Back To The Future gave us the idea of Mr Fusion, a generator of energy that runs on junk. Now Chinese engineers from Tsinghua University in Beijing have come up with a real version of this ultimate recycling powerhouse.
Unlike the fictional Mr Fusion this new development won't create fusion, but rather charges an electrostatic generator. The idea is to install these on space craft allowing them to collect space debris and turn it into propulsion energy.
The idea is that at a high enough temperature any material can be turned into a plasma of positive ions and electrons. This can be used as a propellant by accelerating it through an electric field.
The generator would be able to work on debris of about 10cm or smaller in size. These get broken up by a spinning cylinder with abrasion-resistant balls to grind the debris into powder. It's this spin that will need to be powered and could limit the ship from being perpetually driven by debris.
The work is still in the theoretical stages right now but it's a very interesting way of not only dealing with space debris but powering a craft at the same time.