Scientists are increasingly confident that there is a significant amount of water on the Moon, but there is still uncertainty as to how much. Moon-orbiting satellites that rely upon ultraviolet, visible of near-infrared light to identify ice deposits can sense only a slice of the lunar surface measurable in a few millimeters.
“You really don’t know if it’s just a very thin frost or if it extends deeper,” says Kevin Cannon, a postdoctoral scholar at the University of Central Florida, who has written a paper for non-academics, “Ice Prospecting: Your Guide to Getting Rich on the Moon.” Orbiting instruments that potentially could detect ice deposits beneath the surface — such as radar and neutron spectroscopy — have much much lower spatial resolutions.”
To get better data, NASA has begun planning a mission to send a rover to the Moon with mining instruments, hopefully by late 2023. The golf cart-sized rover will survey and map ice deposits in the lunar south pole. One of the instruments is a one-meter drill called TRIDENT (The Regolith and Ice Drill for Exploring New Terrain), reports Air & Space. Building a drill capable of penetrating the Moon’s surface in subzero temperatures is fraught with challenges. Lunar regolith, highly impacted over billions of years of bombardments, is dense. Add ice, and the soil could be harder than concrete.
“The biggest problem Apollo encountered during drilling was not actually drilling but pulling the drill out of the hole,” says Kris Zacny, vice president of exploration technologies and principal investigator of TRIDENT at Honeybee Robotics. “Regolith is so compacted that it jammed the auger flutes.” In fact, during the Apollo 15 mission, Commander David Scott sprained his shoulder while prying out the Apollo Lunar Surface Drill to obtain a core sample.
Machinists have developed a technique called peck drilling, in which they plunge the drill bit into a hard substance for a short distance, then retract it to remove chips. TRIDENT will do the same, drilling 10 centimeters then retracting to bring back “bites” of regolith. says Air & Space.
Because the drillers will be operating in shadow, solar power is not an option. Future options may include outfitting rovers with rechargeable batteries that use heat from the decay of plutonium-238 to generate electric power.
Another rover envisioned by NASA is RASSOR, the Regolith Advanced Surface Systems Operations Robot. RASSOR will excavate regolith with two counter-rotating drum bucket drums. The counter-rotating drums solve a problem caused by the Moon’s low gravity. On Earth, when a machine pushes a shovel into the ground, it remains stable because its weight acts as a counterforce. On the Moon, rovers designed to be ultra-light for transportation from Earth exert little counter-force. Two bucket drums rotating in opposite directions cancels the digging force of the other.