Lockheed Martin SR-72

The Lockheed Martin SR-72 is a proposed hypersonic aircraft intended for intelligence, surveillance and reconnaissance. It is under development by Lockheed Martin Skunk Works and is seen as a successor to the SR-71 Blackbird, which was retired in 1998.

There were unconfirmed rumours about the SR-72 dating back to 2007, when Defense News disclosed that Lockheed Martin was developing a Mach 6 plane for the US Air Force. Such a development was confirmed on 1 November 2013, when Skunk Works revealed exclusively to Aviation Week & Space Technology's Guy Norris development work on the SR-72.

Design and development

The SR-72 is expected to fill what is considered a coverage gap between satellite surveillance, subsonic manned aircraft, and unmanned aerial vehicles for an intelligence, surveillance and reconnaissance and strike missions. With the growth of anti-satellite weapons, anti-access/area denial tactics, and counter stealth technologies, a high-speed aircraft could penetrate and observe or strike a target before it could be detected or intercepted. It is envisioned with the ability to accelerate from Mach 0.0 to Mach 6.0 using the same air-breathing hypersonic propulsion system, making it about twice as fast as the SR-71. Lockheed is developing the system from the scramjet-powered HTV-3X, which was cancelled in 2008. Normal ramjets cannot typically operate under Mach 4.0, and turbofan engines can perform best at Mach 2.2. The SR-71's specially designed engines converted to low-speed ramjets by redirecting the airflow around the core and into the afterburner for speeds greater than Mach 2.5. The SR-72 will use a turbine-based combined cycle (TBCC) system to use a turbine engine at low speeds and a scramjet engine at high speeds. An optionally-piloted flight research vehicle (FRV) will begin to be built in 2018. It will be about 60 ft long, about the size of an F-22 Raptor, and be powered by one engine to fly it for several minutes at Mach 6. Flights of the FRV are to be conducted starting in 2023. The SR-72 flight testing follows the planned timeline for the hypersonic high-speed strike weapon. The full-sized SR-72 will be of similar size to the SR-71 at over 100 ft long and have the same range, with entry into service by 2030. The SR-72 follows the U.S. Air Forces hypersonic road map for developing a hypersonic strike weapon by 2020, and a penetrating ISR aircraft by 2030. At the time of the concept's unveiling, Lockheed had engaged in talks with officials, but not secured funding for the demonstrator or engine.