Page Text: November 3, 2018Written by Philip Metzger
Final Report: Mining Water on the Moon
Over the past few months, I was part of a study funded by the United Launch Alliance and supported by a large group of technologists to determine if we can mine water on the Moon and turn it into rocket fuel, and to do it economically. The final report can be downloaded here.
Why Mine Water on the Moon?
The lunar water would be launched off the Moon and delivered to a “gas station” in Earth orbit. This propellant depot will use solar energy to turn the water into rocket fuel. Then, space tugs can refill their tanks so they can repeatedly boost spacecraft from Geosynchronous Transfer Orbit (GTO) (where the launch rocket throws them) into Geosynchronous Orbit (GEO) where they can begin operating.
This can save money when putting new telecommunications satellites (or other satellites) into their final orbits. In the old days, every time a satellite was launched, the rocket had to include an upper stage that would boost the satellite from GTO to GEO. The upper stage was used only one time and then thrown away to become space junk. It was very expensive to carry a heavy upper stage, with all of its fuel, and throw it away every time. But we already found a better way.
Nowadays, instead of including an upper stage with every satellite, we use a very lightweight electric thruster instead. These thrusters are highly efficient and don’t cost much to launch with the satellite, but they are very slow. Instead of taking just one day to boost the satellite into its final orbit, an electric thruster takes 6 to 12 months. During that time, the owner of the satellite loses something like $100M in revenues, all the while they are still paying insurance, finance costs, and operational costs for the satellite. So that $100M is a real loss, but it is still cheaper than launching and throwing away an upper stage very time.
How Mining the Moon Helps
But now there is a third alternative. We could have a “gas station” orbiting the Earth, and space tugs can fuel up at the gas station, rendezvous with the newly launched satellite, and push it into its final orbit at GEO in just one day. This can recover the $100M’s of lost revenues for the satellite owners. If the space tug can provide this service for much less than $100M per satellite, then there is a business case. But the cost of providing this service depends critically on how expensive it is to get water off the Moon to the gas station. That is where the United Launch Alliance study came in.
Julie Brisset and I (both at UCF) were funded by the United Launch Alliance to model the physics of extracting water on the Moon. We were collaborating with the Colorado School of Mines, which took our analysis, designed some hardware concepts, and did the economic analysis. An example of a computer simulation I ran is shown below. This uses equations based on lunar soil experiments to describe the transfer of heat through the soil, the sublimation of lunar ice into water vapor, and the diffusion of that vapor through the spaces between the grains of soil to a collector device where it gets captured.
Axisymmetric computer simulation of water vapor pressure forming and dissipating as lunar ice sublimates inside a heated tube that was inserted into the lunar subsurface
The final result of the overall study showed that there is a real business case. Water can be mined on the Moon, delivered to a gas station, sold to operators of the space tug like the United Launch Alliance, who will then boost the satellite to its final orbit for much less than $100M per spacecraft. The cost takes into account the entire expense of mining the Moon and transporting the water to the gas station, etc. The profit margin was not as big as we might want it to be for a risky new business like MINING ON THE MOON. But that changes if NASA decides to be the anchor customer. If they do, and if NASA pumps in a little funding to get the mining operation started, then NASA will make a HUGE profit by dramatically reducing the cost of doing scientific research on the Moon and the cost of doing missions to Mars. Then also the commercial mining operation becomes far more viable: instead of having only a decent profit margin, it will have a really healthy one. And this is great news for us all, not just because we will get data services through those satellites at lower cost, but because it will be a step toward putting industry off of planet Earth, helping us recover the environment of Earth for the benefit of life .
For the lunar mining details, please see the final report .