The moon has water. That’s great news for a future moon-base, but it’s also often talked-up as a resource for creating rocket fuel. Last week NASA announced that it would send a mobile robot, the Volatiles Investigating Polar Exploration Rover (VIPER) to the South Pole of the Moon to find the exact location and concentration of water ice in the region. “The key to living on the Moon is water—the same as here on Earth,” said Daniel Andrews, project manager of the VIPER mission and director of engineering at NASA’s Ames Research Center in Silicon Valley. “Since the confirmation of lunar water-ice ten years ago, the question now is if the Moon could really contain the amount of resources we need to live off-world.”
Another theory goes that if we can use the water on the moon—which is locked-up as ice, but we’ll worry about that later—to power spacecraft, they will be able to go way, way further into the cosmos and kick-start a new era of interstellar mining. Water on the moon would make future Mars missions more affordable and could fuel commercial enterprises that link Earth and the Moon. “Creating space fuel depots would allow spacecraft to travel much farther and allow missions and satellites to sustain operations,” says Karen Panetta, IEEE Fellow, Dean for Graduate Education, Tufts University. “Rather than transporting water into space in heavy loads on rockets, the goal is to extract it (mine it) from the moon and asteroids.” It would also mean rockets don’t have to expend a lot of fuel just to get the fuel for their entire up into space with them. Launch costs would plummet.
Wait. Water into rocket fuel? Surely you cannot fuel a rocket with water; liquid-fuel rockets use liquid oxygen and either kerosene or liquid hydrogen. Ah … oxygen and hydrogen.
So what’s the science behind making rocket fuel from moon-water and asteroid-ice?
How do you make rocket fuel from water?
“Water—h2o—consists of hydrogen and oxygen, which can be refined into high-efficiency fuel,” says Panetta. It’s all about water electrolysis, a technique that uses an electric current (in space, from solar panels) to break down compounds and convert them into something else. In this case, hydrogen fuel. “Electrolysis is one approach that has been used in space to separate h2o to provide oxygen supplies for manned space missions, which helped alleviate the need for high-pressure oxygen storage tanks,” she says. On the International Space Station astronauts use electrolysis to split oxygen from hydrogen in water.
Why don’t we already make rocket fuel from water on Earth?
We could, but water is a precious commodity on Earth. It’s also not economical, and in any case, we’re talking about pretty small amounts of fuel needed by spacecraft. “Propelling an object in zero gravity doesn’t need much fuel, so water offers a viable solution in space,” says Panetta. However, water molecules are already used in many launch systems, albeit in their cryogenic liquid state to increase their density. “Couple this with solar energy for reliable power and it opens up new avenues for not just space exploration, but also for autonomous mining operations,” says Panetta.
Yup—autonomous mining is what the “water into rocket fuel” debate is really all about.
How water-ice at the moon’s South Pole will be ‘mined’
Get ready for autonomous robots on the moon. A lot of work will be needed on developing reliable autonomous mining techniques for docking, drilling, detecting and repairing equipment. “The robots will use artificial intelligence to gather information and communicate among each other what they learn, so each robot doesn’t have to relearn everything from scratch, but rather, just upgrade their knowledge and data models,” says Panetta.
How old is the water-ice at the Moon’s South Pole?
A new study published in the journal Icarus suggests that while a majority of those deposits are likely billions of years old, some may be much more recent. While most of the ice deposits are in patches on the floors of large craters formed about 3.1 billion years or longer ago, the researchers also found evidence for ice in smaller and relatively young craters. It’s argued that older ice could have been sourced from water-bearing comets and asteroids hitting the moon, while newer water-ice might come from bombardment from pea-sized micrometeorites.
What about mining asteroids?
The technology is likely to be perfected on the moon. “Landing and taking off again from an asteroid adds another dimension of challenges,” says Panetta. However, asteroids are a much more exciting prospect. “C-type asteroids contain potentially up to 20% water by mass and will be good targets for mining (and) M-type asteroids contain structural metals like iron, nickel and cobalt which can be used to build structures in space using 3D printing,” says Panetta. It would therefore be possible to fabricate spare parts on site from mined materials, allowing robots to repair each other and drilling equipment.
As natural resources become depleted on Earth, successfully mining and transporting them back could become big business.
Is any of this going to happen soon?
That depends on technology. “The combination of solar energy, artificial intelligence, robotics and materials science are truly responsible for enabling mining in space to become a reality,” says Panetta. “Don’t be surprised if the first successful mining operation on the moon is announced within the next five years.”
Wishing you clear skies and wide eyes.
I’m an experienced science, technology and travel journalist interested in space exploration, moon-gazing, exploring the night sky, solar and lunar eclipses, astro-travel, wildlife conservation and nature. I’m the editor of WhenIsTheNextEclipse.com and the author of “A Stargazing Program for Beginners: A Pocket Field Guide” (Springer, 2015), as well as many eclipse-chasing guides.