# Resources to justify long-distance space mining missions

Earth is setting up mining colonies on Tau Ceti e. But how can they justify the enormous cost of sending people there? ...Because during the initial exploratory missions, it was discovered that in addition to being human-habitable, the geology of TCe is just filthy with some natural resource(s), which are very scarce, very valuable, and most of all, very useful back on Earth.

What are those resources?

For example, some science fiction works revolve around mining the moon for helium-3. Is this a good enough resource to go to TCe for? What about other rare elemental isotopes?

Some notes:

• No unobtainium. I'm looking for some real-life ore or compound. Edit: Creative biological resources are okay, even if they currently do not exist. But if you're going for elements, try to stick to what we know exists.
• Implausibly large deposits of the resource are okay, i.e., I'm not so interested in the geological/biological processes that may account for how the resource got there; I'm more interested in the fact that there is a lot of it, and that there is not much of it on Earth.
• A round trip to Tau Ceti e would take about 30 years (from someone on Earth's frame of reference). It is also very expensive. Earth government can provide a lot of cheap labor, though, and the value of the resource(s) more than make up for the cost.
• To give background, Earth's moon could be made of pure, solid gold and it still wouldn't pay to go there and back with current technology. – Sean Boddy Apr 28 '15 at 19:48
• Worm poop. THE SPICE MUST FLOW! – ckersch Apr 28 '15 at 20:23
• Sure, if the moon was made of gold it still wouldn't be worth getting. Helium-3 is a potentially different story, though. – Doug McClean Apr 29 '15 at 0:52
• @Seth Accelerating a ton of matter to 0.75c and back (as in your other article for the designed speed) requires ~1 ton of antimatter worth of energy as fuel; so anything that is less 'value dense' than antimatter is worthless as the spent fuel would cost more than the cargo. The "exploratory mission" requires energy equal to many years of current worldwide energy consumption, so the energy cost in today's USD would be not 3 billion but larger than global annual GDP, more like 300 000 billion. The earth economy and production has to grow a lot to afford such missions. – Peteris Apr 29 '15 at 14:54
• @Freedom: Also consider that (other than fissionable elements and fossil fuels), nothing that is mined goes away. At some point, it becomes more economical to recycle them rather than mine. A quick pass through Google says that (in the US) about 80% of lead is recycled, 50% of steel, also high percentages of copper, aluminum, precious metals... – jamesqf Apr 29 '15 at 17:54

Antimatter.

It's insanely expensive to produce artificially, with estimates of up to $62.5 trillion per gram of antihydrogen. Naturally occurring antimatter in any decent quantity would be beyond lucrative - it would also provide whoever controlled it with a nearly unbeatable energy and weapon edge. However, it couldn't be laced into the geology of the planet, it would need to be somewhere in space. Probably the most likely source (and I use likely in a very loose sense) would be the remnants of an antimatter solar system - for example, a fragment of a fragment of an anti-matter asteroid belt that traveled through space, has been captured by Tau Ceti's gravity and is now in an eccentric orbit. • I read it somewhere - a brief history of time, maybe? You can get a sense of the problem by asking "How do I turn raw photons into something I can use with existing technology?" This is a solar panel. Then, "how do I control reaction rates of antihydrogen?" This requires a bonkers magnetic field, and only works after you strip the positrons so the particles have a net negative charge. Cheap fusion would be easy to fix if the magnetic field didn't take so much power to sustain - same problem with antimatter reactions. – Sean Boddy Apr 28 '15 at 20:00 • @SeanBoddy: So I found a reference that the worldwide production of antimatter, to date, would only power a light bulb for a couple of minutes. But that's a limitation on how much fuel we've produced, not on using an existing source. Fusion is difficult because you have to maintain high temperatures and pressure - antimatter just needs to be introduced with matter. I'm sure it's a lot harder than it sounds, but it doesn't seem like there's an engineering barrier that would make it impossible. – Dan Smolinske Apr 28 '15 at 20:22 • Producing anti-matter requires boatloads of energy. More energy than we get out of a matter/anti-matter reaction. Producing it isn't good for energy production - only energy storage. Going and scooping up the stuff, after a natural process has made it, is a fantastic source of energy. – user6511 Apr 28 '15 at 23:46 • Note one more thing: After the initial investment of getting there, we obtain a very cheap fuel for awesome interstellar propulsion! Getting the antimatter back to the Solar System would only require developing an anti-matter powered drive. Even if you consume 95% of the "fuel" getting it back to Earth it would leave enough to allow interstellar travel on a tiny fraction of current costs and allow travel at relativistic speeds. – SF. Apr 29 '15 at 6:34 • While an interesting thought, I'm not sure large chunks of antimatter could exist floating around Tau Ceti. There's too much matter floating around for them to react with, and even a small reaction would be likely to blow the asteroid into chunks too small to effectively mine. – ckersch Apr 29 '15 at 15:08 Alien Life (and their byproducts) You can't really mine it, but the presence of alien life would be an incredibly compelling reason to send people to Tau Ceti. It's likely evolved in completely different ways than life on Earth has. Considering that Earth-life has created many substances that we can't reproduce in a lab, it's entirely feasible that Tau Ceti has got some creatures producing incredibly valuable materials. Perhaps there are giant spider-like creatures spinning house sized webs of materials stronger even than what Earth-spiders can weave. Perhaps some large herbivores grow thick carbon plates that are fantastic for space ship armor. Perhaps Tau Ceti is populated by giant worms who produce a substance that enables people to pilot their ship through extra-dimensional spaces, making FTL a reality while also letting them see the future. If any of these things are produced only on Tau Ceti, but not on Earth, sending a crew to harvest them could be hugely worth while. • Hey, please credit Frank when ripping off his ideas ;) – Ghanima Apr 28 '15 at 21:34 • This answer is the best, but you're thinking small. You can only bring back a few spaceship's worth of armor in one spaceship. Think more horseshoe crab extract. Exotic poisons. Powerful drugs. Self-replicating herbivore extract used to make self-repairing spaceship armor. (you can't bring the herbivores back because they're the size of a building, roam hundreds of miles, and breathe elemental fluorine or whatever). – Resonating Apr 28 '15 at 22:05 • You'd call the spice Melange "thinking small"? I guess you're underestimating that "the spice extends life. The spice expands consciousness. The spice is vital to space travel." as well as that it is "the most precious substance in the universe". – Ghanima Apr 28 '15 at 22:43 • Sure, expanding consciousness and allowing interdimensional travel are great benefits. But to make it economically lucrative what you really need is for it to have certain specific anatomical growth effects on humans. – Doug McClean Apr 29 '15 at 0:55 • Oh, and "can't reproduce in a lab" is missing a very crucial yet :D There's no reason to assume we will not be able to reproduce most in the future (it's not too long ago that most scientists were absolutely solid about impossibility of making any organic substance in the lab - they had to concede when that annoying liar managed to synthesize urea). But yeah, even then, as long as you can maintain the monopoly and make sure noone else knows how it's made... More analogous to silk thread than melange. – Luaan Apr 30 '15 at 11:36 "Space," it says, "is big. Really big. You just won't believe how vastly, hugely, mindbogglingly big it is. I mean, you may think it's a long way down the road to the chemist's, but that's just peanuts to space, listen..." -- A quote from The Hitchhiker's Guide to the Galaxy, Douglas Adams Honestly, there's not much the natural world could offer that would make such a trip worthwhile. Some estimate that it would take$ 174 Trillion and 40 years to create and fuel an unmanned, one-way, fly-by type interstellar voyage.

From this number, it is not unreasonable to assume a manned mission that stops at its destination will be significantly (10x - 100x) more difficult (I estimate it at $3,480 Trillion). Any natural element, compound, or other natural resource could be had far more cheaply from sources in our solar system. As I see it, there are only three possibilities and each of these is highly unlikely (which is why they would be potentially so valuable). Basically we're need something worth more than the estimated cost of$3,480 Trillion that we cannot find in our Solar System and cannot make ourselves.

1. Alien Artifacts/Technology
If aliens left clues that a treasure trove of advanced technology were there or sent signals that we should come visit, this might make a economic, military, or even a scientific visit practical. The return on the investment might be very well be worth our while.

Alternatively, a visit to a planet with aliens might similarly be worth the trip, but you'll have to think this through very carefully. What could they offer to make it worth our while that we could not trade via distant communications? Most science, math, music, philosophy, etc. can easily be transmitted. The value of Paintings, sculpture, etc. couldn't justify the tremendous expense of a trip. Materials and building techniques could be transmitted via building plans by long-distance communications.

How about a planet with a Stargate on it?

Active Stargate

2. Survival of the Species
Ultimately, ALL life on Earth will be exterminated. In order to survive, humans and/or our descendents must colonize space and other star systems. The smartest thing we could be doing as a species is to build space colonies.

Unfortunately, only a sort of benevolent dictator or other such long-term thinking government would be capable of diverting resources for such a venture, unless the species were faced with imminent (10s or 100s of year) extinction.

3. Exotic Matter
Exotic particles and matter have been postulated many times. Many of these are not explicitly excluded by modern physics but neither have we seen evidence of them.

Some ideas include

1. Primordial black holes - the potential for cheap, "clean", unlimited energy production
2. Magnetic monopoles - I don't know but I think the concept is cool ;)
3. Strange matter - the potential for cheap, "clean", unlimited energy production
4. A source of Tachyons - potential clues for FTL communications and travel
5. Negative matter - would (theoretically) enable us to build permanent stable wormholes - definitely worth the trip.

The key here is that we could do fantastic things with these but we simply don't see any in our neighborhood.

• When feeding microblackholes, if you have insane energy requirements, you could end up clearcutting the planets for their matter. – PyRulez Jul 24 '15 at 23:36
• The ruins of an alien civilization. There is no one transmitting so you have to go there to find their tech and reverse engineer it. – Donald Hobson May 12 '16 at 14:59

On TCe a very interesting plant was discovered.
It had feathery leaves that were extremely strong, pitchblack and glossy, and while flexible they could not be cut by the probe's tools. It turned out that the plant's leaves were composed mostly of very long carbon nanotubes.
All efforts to cultivate the plant on earth or in a space station have failed, so it was decided to create the colony, which after a few years had a space elevator set up and working

Soon after, the first cargo ships started sending back huge harvests, enabling Earth to build its own array of space elevators.

The real-world cost of interstellar travel is so high that without a real game changer there is nothing worth the cost. If you have a device to allow cheap travel, just make it cheap enough to satisfy the plot.

Someone suggested plutonium: but where does it come from? The stuff decays, so there won’t be any more there than here. And even if present, it’s still cheaper to make it via alchemy than to ship it interstallar distances.

Helium 3: why would it be easier to get there than here? Skim Jupiter or any old comet ice. As for its value, if you can travel between stars, you're already well beyond needing it.

Water/ice: seriously? It’s everywhere including icy moons and billions of comets. It would be orders of magnitude cheaper to synthesize using hydrogen and oxygen from rocks.

Soil: see Farmer in the Sky. Even Heinlein knew that shipping soil within the solar system was not practical. Just take a small amount of culture and grind up the local rock.

Whatever goods you are shipping, remember that shipping time is measured in centuries. No chemical or passing taste will remain valuable for that long.

You can ship information at light speed, and in the information age we understand that this carries value. But what is so interesting there that studying it becomes a valuable industry?

Any substance can be made from atoms and even factoring reasearch and development to figure out how to make that stuff, it’s not worth shipping. Atoms themselves? We know about all the elements and until Mercury is strip-mined out of existence there is no need to find heavy elements elsewhere at higher cost. In short, there is nothing that’s not in our solar system that we expect to find in another.

The antimatter idea from another comment is getting somewhere: energy on a scale that makes interstellar travel worthwhile. More generally, something that enables more-practical travel, but that’s getting into unobtanium (mineral MacGuffin, spice of life) territory. A bank of bulk antimatter begs the question of where it came from (a lost civilization or gift for emerging spacefaring civilizations) and if you go that route it might as well be antigravity goo, space warping marbles, or prefab stasis boxes. At least antimatter itself is a real thing.

To reiterate, for any normal material there is just no way. If you adjust the expense of interstellar travel via cheap energy or hyperspace or somesuch, then it’s a non-question since you can adjust it to fit the plot. Any invented space travel trope can also have a corresponding material needed for that thing: so mine dilithium crystals for your warp drive, or whatever.

The product of immobile alien technology, limited nanogoop etc:

The first scouts found projections from an ancient deeply buried alien artifact (hundreds of miles down)that readily produced nanogoop. It couldn't self replicate but it could do almost anything else imaginable with nanotech and gradually degraded with use.

Reverse aging? no problem! Heal any wound or make any physical alteration to a person? easy! Build any devices not associated with reproducing nanotech? done in a flash! Indeed it's hypothesized that the aliens didn't want any risk of a grey goo scenario no matter what any of the more foolish members of their society might try so the nanotech is quite thoroughly proofed against being used for self replication by any means but otherwise can be used for almost anything.

On the planet it's cheaply available to all and greatly eases the initial groups building their communities.

When news arrived back in the solar system that the literal fountain of youth had been discovered: photos of the now restored older members of the initial scouting party became the top news story on earth for months.

Every aging billionaire, every geriatric politician wants just a gram or 2 of this stuff to regain their youth. It's worth billions per ounce. And so another expedition is funded with the goal of returning with many tonnes of the material.

If you'd prefer a simple solution, let's just look at the rarity of elements in the Earth's crust.

We find Iridium, Rhodium and Osmium down at the bottom of the list. This is overall abundance. Osmium has various stable isotopes of varying abundance. Note that the overall abundance of Osmium is much higher than in the Earth's crust. There is no reason why you might not be able to mine thousands of tons of the stuff from the right source.

So what you then need is a reason why Osmium would be needed in large quantities.

eharper256 mentioned superconductors. Currently, the best superconductors that we know about (in terms of how warm they can be and still be superconducting) still need to be very cold (-140 °C is the current highest). These high temperature superconductors are interesting because:

• We still have an incomplete understanding of how they work
• We do know that complex crystal structures involving rare earth doped ceramics are our best so far.
• This gives scope for requiring just about any element as essential to a future industrial product.
• Having a material that is superconducting at (or near) room temperature would be a civilization transforming technology.

Of course, you can come up with countless other technologies that might require a specific element, or perhaps isotope.

• Yup, that's why Avatar's Unobtanium was a room temperature superconductor. Humans will probably be able to figure out how to synthesize it, but until then, it would be just about the most lucrative trade ever. Adding the "Unobtanium is catalyst for antimatter fusion / antimatter production" is just a cherry on top :) – Luaan Apr 30 '15 at 11:39
• You still fall short of the goal, because Space is Big. really big. walks to the chemist and all that. Making osmium via nuclear transmutation is ridiculously impractical, but a freight run to Tau Ceti is even more impractical, so anything where nuclear transmutation would constitute an alternative source cannot meet the requirements. Unsynthesizable compounds and exotic matter are needed; no conventional elemental material can be good enough. Good, yes, but not good enough. – Matthew Najmon May 1 '15 at 14:48

Well, I'm assuming we're in a time when space travel and escaping a planet's gravity "ain't no thing" anymore and traveling such a long distance is similarly much easier than it is now.

So what resources are valuable?

Precious Gems - NOT needed; bringing heaploads of them back to our solar system will only devalue them until they're not valuable anymore. If everyone was covered in sapphire, and the houses are made out of it, it's really not going to be valuable.

Water/Ice - If it's now easy to lift this from an Earth-like planet, and ship it to our other colonies, this would be helpful not just for consumption, but for their attempts at terraforming (yeah I went there).

Information - This might not fit your story, but if it's revealed that a more advanced society left tremendous information in a format that we should be able to interpret, we'd be there in a New York minute.

Conductive Metals - I'm not sure what will be the best element in your future, but silver, copper and gold are great at electrical conductivity. Whatever your latest conductor is, have lots of it.

Soil - Real, Earth-like soil can only be currently found on Earth. It will be a rarity and a necessity in your other colonies, and I personally think it's one of the most overlooked checklist items for colonization.

Naturally Occurring Beer - ;)

• I don't think that soil is the most overlooked item. You simply would not bother (maybe as a rarity but not as necessity). Go for hydroponics or make do with the stuff you find over there. Teraforming will have to develop plants fitting to the planet anyways and soil will be "naturally" formed in the process along. – Ghanima Apr 28 '15 at 21:29
• Soil will take generations to create artificially. If you could import it quickly and easily, that would be a major boon to agriculture and forestry. Martian regolith, for example, can sit in a lab as long as you like, with as much fertilizer as you like, with as many bugs and worms you want to transport; it will still be dust. – Mikey Apr 29 '15 at 3:17
• As will teraforming itself take generations. That's the point. – Ghanima Apr 29 '15 at 6:58
• – Mikey Feb 17 '19 at 20:32

There's another very fundamental problem that's not been mentioned, which is economic uncertainty. Say you discover some resource at Tau Ceti that is currently extremely valuable, so you invest umpteen trillion (in present-day dollars) to set up a mining/harvesting operation. So 30+ years later (because it takes some time to get operations going), your first cargo ship returns to Earth - only to discover that things have changed. Someone has invented a cheap substitute, the technology that used the resource has become unfashionable, the government's made it illegal, etc.

# Alien Slaves

A common scifi trope

In a harsher world with regressive moral views, or fundamentalist religious views, combined with a sanctity of human life, it may be easier to adbuct aliens from Tau Ceti E to work as slaves in our star system, man ships etc

Human slaves would be morally abhorrent, but those more inclined to morality based on what's socially acceptable would not wince at non-human slaves, in the same way many people enslave bears to dance, or when faced with a sentient AI would think of it as nothing more than a toaster

Make their reproductive cycle involve things only found on Tau Ceti E, or things that are impractical to move ( e.g the female equivalent or queen bee of the species is 30m tall and weighs several hundred tonnes )

# Examples/Precedents

A common scifi trope

## The Ood

An example of such a species in current Scifi would be the Ood from Dr Who, who have a giant primary life form that's trapped and kept under control in order to repress the Ood

The Ood, also known as Oodkind, were a gestalt species of telepathic humanoids native to the Ood Sphere. Humanity enslaved the Ood, mutilating them to ensure a dedication to servitude.

The Ood were a peaceful herd-race originally. In the 39th century, humanity discovered the Ood, enslaved them, and used them to perform menial tasks throughout the three galaxies of the Second Great and Bountiful Human Empire. The external hindbrain of the Ood was extracted by Ood Operations and replaced with their translator globes. With their connection to the Ood Brain severed, they followed the orders of humans. Ood Operations kept this procedure a secret from the rest of humanity, spreading the belief that the Ood were naturally servile and offered themselves for servitude. (TV: Planet of the Ood)

## Goa'uld

A parasitic life form that stole technology and had a restricted number of hosts chanced upon Earth and enslaved the population, farming humans for new bodies to act as hosts

Ironically, the reverse became true in the show when a human civilization chanced upon a Goa'uld queen and farmed her for chemicals. Here is a Goa'uld queen:

That wasn't enough it seems, a new sub-species was genetically engineered for slavery as soldiers and incubators, the Jaffa

## Helots

A real life example from Antiquity, the Helots, slaves of the Spartans

The Helots, slaves/serfs of the Spartans, who outnumbered the Spartan citizenry by so much that the Spartans had a tradition of hunting them down and killing them. This wasn't considered murder; one of the duties of the ephors (Spartan magistrates) was to declare war on the helots every year so that Spartan citizens could legally kill them (the fact that they were surrounded and vastly outnumbered by slaves who had every reason to hate them is believed by some to account for the Spartans' extreme militaristic badassery). The people from Sparta certainly considered themselves to be a breed apart. To the point that, in order to be a Spartan soldier, you had to be able to trace your origins back several generations of pure-blooded Spartans. This... did not work out so well for them, as being so incredibly exclusive in who can be a "soldier" tends to result in running out of trained soldiers. Not all wars are fought in very narrow mountain passes where numbers don't matter.

I could go on, there are many examples from scifi, and many examples of colonial imperial powers in history who've treated continents the same way ( Arab traders in Africa, British Empire, Colonial France, Confederate USA ). If you need inspiration for a slave nation, look the the dominion of Draka series of books by Stirling

Do note that the economics might be quite complicated - the cost of speed grows much faster than the savings, so unless you're transferring human passengers, it would possibly make sense to have simple, reliable ships that travel at half the speed, cutting the costs tremendously. Add in-situ refulelling on both sides (why gather fuel on Earth, when you can mine the comets and asteroids to make fuel and containers you can then drop on Earth?), and the main costs is making the reliable automated systems.

Now, you would need some insanely reliable systems, not even close to what we can make today. But at the same time, you could trade any resource you wanted - you might not want to have an ecology-destroying deep mantle mine on Earth or another populated world, but strip-mining non-populated worlds would be easy and wouldn't make most people mad :)

What technology would this imply?

• All this work must be automated. In space, and especially in a different solar system, humans are extremely expensive. Of course, you would still want a couple humans ready nearby, but there's no point in having humans handling zero-G-jackhammers on some asteroid.
• Insane reliability. You'd need the ships to survive (say) a hundred years with no human maintenance. Auto-mines and auto-factories could do with shorter maintenance cycles, as long as they can also be heavily automated - we're still talking about a huge automation:human ratio.

Humans would still have a reason to travel (and they would usually take the express, 0.75c+ ships). You'd need the architects, technicians, scouts, scientists... it would be a tiny volume compared to the automated traffic, but quite enough to make a story. Maybe it would even be possible to have something akin to Aldrin cyclers, if it makes sense - you'd still need the capability to reach 0.75c (and back again) on your shuttles, but they wouldn't need all the life support space and hardware for the multi-year trip. It would probably be quite tricky to maintain precision, but the cyclers could have crews and limited path correction capabilities. Of course, this would only make sense if you could accelerate fast enough to make it worth it - if you're looking at a 50 year long trip and you spend a year catching up with the cycler's velocity, that's probably a reasonable saving. If your trip takes just four years, though...

There's also a few other options to make the trip more economical, most dealing with in-situ resource utilization as well. For example, the ships could gather their fuel in Bussard Ramjets - though do note that this poses not just a technological challenge, but also a fixed speed limit.

So in the end, really, even with realistic science, it's possible to make money by shipping resources interstellar. However, there's one huge difference between this and "just digging another hole on Mars" - return on investment. The largest investments these days still bring at least some income in a few years (most are more on the line of months), and that's going to be tricky to achieve with interstellar travel. Some part might be paid upfront by other interested parties - say, corporations/countries wanting places on your ship to stake claims, tourists (think more like the pilgrims travelling to America rather than Bill Gates hitching a ride to Tau Ceti and back). This could be used to create drama and tension in the story, of course.

The greatest problem with this approach (e.g. no "one of a kind" resource that simply isn't found in the Solar system) is that it's hard to imagine how insanely huge our economy would have to be to require enough resources to warrant exploiting other solar systems. We're really talking about strip-mining-planets-scale - anything less would be quite possible to do in the solar system as well. So the main incentive should be something that requires both natural resources (so that it makes sense to build it on a planet) and raw surface area. For example, imagine some genetically designed bacteria that feeds on water and light, and produces space-fuel. Spray them on an oceanic world, taking up 95% of the surface area, and even with relatively low efficiency it could be an important source of fuel. It's again something that you don't want to do on your own homeworld, but requiring little in terms of maintenance, and producing immense amounts of usefull resource that isn't found easily on, say, Mars. Of course, with cheap energy, people soon follow, and you have thousands of stories to tell :) The same cheap material, and different bacteria to the mix, and you can go on the scale of terraforming planets for human habitation - remember, we're already on the scale of hundreds of years, so if it's worth it making mining companies over that time-scales, terraforming starts becoming reasonable.

The key point is you have to think of easier or cheaper solutions to the same problems. In my bacteria scenario, I've eliminated these:

• Why planets? We need a spot with liquid or gas water - it makes it easy to supply the bacteria with raw materials. The currents can also be used to transport the finished product to places from where it's actually extracted by the transports.
• Why another solar system? Well, we need an ocean and plenty of sunlight - even if we setup the production on every useful planet in the Solar system, we'll eventually run out of easily accessible raw materials and more importantly, surface area. While you can use space satellites to gather much more of the sunlight's surface area, it's incredibly expensive and tricky, even compared to interstellar travel.
• What's the point? A cheap source of fuel would mean a positive feedback loop on making spaceflight cheaper in turn - it will naturally eliminate the energy costs almost entirely over time. Imagine gas prices of not 1\$ per gallon, not 1c, but 0.000001c! You can again have as big a car as you want! As long as you can also make making the spaceships cheap enough, you can make interstellar explorers a lot more common sight over time; perhaps in ten thousand years, someone found something really interesting, and that's when your story starts?

With the scale we're working with here, the first supply ships would pretty much crash the energy/resource market on Earth (unless you carefully made sure not to increase the supply too fast, which isn't a bad idea from an economical standpoint, really - you want to maximize your profits, so you need to find a nice balance between lowering prices and growing sale amounts). This of course also means that your margins will get smaller over time, but the initial margins possible could be quite interesting. It might be even more interesting if you imagine humanity's future governments being even more socialist and inflationary than today's - you could get around a lot of costs associated with socialism (like having to conform to whatever regulations, paying out social premiums, whatever) and both the spaceships and the mining wetware would tend to maintain value rather well, so even if RoI would be long, it would also be pretty solid. Of course, it also brings another risk - after your first supply ships start arriving, someone might just ban you. Talk about a bummer. Of course, you do have weapons travelling at significant fractions of the speed of light, so who's really going to argue with you, eh? :D

• Sending back a chemical fuel is ridiculous as the kinetic energy needed to get it back dwarfs the energy, even on 1000 year timescales. – Donald Hobson May 12 '16 at 15:19
• @DonaldHobson Yes, but that's not important as long as the kinetic energy is cheap enough - e.g. an in-situ refinery to fuel your fusion-powered spaceships. The main competition is from "can we make this with a lower investment somewhere else?" and that's a problem that applies to pretty much everything interstellar :) The main thing that would allow this to happen really would be restrictive governments - that's really the only thing that can drive costs high enough. Of course, assuming they wouldn't ban you :P – Luaan May 12 '16 at 16:48

I was going to say loads of naturally occuring hydrocarbons; but if we've reached a point where we can get to Tau Ceti in 30 years, I don't think we need Crude Oil anymore. Still, it could allow further plastic production I suppose so its not completely worthless.

Rare Earths; because hey, they're difficult to mine on earth, hence the name. However, they're also typically pretty useful in engineering and electronics. Promethium makes for nice atomic batteries; and most Rare Earths are useful for making lasers and awesomely powerful magnets (Neodymium magnets can be up to twice as powerful as iron ones).

Finally, I know you're against Unobtainiums; but there are a couple of real-life unobtainium's that, if available naturally somewhere would be at the very least of great interest to science: Ununtrium-113 (which might be an amazing superconductor?), Ununpentium-115 (the real life version of X-Com's Elerium-115), and Ununoctium-118 (a bizarre pseudo-solid noble-gas).

• Actually so-called rare earth elements aren't all that rare, nor that difficult to mine. The problem in recent years has been that the Chinese undercut everyone else on price (due to lack of any environmental standards), so otherwise viable mines elsewhere closed down. – jamesqf Apr 28 '15 at 23:02
• Your "real-life unobtainiums" are unstable. – CodesInChaos Apr 30 '15 at 9:50
• Indeed, thats why if they were somehow naturally occuring without exploding, everyone would be fascinated. – eharper256 Apr 30 '15 at 16:07
• @eharper256: But if you somehow loaded your ship with them at Tau Ceti, they would decay before you got them back to Earth :-) – jamesqf Apr 30 '15 at 17:53
• Elements 113 through 118 have official names now! It would be cool to edit the post to use them rather than the placeholder names. But the problem is that these all have very short half lives. The most stable isotope of Nihonium has a half life of 8 seconds. – JDługosz Jan 12 '17 at 7:37

Since nothing currently known is worth the cost of the trip, and since you are ruling out all the magical minerals which we don't know about yet, the simplest answer is to change the values we currently put on things.

For example, if non-irradiated water suddenly became unavailable on Earth, there is no cost which we wouldn't pay to get to a source of more drinkable water.

That is an extreme example, probably too extreme as we would probably go extinct without water, long before we could get more. But the theory will work. Just make the unexpected scarcity something that we can survive without for a few generations. Like ozone, or...?

The trick with all of this is that the value of any compound is dynamic, base upon its future scarcity rather than the way we currently think about it.

Uranium, plutonium, thorium.

Tau Ceti is significantly younger than Sol system (at least it is in your story) so far less of the heavy radioactive elemts have decayed. Instead, there's an abundance in TC asteroid belt.

So the 'business' plan is like this:

• fly to TC with a generation ship are large fleet
• set up asteroid mining operation and self sustaining colony
• set up manufactoring base for enriched uranium and spaceships
• send back uncrewed ships with Orion-drives or thorium salt-water rockets, fueled by the radioactives you find
• these trasnport more radioactive materials to Sol where ...
• they power reactors housed in satellites beaming energy via microwave to where it's needed

This assumes that all interesting uranium deposits on earth are depleted and the rest is so diluted mining is not ecnomical.

• who need uranium (except special cases) for energy supply if there is thermonuclear. Even solar on earth orbit is better. Energy density in uranium not worth it to transport interstellar. – MolbOrg May 12 '16 at 21:20

When you say "rare elemental isotopes" you put it in the present way. But there is the situation in which a given element, now widely available, will become in the future invaluable to supply the huge energy demands on Earth. For example, Thorium! Thorium-based reactions have been demonstrated to produce lot of energy, and without major risks as it works as ambient pressure. Maybe solar Panels will be very efficient by then, but energy demand and consumption can't help but rising. So Thorium power it is. And Tau Ceti's planet systems may happen to be full of Thorium.... I think you could adapt this scenario to your needs?

Say that the world population cannot stop growing. With a world population growth rate of 1.2%, we will hit 3328 billion by the year 2555. In 2006 we were at 6.5 billion. Those people have to live somewhere and will consume resources. Food, water, air, metals, plastics, etc. We recycle, but there is always some loss. We have colonized all bodies large enough, and melted down all of the asteroids/planetoids. Planets like Venus were harvested a century ago and there is nothing left. We need space to live. We need space to grow food. We need any raw materials we can get, even something as common as iron. Off hand, I would expect that war, famine, or disease would solve the problem for us. However, that did not happen in this case. What we see as limitless resources in 2006 are all rationed for our great great grandchildren. Bathing was outlawed in 2372. Everyone gets 1.38754 liters of fresh water per day. You can use this ration to drink, brush teeth, or whatever you want. There is no increasing your ration. Would you like to go to TCe with a current population of 200? It is a 5-year labor contract to cover one-way travel costs.

In comments there are questions related to resource abundance. Iron is common and will always be plentiful. Same with things like plastic, copper etc. Without invoking scientific innovation (to give us fusion and warp drive) we have a problem that I will demonstrate using gold.

There are ten ounces of gold in a ton of smart phones. http://en.community.dell.com/dell-blogs/direct2dell/b/direct2dell/archive/2013/03/20/how-much-gold-is-in-smartphones-and-computers. Troy ounce is 31 grams, so this equals 310 grams of gold in a ton of smart phones. Say that the ton is 2000 pounds, or 907 kilograms. The better value here is 907.1847 and even that is not exact. These are rough calculations. My smart phone weights 127 grams. So there are 7100 smartphones/ton. If the world population is 6.5 billion people, then we need 6.5 billion smart phones to stay connected. 6.5 billion smart phones weigh 910000 tons which is 28000 grams. One web site posted that the world’s gold is 165,000,000 kilograms. http://www.numbersleuth.org/worlds-gold/ The world’s population can increase by a factor of 600 before we run out of gold for everyone to have a smart phone. This means that the population can reach 3900 billion. However, this assumes that the entire plant earth’s supply of gold is available for use. That cannot happen unless mining earth destroys the planet down to the core. We do not currently have the technology to do this even if we wanted to.

Everyone now has a smart phone. However, many other things use gold. Your computer (laptop or desk top) are great examples. Two hundred laptops have 5 ounces of gold. Rerun the numbers to find out how many people can have both a laptop and smartphone. Then keep going.

In science fiction, we can always invent new technologies. All electronics uses a monomolecular layer of gold, or we find some way of using sliver instead of gold. We develop methods of recycling where everyone participates. There is no more trash along the highway because it is all perfectly recycled. Such utopian society is not currently available.

One temporary solution is to improve manufacturing to use less. So gold plating in now exactly one molecule thick. Now the smart phone has 1/100 the gold. We then have the ability to make more phones, but the problems with recycling have increased because we now need 600 tons of phones to get one ounce of gold. How do you get every single atom of gold out of that volume? We can turn it into plasma and then separate the individual atoms into ingots of gold, palladium, aluminum, copper, and so forth. How? Well we need a new source of energy. So we have fusion power, or have huge solar arrays with 98% efficient solar cells. Such technology is not currently available, but maybe it is invented. Given that we can cheaply turn waste into plasma, do we have a molecular sieve that will separate the elements? Not that I know of. Maybe some adaptation of the centrifuges used to separate weapon grade uranium? The key is to decide what parts will be science fantasy (anything is then possible), versus based on current science. With current science (and in the absence of war, famine, disease), we will likely run out of resources to sustain growth in a few hundred years. We can give ourselves more time by decreasing growth rates, and growth rates have been declining. However, the increase in mining production does not keep up with population growth rates. So more people will have to be satisfied with less. How much less are we willing to accept before the billions that have not arise to rework the social order?

With current technology we do not have the energy resources to reach Tau Ceti e in a time frame necessary given the reliability of current technology. If it takes 60 years to make the trip then the equipment has to function well for at least 60 years. So maybe we need to know what technological advancements have been made that allows this to happen and some estimate of the "real" cost. Consolidate Earth builds a generation ship outside Pluto orbit and ..... I have no idea how much this would cost. I am certain we cannot even get this far with current technology.

Given that we have people there: What would cost less is to set up a Tau Ceti e colony and then refine metals. These would be built as solid blocks of (gold, silver, etc...) that would be thrown at earth. They would enter the solar system as a comet and then be captured in some way. Manned ships would not be necessary to ship materials home. As long as the 500 meter diameter gold block is not hit off course, it will have no trouble making the journey no matter how long it takes. However, if Tau Ceti e was now my home why should I send Earth free gifts?

• we do not consume resources. I mean we do not consume chemical elements. And we do not loose them(chemical elements) in the processes where chemistry works. – MolbOrg Feb 17 '17 at 3:15
• Ok, I was not exact enough. I was thinking more about dilution. We convert a high concentration ore into a low concentration waste product. This happens from the tungsten in our lights to the rare earths in our smart phones. Unless 100% of the smart phones are recycled there will be loss. Also, 6.5 billion people require a smart phone now, but it will be 3 trillion in 500 years. Nothing is 100% efficient. – TimothyEbert Feb 18 '17 at 4:37
• tungsten gets into grabage - recycle garbge, recycle water from water drains. Without a proper energy source, 3 trillion people will have a problem to make the food, but they still will have no big problems with alluminium, silica, water, iron, plastic. – MolbOrg Feb 18 '17 at 8:45