One of the big problems by manned space exploration and colonization, that it's insanely expensive. Building a colony on other celestial bodies - since it's impractical to bring back the acquired resources to Earth - is surely a lossmaking enterprise, and therefore must be funded from the profit of other activities.

But it seems to me, that if there would be enough humans living on other bodies and in space habitats, it would become profitable to construct new, more safe and comfortable hab modules, develop new hydroponics technology, establish new mining settlements on new asteroids, build fast internet to the Jovian moons, etc... since those, who are already in space would be willing to pay for these services and goods.

Eventually, it could come to pass, that the majority of the investments would go into extraterrestrial investments, making Earth into a uncool rust belt, and encouraging even more people to migrate into space, making the colonization of the solar system into a self generating process?

Where is this critical point? How much human presence in the space would be needed (How many humans, how much dollar worth infrastructure... ) in order to make supplying them a profitable undertaking?

Conditions: Fission, fusion, and electric engines exist. (were used in early colonization efforts.) There is no significant antimatter technology, and no gravity manipulation. Nanostructure materials (like carbon nanotubes) are permitted, but nanobots not. The economic environment on the Earth is not bad.

Edit: The cost of bringing them there doesn't matter, the scenario only has to be economical after the critical point is reached. So the question is not: Why would we need sending X men to Moon, Mars, Calisto, Titan...?, But how many many men should be there, to make the expanding and further developing their colonies into a good business?

  • $\begingroup$ The answerer is free to decide this. The question is about the size and complexity of the required colony. But the scenario takes place in our Solar System, which lacks really habitable planets. (except Earth) $\endgroup$
    – b.Lorenz
    Mar 1, 2017 at 19:31
  • $\begingroup$ related: worldbuilding.stackexchange.com/questions/50579/… $\endgroup$
    – kingledion
    Mar 2, 2017 at 3:21

4 Answers 4


As a few others have pointed out, your assertion if insanely expensive may not be the case.

To make this more clear as in answering your question more literally, the initial business's I list here require few people and have high-value profits. This is based on revising the one and done OR disposable approach we currently have. So a few people, initially maintained by Earth Resources have to provide cheaper solutions to existing problems we have. That is a formula for immediate profit. There are a lot of these things and that means a lot of jobs in space, just the cleaning up part and then add on the repair and refueling. This phase basically pays for the next phase the colonization and industrialization of the Moon. The people doing the initial jobs need someplace to go and Earth is expensive, the moon is cheap. The money flows.

Ways to be profitable.

The ability to refuel and repair existing space assets. What would one pay to be able to repair and upgrade Kepler, Hubble, etc?

The ability to cheaply build and implement new assets. How much would one pay to have new telescopes, satellites, etc; build in space then moved to the position?

The ability to provide Low Earth Orbit Habitats and provision them. How much would one pay to have large-scale habitats build in space and moved to low earth orbit, supply food and water grown by the Lunar Colony?

The ability to mitigate space hazards in Earth Space. How much would one pay to clean up the debris orbiting the Earth, to capture and utilize the Near Earth Orbit objects?

The ability to build, maintain and operate power sources for Earth. How much would one pay for the ability to build, maintain and operate a series of Solar Mirrors to provide clean cheap power to Earth ... as just one such method, X-Ray lasers and others would work as well.

The ability to Build and Launch exploration vehicles. How much does one pay to do this from Earth vs from an established Lunar Colony with infrastructure?

The list is rather long on ways to make money / be profitable in space.

We just need to start thinking like a Space-faring species, rather than a Planetary Species.

And what value would one put on being able to Reboot Humanity in the event of some self-inflicted devastation or some devastation from an external source? Just how much is that worth .....

To Expand ....

This is not about choosing Robots OR Humans. The state of the art in Robotic AI is not going to replace the flexibility, adaptability, or creativeness of Humans any time soon. So the relationship between Humans and Robots is cooperative existence. The number of Humans starts small and grows as the Job Opening / opportunities are created. Aside from the imperative of being profitable, the next greatest imperative is increasing Human presence. I want to see Blue Origin's goal of Millions of Humans working and living in Space to be a reality.

Phase 1 “We need to start somewhere”

So a few good people …..

For 40+ Years we have spent a lot of money doing the same things. There is an opportunity now to do something … very differently. SpaceX, Blue Origin, and others are providing the means for things to change. Not directly at this time, but indirectly. Right now Boeing, SpaceX, and others are providing for transfer vehicles from Earth to the ISS and back.

What would these companies love more than anything else right now? New customers doing new things. Also known as growth. For new customers, as in Humans in space … remember the opportunity to change ….

We have two very distinct and well-documented problems.

Japan has attempted to address one of them. We have a highly polluted space where a lot of our assets orbit. This needs to be cleaned up.

Japan’s current plan is to burn it up by reentry. BUT is that really the most economical way to do this? A lot of money was spent on getting it up there.

Is all of it really of no value? Why can’t we take it and use the Sun, as in a Solar Furnace to process it to a reusable form? I mean that is mass that has already been paid for to get it up there. Ok, let's assume I can do this and am building a stockpile of Gold, Silver, Platinum, Copper, etc. It will obviously have some value and would be rather easy to return to Earth for sale. BUT its mass has already been paid for to get to space. Well, now we have resources that can be used in the 3rd phase.

Phase 2 “I can repair, upgrade and refuel your Satellites”

So a lot more good people …….

Being in space and time on my hands, I can go to your Space Assets and do diagnostics, preventive maintenance, repairs, refuel, upgrades … you name it we will quote it and I am quite sure it will be significantly cheaper and significantly faster than you building a brand new one, insurance vs loss at launch, potentials for dysfunction etc.

We will be there, we will guarantee our work. Need that Satellite moved to a new orbit? We will quote that. Have a set of experiments you want to run? We will quote that.

Phase 3 “We can build it cheaper and faster in Space”

So a whole lot more people …...

Being in space and having the time, materials and facilities (see phase 1 and phase 2).

We can build your Satellite in space for you and deliver it to the desired orbit. We guarantee the price will be significantly cheaper than for you to build it on Earth and Launch it, with all of the attendant risk’s for failure. Remember we guarantee our work. It is even feasible we can build you two for the price of one, with the second being a backup/redundancy to the first one so you will not experience downtime, during our maintenance/upgrades.

What does all of this achieve?

For SpaceX, Blue Origin, Boeing etc. they now have a customer that is NOT politically fickle or driven. They have regular schedules to deliver food, water, and customer-supplied parts, in greater quantities than currently available to them.

For 3D Printers looking for a need to fill. Well with the accumulated resources and more economical deliveries from Earth based on competition and increased frequencies, it will become more economical for us to fabricate the parts in space than to have them built and launched from Earth.

We have learned how to Live and Work in Space and established a Space Population.

We need to be independant of Earth Resources.

Well, now then SpaceX, Blue Origin, Boeing etc have had time to see this coming. We need to become independant from Earth Resources. The thing we will need most are Space Transfer Vehicles. The ability to move around from point x to point y. The ability to move mass from point x to point y. They should be able to supply these vehicles and if they do not then we can supply them ourselves.

So the next phase Colonize the Moon.

Phase 4

Very little change in the number of Humans ...

Identify the easy picking resource of the Moon, focus on Water and Lava Tubes suitable for Human Habitation. Secondary any and all other resources that provide a source for materials currently supplied by Earth.

Phase 5.a

Very little change in the number of Humans ...

Select a Lava Tube for Habitation. Seal it, pressurize it, establish a power supply, establish a water source, both at the habitat and the source. Bad habits are hard to break, so we must keep this in mind. Use the water and other resources to establish a viable atmosphere. Establish a Life Cycle system. One might look at current Fish Farms. The ideal system will at a minimum provide food, filter the water, and prep waste for use in more traditional farm products. Ideally, in the end, it can do recycling of the atmosphere (plants … whatever).

Phase 5.b

Very little change in the number of Humans ...

Establish manufacturing systems and supplies. This means all the equipment and resources to produce the things used in Phase 1 through Phase 3 and the Space Transfer Vehicles.

Phase 5.c

Very little change in the number of Humans ...

It is imperative that any bad habits as using the Water etc for things that have very little to nothing to do with supporting Life need to be ended. I will go so far as to say creating a Space Vehicle that can be used to scoop the upper atmosphere of Earth (later the other planets/moons) for required gas’s. The focus needs to be on how to produce these gases from existing resources, other than water.

At the conclusion of Phase 5 we will have a model of how to Live, Work and be self sufficient on the Moon. This model can be used by any group to expand the Human Population on the Moon.

Phase 6

So a Human Civilization an explosion in the numbers of Humans in Space ……

Go Crazy

Build Survey Ships capable of building a data repository of the objects in OUR Solar System … all the way out to the Heliosheath / Heliopause.

Build Colonization Ships to be used to 1 shot colonize planets, moons, asteroids.

Build reservoirs of Water, from Comets … whatever.

Transition Humans to a Space-faring Species from a Planetary Species shall continue.

  • $\begingroup$ Good ideas. But all your suggestions (except orbital habitats) are doable by robots. $\endgroup$
    – b.Lorenz
    Mar 1, 2017 at 21:15
  • 1
    $\begingroup$ I dispute that, Repair and Refuel by Robots do not have the adaptability of Humans. The building of new Assets by Robot alone is going to be more prone to failure and / or extends the time to delivery vs Humans on site supervising and diagnosing the problem. In short to say it can be dose Roboticly does not really look at the Cost Equation. IF one justifies an asset or project based on return then extensions to the implementation / delivery are a valid loss of return. Etc. Maybe I should edit the answer and start explaing the why humans prefered vs pure robotics $\endgroup$ Mar 1, 2017 at 21:24
  • $\begingroup$ You have convicted me. I want sent up humans there is my story. $\endgroup$
    – b.Lorenz
    Mar 1, 2017 at 21:28
  • $\begingroup$ @b.Lorenz I think this is an excellent question and is a topic deserving conversation. :) $\endgroup$ Mar 1, 2017 at 21:49
  • $\begingroup$ @EnigmaMaitreya, as a long time member of several spacer groups, I agree. 15 years ago everyone was moaning about how no one was doing anything new in space. 8 years ago, several small launch companies were talking with the FAA for launch licenses. Some of those have gone (Armadillo) and others have entered the field. For a totally different take on getting off the rock from someone who's been in it for a while now, look at jpaerospace.com (airship to orbit). $\endgroup$
    – ShadoCat
    Mar 2, 2017 at 1:04

The minimum? About ten. If they can research compounds and alloys that cannot be made in a gravity well, it might be possible to make your money back with just the research results.

Energy: harvesting He3 on the Moon would take a couple hundred people. Building large solar arrays to microwave the energy back to Earth would take up to 1000 (probably less) to build and position the arrays.

Manufacturing: Making things that cannot be made in a gravity well like alloys of compounds with very different specific densities, foam steel, flawless crystals: Unknown, it depends on how fragile and heavy the items are. If it not fragile at all, put it in a pod with a heat shield and aim for some place safe. If it is slightly fragile, put a parachute on it. If it is really delicate, you need something that can land gently; that might be expensive enough that you would want to send it back into space instead of build one use vehicles.

Another question is: how many people do you need to get into space before they say, "No."

  • $\begingroup$ Thanks. But your first example (10 researchers doing material science), although fulfills my requirement, since it's recoverable, will make profit for an earth-bound company, and it's findings would be used on the Earth, therefore it won't really accelerate manned colonization. $\endgroup$
    – b.Lorenz
    Mar 1, 2017 at 19:57
  • $\begingroup$ @b.Lorenz, possibly true. However, it shows the value of having people in space. If it is profitable, companies will do it more. It might be the toe in the door. That is why I gave multiples. Not every one if them will work for every story. $\endgroup$
    – ShadoCat
    Mar 1, 2017 at 20:08

How much human presence in the space would be needed (How many humans, how much dollar worth infrastructure... ) in order to make supplying them a profitable undertaking?

In my opinion, never. The space infrastructure would need to be self-sustaining. It doesn't matter how many people are in space. It's never profitable to supply them from Earth. They need to be able to produce their own food, etc.

We can supply small colonies for scientific purposes. One can argue that the scientific value of those colonies outweighs their expense. But that scientific value doesn't scale up. Yes, more people could do more work, but the best work is the first work. It scales down from there.

There are similar problems with tourism, etc. The first purchasers produce the most revenue per capita. At scale, they lose more money.

Goods are even worse. Shipping goods from the Earth to space is simply not profitable. You'd be better off keeping the people on Earth. It may eventually be profitable to ship goods from space to Earth. For example, with sufficient automation, shipping goods or raw materials from the asteroid belt might make sense. Using solar energy and asteroid materials makes everything essentially free in terms of Earth resources. Landing them might be more expensive than building on Earth though.

The expensive part is lifting into Earth orbit. From there, we could use mostly space-based resources to ship to the rest of the solar system. Even using Earth-resources, lifting into orbit is the greater portion of the cost. It's actually cheaper in terms of energy to ship from the asteroid belt than from the surface of the Earth. It's just that we don't have the facilities in the asteroid belt to do that shipping.

We can transfer energy from space to Earth, but we are already complaining about global warming. Increasing the amount of energy sent to Earth would only make that worse. It might make more sense to direct energy away or better collect the energy that giant fusion plant (the Sun) is constantly sending us.

Knowledge can just justify a modest amount of transit from Earth to space, but the real thing that space has in abundance is, well, space. Once space is self-sustaining, people may spend Earth resources to get there.

I previously asked a question about how much it would cost to set up asteroid mining versus just supplying from Earth. Unfortunately there still hasn't been anything that I'd consider an answer. Maybe it's just a hard question with too many unknowns. If there was an answer to that question, I would list it as the answer to this question as well.

That would be the point when space was self-sustaining. But that gets back to my original point. It's still not profitable to send stuff from Earth to space. It's only ever profitable to send people, at least at any scale.

  • $\begingroup$ That first step is a doozy. As you said, once we get out there, things get much cheaper. A base on the Moon would reduce costs significantly because of the shallower gravity well. However, setting that up will be expensive. $\endgroup$
    – ShadoCat
    Mar 1, 2017 at 20:35
  • $\begingroup$ I didn't said that colonist should be feed from the Earth, or profits realized on Earth. The question includes is situ production of goods and trade between colonies, as long as it's profitable enough, that it's makes companies invest into this, instead of doing things on the Earth. $\endgroup$
    – b.Lorenz
    Mar 1, 2017 at 20:36
  • $\begingroup$ @b.Lorenz But if that's all you want, then this question is entirely a duplicate of my previous question. $\endgroup$
    – Brythan
    Mar 1, 2017 at 20:37
  • $\begingroup$ I assume you are thinking about this question: worldbuilding.stackexchange.com/questions/3943/… But my question is not the duplicate of it. You are asking about the costs (in launched mass) of the starting of an asteroid mining operation, while my question includes all industries and services needed to maintain space colonies. $\endgroup$
    – b.Lorenz
    Mar 1, 2017 at 20:42

One of the main reasons why getting things to and from space is this impractical gravity well we live in.

Yo ruled out antigravity, and for good reasons. But since you do allow nanostructure materials, you should be able to build a space elevator.

Once that is in place, your costs for lifting things out of the gravity well, and for making a safe re-entry, are next to nothing.

You also allow for fusion tech, so you get quasi-limitless power.
In my opinion that means you could have a post-scarcity scenario. This means, that the question of profit is no longer a delta-dollar-question, but much more humanistic. Or, in other words, 'profitable' can be anything you like it to be. It might even be "trading huge amounts of ugly and heavy gold for super-delicious mars strawberries".

But putting that aside: Others have described that producing things in zero (or low) gravity might be interesting. But also producing things in a non-corrosive (or non-existent) atmosphere might be interesting, too.

So, after effectively removing energy cost from your scenario, profitability is more or less guaranteed.
And how many people: Groups of up to 120 individuals, since apparently that is a rough number people generally feel comfortable with.


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