During the war in Vietnam, the US Navy monitored the heart rates of some of their pilots. Flying though Hanoi’s air defenses understandably raised their pulse. However, their hearts went even faster at the end of the flight, when they had to land their jets on an aircraft carrier. These may be big for a ship, but they are very small for an airport. Unlike pilots, unmanned aircraft or ‘drones’ don’t have hearts and they are never tired. If a drone crashes or gets shot down, its pilot can’t get hurt or taken hostage. Instead, the operator is safely at his or her home base, in a comfortable chair in an air-conditioned container. So, it’s easy to see the attraction of unmanned aircraft. For the US Navy carrier landings remained a major hurdle, though. Enter the X-47B. Northrop Grumman built two of these weird-looking experimental jets, to demonstrate integrating unmanned combat...







