Purdue researcher develops "drag sail" to bring satellites back to Earth on completing their mission

The problem of "space junk" – satellites that have reached the end of their lives, discarded rocket stagings and fairings, space rocks trapped in orbit and items that have simply fallen off spacecraft – has been known for some time, but is beginning to approach critical levels. While most pieces of hardware in orbit fall back into the Earth's atmosphere within a couple of years and burn up harmlessly, items in higher orbits can remain circling the planet for more than a century.

David Spencer, a specialist in space robotics at Purdue University in Indiana, explains why this is a problem. "There are a number of high-value orbits that have become so populated with defunct satellites and debris spacecraft that they’re approaching a tipping point,” he says. “Once that tipping point is reached, a cascade of uncontrolled collisions can occur, rendering the orbit unusable. Add into the mix the thousands of satellites that companies plan to launch into orbit in the next several years, and the problem becomes much worse.”