Mining Space Water
There are several companies that plan to mine asteroids and several more that plan to mine the Moon. In addition, Elon Musk wants to start a colony on Mars, and that will necessitate the mining of Mars. Furthermore, government space agencies plan to do missions to Mars and those missions will be far more affordable if they include mining of the resources of space as part of the mission. So get ready for mining in space!
There is broad consensus that the first and most economic resource to be mined in space will be water. On Earth we don’t call it mining when we get some water. We call it digging a well. However, everywhere we want to go in space the water will be frozen, and since it is usually chemically bonded inside minerals, or at least buried under regolith, and sometimes cryogenically cold and thus harder than granite, getting water in space really is mining.
And where do we get space water in space? It can be obtained from the hydrated minerals of certain types of asteroids. It can be obtained from the polar regions of the Moon. It can be obtained just beneath the surface of Mars. Or we can get it by catching a comet or another icy body from the outer solar system. Water is abundant in our solar system.
What to Do with Space Water?
So what will we do with all that water once we mine it in space? Here is a list of 13 things:
1. Rocket propellants
Water is H2O, two hydrogen atoms for every oxygen atom. It can be split into separate hydrogen and oxygen using an electrical current in a process known as electrolysis. The power to drive this process can come from solar cells, capturing the sun’s energy to split the water. Then, the hydrogen and oxygen can be stored and eventually burned together in a rocket engine to provide thrust for the mission. That is the kind of fuel used by the Space Shuttle’s main engines. Most people don’t realize that the Shuttle used to fly into space on a flame of water. Used this way, water is simply an energy storage medium, slowly taking in the energy required to split it apart, storing that energy in concentrated form as chemical energy, and giving it back as thermal energy very rapidly when we burn it, so that the rocket nozzle converts it into kinetic energy by pushing the rocket. Water: the energy food for rockets!
2. Electrical power generation
After we have electrolyzed the water into hydrogen and oxygen, there is more that we can do than burn it for rocket propulsion. We can also use it in fuel cells to generate electricity through a slightly more subdued process. Think of it as electrolysis in reverse. We put the hydrogen and oxygen into the fuel cell and out comes an electrical current and water. Fuel cells are great for generating electrical power when we don’t have enough sunlight, such as when we are in the shadow of a planet or in a permanently shadowed crater or deep underground or during the lunar night. Once again, the water is used as an energy storage medium.
3. Radiation shielding
Water can also stop energy — the energy of high velocity cosmic radiation particles. Cosmic radiation is the biggest hindrance to sending humans to Mars. It can cause cancer such as leukemia at a rate that is too high to accept. Cosmic radiation consists of the nuclei of atoms from far, far away in our galaxy. They were accelerated by the shockwaves of exploded stars. It is hard to understand how they got going so fast, so extremely close to the speed of light. Perhaps they have been bouncing around the galaxy for a very long time, passing through the shockwaves of many different exploded stars, gaining energy every time. In any case, they are going so fast that they are very difficult to stop. Here on the Earth we have a a nice strong global magnetic field to deflect much of the cosmic radiation and a nice thick atmosphere to absorb the rest. On a journey in space we can’t afford to take along tens of miles of atmosphere around our spacecraft and it is hard to make a big enough magnetic field when the spacecraft is supposed to be small and lightweight, so what can we use instead? We can put some other kind of absorber around the spacecraft. It turns out the worst absorber for cosmic radiation would be a heavy element like lead. Lead works great for x-rays, but for cosmic radiation the lead nuclei are shattered by the high velocity particles and then the astronauts are bombarded by all the fragments of the lead nuclei, so the radiation dose would be actually increased instead of decreased! The best radiation shield is hydrogen, an element that consists of just one proton so its nucleus cannot shatter. The second best radiation shield is anything that contains a lot of hydrogen. One excellent material is therefore water, good ol’ H2O. If we can mine enough water in space then we can put nice thick quantities of it around our spacecraft to keep the crew healthy and safe. That will make the spacecraft heavier, of course, but then we can use more of the same water as additional rocket propellant to push it all to Mars (or wherever it is that we want to go).
Technically we don’t need water in space for drinking because we can recycle our pee. If you’re not really fond of that idea, then you must be very fond of space mining, because otherwise recycled pee is on the menu. It’s really not so bad to drink recycled pee. Here on Earth you do it all the time. It’s just not as easy on a tiny spaceship where the proximity of the recycling equipment forces you to remember where your beverage came from. And recycling on such a small scale as a spaceship is expensive and tricky. Giant spaceships like Earth are better at that stuff. Anyhow, without space mining, you’ll be drinking lots of pee. If on the other hand you have lots of water from mining in space, then your pee can be dumped overboard to make miniature yellow comets in orbit around the sun. Consider it a form of art. So it’s your choice: making space art, or drinking pee.
5. Plant growth
Plants need a lot of water. The water we use for our space plants can be recycled (like our pee) because whatever water the plants transpire through their leaves can be recaptured by equipment that dehumidifies the air, and whatever water is still in the plants when we eat them will be…well, you know. Anyhow, no recycling process is 100% efficient and we will constantly lose some water from our spacecraft into space during long journeys or into the Martian atmosphere at a colony on its surface. And where do we get all that water from, in the first place? It is too expensive to launch all the plants’ water from Earth. It’s much better to get our plants’ water in space: on Mars, or the Moon, or wherever we’re going to be growing them.
The largest cost of spaceflight is launching oxygen from the Earth. The majority of the oxygen we usually launch into space is used for rocket propellants and for fuel cells. However, we also bring along some oxygen to breath. As our bodies burn carbohydrates for energy, some of the carbon from them is oxidized in our cells to make carbon dioxide (CO2) and we breathe it out into the air around us. We have to remove the CO2 from the air because otherwise it would build up too much and suffocate us. Normally we just sequester the CO2 for the duration of the mission and dispose of it after landing. If we want to recycle the oxygen contained in the CO2 during the mission, then we will need to use energy to split it back into carbon and oxygen. Plants do that for us naturally as part of their photosynthesis process, recycling not just the oxygen but the carbon, too, turning it into plant tissues, which also store up chemical energy. Unfortunately, we would have to take huge forests of plants to support the oxygen needs of just a few astronauts, and that would make the spacecraft to heavy and too expensive to fly. To recycle the oxygen artificially we would need chemical processing machinery to replace the plants, plus a big enough energy source to run it. It might be less weight to simply bring the carbon and the oxygen to use up during the trip. That’s how we do it now. The carbon is brought in little baggies in the form of astronaut food. The oxygen is brought in tanks. The carbon dioxide is cleaned out of the air and sequestered until the spacecraft lands – or it could be vented overboard. Thus, we aren’t currently recycling them in space. And currently we launch all the oxygen needed for the entire mission from Earth. For longer journeys where we will need more oxygen we could do this more affordably if we got the oxygen by mining and electrolyzing water in space.
7. Manufacturing processes
Eventually we need to make more and more things in space rather than launching them all from Earth. Many manufacturing processes require water. As time goes on we will be doing more and more of these processes on the Moon or on Mars or elsewhere, and so we will need an expanding supply of water.
8. Spacecraft cooling
Everything that does useful activity produces waste heat. Even if you are just huddled in a furry jacket in the howling winter winds of Antarctica thinking about your financial situation, your body needs — needs — to get rid of heat. A perfect jacket would kill you. That is one of the laws of thermodynamics. Heat is what carries away increased entropy from our bodies, and unless our bodies are continuously producing and shedding entropy then we aren’t doing anything useful; we would be dead. Well, space is really cold, but the vacuum of space is like an excellent jacket that keeps us from losing heat very easily. And so after a little while our spaceship will get too hot and be dead. We solve this problem by using radiator panels. When a spacecraft has its radiator panels pointed toward the cool darkness of space, it can radiate away its waste heat and entropy in the form of infrared radiation. On the Space Shuttle the radiators were just inside the payload bay doors. So when the doors were closed, how did the Space Shuttle get rid of waste heat? By dumping heated water into space! That can be an important way to shed waste heat when you can’t get a radiator pointed toward cold space or when you have a huge amount of heat that needs to be dumped in an emergency. Water to the rescue! Dumping it for thermal control will probably always be a part of how we explore space. Our bodies also use water this way, too; it’s called sweating.
9. Scientific research
Already we are studying water’s properties in space, as illustrated in the photograph above. We will also want to mine water in space to study what’s in the water and learn more about our solar system and galaxy and universe. Also, some scientific instruments rely on large amounts of water. One proposal, championed by Alex Ignatiev at the University of Houston, is to create a huge bath of water on the Moon to detect neutrinos. Melt the lunar ice; form a giant swimming pool; look for neutrinos passing through the water. Very cool!
Not only neutrinos, but also humans would like to get wet in space. I wonder what it’s like to take a shower in zero-g? It must be really fun! And it’s necessary. Astronauts get dirty, too.
11. Swimming and recreation
And getting wet isn’t just to get clean. When we have space resorts, we will want them to have swimming pools! In lunar gravity you could swim so easily, floating with only a tiny amount of your body underwater. But on the other hand, the tiniest disturbance would create huge waves so that might make lunar swimming a bit more adventurous. Come to think of it, we could have excellent surfing resorts with artificial wave generators on the Moon! And when we do, remember to thank a space miner.
12. Spacecraft life support for aquatic astronauts
Will humans be the only species to leave planet Earth? I sure hope not! All species bound to the Earth will eventually go extinct unless they find a way into space. That’s because eventually the sun will expand and burn up the Earth, and before then the Earth will get too hot and boil its oceans away, and before then a blackhole might swing by and eat us up, and before then a comet might hit the Earth and wipe out life, and before then the Yellowstone supervolcano might blow, etc., etc. So the question is, do you really want to save the whales? If you do, then start making plans to turn them into whale astronauts. We will need giant spaceships for these whales, with giant amounts of ocean water inside. Or we can just take baby whales…with giant amounts of ocean water inside. When we have ocean spacecraft, we can take whales to other stars where we will terraform new ocean-bearing worlds where they can live. You might think this is a crazy idea, but space mining will take our civilization to the next level where we will have millions or even billions of times the capacity to do amazing things. When that day comes, crazy-sounding ideas like saving all the species of the Earth and spreading them to more worlds will suddenly not be crazy any more. Remember, if you told the ancient hunter-gatherers about an iPhone or an airplane or a gasoline-powered car, they would consider you crazy. And yet here we are.
13. Terraforming planets
And that brings us to the biggest need for water of them all: terraforming. Huge amounts of water will be needed to terraform a dry planet. As Freeman Dyson once pointed out, we can quickly soak a dry world by crashing an icy moon from the outer solar system into it. Maybe we won’t want to do that with our own dear Mars for sentimental and historic reasons — I mean, who wants to destroy one of our own solar system’s moons? But we can certainly do it at another solar system where we aren’t so attached to all its stinking little moons. One way or another, space resources will lead us to the day when we can engineer new worlds complete with oceans and water cycles, where we and the whales and all the other species from Earth can carry on.
As the miners like to say: if you can’t grow it, you have to mine it. Mining water in space is a first step toward establishing a space economy, taking civilization to the next level, and becoming a multi-world species.