Along with satellites and space stations, Earth is surrounded by tens of millions of pieces of floating space debris. Like any landfill, the trash is diverse, ranging from dead satellites to castaway rocket parts to flecks of paint. On average, over the past 40 years, one piece of space junk has fallen to Earth every day.

Laser Brooms: Baseball-size pieces of debris are too small for tethers but large enough to pierce spacecraft. Hitting them with lasers would disrupt their orbit, causing them to fall and burn up. Photo by John MacNeil

 

Space agencies have managed to avoid major in-flight catastrophes with protective shielding and deft maneuvering of manned vehicles and satellites. But if we keep launching satellites and do nothing about the mess, the amount of unpredictable debris in orbit will make already-risky manned spaceflight more dangerous.

Scientists at NASA and private companies have devised several ways for clearing the sky. Although some methods are admittedly outlandish, says Nicholas Johnson, the chief scientist for orbital debris at NASA’s Johnson Space Center in Houston, Texas, a few are possible with today’s technology.
One early idea was to have robotic trash collectors shove large pieces of junk through the atmosphere so that they mostly burn up before hitting the ground. But the fuel costs for destroying a significant amount of debris with such craft has quashed this approach.

Space Flypaper: A half-mile-wide “Nerf ball” could intercept small debris, reducing their orbital energy so that they lose altitude quickly. Hang-ups include keeping the ball afloat and away from functional satellites. Photo by John MacNeil

 

A more feasible plan is to attach miles-long “electrodynamic tethers,” wound on a spool, to all new satellites. Once a satellite ends its mission, it would deploy the cable and Earth’s magnetic field would induce an electric current in it. This interaction imparts a force on the craft that pushes it through the atmosphere until most of it burns up harmlessly, says Rob Hoyt, the president and chief scientist of Tethers Unlimited, a company working to develop the technology.

Tether demonstrations have so far yielded limited success or failed outright, but despite the setbacks, Johnson and others are optimistic that the tech could be ready in a few years. Here, a look at how the tethers might make the sky safe for space travel.

• Step 1 After a spacecraft completes its mission, a three-mile-long Terminator Tether that is attached to the satellite unravels from its spool.

• Step 2 Interactions between the Earth’s magnetic field and the charged ionosphere create and drive an electrical current in the metal tether.

• Step 3 The current generates a Lorentz force—a phenomenon that affects charged particles moving in magnetic fields—that opposes the spacecraft’s orbital motion.

• Step 4 Over the next weeks or months, the Lorentz force pushes the craft to lower altitudes, until it mostly burns up in Earth’s atmosphere. 

• Popular Science