Zachary Tong Investigates a Potential Future for Satellite Steering: Liquid-Metal Reaction Wheels

YouTuber and former neurobiologist turned software engineer Zachary Tong has built a motor with no moving parts, bar a helping of liquid metal — as a demonstration of a device that could help steer satellites in space.

"This little device is a motor, and it has no moving parts other than a cavity filled with liquid metal," Tong explains in the introduction to his latest video, "and it could potentially revolutionize how satellites control their orientation in space. Or maybe not, I don't know, I'm just a guy making videos on YouTube, but it is a really cool idea and there are some attractive features to a liquid metal motor like this one."

The device in question is based on the oncept of magnetohydrodynamics, replacing the solid lump of a flywheel in a typical reaction wheel with liquid metal — something which doesn't require bearings that could get damaged in space. Using a magnetohydrodynamic pump, the liquid metal can be convinced to flow — and if that flow goes in a circle, you've basically created a liquid flywheel.

"It's a reversible reaction wheel," Tong says of his creation, "but, you know, without the mechanical bits like ball bearings and spinning rotors, and that's precisely why they're being studied: one of the main failure points of satellites are the reaction wheels, specifically the ball bearings that allow the rotor to spin. Bearings need to be lubricated, but lubricants don't really like the deep vacuum of space much so you either need lubricants that are space-rated, which aren't as good, or you need to enclose the entire reaction wheel in a pressurized chamber, which adds weight and complexity."

Tong demonstrates two prototypes in his latest video, embedded above and available on his YouTube channel — and warns of some drawbacks, such as the liquid metal "eat[ing] your satellite from the inside out" should it leak out of the reaction wheel.