each day. If starship fuel is shuttled up from surface, some 150 daily tankers arrivals are needed as well (if 4 daily flights per shuttle, about 65 physical shuttles are needed).
This is for a typical station. The busiest station in the trade network might have twice the traffic volume.
At any one time we might expect to find 200 to 300 off-duty starship crew at a typical station (probably all in bars). Unlike airports, passenger traffic is small. 200 or so arrive and depart each day. Passenger shuttles will also carry station crew, ship's crew going sightseeing, so there will be a few daily passenger flights.
A station is a ship without a drive engine, so its capacities can be estimated the same way.
If 10% of the overall cost of the merchant fleet goes to support the stations (since the stations maintain the ships) then the stations taken together will have about a tenth of the fleet's deadweight mass, or 180,000 tons all told. A typical station would then have a mass of 15,000 tons, not counting cargo awaiting loading, fuel in storage tanks, etc. But stations are likely to grow by accretions over the years and become sprawling structures extending hundreds of meters in all directions.
Using same estimates for cargo ships, the maintenance crew of an average station would be about 150. However, stations provide the major ship maintenance, so they probably have about as many technicians altogether as the ships themselves do. They alone will multiply the station population by tenfold; support staff and miscellaneous services might double it again, so a typical station could have some 3000 workers. The largest stations might have two or three times as many.
Living quarters will be nearly as expensive ship quarters, but frequent shuttle fare also add up. The income from shuttle fare can be used to subsidize living quarters rent, so many people could live on board, even with families. Station could be a cosmopolitan orbiting town.
The entire space-faring population of the trade network, ship crews and stationers, come to well over 50,000, maybe as many as 100,000 (out of a total population on 12 colonies of some 120 million). The space economy as a whole however employs many times more. If the merchant marine industry accounts for 3% of the economy it will also employ 3% of the workforce, 2 million people. With a similar number employed in the import/export industries.
The expense of a trade-protection navy is an insurance premium charged against trade.
Assumption: the insurance premium to fund the navy is 10% of total value of trade.
Say the 12 colony network is a trade federation and the insurance premium for defense is 10% of total value of trade (this setup could just as well be one planet monopolizing trade, in which case the navy protects the franchise. We will call it a federation anyway). Half the value of trade goes to support the merchant fleet (the other half is initial purchase cost of shipped goods) therefore the cost of the war fleet will be about 1/5 of the merchant marine
Assumption: warships have the same relationship to cargo ships as cruisers do to ocean liners or jet bombers to airliners.
Instead of cargo, warships carry weapons, sensors, armor, more powerful engines, and greater fuel capacity. Ton for full-loaded ton they are more expensive than trade ships (maybe x2) but cost per deadweight ton is about the same since technology going into it is similar. (some present day warplanes have higher cost-to-mass ratio than jetliners. This is due partially to "gold-plating" of weapon systems and partial due to false economies such as small orders that reduce production efficiencies. We will assume that a navy funded by merchants will not allow such expensive stupidities)
Assumption: For first approximation, scale down merchant marine by factor of 5 to get war fleet.
- 1 battlecruiser per 5 heavy freighters
- 1 cruiser per 5 medium freighters
- 1 corvette per 5 small freighters
This will give the following order of battle:
- 15 battlecruisers
- 60 cruisers
- 80 corvettes
This may or may not be balanced, substitute as needed.
(ed note: for a discussion of what Rick Robinson means by those three ship classes see his analysis here)
Space navy combat starships will require auxiliary starships to support them: food supply ships, ammo and missile supply ships, repair ships, hospital ships, fuel ships, etc. So some of the cruisers and corvettes in the order of battle will have to be traded for auxiliaries of various kinds. Some civilian cargo ships can be requisitioned in wartime for auxiliary missions (such as tankers). Depending upon technology and threat level, it might be feasible to fit cargo ships with weapon pods instead of cargo and use them as armed merchant cruisers. And warships might be fitted with cargo pods to become very well-armed transports.
Assumption: a warship's deadweight mass is 1/3rd (0.33) of loaded mass (propellant always dominates a reaction-drive spaceship's mass). You could call the deadweight mass the Washington Treaty Mass.
Assumption: the following deadweight mass values in the following table.
Assumption: warships are always cigar shapes because Hollywood hates spheres
We have already assumed that purchase cost of a spacecraft is $1 million per ton of deadweight. We have also assumed that each ton of loaded mass equals 3 m3 of volume.
Result of assumptions:
|Battlecruiser||30,000 tons||10,000 tons||$10 billion||90,000 m3||200m × 30m|
|Cruiser||7500 tons||2500 tons||$2.5 billion||22,500 m3||120m × 20m|
|Corvette||2000 tons||700 tons||$700 million||6000 m3||75m × 12.5m|
Corvette are the length of a 747 or C-5 Galaxy but larger diameter. Very close to space shuttle in launch configuration. Since corvettes will have a surface landing module (for gunboat diplomacy) they may even look like space shuttle stack (with a big winged thing stuck on the side). Merchant express mail couriers might be a civilian version of courvette.
During peace time war fleet has lower operating tempo than merchant marine. May spend half their their time docked instead of the one-quarter that merchants do. This saves operating expenses. The savings allows greater procurement, so they are replaced and retired from active duty after 20 years instead of 30. Then they go into a mothballed reserve force for another 20 years, so reserve is the same size as active fleet. As with cargo ships, warships might undergo top-to-bottom overhauls and remain in service longer.
Crews are larger in proportion than for cargo ships. Operating crew will be augmented with offensive and defensive weapon controllers, scan/ECM, and communication/intelligence; larger ships will have in addition a command staff.
The maintenance technicians will be larger per unit cost because they have to repair battle damage, during or after the battle.
Of course there is no hotel staff.
Some warships will carry a landing force of marines or espatiers. Due to berthing cost and limited space (mass ratio of 2.0, remember?) there won't be many marines, but they will be highly trained (SEALS).
Crew numbers will be higher if they have a landing strike team embarked
This is not a huge crew force. about 10,000 for the entire fleet, with probably a similar number on shore duty at any given time. Add in the marines and the total wearing uniforms is still no more than 25,000 to 30,000. Perhaps with a similar number of civilian employees.
Defense spending for running the fleet (by far the largest budget item) is a modest $72 billion, 0.6% of trade federation's combined GPP. In a prolonged major war this would expand greatly. But this is supported by trade. If the cost of trade protection (the insurance premium) approaches or even exceeds the value of trade itself, there will be a collapse of political support.
Operations in a trade war will be primarily in space. If large scale planetary landings are required, cargo ships can be pressed into service as troop transports. Light infantry is roughly equivalent to civil passengers: 1 ton equivalent cargo capacity per soldier. However heavier equipment, shuttles to carry troops/gear/provisions to surface, armed shuttles for close air support, will all be required. So for an invasion force, 3 ton equivalent cargo capacity per soldier, not counting the naval escort.
If 1/10th of the entire merchant marine is gathered as an invasion force it can transport and land 120,000 light troops, less if heavy equipment is required. But 120,000 troops is a pretty big force to invade a planet of 10 million people.
Suppose instead of 12 worlds, the empire had a thousand worlds, each with a population of 100 million. Then all the above can be multiplied by a factor of over 800. Improved technology will increase size and number of ships. If typical ships is x3 in linear dimensions they will be x27 greater in mass, and fleet can have x30 as many of them.
Large cargo starships: if spherical 300m diameter, if cigar 1,000 km long. Cargo capacity 1 million tons. Full-load mass of 5 million tons each. Empire will have about 1000 ships of that size (and some larger). It will have 50,000 medium cargo ships with cargo capacity of 20,000 tons, and hundreds of thousands of smaller vessels.
Great hub-route stations will have population in the millions.
Navy battlecruisers will be 1 km long, full-load mass of 3 million tons. Build cost $1 trillion. Crew of 30,000. Empire will have 125 battlecruisers in the fleet. It will have thousands of cruisers with a full-load mass of 100,000 tons. Naval budget can be held down to $60 trillion.
100,000 worlds with average population of few billion each. The scale factor is another x3000. You can do the math yourself.