If you look closely enough, Earth has rings. NASA estimates there are some 500,000 pieces of space debris in orbit. Space junk, traveling up to ten times the speed of a bullet, endangers satellites and spacecraft—and it is very, very hard to remove. A team of scientists, however, think they have a way: Lasers.
A recent paper by Tokyo’s Riken institute proposes using a telescope on the International Space Station (ISS) to track small bits of space junk. A laser on the telescope would target and zap the junk, sending it crashing into the atmosphere, where it would vaporize—no longer a threat to humans or satellites.
The system would be effective against debris roughly a centimeter in size. These objects pose the greatest danger because they’re big enough to do damage but too small to track and evade in orbit.
Ground-based laser systems have been proposed in the past, but the researchers believe theirs is more manageable, more accurate, cheaper, and faster. (And it’s a laser, in space. Which is pretty awesome.)
The system would consist of the EUSO super-wide field-of-view telescope (originally developed by Riken to detect cosmic rays) and a high efficiency CAN laser (developed to power particle accelerators). The laser, a bundle of fiber optic cable, rapidly produces high-power laser pulses. When trained on debris, the reactive force would slow its orbital velocity, pushing it into the atmosphere.
“We believe that this dedicated system could remove most of the centimeter-sized debris within five years of operation,” said Toshikazu Ebisuzaki, the scientist leading up the research effort.
And some urgency is warranted. According to a statement released by the team, pieces of orbital space junk—derelict satellites, old rockets and rocket parts, and small fragments from collisions—almost doubled between 2000 and 2014. It’s estimated there is nearly 3,000 tons of the stuff orbiting the planet in total.
A European Space Agency (ESA) report released in 2013 said that roughly ten objects a week pass within two kilometers of each other. Even a single collision can significantly worsen the problem. A 2009 crash between two defunct satellites added some 2,000 smaller objects to already crowded polar orbits.
ESA estimates that, lacking remediation, collisions could ultimately reach 25 times today’s rate in coming decades, rendering low-Earth orbit unusable for satellites and other spacecraft.
The Riken proposal might prove one elegant solution for a tough problem.
The military, for example, is testing lasers as a cheap, accurate way to bring down fast-moving missiles or aircraft. One US Army laser costs a “cup of diesel fuel” per shot. Traveling at light speed, it can acquire and hit targets instantly. The Riken laser may offer similar advantages over more complicated ideas.
The team says they plan to test a scaled down prototype of their proposed system on the ISS, and if it’s successful, they hope to install the full-scale version, incorporating a three-meter telescope and 10,000-fiber CAN laser on the space station. The full-scale system would have a range of 100 kilometers.
It’s worth noting that the laser, as proposed, wouldn’t be used on large objects, like abandoned satellites.
Ideas for handling such objects include rockets, nets, sails, and even ion drives. But a practical solution for de-orbiting the biggest bits of junk remains elusive. Still, if Riken’s proposed solution works as advertised, it would be a big improvement on today’s state of affairs. And more lasers could be deployed.
“Looking further to the future,” Ebisuzaki said, “We could create a free-flyer mission and put it into a polar orbit at an altitude near 800 kilometers, where the greatest concentration of debris is found.”
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