You can do a lot with 3D printing—even create a working model jet engine. As a final project for a jet engine manufacturing course at the University of Virginia, students led by Professor David Sheffler constructed a one-quarter-scale working replica of the Rolls-Royce AE3007 turbofan jet engine (which is found on the Air Force's RQ-4 Global Hawk UAV) that spins and whirs furiously, and that was built from plastic using 3D printing.