One thing that the film “Gravity” illustrated in a dramatic way was the vexing problem of space junk, satellites and pieces of satellites that continue to orbit the Earth, long after they passed their useful lives, making a hazard to navigation.
Wired recently ran an article about a new method to remove space junk. It won’t work in low Earth orbit, but will apparently be just the thing to clean up geosynchronous orbit where most communication satellites are deployed.
“This solution relies on what are known as electrostatic forces, which occur whenever electrons build up on something. Bombarding a piece of space junk with electrons could give it a modest negative charge of a few tens of kilovolts, roughly the equivalent charge stored in a car spark plug. An unmanned space probe with a positive charge could then tow it in a tractor-beam-like fashion.”
Most other methods of cleaning space junk, pushing, harpooning, and so on require physical contact with the junk in question, which can be problematic if it is tumbling. The use of an electron beam does not require such contact. The Geosynchronous Large Debris Reorbiter (GLiDer) would fire an electron beam at a large piece of space junk like a defunct satellite. The satellite would get a small electrostatic charge while GLiDeR would become relatively positive. Since positive and negative attract, the orbital debris would then follow the spacecraft, which would fly to remain about 15 to 25 meters in front of the junk.”
The idea is that after two or three months the space junk will have accumulated enough speed that when released from the electron tractor beam it would break out of orbit and move into deep space, thus no longer providing a hazard to navigation in orbit around the Earth. With a little tweaking, perhaps, the space junk could be flung into the sun.
It would take a small fleet of GLiDeRs to make a dent in the roughly 1,200 large scale pieces of space junk that infest geosynchronous orbit.
The reason that this method wouldn’t work in low Earth orbit is because “the sun produces a charged plasma that streams out everywhere in our solar system. This is the plasma that dominates at geostationary orbit and it is relatively hot and diffuse. The plasma at low-Earth orbit, in contrast, is given off by our planet’s ionosphere and is cooler and denser. At low-Earth orbit, anything that gains a charge, like a piece of space junk shot with an electron beam, will quickly attract these colder charged plasma particles and become neutral again very quickly.” Thus something else will have to be employed to deal with a situation such as depicted in “Gravity” in which the destruction of several hundred billion dollars in space hardware is quickly reduced to a debris field.