NASA Turns to 3D Printing for Self-Building Spacecraft

"Spacecraft could build themselves or huge space
telescopes someday by scavenging materials from
space junk or asteroids. That wild vision stems from
a modest proposal to use 3D printing technology
aboard a tiny satellite to create a much larger
structure in space."

See:

http://www.space.com/17577-nasa-spac...-printing.html