Developed with the same primary mission as the Cold War-era SR-71 "Blackbird", the new high-speed, high-altitude-minded SR-72 "Son of the Blackbird" (the nickname fittingly bestowed by Aviation Week magazine) was unveiled by Lockheed Martin in November of 2013. The aircraft was conceived as an unmanned system which would not risk pilots to the extreme conditions and dangers expected of its super high-speed/high-altitude flight with the SR-72 estimated to reach speeds around Mach 6. As with the SR-71 before it, the SR-72 is designed to simply outrun any intercepting threats from the ground.
The original SR-71 Blackbird saw its first flight on December 22nd, 1964 and was introduced in 1966, completing its excellent service tenure with the USAF in 1998 through formal retirement. Despite never being armed, the SR-71 became the "...most feared aircraft of the Cold War" due to its inherent capabilities in flying higher and faster than any weapon the Soviets could field. Amazingly, the SR-71 was commanded through conventional means and its instrument panel dominated by needled dials with no high-speed digital processing available then. The SR-72 intends to continue the legacy that was brought about by the original Blackbird spyplane and bring all-modern advanced technologies into the fold.
Hypersonic flight, the speeds at which the SR-72 is being designed for, covers the envelope of "highly supersonic" speeds which persist at Mach 5 and beyond. Such speeds bring additional, some not entirely understood, characteristics during flight which require specific design qualities of a given airframe. Hypersonic flight exists beyond supersonic flight (the BAC Concorde airliner) and high-hypersonic flight.
The SR-72 will rely heavily on data collected during the testing of the DARPA-directed "Falcon HTV-2" (Hypersonic Technology Vehicle). The test vehicle served to provide information on aspects concerning extreme high-speed flight and associated (remote) guidance and control at such speeds. The three concentrated phases included aerodynamics (airflow at extreme speeds), aerothermal effects (air temps at extreme speeds) and guidance/navigation/control. The HTV-2 was able to reach speeds of 13,000 miles per hour (Mach 20) with recorded outside surface temperatures of 3,500F degrees.
Concept art for the SR-72 currently indicates a futuristic though still-conventional aircraft form with underslung twin air intakes, slim low-mounted delta-type wing assemblies and a single vertical tail fin. The SR-72 is designed from the outset as an unmanned system and thusly does not feature a cockpit but instead a solid fuselage containing avionics, mission systems and fuel stores. Its flight characteristics and inherent power will allow the vehicle to transition into near-space altitudes as the SR-71 before it (the SR-71 operated up to 85,000 feet). A retractable undercarriage will allow the SR-72 to land and be recovered as a traditional aircraft.
The key ingredient to the success of a physically-realized and performing SR-72 will be its powerplant which is comprised of a turbine-based "combined cycle" propulsion system. The arrangement will feature a base turbine engine to provide the necessary thrust from take-off to Mach 3 speeds. From there, the system's dual-mode ramjet will take over to deliver the required hypersonic speeds. The engines will be aspirated through a common inlet at the front of the engine housing and exhausted through a common nozzle at the rear of the aircraft. Internal ductwork will provide the channels needed to access one propulsion method over the other. The engines are provided by Aerojet Rocketdyne. Concept artwork showcases the engines installed in underslung forms outboard of fuselage centerline.
Beyond its presented reconnaissance capabilities, other military-minded mission roles for such a vehicle include may include a missile-carrying platform - the missiles themselves developed around the concept of hypersonic flight to coincide with their hypersonic delivery vehicle. Conceivably, such an aircraft will be able to defy conventional air defenses, swoop in from extremely high altitudes and launch its payload before even being recognized. Additionally, high-speed flight will enable it to reach any place on earth in a matter of minutes or within hours - leaving little time for an enemy to react and allowing US airpower the capability to strike any global target in short order. The technology brought about by this military project could also have a revolutionary impact on future passenger airline travel between major hubs.
Lockheed expects a functional SR-72 test vehicle to be ready by 2030. Its development is being headed by the secretive Lockheed "Skunk Works" facility which developed the famous SR-71.
June 2017 - Lockheed sources have confirmed the existence of SR-72 plans. A prototype is tentatively scheduled for readiness for the early 2020s.
September 2017 - It was revealed that work on the SR-72 project has accelerated as initial sightings of a technology demonstrator, dating back to July, have been reported near the Skunk Works facility (Palmdale, California). This aircraft was reportedly flanked by a pair of T-38 chase planes.