What would interstellar war really look like? Part 1 - Economics

This is a question that I've been pondering for a while, because I watch a lot of science fiction, read quite a bit of it, and of course quite a lot involves two or more civilisations 9either human versus alien, or human versus human) fighting each other over many star systems - in other words, interstellar war. There seem to be a lot of ideas about how that happens, but I wanted to see how much I could figure out about what it might really look like, based on first principles.

The first "first principle" I want to address is that in general, people fight each other for a reason, they don't just start it for the sake of it. In other words, people have a reason for making war.

People make war on other people, in general, for one of two reasons: they want something the other side has and think they can take it by force; or they think the other people are a threat to them (i.e. that the other people are going to try to take something of theirs by force, which may threaten lives/existence). Both of these reasons effectively boil down to economics. If you've got something I want, then to try to take it from you I have to make the calculation that the cost of taking it will be less than the value of that thing to me. If I am trying to prevent you taking something from me, then I am trying to make it so that the cost of doing so is greater than the value of the thing.

For there to be interstellar war, therefore, there has to be some viable form of economy so that taking something from one star system to another will have a lower cost than the value of that thing to the ones taking it.

For a viable economy, there has to be a reasonable communication time across the known space. Otherwise the chief condition for trade (namely that people can get items they desire more easily and cheaply from someone else than by making them themselves) will almost certainly not be met. If interstellar settlements are too far apart in terms of travelling time as observed by the inhabitants of those settlements, then they will need to be completely self-supporting, and so won't need to trade for things. If they are dependent upon trade for any items then they need to be close enough that trade will be able to provide those items in a timely fashion. The exception being where there is some form of extortion involved (that is, if they fail to provide goods to the central world(s) then they will be attacked). In this case, the war is unlikely to be interstellar, but take place entirely within one system, or even on one world. One other possibility is that colonised worlds will eventually develop full economies on their own worlds and then have commodities to trade with other worlds while being self-supporting; but in this case, trade will only be possible if interstellar travel is relatively cheap (otherwise the chief component of price for traded commodities would be the transport costs, which would be a deterrent to buyers, except for the most valuable and desirable of articles). However, a war might take place to take more basic items by force to enrich the fortunes of the attacking force, reducing the inhabitants of a defeated world to slave status.

To get a basic idea of the limits of the range of this economy, I looked at the sizes of various empires in human history. With the exception of the Mongol Empire (which was roughly 2 years radius in journey time), most seem to have been well under a year in radius in terms of command and trade route times: the largest maritime empire, the British Empire, crossed the Atlantic ocean in under 100 days and transportation ships reached Australia in under a year. So we can estimate that for a functioning economy such that there is something worth fighting for, then the things worth fighting for will need to be within a distance of 1 year's journey from the hub of the interstellar trading system.

Why have I chosen empires as the model? Well, because if civilisation A is fighting to gain the resources possessed by civilisation B, then A will need to establish direct control over those resources - that means a settlement controlled from a central government, probably by means of an appointed ruler with some leeway to govern, but answerable to the centre. That means an empire of some description.

If the travel time has to be in the region of under a year from centre to edge, then some form of faster-than-light travel is going to be needed. The point of these essays is not to talk about the physics of whether that's possible (plenty of scientists have written about it, and there is a very good wikipedia entry that also helped with discussing distances and time). I'm just looking at what you need to have in order to make an interstellar economy (and therefore, war) viable.

So, how fast do you have to travel to get enough stars to make an interstellar economy? For reference, the letter c refers to the speed of light here, so 2c means twice the speed of light.

Within 10 light-years of Earth, there are 7 star systems known to astronomers, most of which are red dwarf stars. So 10c is not fast enough.

If we go up by another power of 10, to 100c, then we get 511 stars similar to the Sun; the same link provides us that within 30 light-years there are 11 stars like the Sun. It may be that not every such star will have resources orbiting it that are useful to the economy, so we might need a few more: if we extend the radius to 50 light-years then we get 34 such stars, and the likelihood of several having exploitable resources starts to look reasonable.

So the minimum top speed of starships before interstellar war becomes realistic looks to be around 30-50c. Less than that, and fighting for the resources over interstellar distances looks impractical (you can't defend them if attacked, and if you attack them you can't hold onto them easily). At the extreme range, it is likely that interstellar manoeuvres would be unrealistic anyway, so the war would again most likely be fought within a single star system, albeit by forces that might have travelled from other systems. To get the kind of interstellar war that takes in several star systems at once, the top speed might need to be 100c or higher.

All of which leads to the next big question for our interstellar economy: how much does the journey cost? Travelling at 30-50c is almost certainly going to require vast amounts of energy to operate whatever faster-than-light drive powers the starships involved. The starships are going to need to carry that energy in the form of fuel of some sort, of which they will probably need large amounts for a single round trip.

For a sustainable economy, it's no good having lots of resources in another star system if getting to them costs so much in fuel that you can only afford a few trips before you have no fuel left on your home world. That means that at least one of the resources you're going to need to find at the destination is fuel: either every destination has enough to refill the starship's fuel tanks completely for another round trip, or else one destination supplies the needs of many round trips to other locations as well (which means that some starships would have the role of fuel tankers).

As in modern economics, who controls the fuel will tend to have a much bigger influence over the economy than others: oil is, in the modern world, the essential ingredient for the economy to function. In interstellar economy, whatever fuel makes the starships work will be the essential ingredient. It will also be the essential ingredient in making war, since starships of some design will be the means of conducting that war, and the starships need fuel.

It follows from this that at least one common cause of war in space will be the same as it is on Earth: the need for fuel, or the desire to control fuel in order to have economic power.

Finally, there needs to be something worth trading for. The basic assumption is that, when interstellar travel becomes economically viable, the first colonies will be established for the purpose of producing some commodity that is useful to the central world, and that those establishing the colonies expect to make a profit by doing so. Colonies will therefore not necessarily be in hospitable environments but in profitable ones. It may be that scientific colonies - for the purpose of exploration, study and just to prove that people can live elsewhere in the cosmos than the central world - would precede the economic colonies, but they would not be economically active and would cost resources to maintain.

What sort of commodity would be being produced depends on the shape of the economy on the central world at the time of the colony being established. That at least some colonies will be producing fuel seems assured, since (as already discussed) interstellar travel will need to be able to replenish its own fuel supplies in order to be economically viable in the long-term. What else would be being produced is open to conjecture. We can guess that mineral wealth would be one likely commodity desired by the central world: in developing a technological society capable of interstellar flight, it is a fair guess that a large proportion of the central world's own metals and other minerals would already have been consumed, and certainly that there is a limited supply of those things on the central world. It is also possible that some form of organic material might be in high demand (if, for example, there is a food shortage on the central world; in Ursula Le Guin's The Word for World Is Forest, she posits wood as the chief commodity sought by he central world).

If the commodity for which a colony is established is mineral in nature, then the colony could be established almost anywhere: as long as a self-contained environment can be maintained then the outside world, moon or asteroid can be totally inhospitable to the colonisers. The colonists will simply stay in the colony and operate the mining gear to produce the minerals. This does, however, mean that they will need very good back-ups. If something important for life-support fails (food storage, air circulation or processing back to oxygen, etc) then because there's a year-long wait for rescue, they will be dead long before help arrives. They need back-up systems, and the ability to repair broken systems themselves. It seems prudent that supply ships coming to take the minerals back to the central world would carry all manner of spare parts to enable the colony to replace or repair any damaged systems sufficiently so that the year's wait for a full replacement will not be as perilous.

Such a colony is always going to be dependent upon the central world to stay functional. The likelihood that they will be able to produce sufficient food themselves to meet the needs of a full colony seems very small, which means they will need food supplies which would form part of the payment of the workers. Alternatively, such a colony might not be operated as a colony at all, but instead might be treated in the way that oil rigs are today: that is, crew members would spend a certain amount of time on the mining colony and a certain amount of time back home (bearing in mind that the round trip could be a year long, this might not be viable from the workers' point of view). While the colony might be able to build some replacement parts themselves from the minerals they are mining, it is likely that they will still be dependent upon the central world for essential spares. In this way, the central world maintains control over the colony, which will be unable to make war on anyone else. It might, however, be a desired target for some other world to make war.

If a colony is to provide food, wood or other organic materials, then the chances are good that it will have to be based on a world that is similar to the central world, and thus in terms of the basic environment is hospitable to the colonists. While there may be all manner of hostile lifeforms, or sources of poison or venom (whether living or not), it will probably be possible to breathe the atmosphere, tolerate the temperatures and cope with the gravity. That means that the colony will not be directly dependent on the central world for its basic survival. This gives it more economic power than is enjoyed by the colonies producing mineral wealth in inhospitable environments. By the fact that they are producing organic wealth, they are able to be self-supporting in food, water and air. This in turn means that they will be able to trade for commodities beyond basic survival needs (including mineral wealth). An ambitious colony could therefore seek to attract engineers and geologists and thereby develop its own mining operations. While it is unlikely that the central world would want to allow them such independence, and therefore would not sell fully-functional mining equipment to the colony, the colony would be trying to bring in people with the knowledge and skills to build small-scale mining equipment and would try to develop from there. This is one way in which a colonised world could become independent of the central world, and become its own central world. Naturally, the central world might make war against the colony seeking independence, to prevent the loss of that source.

A final possibility is that a hospitable world is mostly rich in mineral wealth. In this case, it is unlikely that a central world would provide a colony with the means of growing their own food in the form of plants native to the central world. However, if it turns out that there is local flora and fauna that is edible and provides good sustenance, then this colony would already be independent economically; if its mineral wealth is a tradable commodity then its inhabitants would have the greatest economic power of any colonies. The chief issue would be that their prices would still be brought down by the existence of colonies on inhospitable worlds. Again, their best chance for expansion is to attract engineers and scientists to their world and seek to develop technology of their own to make use of the mineral wealth themselves. In this way, they would be most likely to be able to build their own starships (or, potentially, capture a visiting starship from the central world) and thus establish independent trading relationships with neighbouring colonies (such as, a colony producing fuel).

Those colonies that sought to expand and diversify could thus end up forming the basis of independent governments and trading blocs, so long as they managed to break away successfully and their revolts were not crushed by the central world. These groups would then trade with the original central world on an equal basis. At some point, economic conditions might prove such that one or other of these blocs will feel a shortage of some resource and will seek to take it from another bloc; or that one bloc will fear that another bloc has expansionist tendencies. At this point, interstellar war will begin.

The alternative, of course, is if two races from different central worlds come into contact and are competing for the same resources in the same star systems. In this case, it is likely that both races will be at the maximum range of their economic viability (otherwise they would have come into contact sooner). This means that sustainable warfare would not be possible: either colonies are given the ability to defend themselves from attack, or else taking a world will simply result in a huge resources drain (by stationing warships there) or else the colony will be retaken by the enemy and vice versa over and over again: a waste of resources. In order to be able to conduct such a war and have it , the technology of faster-than-light travel will need to advance so that it is possible to travel much faster, more economically. Eventually, of course, that will bring the enemy's central world within the economic radius, and then war will be extremely likely.

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Having looked here at the reasons why an interstellar war might start, and what the background might be, in the next section I'll look at how it might be conducted, what the strategic and tactical problems might be.