Rogue space junk poses a serious threat to both manned and unmanned spacecraft, since it just takes one wayward screw or fleck of paint to potentially punch a hole in some critical system. NASA has considered everything from balloons to sails to help mitigate the problem, and now the agency is thinking about a laser.
The idea of shooting down space junk with a gigantic ground-based laser has been around since the 90s, when the U.S. Air Force toyed with the concept. The primary issue with the idea is that if you have a big enough laser to blast space junk out of orbit, you also have a big enough laser to blast space non-junk out of orbit, which makes anyone with a military satellite understandably nervous.
This latest proposal relies on a much less powerful laser, something on the order of five kilowatts, which is ten times less powerful than this weapons-grade laser. Instead of vaporizing the junk, the laser would just slow it down enough that it would eventually burn up in our atmosphere all by itself. One system could take care of about ten different pieces of junk per day, which is enough to get ahead of the space junk curve, meaning that eventually, the skies would be clean, clear, and safe.
The laser is only estimated to cost about a million dollars, which is absurdly cheap considering how much it costs to launch one single satellite, and the system could even pay for itself by being used for fuel-free orbital adjustments to existing satellites designed to absorb laser blasts.