What are humans best at? Is it engineering new technologies, or sharing information? No, it’s making trash. Wherever we go, trash follows – even outer space. Between 2000 and 2014, the amount of space trash orbiting Earth doubled, and is now estimated to be about 3,000 tons in volume. Now, engineers at Riken believe the ISS is in the best position to clean up that trash – using a combination of a high-powered telescope and, yes, a bonafide laser cannon.
“Our proposal is radically different from the more conventional approach that is ground based, and we believe it is a more manageable approach that will be accurate, fast, and cheap. We may finally have a way to stop the headache of rapidly growing space debris that endangers space activities. We believe that this dedicated system could remove most of the centimeter-sized debris within five years of operation,” says Toshikazu Ebisuzaki, who led the research.
Space debris consists of all all sorts of detritus. The biggest items are wayward satellites, which are easy enough to spot. Then come the ejected rocket bodies, as well as the shrapnel created by collisions between larger debris. The largest debris aren’t the problem, as they’re big enough to be seen here on Earth. Nor are the smallest, as most spacecraft (including the ISS) are constructed in such a way that they can resist those impacts. The dangerous sweet spot consists of objects between 0.4 and 4 inches – too small to spot from Earth, but big enough to do some damage.
If that still doesn’t sound very large, consider the damage done by, say, an errant golf ball. Now imagine that golf ball hurtling through space, without air resistance, at 22,370 mph.
The plan to clean up Earth’s enear-orbit consists of two components. The first is the installation of the Extreme Universe Space Observatory (EUSO), a telescope originally designed to detect ultraviolet rays entering Earth’s atmosphere at night. Eventually, scientists reasoned that if the telescope could detect cosmic rays, it could probably be used to pick up smaller debris as well.
“We realized,” says Ebisuzaki “that we could put it to another use. During twilight, thanks to EUSO’s wide field of view and powerful optics, we could adapt it to the new mission of detecting high-velocity debris in orbit near the ISS.”
Step two of the plan is blasting the debris into oblivion. For that they’ll use the CAN laser, a high-efficiency laser originally meant to power particle accelerators. The plasma ablation produced by the laser beam should have enough energy to slow or stop small pieces of debris in their orbits, which will send them back towards Earth where they’ll be destroyed upon reentry.
Riken intends to start with small scale-model testing on ISS, with a 20-centimeter version of the EUSO telescope and a version of the CAN laser with 100 fibers. Should they be able to achieve proof of concept, the full-scale devices (a three-meter telescope and a 10,000 fiber laser) would come next. The project has been put on a fast track, and the first prototypes could be built and installed as soon as 2017.