3D printing spacecraft engine parts. Close-up of a prototype rocket engine part being made in a 3d printer that uses the process of selective laser melting. This process allows engineers to create complex, full-scale rocket-engine parts without welding. The use of 3D printing and prototyping technologies like this is critical to NASA's development of the Space Launch System, the next-generation rocket that will launch astronauts to more distant destinations than ever before. Photographed at the Rapid Prototyping Facility of the National Center for Advanced Manufacturing, Marshall Space Flight Center, USA.