For years – 74.52 years, to be precise – the idea of interplanetary travelers visiting us in flying saucers has been a mainstay of science fiction and conspiracy theories. But here’s the twist: what if we were the flying saucers all along?
Enter MIT’s Department of Aeronautics and Astronautics, where engineers have been working on something straight out of an H. G. Wells novel: a disk-shaped lunar rover that can levitate across the Moon using tiny ionic thrusters powered by the Moon’s natural force field.
“We think of using this like the Hayabusa missions that were launched by the Japanese space agency,” explained Oliver Jia-Richards, lead author of a feasibility study on the project published back in March. “That spacecraft operated around a small asteroid and deployed small rovers to its surface. Similarly, we think a future mission could send out small hovering rovers to explore the surface of the Moon and other asteroids.”
It’s not as farfetched as it sounds. Unlike Earth, and even (albeit to a much lesser extent in some cases) the other planets in our Solar System, the Moon and asteroids have basically zero atmosphere. That can lead to some pretty strange effects: their surfaces, essentially naked to radiation from the Sun and surrounding plasma, build up electric fields that repel objects away from the ground. On the Moon, it’s powerful enough to levitate dust more than a meter high.
Of course, spacecraft are often quite a bit larger than dust particles – but that’s no problem for a team of MIT and NASA-trained engineers. The rover is made with Mylar: a type of polyester film prized in the aerospace industry for its high tensile strength, stability, and electrical insulation. In an airless, barren environment, Mylar would naturally match the charge coming from the ground and, like the magnets we experimented with in eighth-grade physics, the two surfaces would therefore repel each other, thus levitating the rover.
“This kind of ionic design uses very little power to generate a lot of voltage,” explained study co-author Paolo Lozano. “The power needed is so small, you could do this almost for free.”
That natural repulsion may be fine for small asteroids, but the Moon comes with one extra snag: its size. While it’s comparatively tiny from our vantage point – the Moon is, after all, not even as wide as Australia – our nearest neighbor in the night sky is easily massive enough to pull a small rover into its gravitational field.
At first, the team modeled the rover as being equipped with thrusters that pumped out negatively charged ions – effectively making it positively charged, like the lunar surface. In theory, this should make the two bodies repel each other, and push the rover away from the ground, but the team soon found that the force generated was not enough.
“Then we thought, what if we transfer our own charge to the surface to supplement its natural charge?” Jia-Richards said. In other words, the team was suggesting, what if the rover could send out positive ion beams onto the Moon, boosting its natural electrical field? Could that be enough to get the rover off the ground?
A short mathematical model later, and the team were convinced: in principle, it could work. With extra thrusters to amplify the Moon’s force against it, a small, roughly 0.9-kilogram (2-pound) rover would be able to hover about a centimeter (0.4 inches) off the lunar surface – opening new corridors into extraterrestrial exploration.
“With a levitating rover, you don’t have to worry about wheels or moving parts,” Lozano says. “An asteroid’s terrain could be totally uneven, and as long as you had a controlled mechanism to keep your rover floating, then you could go over very rough, unexplored terrain, without having to dodge the asteroid physically.”
The best part? This sci-fi-sounding idea has already been shown to work in the real world. The researchers have been experimenting with a small hexagonal test vehicle – about the size of your palm, and weighing just 60 grams (2.1 ounces) – equipped with five ion thrusters: one pointing upwards, the rest down. In a specialized setup designed to counteract the Earth’s atmospheric conditions and gravitational force, the team were able to levitate the hexagonal test rover with results that matched their predictions exactly.
And while lifting a 2-pound rover 1 centimeter off the floor may not sound like much of an achievement, Jia-Richards explained that this is just the beginning.
“In principle, with better modeling, we could levitate to much higher heights,” he said – and while we know he was probably just talking about uncrewed exploration, we can’t help but hope this means future Moon bases will come with their own fleet of flying cars, à la The Jetsons. Hooba-dooba-dooba!