Trade routes for my world

I created the above illustration to help convey my meaning, here is what everything means so that you can read it effectively:

  • E = Earth
  • V = Venus
  • M = Mars

The dots in the lower left hand corner represent the asteroid belt. The small circles close to the circles with letters in them are meant to represent moons.

The color of each arrow notes what material the arrow represents, and the direction of the arrow indicates where the represented resource is heading.

The key for which color means what is at the very bottom of the image.

My question is: in a future setting (one far enough away that following scenario be reasonably possible), would this sort of basic flow of trade and goods make for a stable economic base for an interplanetary society that is still growing? This method is sort of inspired by the way the triangle trade worked (not the slavery part though), where one area of the world produced raw materials, which in turn were brought to another area where they were processed, to another area where they were traded for labor. I envision a similar process here, but with just people who need jobs rather than slaves. Does this system work or is something missing?

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    $\begingroup$ Assuming that starships are sufficiently fast and affordable, this doesn't seem implausible. One question I have - assuming that Deimos and Phobos are meant as high ports that goods just pass through, why use both? $\endgroup$
    – Cadence
    Jul 23, 2018 at 2:33
  • $\begingroup$ @Cadence You use both become I'm assuming the volume of material coming through one is very large, shipments of water, food, rocket fuel, and labor would likely crowd the moon. Because of the high demand of manufactured goods across every inhabited bit of this chart, a seperate post to launch them from would allow for an increased flow because of reduced traffic in the area of shipment. Essentially, it's to avoid congestion. $\endgroup$
    – user49634
    Jul 23, 2018 at 2:59
  • $\begingroup$ What system is used to lift material from the planets? For example, why is it more cost effective to drop raw materials into Mars' gravity well, transform them to finished good, lift them back out of the gravity well and then ship them to Earth rather than to simply send the raw materials directly to Earth? $\endgroup$ Jul 26, 2018 at 16:29

6 Answers 6


In short:

This is fine.

One major feature of modern economics is comparative advantage. In short, the idea is that some regions are better suited for producing specific goods. Therefore, when each region specializes in whatever they are best at, the overall system works with more efficiency.

I think there's a lot to be challenged with this idea, but let's leave it unchallenged for the purposes of this experiment, and assume your system is capitalist and obeys the canon of neoclassical econ.

The bottom line is why certain regions would have those advantages. What makes mars (for example) better suited to manufacturing than earth? What makes earth a better labor pool than martian workers? Also, what is labor even used for in an interplanetary context? Assuming that automation continues unchecked, what role does physical labor even play in your universe?

Once you know the material basis of your environment, (puts marxist hat on top of neoclassical hat): what sort of socioeconomic structures does this produce and how do they effect resource flows? Maybe mars is a hub of manufacturing because Jeff Bezos IV settled it with a bunch of drones maintained by genetically modified Amazonian(tm) neo-serfs in violation of U.N. law, so it produces goods at a cheaper cost than anywhere else in the solar system.

What does this imply about the relationship between the martian colonies and earth? Maybe this creates embargoes against that cheap martian merch, earthside. Are those savings worth the exorbitant cost of shipping through interplanetary space? Are they negated by U.N. tariffs? The cost would almost certainly be worth it for certain raw materials, like rare minerals that are plentiful in the asteroid belt...but maybe it would be more economical to drag asteroids, piecemeal, inner system to reduce costs.

So now, your triangle trade doesn't involve the belt at all, but a series of near-martian satellites.

Just start with research: What are the technological capacities What are the useful resources What is the history of this setting

Then add a bit of sociology and econ, and your concept will grow from there.

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    $\begingroup$ Thank you for posing so many questions for me to think about. What I am trying to do is build this world in "layers". Starting with an economic system that would function well enough for a society to benefit from it and also justify creating such a system. A lot of your questions are things I don't have answers to, because this is the first part of the society I am constructing. But please do challenge everything you can, I want to do my best to make my system not just plausible but really believable as how society in space functions. $\endgroup$
    – user49634
    Jul 23, 2018 at 3:04
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    $\begingroup$ "Maybe mars is a hub of manufacturing because Jeff Bezos IV settled it with a bunch of drones maintained by..." Of course, this doesn't answer where you're going to get the (lot's of) energy needed for manufacturing, all the raw materials, etc. $\endgroup$
    – RonJohn
    Jul 23, 2018 at 3:36
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    $\begingroup$ @user49634 You don't start with an economic model. Those are secondary to material conditions. Unless the economic angle is the point of the story. If you really want a particular economic arrangement to be in there, and it is thematically important, then you need to work backwards: pick an economic arrangement and then create the conditions necessary for it to exist in your world, via things like technological constraints and socio-historic events. $\endgroup$
    – user49466
    Jul 23, 2018 at 3:44
  • $\begingroup$ @ronjohn i asked that very question in the next paragraph 😉 $\endgroup$
    – user49466
    Jul 23, 2018 at 3:45

The Moon

Water may be the moon's first export. There seems to be massive ice deposits at the lunar poles.

A propellent source not at the bottom of an 11.2 km/s gravity well would be a major game changer.

Given a big delta V budget, an upper stage can have a dry mass fraction of around 4%, about as tenuous as an aluminum Coke can. Sturdy structure and thermal protection is needed to survive the extreme conditions of re-entry.

Given a lunar propellent source, propellent tankers don't ever have to enter the earth's atmosphere. These would enable inter orbital ferries which also would never have to endure the extreme conditions of re-entry. Also, given 4 km/s delta V budgets, these tankers and ferries could have a more substantial dry mass fraction.

enter image description here

Lunar propellent exported to EML2 would be close to important earth orbits as well as other destinations in the solar system.

If extraterrestrial propellent enables economical re-use of spacecraft, other lunar commodities become plausible. Lunar KREEP is rich in rare earth metals and thorium. Rare earth metals aren't really rare but mining them is very damaging to the environment. Lunar mines aren't within the biosphere. We could mine these commodities without soiling our own next.

Abundant commodities without damage to our ecosphere is Jeff Bezos' reason for investing in space.

Phobos and Deimos

These moons offer a commodity few have heard of: orbital momentum.

With Deimos 1.5e15 kilograms and Phobos 1e16 kilograms, these moons are huge momentum banks. Elevators or tethers anchored to these moons could catch or throw payloads for thousands of years with very little effect on their orbits. Catching a payload would have less effect on Phobos than a gnat landing on an 18 wheeler.

Given an ~1000 km elevator ascending from Phobos and an ~3000 km elevator descending from Deimos, these moons could exchange payloads via a ZRVTO (Zero Relative Velocity Transfer Orbit). The moons could exchange cargo and passengers with the use of nearly zero propellent.

enter image description here

More ambitious Phobos tethers can fling payloads down a 1 A.U. perihelion (in other words, a transfer orbit to earth) or up to 3 A.U. aphelions (in other words, a transfer orbit to the Main Asteroid Belt).

enter image description here

A Phobos tether descending to the top of Mars' atmosphere could drop payloads into Mars atmosphere at .6 km/s. About mach 2, the Concorde would routinely do this through a much thicker atmosphere. As it now stands, earth to Mars spacecraft enter Mars atmosphere at about 6 km/s. Entry, Descent and Landing (EDL) for Mars would be vastly easier.

More on Phobos tethers at:
Mars Panama Canal of the Inner Solar System.
Upper Phobos Tether.
Lower Phobos Tether.

Once Deimos and Phobos enables economic transportation to and from Mars, Martian commodities become plausible. Martian water and carbon dioxide would be big. Argon is a good propellent for ion engines. And of course Mars has metals deposits.

And if Phobos becomes a gate way to the Main Belt, the resources of the asteroids become accessible.

Not only metals, water and organic compounds but the asteroids could offer real estate.

Only the thin outer shell is accessible on rocky planets and large moons. Heat and pressure prevent us from tunneling too deep. In contrast, the entire volume of small bodies are accessible.

If the entire volume of Ceres were utilized, this asteroid could make Trantor look like Dogpatch.


The problem that I have with this depiction is that I find it very unlikely that water, food, and other commodities and goods will be shipped on an interplanetary basis.

Raw materials will ship from the asteroid belt and possibly Jupiter's moons. Manufacture may be done in orbit (not necessarily at the moons; zero-g and low g factories seem more likely). Energy is plentiful in space, as there is a giant fusion plant (colloquially known as the Sun) in the middle of the solar system that is constantly broadcasting energy.

The primary things that will move between planets are people and knowledge. Knowledge because it is cheap to move. People because they will want to move.

It is going to be much cheaper to ship water from Jupiter's moons or the asteroid belt than to bring it out of the Earth's gravity well. Space ships are horribly inefficient in environmental terms. This doesn't currently matter, as we have so few space ships that their overall effect on the environment is negligible. But your diagram suggests regular trade in bulk, and that simply won't work at that level. It is always going to be cheaper to produce locally or in space than on another planet.

The only goods that are going to be produced on a planet and shipped through space are going to be luxury goods. Genuine Kentucky bourbon, Scotch whiskey, and French champagne are examples of goods that will ship. In value terms, they may represent significant expense, but this will be almost entirely transport costs.

You don't mention what kind of fuel that you are shipping from Venus. But remember that there is no current shortage of fuel on Earth. We have plenty of fuel. The problem is that when we burn it, there are environmental effects. Shifting the source of the fuel from the Earth to elsewhere doesn't help that. We still create pollution when we burn it. We need pollution-free fuel, not more fuel. And by definition, fuel shipped from another planet is not renewable. It does not pull pollution (e.g. carbon dioxide) out of the air in order to form its fuel as biofuels do.

It would make more sense for Venus to ship us solar panels than fuel. And still, it would make more sense for the Earth to build its own solar panels. The cost of lifting Venusian sand into orbit would dwarf any cost we might have in producing solar panels.

At the time of the Triangular Trade, shipping between the continents relied on wind and ocean currents. If you want something similar in space, I would suggest going beyond the solar system. You need some sort of (from the perspective of our current technology) magical transportation that costs very little in terms of energy and operates rather quickly (days/months rather than years/decades).

If instead you are trying to make your space economy realistic, I would base trade on luxuries, knowledge, and people. Have things manufactured locally or in space, not on planet. People may migrate or even engage in interplanetary tourism. Some people will miss things that are only available in one place and so support luxuries. Or people who can't afford to travel to another planet may find it cheaper to import curios. But for the most part, people will be satisfied with the local versions.

I'm not entirely convinced that planets other than Earth are really viable places to live. Perhaps people move into giant space habitats instead. Space habitats have the advantage of plentiful energy. If environmental restrictions limit the amount of energy available on Earth, emigration may be how the rich maintain access to energy. So Hollywood and other such things may move off-world so as to allow access to the energy that they need.

  • $\begingroup$ I also do think that if water is to be shipped to other planets, if the container is at 100%, after it leaves Earth's Gravity, I think it would be reduced into some 70% or more because of the heat from the rockets, or from the shaking of the container. $\endgroup$
    – Mr.J
    Jul 23, 2018 at 7:12

Obviously, macro-economic modelling is a very complex and sophisticated topic so there's not going to be a simple YES/NO answer to your question, but even when we look at the current global market we've seen challenges in that environment which go some way to highlighting what you need to consider for your hypothetical market. There are a few more to consider beyond the global market as well, but one thing at a time...

Why we call it trade

The one thing that your diagram has is arrows in both directions to each 'zone'. (I'll call them zones as I'm assuming that Earth, Mars, et al are acting as a single market in your diagram - if not, this gets far more complex.) This is a good thing, as it's important that you not have one group entirely dependent on supply of goods, with no demand for what they can provide back. That isn't trade and would cause it to be uneconomic to sustain such a zone.

But, there must be balance

What we don't see in your diagram is how much of each commodity is being traded. If one zone needs a lot of commodity X but can only offer a little of commodity y in return, this creates challenges. Ideally, this is managed through currency exchange. Let's say Venus is buying more than it sells, then (in theory) the value of its currency goes down by comparison to other currencies, because less people need to buy it to trade for goods, and more people are trying to offload it to buy the goods of others.

If the commodity in question is not life sustaining, this pressure causes less Venusians to buy goods from other zones, and Venusian goods become more attractive because they cost less outside Venus. This creates a self-balancing effect.

Cost of shipping

On Earth, the only metrics to consider for shipping is how far away the two parties are from each other, and what's in between them. Goods are shipped by road, sea and air, and some other mechanisms besides, like pipeline. The point being that for the most part, countries don't have the complexities that you would expect of space in terms of shipping cost.

Earth and Venus (in your model) are going to cost a LOT to ship from because of the gravity well. Let's assume that spaceflight is relatively common, the energy requirement is still there (even if the cost of energy has diminished) meaning that it will cost more to get goods off those planets than it would off Mars or the Asteroid belt. This also needs to be considered in your economic model because the cost of shipping alone may well make the same commodity at the same price from (say) the Asteroid belt more attractive than it would from Earth.

Life Sustainability

The other wrinkle you have that Earth doesn't have is the essentials for life. People use the same amount of O2 (for example) whether they are on Earth or the asteroid belt. That said, the asteroid belt has far less O2 than Earth does. Same would go for (say) wheat.

Ultimately, the supply and demand curve that we see in modern economics only really works if the commodity is not seen as essential. When it is, there are other forces at work and these are often not left to a free market economy to manage because of the humanitarian factors. To be frank, we've never had a country that has needed water to be shipped to it on an ongoing basis because it has none of its own. If we did, people just wouldn't live there in the first place. In this situation though, one has to ask whether or not these 'colonies' are now independent of the powers that first invested the tremendous resources required to establish them initially. If not, then one would expect the essential commodities to be a state run supply model. If not, then these independent economic 'states' have a bargaining weakness insofar as they can't afford to risk losing such supplies meaning that unscrupulous merchants would be able to charge whatever they wanted for critical shipments, effectively bankrupting most of these states for vital supplies.

In Conclusion

If the question is really 'is it plausible' then the answer is yes. You have supply and demand to all zones, which makes it possible. For some commodities, you have multiple sources, making for competition and generally you're looking at a larger scale and slightly more complex version of the existing global marketplace.

If you're asking 'is it viable' then there are some challenges that we face before even getting off this planet that may introduce difficulties that in your world may prove insurmountable. The issue of vital supplies for one is something that ideally would be heavily regulated because otherwise you have people entirely dependent on trade for their survival, which while it has happened for relatively short periods in history before, doesn't work economically as part of a 'chronic condition'.

Finally, if you're asking is it probable, the answer is no. The simple reason for that is that these colonies cost something to set up in the first place and the state or company that set them up is going to want a return on its investment before letting them go independent. What that means in practice is that by the time they have the opportunity to do so, these zones have lost most (if not all) of the commodities they have to trade for what they need. It's almost a joke to let them become independent at that point because they'd be entirely dependent on the supplies of others to survive.

To that end; I'd have to say that the basics are there, but in practice I can't see it being viable unless the zones in question have massive reserves of commodities that they've hidden before becoming independent. Without that, they're just not economically viable unless they have some unique manufacturing process or service which simply isn't possible in a different set of environmental conditions or within Earth's gravity well.

  • $\begingroup$ So supposing, for example, that the low gravity on mars makes an experimental manufacturing process that allows for much cheaper manufacturing (enough to justify the cost) of almost anything, is that the sort of unique benefit that you say would be required to justify colonies en masse? $\endgroup$
    – user49634
    Jul 23, 2018 at 3:14
  • $\begingroup$ @user49634 yes, pretty much. Asteroid belts are obvious sources of minerals (if they're there) because getting off the asteroids is far cheaper in energy than getting them off Earth. Mars may have a very specific engineering capability that can only be done in a lower gravitational well (like high grade steel) so that may make it worth it. But, if a country colonises Mars for that, they're unlikely to want to give up exclusive access to that capability given the establishment cost. $\endgroup$
    – Tim B II
    Jul 23, 2018 at 3:27
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    $\begingroup$ @user49634 "cheaper manufacturing" is great only if you have not only the raw materials for your manufacturing, but the materials needed to manufacture the manufacturing materials. On Earth, the trail backwards from any complex manufactured part is shockingly long, complicated and energy intensive. $\endgroup$
    – RonJohn
    Jul 23, 2018 at 3:39

I am late to the party, and answers above make sense, but let me expand some more on shipping cost and comparative advantage that others mentioned:

  • Water will be recycled, as it it is on ISS today, or harvested locally. The only place that does not have a whole lot of water is Venus, so it can get shipments from moon or asteroid belts.

  • Food can be likely be grown locally. The only thing that makes sense to ship will be seeds, soil and (mineral) fertilizers, as well as vitamins and supplements.

  • Labor flow will not be as major part of transport. In triangular trade, slaves died a lot and needed replacements; free humans will not travel somewhere if they are likely to die soon. In triangular trade, a slave could be used to build his own hut. In space, you need a new habitat unit for each settler.

  • Earth's main export will be high-tech goods: robots, computers, and software that runs them (or rather upgrades to it).


The primary factors affecting trade are time and energy. Distance is not a factor (at least in the way we think of it) since it is constantly changing as the planets orbit, and the energy cost is determined by both the distance and the gravity well you are entering/exiting.

The amount of energy needed can be determined by looking at a factor called "deltaV", which is the change in velocity you need to go places. To go from the surface of the Earth to Low Earth Orbit requires a deltaV of @ 7Km/sec, regardless of how you do it. A rocket is how we do it with current technology, but enormous tethers or other mechanical devices could be used as well. This energy cost needs to be paid somehow just to get into orbit, and before you can even consider going anywhere else.

There are tables on the Internet showing the deltaV for most other destinations in the solar system, one interesting deduction is once you get into space, you are "halfway to anywhere", in the sense that you only need to add up to another 7km/sec to get to most of the places you mentioned in your example.

The energy cost to accelerate or decelerate will depend on how exactly you do this. Chemical rocket engines can provide the deltaV but at the cost of a huge fuel burn. Nuclear rockets are better, but you need to add mass in the form of reactor shielding to protect the crew. Other technologies exist or are under investigation, see the "Atomic Rockets" Engine list to choose how you want to do this.

This brings up the second factor of time. You can choose to save a lot of money using a minimum energy orbit, but you could be months to years getting to your destinations. As well, minimum energy orbits work on what are called synodic periods, i.e. when the planets line up correctly. The reason missions to Mars occur about every 18 months is that is when the two planet are in the proper alignment. This could be much longer in the case of asteroids.

You can use much more energy to get there faster, but that impacts costs, and cargo (especially bulk cargo) is most profitable when sent by the most energy efficient method possible. This is why pipelines beat tanker cars on trains for oil, and "unit trains" beat trucks for bulk dry cargo like coal or ore.

So your civilization will be underpinned by a complex calculus of shipping costs and time. Valuable cargo like people may be sent on elaborate spaceships with powerful engines at a steep energy cost, while chunks of ice might be wrapped in a foil bag and shot at minimum energy to the destination planet.


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