Let’s not sugarcoat it. Exploring the Moon is not for the faint of heart! It’s an airless body, which means there is no atmosphere, the surface temperatures are extreme, and there’s lots of radiation. The low gravity also means you can never really walk on the surface and have to bounce around in a bulky spacesuit until you fall over. And you can bet your bottom dollar people will make a supercut of the footage someday (see below). Then there’s that awful moondust (aka. lunar regolith), which is electrostatically charged and sticks to EVERYTHING!
Looking to take advantage of this, researchers from the Massachusetts Institute of Technology (MIT) began testing a new concept for a hovering rover that harnesses the Moon’s natural charge to levitate across the surface. On the Moon, this surface charge is strong enough to levitate moon dust more than 1 meter (3.3 ft) above the surface. With support from NASA, this research could lead to a new type of robotic exploration vehicle that will help astronauts explore the Moon in the coming years.
Electrostatically charged regolith is a problem on all airless rocky bodies in the Solar System, ranging from Mercury to asteroids. The lack of an atmosphere means these bodies are subject to regular bombardment from micrometeoroids and larger objects that pulverize the surface, creating fine silica dust. No atmosphere also means no wind or water erosion and that this dust is exposed to a constant stream of charged solar particles.
“Earthrise,” the iconic image taken before the separation of the Lunar Module (LM) and the Command Module (CM) during the Apollo 11 Mission. Credit: NASA
The team behind this concept consisted of two student researchers and one professor with the Department of Aeronautics and Astronautics at MIT (MIT AeroAstro). Along with engineers from NASA, the team investigated how a lunar glider made of Mylar could take advantage of the Moon’s natural surface charge. Their research is summarized in a paper that recently appeared in the Journal of Spacecraft and Rockets (JSR).
Much like how a MagLev train relies on magnetic induction between the train cars and the tracks to travel at very fast speeds, this Mylar glider naturally holds the same charge as surfaces on airless bodies. This creates a repelling effect between the two similarly-charged surfaces that will keep the glider aloft as it explores airless celestial bodies. According to previous NASA studies, Mylar gliders could explore small asteroids, but not planets or Moons (due to their stronger gravitational pull).
The MIT team’s concept is designed to get around this size limitation by equipping a disc-shaped Mylar glider (that resembles a flying saucer) with tiny ion thrusters – known as ionic-liquid ion sources. These consist of microfabricated nozzles connected to reservoirs containing room temperature molten salt (an ionic liquid). When a small voltage is applied, these salt’s ions become charged and are emitted as a tight beam through the nozzles.
This is similar in concept to Hall-Effect propulsion (aka. ion engines), where an inert gas like Xenon is exposed to electromagnetic fields to charge its particles, which are then magnetically focused through a nozzle to generate thrust. In this case, the overall effect is to charge up the vehicle and the surface’s natural charge to generate a stronger repulsive force that would allow the vehicle to operate in environments with higher gravity (using little energy).