"The part was made using a laser sintering technique, which scans a laser beam over copper powder, selectively melting it—after which it cools to form solid copper. Over the course of 10 days and 18 hours, 8,255 layers of copper powder were fused to form the final result."
http://gizmodo.com/this-is-nasas-first-3d-printed-full-scale-copper-rocket-1699394241
