Even on military flights, regular manned aircraft need to stop regularly so the crew can rest, bathe and unwind. But an unmanned drone can keep flying until it runs low on fuel, so the U.S. military drew up plans for nuclear powered drones that could stay airborne for months at a time. The catch 22 is that while a manned aircraft can stay airborne for extended periods using mid-air refueling, this requires a skilled team on the plane making true long tern endurance impossible. Working in collaboration with Sandia National Labs, Northrup Grumman drew up plans for a drone powered...