In order to at least begin addressing the growing problem of space debris, numerous groups are now looking into methods of de-orbiting satellites once their operational lives have ended. One of the latest approaches involves getting the spacecraft to dispense a long strip of sunlight-catching tape, instead of using their own propellant.
The technology is being developed via the three-year European Union E.T.PACK project, led by Spain's Universidad Carlos III de Madrid.
It would involve equipping satellites with a rolled-up strip of aluminum tape, prior to launch. Known as a low work-function tether, that tape would be several kilometers long but just 2 cm wide (0.8 inches) and only 50 microns thick – that's thinner than a human hair. It would additionally be coated with a thermionic material, which would emit electrons when heated by sunlight.
Once they were at the end of their mission, the orbiting satellites would allow that tape to unravel out of them, exposing it to the sun and to Earth's geomagnetic field. Thanks to a phenomenon known as Lorentz force, which is defined as the force exerted by a magnetic field on a moving electric charge, that tape would then generate electricity. That current would in turn be relayed to the satellite, where it would power up onboard electric thrusters to push the spacecraft down and out of orbit.
It is hoped that E.T.PACK will culminate in the creation of a tether kit, that could be added to and tested on satellites in a subsequent project.
"A low work-function tether transforms orbital energy into electrical energy while it de-orbits the satellite without using any type of fuel," says project coordinator Gonzalo Sánchez-Arriaga. "Unlike current propulsion systems, a low work-function tether does not need propellant and uses natural resources in the space environment, such as the geomagnetic field, ionospheric plasma and solar radiation."
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