The concept hovering rover could tap into the moon's natural charge for levitation and navigation, allowing it to seamlessly glide over its surface. (Image credit: MIT)
The moon's surface is covered in fine powder-like dust known as regolith, which can be hazardous to astronauts and wreak havoc on electrical equipment and spacecraft's skin. Those that walked on the moon, including Glenn and Aldrin, found that it got everywhere and was challenging to remove, making it detrimental in an already extreme environment devoid of air, temperature swings and radiation. What's more, that dust can levitate up to 1-meter off the surface due to the moon's natural electrostatic charge. Think of it as similar to how static electricity can cause hair to stand on end.
To that end, engineers from NASA, MIT and other institutions have proposed creating rovers that could harness that electrostatic charge and use it for exploring the moon, asteroids and other airless celestial bodies. The idea is to outfit the craft with mylar, which can have the same charge as surfaces of airless bodies, to lift the vehicle off the ground, although this would have little to no effect on large bodies, such as planets.
To potentially get around that problem, MIT engineers propose outfitting the craft with tiny ion beams to boost the charge of the vehicle, as well as the planet's natural surface charge. The overall effect is to generate a sizeable repulsive force while using very little energy. Initial feasibility studies show that the ion boost would be sufficient to levitate a 2-pound vehicle on the moon and large asteroids. The engineer's design makes use of tiny ion thrusters, known as ionic-liquid ion sources, which are designed using microfabricated nozzles connected to a tiny tank filled with ionic liquid in the form of room-temperature molten salt. When a voltage is applied, the ions are charged and emitted through the nozzles with a certain amount of force.
The engineers tested their design using a small disc-shaped rover outfitted with the ion thrusters, which forced negatively-charged ions out of the nozzles but didn't generate any lift. They then surmised that if they added additional nozzles and blasted out positive ions (along with the negatives), it would be enough to get the craft to hover.
They tested the theory using a 60-gram hexagonal-shaped craft about the size of a human palm with one ion thruster pointing up and four pointing down from the craft. The engineers then suspended the vehicle over a piece of aluminum using springs to counteract the earth's gravity and placed the assembly in a vacuum chamber. A tungsten rod was suspended from the springs to measure the amount of thrust produced from each ion-fired nozzle and applied various voltages to gain how much force was needed just to levitate the craft. The engineers found that they could levitate a 2-pound craft 1-centimeter off the test surface by using larger voltages. Of course, the higher the voltage, the higher the levitation, but more research will be needed before large-scale tests can take place, including how ion thrusters would behave at higher altitudes.
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