The XRQ-73 flew in April in California, DARPA said. DARPA An experimental US tactical stealth drone called the XRQ-73 just took flight in California. The US military said the stealth drone mixes electric and jet fuel propulsion for better efficiency. The drone is shaped like other stealth aircraft, such as the B-2 Spirit and the RQ-170 Sentinel. The US military's defense tech agency said on Wednesday that it flew an experimental hybrid-electric drone called the XRQ-73, testing a next-gen propulsion system for longer, quieter flight. The drone, built by Northrop Grumman , flew at Edwards Air Force Base in California in April, the Defense Advanced Research Projects Agency said in a statement. The new tech uses a mix of electric and jet-fuel propulsion, which is meant to help the drone burn less fuel and reduce emissions for better stealth. Most medium- to long-range military drones use jet engines or propellers. "This milestone is not just about a single flight," said Lt. Col.…