Casting a Net for Space Debris

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You wouldn’t think a Japanese company that built its business on manufacturing strong knotless fishing nets would have any interest in teaming up with the Japan Aerospace Exploration Agency (JAXA). But you’d be mistaken. The two entities are collaborating on an unusual new scheme for clearing away the space junk littering Earth’s orbit: a giant fishing net in space.

Space junk is a mix of things, ranging from spent rocket stages, defunct satellites, fragments from explosions of various space gear, paint flakes, dust, and so forth, all dating back to the launch of Sputnik in the 1950s.

Haven’t you ever lost a glove? Astronaut Ed White did, on the very first US space-walk, except his just floated around for a weeks until it re-entered the atmosphere and burned up. Lost pliers, cameras, even jettisoned garbage bags, routinely drift around a bit, but they’re not major contributors to the space debris problem because they don’t stay up very long.

ANALYSIS: CubeSails to Drag Space Junk from Orbit

Most of us just don’t think about the potential consequences of littering the Earth’s orbit with all our communication satellites: we need our GPS, our satellite radios, and our satellite TV. Those are very real, much appreciated technological benefits. But we have them at a cost.

The truth is, the “human footprint” in space is starting to get a bit too big to ignore. (The Union of Concerned Scientists maintains an extensive satellite database to keep track of them all.)

A 2006 study by NASA’s Orbital Debris Program that found certain parts of space (the 900 to 1000 km band in particular, part of the Lower Earth Orbit, or LEO) had already reached “supercritical” debris densities; it estimated that an active satellite in LEO will collide with a piece of debris larger than 1 centimeter every five to six years.

Last year, a review sponsored by the Department of Defense warned that all those abandoned rockets, defunct satellites and fragments from collisions pose a serious threat to the space services and telecommunications industry — as well as national defense.

A one-centimeter piece of debris doesn’t sound like much, but at the high orbital velocities in space, it can pack a wallop. Orbital speeds in LEO are typically greater than 7 kilometers per second (30 times faster than a jet aircraft).

That means that the relative speed of debris could be 10 kilometers per second or more. That’s a lot of kinetic energy. A speck of paint from a satellite once dug a pit in a space shuttle window nearly a quarter-inch wide (see photo).

ANALYSIS: Orbital Debris from Chinese Satellite Tops 3,000 Pieces

Lots of things have been proposed to “sweep” space debris back into the atmosphere: laser “brooms” that “vaporize or nudge particles into rapidly-decaying orbits, or huge aerogel blobs to absorb impacting junk and eventually fall out of orbit with them trapped inside,” per Wikipedia.

We could design our satellites and spacecraft with engines to direct them back to Earth, but this is really expensive (it adds considerable weight, for starters), for what is deemed to be very little benefit.

People have also toyed with the notion of using ground-based lasers to disturb the orbits of defunct satellites, but the darn things are so big, it would take a huge amount of laser energy to make any kind of difference.

My personal favorite is a proposed “terminator tether” for any future launched spacecraft or satellites, which would use electromagnetic effects to slow down a spacecraft sufficiently that it can no longer stay in orbit. Apparently France did this successfully in 2003 with one of its satellites, which is expected to re-enter the atmosphere in about 15 years.

And now we have this new scheme cooked up between JAXA and the Nitto Seimo Company. The idea is to attach a satellite to a thin metal net and then launch it into space. Once in orbit, the net is detached and sweeps up space debris lying in its wake. It will do this for several weeks — it’s costly to send a satellite into space, after all, and you want to make sure it’s worth the trip — during which time the net will become supercharged with electricity, so that Earth’s magnetic fields can draw it back down. And all that debris (plus the net itself) should burn up as it re-enters the atmosphere.

Sounds simple, doesn’t it? Naturally, there will be technical challenges and the inevitable glitches in operation. Of most concern is the possibility that the net will sweep up functioning satellites along with the debris. But something’s got to be done about all that space junk, and this plan just might be viable.

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