This Rocket Engine Design Would Turn Space Junk Into Propellant

Amber Case via Flickr // CC BY-NC 2.0
Amber Case via Flickr // CC BY-NC 2.0 / Amber Case via Flickr // CC BY-NC 2.0

With each passing year, the Earth's orbit becomes increasingly congested with hazardous space debris. The junk poses a real threat to spacecraft, and it's one that’s only expected to grow worse over time—the more debris that accumulates, the more collisions are expected to occur, eventually generating more debris and more collisions as part of a domino effect called the Kessler Syndrome. Scientists have been brainstorming ways to tackle this problem for years, and now one team from Tsinghua University in Beijing is proposing an idea for a rocket engine that converts space junk into propellant [PDF].

Spacecraft designed to rein in debris with a net or some other mechanism have been suggested in the past, but the issue has always been fuel supply. This rocket would help solve that problem by producing the energy needed to maneuver itself around via the space junk it cleared. The proposed rocket design relies on the scientific principle that any element can be transformed into a plasma of positive ions and electrons when heated at a high enough temperature. Using a net, the craft would harness debris less than 10 centimeters in size and transport it to a ball mill where it would be pulverized into a powder. The powder would then be heated and transferred to a system that separates positively charged ions from negatively charged electrons. A powerful electric field would accelerate the ions to high energy before expelling them as exhaust, thus producing thrust. 

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It sounds straightforward in theory, but many of the crucial details would be harder to gauge. Factors like the size of the positive ions, the nature of the powder, and the density of the debris would all need to be calculated to get a better understanding of what type of thrust would actually be produced. And while the spacecraft would produce its own propellant, it would still require an energy source. The Tsinghua University team suggested nuclear power, but that would present an entirely new set of complications. It’s possible that the space-junk-eating engine will never make it into orbit, but it could inspire similar creative solutions to our planet’s growing space junk problem. And if worse to comes to worst, we always have giant lasers to fall back on.

[h/t: MIT Technology Review]