A Distributed Mind

Thoughts on a Mars Colony

(Note: I wrote this as an answer for a Quora question originally.)

How many people are required for a self-sustaining Mars colony?

What level of technology would be required to survive several generations?

These are two separate questions.

  1. How many people are required for a self-sustaining population anywhere (genetically speaking)?

The answer seems to be: about the size of a small village. (Incidentally, these are historically proven to support stable populations almost indefinitely).

This article, for example: "Magic number" for space pioneers calculated gives the number at about 160.

With some luck, realllly good medical care, and careful genetic screening (to watch out for harmful recessive genes, etc), you could probably bump that down to about 100. But you know how it is, the more, the better.

See also: Planetary Science: How many people would we need to send to a distant planet to colonise it?

  1. What level of technology would be required to survive several generations on Mars?

(To be specific, this includes "What level of technology is required to GET (a bunch of people) to Mars" and "What level of technology is required to sustainably live on Mars? (versus, the Moon, for example - it's very slightly different").

First of all, this is a popular question to ask. We all want to know this!

See for example:

But, let's take a stab at outlining what's involved.

Getting to Mars

What we need, to get a village full of people to Mars:

#1 (by a big margin) Better Propulsion!

Here's the thing you need to understand about space colonization. It's all about how much mass you can haul across long distances (and how fast). Everything else is secondary. If you can bring a lot of mass with you, you can colonize with very primitive technology. If you can't, that's when high tech becomes the limiting factor - that's when you need all sorts of research and invention, on how to make everything super small and efficient, and to learn how to make everything when you get there.

This is the biggest challenge we have. Our current engines (Apollo style chemical rockets) are just not enough.

Analogy Alert: Think of a modern highrise hotel. Now imagine that you have to pick up and move the hotel (all of its people and equipment) to a nearby city (let's say from New York to Boston), and all you had for transportation was a shopping cart.

(Even if it's a big shopping cart, like from Home Depot).

Can you do it? Sure. It's theoretically possible.

But if all you have is a shopping cart, it's going to take a long time (think of all of the trips you have to take!) and is going to be insanely difficult.

And even aside from time and effort, you're going to have to invent and manufacture a lot of custom equipment.

For example, that giant industrial stove in the hotel kitchen, or the massive washing machines in the basement? How are you going to fit that onto your shopping cart? You aren't. You'll need to pay an industrial engineering company to design and make a big stove/washing machine/whatever that can be disassembled into small pieces which fit into the cart (plus careful instruction manuals on how to do it) and reassembled at the destination. The cost adds up.

How about that swimming pool? (You'll probably have to take all of the water with you to the new hotel!) That's going to take a LOT of gallon jugs, to move all that.

And that's assuming that you have a building waiting for you in that other city.

With space colonization, it's even worse -- not only do you have to transport the people and the equipment, you'll also be needing to transport all of the building materials to build a new highrise hotel on the other side. (Again, good design can help - see Meet the Man Who Built a 30-Story Building in 15 Days for example - but only up to a point).

So that's the problem. What we have, at best, is a shopping cart. What we need, for this project to be anything more than a pipe dream, is at least a modest fleet of big U-Haul trucks.

Our best hopes, in terms of propulsion (getting to Mars will require a combination of these, most likely) are:

A) Better chemical rockets. We're slowwwly working on these. See for example: NASA | Exploration Systems Development page. Even so, chemical rockets, no matter how good, are still going to be closer to the "shopping cart" end of the scale.

B) Nuclear propulsion. Which would be amazing. You can haul a LOT of mass using nuclear-powered engines. The problem is - politics and legislation and international treaties (people get seriously worked up when you start talking about putting nuclear anything into orbit). Oh, one more thing - you really can't use these methods to get from the ground to Earth orbit. You'll still need good chemical orbital launch systems.

Nuclear space propulsion tech includes:

C) (non-nuclear) Electrically powered spacecraft propulsion

Electric rocket engines are great - they're not powerful like chemical rockets, but they can run continuously. (If you had to go a couple dozen miles on a skateboard, which would you rather have - a single initial push (no matter how powerful), or a small two-stroke engine for a motorized skateboard that ran the whole time?). (These also, obviously, work only in deep space, and won't help you with getting things into Earth orbit).

Some examples of this include:

The problem with electric propulsion (aside from the fact that it's very complicated high tech, and much further research is needed) is: What are you going to power it with? Wouldn't it be great to hook it up to a nice nuclear reactor? Even if it's a low-powered Radioisotope thermoelectric generator like what the Galileo (spacecraft) had? But again, for various political and practical reasons, for the moment, Solar Panels is likely the power source you're going to get.

D) Solar Sails

If you're going to be relying on the sun for power anyways (solar panels powering, say, an ion thruster), the thinking goes - why not skip the middle steps and just have the sunlight bounce off of a sail and provide propulsion more directly?

These can be either physical Solar sails (really thin very tough foil / mirrors) like project Sunjammer (spacecraft), or a Magnetic sail (have the sunlight bounce off of a magnetic field. Still very theoretical).

Solar sails have probably the least amount of research and development so far, among the propulsion systems. If we do get them working, they'll be pretty great - free power/propulsion!

Whew! That was a long section. But that's because Propulsion is 90% of what matters to a colonization effort. All right, what else do we need?

#2 Better Life support systems (we're still on the subject of Getting to Mars)

People will need to breathe, stay warm, drink and eat on the way to Mars (and also while living there - #2 applies to the Living on Mars section as well). Oh, we'll also need better space-toilets. (See Astronautical hygiene)

"A crewmember of typical size requires approximately 5 kg (total) of food, water, and oxygen per day" (from that Life Support systems entry on Wikipedia).
That means - we'll need to both bring a lot of supplies, and learn to recycle the ones we have. And hopefully even produce some, along the way.

How are we doing, in this area? Not so good. Our state of the art is fairly primitive, at the moment (see International Space Station ECLSS for a discussion of the current ISS life support systems).

Evaluation of individual systems:

Heat: pretty good, actually. Like a server room on Earth, all the electric systems on a spacecraft output a lot of heat. Needs power (see below).

Air: Passable. (Pack lots of oxygen, or water (to derive oxygen from)). Also pack plenty of CO2 scrubbers.

Water: Problematic. You'll need to bring along a lot of water (to drink, wash, and electrolyze to produce oxygen). And water recycling is difficult.

For example, the ISS currently has a Urine Processor Assembly and a Water Processor Assembly. (And regular water deliveries from Earth - four per year, minimum). The reclaimed water is mostly fed to the oxygen generating machines, though it is available for drinking in emergencies.

Closed Circuit Air/Water Recycling Systems: Forget it. We have never even experimented with closed life support systems in space. Our best state-of-the-art biosphere tech is something like BIOS-3 (which could support 3 people for 180 days) - and that thing was HUGE. Oh, there was also Biosphere 2, which, again, is the size of several football fields, and even so, had very inconclusive results, in terms of closed system life support. Lots of progress needed here.

Food production: Nope. Meaning, we do not have any experience with growing food in space, so a lot of research needs to be done. On the other hand, given a big enough mass allowance (propulsion again), we can figure this part out.

Sanitation: Passable. (Given enough water). Space toilets, sponge baths (Skylab had enclosed showers), air scrubbers to get sweat/odors/bacteria/vomit (see gravity, below) out of the air. No washing dishes, obviously. Oh, and no laundry - disposable clothes only, currently. See Space Station | The Station | Living in Space

By the way - do you see how this part very much depends on how good your Propulsion systems are? If you can get to Mars fast, you need less supplies and you can get away with more primitive systems. If you can haul a lot of supplies with you, your recycling systems don't need to be as advanced (and you can afford the luxury of oxygen- and food-producing plants).

#3 Power Generation You need a lot of electricity, on the way to Mars , for lights, air conditioning, to power life support and computers, and likely the engines, too, for course correction.

Your options are:

Incidentally, if you solve the problem of Power Generation and have lots of power to spare (such as, say, with a reactor), you get better propulsion for free (hook up the excess juice to an electric thruster, as discussed above).

#4 Radiation Shielding (extremely helpful) Outside of Earth's protective atmosphere and magnetosphere, you're exposed to high levels of radiation. How bad is it? Well, it depends on how fast you get there. Exposure estimates for a 280-day trip to Mars (see How much radiation will the settlers be exposed to? - Health and Ethics - Mars One) are reasonable (high, but within NASA limits for astronauts).

Obviously, the more protection from radiation you have, the better (less chances of dying from rad poisoning, cancer, etc). Unfortunately, radiation is hard to shield against. You basically need either lots of water (which would also help with life support, obviously), or lots of stone. In short, shielding is incredibly heavy. (But would be solved with better propulsion tech.)

#5 Artificial Gravity (extremely helpful) Space is rough on humans. Aside from radiation exposure, it turns out that being weightless for long periods of time is incredibly hard to deal with (see Effect of spaceflight on the human body). For one, you get serious Motion Sickness (even if you're a highly trained astronaut and are full of anti-motion-sickness meds).

More importantly, you start losing muscle mass and bone mass (see Spaceflight osteopenia), at an average rate of 1-2% bone mass loss per month in zero G. Given the typical flight time to Mars, this starts to add up quickly. (Though hey, what do you know, if you can get there faster (see Propulsion above), you don't need to worry about this as much).

To manage all of this, it would be really nice to have artificial gravity on the way to Mars.

Now, until we have a much better grasp of physics and can generate artificial gravity fields or some such convenience, we either need to rely on centrifugal acceleration (spin the ship/habitat around really fast), or on linear acceleration (step on the gas halfway to Mars, and then step on the brakes the other half. Though this requires better propulsion.) See Artificial gravity (methods of generating section).

#6 Careful Thought/Design to Mitigate Psychological Effects

This one's not so bad. Yes, being enclosed in tiny spaces for months and months is hard psychologically. But at least in this area, we have LOTS of research, throughout history. Monks, prisoners, sailors, submarine crew, astronauts, and so on. Obviously lots of room for improvement, but manageable.

Living on Mars

OK! Assuming we got some people to Mars (a hundred or two) and they survived. What is needed for a self-sustaining colony?

Power Generation Your options are: nuclear reactors, and wind turbines. Fortunately, Mars at least has an atmosphere, and occasionally has wind storms. So that's at least something.

But really, you need decent (lightweight, safe) nuclear reactors. You're not going to be burning coal or oil or gas. No hydroelectric dams. And wind, while possible (not really studied), will not be reliable enough to power a whole colony.

Closed System Life Support Given the cost and the distance (not to mention, risk) involved in shipping things from Earth, the colony is not going to be able to rely on regular care packages from home. It'll need to be able to provide its own air, water, food, and waste recycling.

We do not currently have the technology for closed-system life support, so again, a lot of research will need to be done in this area. We will probably be growing a lot of carefully engineered algae in tanks, use ingenious hydroponics, and so on.

Given enough weight allowance, can can probably set up something like Biosphere-2 or -3, eventually. Though again, think of how much soil - carefully engineered biomass - a farm of that size would require. Soil is something we get for free on Earth, and take very much for granted. Whereas it would take a LOT of composting and poop recycling to make enough soil out of the salty and alkaline Martian sand.

Mining (Water, Oxygen, Metals, Minerals) Even if you figure out all of the details of an efficient closed life-support system, you will still need to keep supplying it with raw materials, constantly.

For example - people, plants and machinery need LOTS OF WATER. You can recycle a lot of it, but you will still need more, no matter what. That means - the colonists must figure out how to find and extract water/ice from Mars surface. We know there's some water ice on Martian polar icecaps. We suspect there might be some hidden underground, but all of that needs to be explored/investigated.

If you find enough water, you can make oxygen out of it. (If you can figure out ways of mining oxygen from Martian soil, even better).

Beyond those two necessities, you will need to learn how to mine and extract everything else you need for a self-sustaining Advanced Manufacturing infrastructure (see below). Think of all of the metals and minerals that we mine and fight over on Earth -- we will need to re-learn new methods of mining/extracting, transporting and processing them on Mars.

Radiation Shielding Though not as bad as outer space, living on Mars also incurs a lot of radiation exposure. Fortunately, once you're on a planet, rad shielding is easy: pile lots and lots of sand and stone on top. Meaning: you're going to build your colony underground. While we don't have a good handle on how to build underground cities (or even small habitats) on Mars, I'm sure we can at least figure this part out, assuming we've solved all of the other problems.

Advanced Manufacturing Same deal as with life support. To be truly self-sustaining, a colony would need to have the tools and knowledge to essentially replicate, on a small scale, a high technological civilization. This will mean: a lot of luck, spare parts, resupply trips from earth. But also, mining robots, 3D printers (though we would need to figure out how to make plastics on Mars), CNC machines & lathes, lots of power tools and hardware.

Basically, we'll need a Martian equivalent of the Global Village Construction Set - a set of self-replicating tools needed to make all of the tools, spacesuits, robots, computers, air filters, life support machines, and everything else people would need.

We do not have this technological capability yet, though we are slowwwly getting there.

Communication (with Earth) At least have a good handle on communication satellite technology. Still, that's a hell of a ping / response time - 4 to 24 minutes, one way, depending on how far apart Mars and Earth are at any time.

Research into Long Term Effects of Low Gravity Will humans be able to survive in the weak gravity field on Mars? Without catastrophic bone loss and so on? We don't know.

Maybe, maybe not. If not, we will need to figure out treatment options (gene therapies, etc) to treat and mitigate this.

All right! Lots to do, better get to it.