At 16:56 UTC on August 29, 2009, an Iridium communications satellite fell silent. It was determined a few hours after by the U.S. Space Surveillance Network that two large clouds of debris, one from the Iridium and another from a defunct Russian military satellite called Cosmos 2251 were being tracked.
The clouds of debris were the result of a high-speed orbital collision. It was the first collision recorded between two orbiting satellites. The collision created thousands of tiny fragments, some greater than 10 centimeters in size, and a many more smaller ones.
Space debris is a big problem for spacecraft. Aside from the catastrophes already depicted in movies, it is predicted that when space debris reaches a particular threshold, a chain reaction can happen that will fill our skies with the remains of our all-important satellites.
Technology Review reported that one solution is being proposed by researcher Lei Lan and his team from Tsinghua University in Beijing, China. They would like to build an engine that eats up space debris and converts it into plasma energy. This solution, if successful, would not only clean up orbital space but also provide practically unlimited fuel for the spacecraft.
See proposed spacecraft specs here.
Larger pieces of debris can be zapped by lasers but smaller pieces pose a much larger problem. Mopping up debris using some kind of net or capture method is possible but these are currently highly limited by the fuel capacity of current spacecraft.
The idea is simple in theory. Any element can be converted to plasma of positive ions and electrons at a high enough temperature. This can then be used as a propellant by spacecraft. However, this is rocket science and the process is not straightforward.
Lei and team would create a rocket that can capture debris and transfer it to a ball mill. This rotating cylinder is partially filled with balls that would grind up the debris into powder. The powder would be heated and the positive ions would be passed on to an electric field, accelerating them to high energy and generating thrust. Electrons are expelled to keep the spacecraft eletrically neutral.
