Dr. Phil Metzger, Ph.D. is the Lead Research Physicist and founder of NASA’s Granular Mechanics and Regolith Operations (GMRO) Lab, which is part of the Surface Systems Swamp Works (gotta love it).
Here’s Phil’s explanation of what the GMRO does: “The GMRO Lab develops technologies primarily related to regolith [Ed. loose rock that sits on top of bedrock] – that is, excavation, conveyance, in and out of chemical processors, manufacturing and construction with regolith, site preparation, landing pad construction, prediction of rocket exhaust blast effects, etc.”
It is the GMRO’s work that will make lunar 3D printing possible. Here’s Phil’s mind-expanding take on the motivation, challenges and possibilities.
“The cost of a lunar mission is directly proportional to the mass to be delivered. Lifting everything we need becomes really expensive. We thought, what if we could make what we need on the lunar surface? Launch pads, buildings, roads, robots, machines, spare parts? That would bring the cost down.”
“We identified two types of Additive Fabrication that NASA would use: Additive Construction for infrastructure and Additive Manufacturing for machines and replacement parts. 3D printing was a logical choice. Next we thought about which 3D printing processes would make the most sense in the extreme environment. We decided that some sort of extrusion process would work as would sintering, if we could counteract the reduced gravitational pull.”
How does what we know about mining and manufacturing relate to the lunar version?
“On earth, mineral deposits, ore bodies as we call them, are mined based upon economic benefit. That is to say, when the projected cost of mining, transporting, refining and sale will yield a profit, the ore is removed from the ground. On the moon, there is an entirely different set of economics because moving mass there is so expensive.”
“Surprising as it may seem, all of the raw materials required to manufacture what we need are available on the Moon, thanks to comets and asteroids bombarding its surface. We’d site the manufacturing plant near the ice that has collected in a permanently shadowed crater. These are located in the polar regions. This would provide access to the hydrogen and oxygen that comprise the water, as well as the carbon and nitrogen compounds that are also in abundance in the ice.”
“Of course, manufacturing in that environment would be challenging because the surface temperature down inside the craters is only 40 degrees above absolute zero. We’d have to figure out not only how to keep the equipment operating, but how to free the elements from the polar ice and refine them.”
“On the other hand, if we keep the manufacturing outside the craters in the sunlight, which seems more feasible, then we still have to do the mining down in the cold, dark craters, and we also have a transportation challenge bringing the ice back up. The terrain is very rough and the distances are huge. It is difficult to design machinery that can operate at such cold temperatures. We also need to separate the ice from the soil to avoid carrying excess mass out of the craters, and then we need to refine the ice to isolate the compounds that we need for manufacturing.”
Metzger says that one of the materials they would use to fabricate items on the moon is a concrete-like building material. He says that they would also create a plant that would take the lunar soil, crush it, remove the beneficial ores, separate and refine them before they would be fed into 3D printers to make parts from which we would build machines and robots. A similar process would be used to extract the oxides needed to produce ceramics. The good news is that the moon has been continuously pinged with micro-meteorites for most of its life and the surface is mostly powder, which would be relatively easy-to-use.
The downside to this is that dust will be a huge issue. Metzger says that he has written a number of research papers on how this dust interacts with rocket exhaust. Another researcher at the Kennedy Space Center Swamp Works, Dr. Carlos Calle, has created an ingenious electrodynamic dust shield system that uses a series of transparent electrodes. This technology may allow NASA to overcome the dust problem, especially when it comes to the visors that the astronaut/manufacturers will wear.
What began as a quest to learn about lunar 3D printing turned into a detailed discussion of how to make this process work. I found my discussion with Dr. Metzger to be really interesting, especially the brief view into the depth of thought that these folks put into their work.
Kind of makes sending an stl file to a terrestrial 3D printer look pretty trivial, don’t you think?