You can't talk space junk without mentioning lasers. Laser-based clean-up ideas range from satellite-mounted lasers that zap debris out of orbit, to the aptly named "laser broom" that sweeps debris out of the path of the International Space Station. Always cool--always costly.

On Earth, lasers help measure the effects of micrometeoroid collisions at the Hypervelocity Ballistic Range at NASA's Ames Research Center in California. Projectiles launched at speeds of up to 17,000 miles per hour pass through two laser curtains, which detect their velocity. The "energy flash" seen here is caused by the high-speed projectile striking a solid surface.