22,000 miles above the Earth sit billions of dollars worth of satellites that aren't being used anymore — some are broken, others are just at the end of their useful life. A new DARPA project, called the Phoenix Program, aims to harvest those satellites, and reuse the useful parts — especially the antenna, the largest and most expensive piece — to form new ones.

Satellites aren't meant to be taken apart, however, so DARPA is looking to multiple disciplines to solve the various challenges involved, from technology for conducting surgery remotely to imaging systems used in underwater drilling. Fastening the pieces together in zero gravity is similarly difficult — the Phoenix program manager likened it to assembling multiple Legos at the same time while looking through a telescope. DARPA and its partners are moving quickly, though, and plan to demonstrate the working system in 2015.