Lockheed Martin SR-72

The Lockheed Martin SR-72, nicknamed Son of Blackbird, is an American hypersonic aircraft concept for intelligence, surveillance and reconnaissance, proposed privately by Lockheed Martin in 2013 as a successor to the retired SR-71 Blackbird. Lockheed's Skunk Works described a vehicle able to fly at about Mach 6, roughly twice the speed of the SR-71, using a turbine-based combined cycle propulsion system in which a turbine engine handles low speeds and a scramjet takes over at high speed, developed with Aerojet Rocketdyne. The company spoke of an optionally piloted demonstrator about 60 feet long, comparable in size to an F-22, and a production aircraft more than 100 feet long entering service around 2030. The US Air Force declined to fund it in December 2013 and chose instead to pursue the Northrop Grumman RQ-180, NASA funded a propulsion study in 2014, and in 2018 Lockheed Martin's aeronautics chief denied that any such aircraft had been built. No flight tests have been confirmed, so it remains a design concept rather than a flown vehicle.