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I'm picturing an universe where FTL travel was invented as a sort-of-fluke, and artificial gravity technology isn't available. Transit between star-systems takes at least a few days and a star's gravity well slows the FTL down to a point that it's STL anywhere around the Goldilocks zone.

Also present in the universe are megacorporations that purchase entire planets for resource mining purposes (the lack of breathable atmosphere or magnetosphere having brought real estate prices down somewhat). All the habitats on the planet are company towns built around mining and processing the planet's resources and shipping them home.

Where my understanding of the economics of interstellar bulk transport fails me is this: just how much processing would be done on the mining planet before the end result is shipped back to the homeworld?

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    $\begingroup$ It depends on the cost of shipping. If shipping is dirt cheap it may be the case that ore is shipped to massive processing plants elsewhere to take advantage of economies of scale or of higher tech. On our present world, it is sometimes cost effective to ship iron ore from Brazil to China, or crude petroleum from Arabia to Europe. $\endgroup$
    – AlexP
    Aug 7, 2017 at 14:24
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    $\begingroup$ I'd need to see your W2s from the last five years... how much shipping costs per gram - per gravity well, and how much the unprocessed ore and the end results are worth - per gravity well. And if there are any other companies who can do this, in part or in whole - and their prices for such. And the costs of all the facilities required, in all conceivable locations, levied by their percentage utilization and output. In short, enumerate your entire economy (no problem, right?), and then you can see what supply does to demand, and vice versa. Math.SE is next door ;) $\endgroup$
    – Mazura
    Aug 7, 2017 at 19:01
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    $\begingroup$ @AlexP Crude oil and ore are two rather different things from that perspective. The overwhelming majority of crude is turned into something useful via refining. The majority of ore, being something other than the metal/etc being mined for, is a waste product at the end of the refining/smelting process. That means it doesn't matter where on the transit from producer to consumer oil is refined, but the relative concentration of the material being extracted has a huge impact on if and how completely ore is processed on site. $\endgroup$
    – Dan Is Fiddling By Firelight
    Aug 7, 2017 at 21:02
  • $\begingroup$ Depending on travel times, you would probably have a local manufacturing industry making spare parts for the mining equipment too. $\endgroup$
    – pjc50
    Aug 8, 2017 at 9:27

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OP Q: just how much processing would be done on the mining planet before the end result is shipped back to the homeworld?

Presumably all of it; to reduce both the size and mass of the "end result" before shipping. There is no point in shipping slag which is going to be discarded anyway; and for some mining operations (like rare metals and gems) the "end result" is on the order of one millionth the mass of the processed ore. Why ship a hundred thousand tons of garbage rocks to another star system when they contain only a few ounces of the "end result"?

That stuff should never leave the planet surface; all refinement and extraction of the "end result" should occur on the surface. Or in a few rare circumstances, in orbit around the target planet can be more cost effective despite the work of getting the ore up there (or partially processed ore up there); because a zero gravity environment is (theoretically) very useful for certain types of extraction or metallurgy.

Just like Earth corporations, your customers will want the ore in a finished generic form; like sheets, coils, blocks or spools of wire in various gauges. That is what should be shipped from the planet.

The expense of separate factories for doing that, on each planet, might warrant shipping some single form (like easily stackable cubes, or grains (small spheres)) of the pure "end result" to a post-processing plant where those can be formed into customer-desired configurations, or combined into alloys for that purpose.

I am presuming the mining company is not in the business of producing end-consumer products and only producing materials to be melted down (or cut and polished or otherwise processed) by their customer companies.

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    $\begingroup$ +1: Per unit mass, getting stuff into orbit is insanely expensive with our current level of technology (and presumably the technology which OP is contemplating). Gravity wells may distort space, but they really mess with economics. Putting anything into space is basically a last resort - you only do it when there's literally no other way of accomplishing your objectives. $\endgroup$
    – Kevin
    Aug 8, 2017 at 5:09
  • $\begingroup$ @Kevin Agreed. The advantage of space is effectively infinite solar thermal power focused by simple (giant) aluminum mirrors, and centrifugal sorting of molten metals. Don't forget the costs of transporting our current-day fuel options from some planet where they get made down to the mining plant surface. If we must melt tons of rock to get a gram of product, it would require tons of fuel down on the planet, thus tons of fuel transported to the planet. With current tech, maybe rail-gunning rocks to space for extraction in zero-g with solar power could be more cost-effective overall. $\endgroup$
    – Amadeus
    Aug 8, 2017 at 9:26
  • $\begingroup$ @Kevin (continued) especially on a non-atmosphere planet as OP envisions; or a relatively low gravity planet (Moon, Mars). Rail guns are just electro-magnetic and can be powered by solar cells. That is a more transportable and reusable than a few hundred tons of fuel. With no (or very thin) atmosphere, there is no air friction or drag to overcome (and no sunlight diffusion); rocks can be accelerated into low orbit and collected by the mining ship for processing. Making small no atmosphere (or thin atmosphere) planets better real-estate for miners than planets suitable for settlers. $\endgroup$
    – Amadeus
    Aug 8, 2017 at 11:31
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I think you could find lots of models for this here on Earth. Examples:

  • Kitimat Aluminum refinery was built in B.C. where they were able to put a tunnel through a mountain and tap a near 3000 foot high lake. The generated power was really cheap. Bauxite is shipped from Southeast Asia (Burma, I think, or what used to be Burma) Aluminum ore is cheap to mine, but expensive to refine. Ocean transport is cheap.

  • Eldorado at Uranium City was mining ore that ran 0.25% U. They had a huge concentrating mill that brought it up to a much higher percentage, before packing in drums for barge transport.

  • But at Port Radium on Great Bear lake, they found deposits rich enough that they just loaded the ore into burlap sacks and barged it down the McKenzie.

  • In the U.S. Iron ore is loaded into big bulk carrier cargo boats, and run down the Great lakes to the refineries.

Things to model: * How expensive is it to keep a worker on a mining world? Look at Fort MacMurray for examples. Typical northern camp costs are 2-3 times per worker. E.g. A millwright in Ft. Mac gets about $48/hour plus room and board, plus time and a half for anything over 40 hours a week and double time for anything over 60, and triple time on Sunday.

  • How expensive is it to construct the infra-structure to support the crew that runs the refinery.

  • Are the ancillary processing materials insystem? E.g. If you are mining a baked rock, do you have an oort cloud full of comets, or an ice moon somewhere where you can get water for processing the ore.

  • What is the relative value of automation to worker's efforts? Will a mining world be a million hard rock miners, with saloons, gambling, or will it be a team of 500 programmers, and robot repair techs.

  • Is it cheaper to run a FTL ship slower. E.g. On earth ocean freighters run at 10 knots or so, while passenger ships go much faster. Freight trains putter along at 30-50 mph while on good track passenger trains do 70-80, and dedicated passenger service at 300 mph is possible.

  • Can FTL be automated. Can you program a ship to take a megaton of stuff to another system, halt just outside the system, and beep "Come get me" ? This lowers the cost of transport.

  • What is the relative cost of distance? Does it cost twice as much to go twice as far? Or is it a matter of it costs X to go in and out of FTL and the distance doesn't matter much. In the first case, a deposit of 10% purity nearby may compete with one of 30% purity several times as far away. In the second case a richer deposit may make the company with the poor deposit go broke.

(This happened with Uranium City. The Wollaston Lake deposits at the Rabbit Lake Mine run about 40% -- 160 times richer.)

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  • $\begingroup$ Iron ore is usually transported because the other commodity for smelting is coal, which would be even more to transport... $\endgroup$
    – I'm with Monica
    Aug 8, 2017 at 8:16
  • $\begingroup$ @AlexanderKosubek That is a good point. A lifeless world generally wouldn't have fossil fuels. $\endgroup$
    – HAEM
    Aug 8, 2017 at 11:06
  • $\begingroup$ @HeikkiMäenpää Yes, in the spaceex context, fossil fuels might be a scarce resource. But whoever has enough spendable energy to put iron ore to orbit has enough energy to smelt it first. A very rough estimate of energy per mass to LEO given on space.se is ~100 MJ/kg. According to this external source energy to produce iron from ore is about 25 MJ/kg. So, by reducing the mass of the payload by 50% you save at least 25% of total energy spent... (All very rough estimates...) $\endgroup$
    – I'm with Monica
    Aug 8, 2017 at 12:43
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As much as can be economically defensible.

What's the extraction rate of the ore? Gold for example has an average concentration of about 5 grams per tonne of ore (though is from my understanding usually not mined unless you can get out at least five kilos per tonne, or 17 furbnings to the boartload if you're using Imperial measurements). So... is it cheaper to refine ore on site and just ship gold (which also has the benefit of being very compact and not need huge storage bays)? I'm fairly sure it would. So for rare metals this is definitely the most viable method.

But I'd say that even for common metals such as Iron (which is deemed commercially viable at around 56% (or 560 kilos per tonne) if my research holds up it makes sense to not lug a lot of useless stone over the planetary system if for nothing else then to reduce inertia.

I'll assume here, of course, that mining and refining at your suggested tech level is highly automated and can be maintained by a small crew of humans who's life support doesn't significantly impact on profit.

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In practice this is about your own world and story as it's a cost-benefit-regulations game.

We've previously discussed the fact that almost nothing is worth shipping across interstellar distances, so where you do your processing is up to you.

Your questions are:

  • Are there pollution regulations on the destination worlds that mean you have to process on the mining world or other equivalent manufacturing world
  • Are the costs different for processing at source and destination
  • How many people are required for processing
  • How much mass is removed by processing
  • How many tons can you process per day
  • What is the cost per person-day for keeping people on the mining world
  • What is the cost per ton for hauling cargo

This is only a quick summary of basic questions to consider, there are far more in the real world.

At the end of this line of questioning you get a couple of numbers that tell you how much work you need to do and where.

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  • $\begingroup$ I don't think any of those previous questions about interstellar shipping allow for FTL, so they not quite relevant for this scenario. $\endgroup$
    – Rob Watts
    Aug 7, 2017 at 20:16
  • $\begingroup$ @RobWatts, the one I linked does allow FTL but not 0 cost FTL $\endgroup$
    – Separatrix
    Aug 7, 2017 at 21:16
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Just adding some examples from real mines in Western Australia, to reinforce that it depends on the economics of the processing as mentioned in other answers:

  • Gold grades are around 5-20 grams per tonne, so it is usually refined at the mine.
  • Iron ore grades are around 60%, and the raw ore is loaded onto trains for hundreds of kilometres and then onto boats to be shipped thousands of kilometres to China to be refined there.
  • Bauxite (aluminium ore) grades are around 30%, and are often refined at site or nearby (into alumina - a white powder), but then exported thousands of kilometres around the world to a smelter to make into aluminium metal, since the smelting requires a huge amount of electricity (which would be expensive to produce locally).
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There is almost no bulk element that's worth enough to make the cost of getting it out of a gravity well worth it. The only resource extraction I can see being worth it would be something like bioprospecting, where the giant corporate behemoth would discover and commercialize novel organisms, biochemistry, and genes.

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  • $\begingroup$ Look, those two specimens are worth millions to the bio-weapons division, right? Now, if you're smart, we can both come out of it as heroes, and we will be set up for life. $\endgroup$
    – Mazura
    Aug 7, 2017 at 18:46
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Its all about the gravity well. Getting material off a planet is going to be expensive, unless you are using a space elevator and have fusion powering everything.

So, without those the cost to transport unprocessed ore would be a crazy waste of resources. Its already being done here.. Vollrath makes all their stainless steel sheep pans and whatnot up near GreenBay. I met the owner once, and asked him why they don't do it in China. Turns out shipping sheet pans is really expensive. So, they do it all here..

On the other hand mining the smaller objects would be easier and more profitable. As Asteroids, don't have as much of a gravity well. They are also easier access to the valuable materials.

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