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The Lockheed Martin SR-72, commonly referred to as "Son of Blackbird," is an American hypersonic concept intended for
intelligence, surveillance, and reconnaissance ISTAR stands for Military intelligence, intelligence, surveillance, target acquisition, and reconnaissance. In its macroscopic sense, #ISTAR, ISTAR is a practice that links several battlefield functions together to assist a combat force in employ ...
(ISR). Proposed privately in 2013 by
Lockheed Martin The Lockheed Martin Corporation is an American Arms industry, defense and aerospace manufacturer with worldwide interests. It was formed by the merger of Lockheed Corporation with Martin Marietta on March 15, 1995. It is headquartered in North ...
as a successor to the retired
Lockheed SR-71 Blackbird The Lockheed SR-71 "Blackbird" is a retired long-range, high-altitude, Mach 3+ strategic reconnaissance aircraft developed and manufactured by the American aerospace company Lockheed Corporation. Its nicknames include " Blackbird" and ...
, the SR-72 was projected by Lockheed Martin executives in 2018 to have a test vehicle fly by 2025 and potentially enter service in the 2030s.


Background

The SR-71 Blackbird was retired by the
United States Air Force The United States Air Force (USAF) is the Air force, air service branch of the United States Department of Defense. It is one of the six United States Armed Forces and one of the eight uniformed services of the United States. Tracing its ori ...
in 1998, eliminating a unique and valuable
intelligence, surveillance, and reconnaissance ISTAR stands for Military intelligence, intelligence, surveillance, target acquisition, and reconnaissance. In its macroscopic sense, #ISTAR, ISTAR is a practice that links several battlefield functions together to assist a combat force in employ ...
(ISR) capability. Although most
fifth-generation jet fighter A fifth-generation fighter is a Jet fighter generations, jet fighter aircraft classification which includes major technologies developed during the first part of the 21st century. these are the most advanced fighters in operation. The characteri ...
s and planned drones intended for enemy airspace rely on anti-radar stealth technologies, Professor Justin Bronk, a senior research fellow in airpower and technology at the
Royal United Services Institute The Royal United Services Institute (RUSI, Rusi) is a defence and security think tank with its headquarters in London, United Kingdom. It was founded in 1831 by the Arthur Wellesley, 1st Duke of Wellington, Duke of Wellington, Arthur Wellesley ...
(RUSI), argues that the rise of anti-access/area denial tactics and counter-stealth technologies renders speed more promising than stealth for penetrating protected airspace. The first unconfirmed reports about the SR-72 emerged in 2007, when various sources reported that Lockheed Martin's Advanced Development Programs (ADP) division, Skunk Works, was developing an aircraft capable of flying at six times the speed of sound, or , for the United States Air Force—about twice as fast as the SR-71.


Design and development


Early work

Since 2006, Lockheed Martin had been working to develop a suitable engine with Aerojet Rocketdyne. After the HTV-3X (DARPA FALCON Project) was cancelled in 2008, Aerojet Rocketdyne applied its
scramjet A scramjet (supersonic combustion ramjet) is a variant of a ramjet airbreathing jet engine in which combustion takes place in supersonic airflow. As in ramjets, a scramjet relies on high vehicle speed to compress the incoming air forcefully b ...
(supersonic combustion ramjet) technology to the SR-72's engine design. The SR-72 was envisioned to have an air-breathing propulsion system that could operate at subsonic,
transonic Transonic (or transsonic) flow is air flowing around an object at a speed that generates regions of both subsonic and Supersonic speed, supersonic airflow around that object. The exact range of speeds depends on the object's critical Mach numb ...
,
supersonic Supersonic speed is the speed of an object that exceeds the speed of sound (Mach 1). For objects traveling in dry air of a temperature of 20 °C (68 °F) at sea level, this speed is approximately . Speeds greater than five times ...
, and hypersonic speeds.
Turbojet The turbojet is an airbreathing jet engine which is typically used in aircraft. It consists of a gas turbine with a propelling nozzle. The gas turbine has an air inlet which includes inlet guide vanes, a compressor, a combustion chamber, and ...
engines can function from zero speed and typically perform best up to Mach 2.2. Ramjets, which rely on aerodynamic compression with subsonic combustion, perform poorly below Mach 0.5, are most efficient around Mach 3, and can operate up to about Mach 6. (The SR-71's engines shifted to low-speed ramjets by redirecting airflow around the core and into the afterburner at speeds exceeding Mach 2.5.) Scramjets can cover the high-supersonic-to-hypersonic range. The SR-72 was to employ a turbine-based combined cycle (TBCC) system, with a turbine engine for low speeds and a scramjet for high speeds. The engines would share an inlet and nozzle but have separate airflow paths. At speeds of Mach 5 and above, aerodynamic heating generates temperatures sufficient to melt conventional metallic airframes, prompting engineers to consider making critical components from composites such as the high-performance carbon, ceramic, and metal mixes used in
intercontinental ballistic missile An intercontinental ballistic missile (ICBM) is a ballistic missile with a range (aeronautics), range greater than , primarily designed for nuclear weapons delivery (delivering one or more Thermonuclear weapon, thermonuclear warheads). Conven ...
s (ICBMs) and the retired
Space Shuttle The Space Shuttle is a retired, partially reusable launch system, reusable low Earth orbital spacecraft system operated from 1981 to 2011 by the U.S. National Aeronautics and Space Administration (NASA) as part of the Space Shuttle program. ...
.


Plans for a prototype

On November 1, 2013, '' Aviation Week & Space Technology'' published an article on the SR-72's development. Public interest in the news was so intense that it overwhelmed the magazine's servers. Lockheed Martin officials announced plans to build an optionally piloted scaled demonstrator, about 60 feet (~18 meters) long—comparable in size to a Lockheed Martin F-22 Raptor—powered by a single full-scale engine to achieve Mach 6 for several minutes. They projected it would be ready by 2018 for flight testing aligned with the High Speed Strike Weapon timeline. The production version of the SR-72, company officials said, would resemble the SR-71 in size at over long, share its range, and enter service by 2030. It was intended to follow the U.S. Air Force's hypersonic roadmap, targeting a hypersonic strike weapon by 2020 and a penetrating ISR aircraft by 2030. Lockheed officials noted they had discussed the project with government officials but had not secured funding for the prototype or engine.


The Air Force's thoughts

On November 13, 2013, Air Force Chief of Staff
General A general officer is an Officer (armed forces), officer of high rank in the army, armies, and in some nations' air force, air and space forces, marines or naval infantry. In some usages, the term "general officer" refers to a rank above colone ...
Mark Welsh expressed the Air Force's interest in hypersonic flight, noting it would shorten an adversary's reaction time to operations. He highlighted it as one of several capabilities that could counter advanced air defenses. Welsh acknowledged the service was pursuing hypersonic technology but lacked the materials to build a full-sized aircraft like the uncrewed SR-72. He also clarified that the Air Force had not engaged with Lockheed Martin regarding the SR-72. By December 2013, the Air Force declined to fund the SR-72 program. Facing budget constraints, the service chose instead to develop the
Northrop Grumman RQ-180 The Northrop Grumman RQ-180 is an American Stealth aircraft, stealth unmanned aerial vehicle (UAV) surveillance aircraft intended for contested airspace. , there had been no images or statements released, but evidence points to the existence o ...
stealth UAV—anticipated to be less costly and complex to design and produce—for ISR missions in contested airspace.


Timeline


2014 NASA contracts

In December 2014,
NASA The National Aeronautics and Space Administration (NASA ) is an independent agencies of the United States government, independent agency of the federal government of the United States, US federal government responsible for the United States ...
awarded Lockheed Martin a contract to study the feasibility of developing the SR-72's propulsion system using existing turbine-engine technologies. The $892,292 (~$1.19 million in 2025) contract funded a design study to evaluate the viability of a TBCC propulsion system, integrating one of several current turbine engines with a very-low-Mach-ignition Dual Mode Ramjet (DMRJ). NASA had previously funded a Lockheed Martin study that determined speeds up to Mach 7 were achievable with a dual-mode engine combining turbine and ramjet technologies. The primary challenge in hypersonic propulsion has been bridging the gap between the top speed of a
turbojet The turbojet is an airbreathing jet engine which is typically used in aircraft. It consists of a gas turbine with a propelling nozzle. The gas turbine has an air inlet which includes inlet guide vanes, a compressor, a combustion chamber, and ...
(around Mach 2.2) and the minimum operational speed of a
scramjet A scramjet (supersonic combustion ramjet) is a variant of a ramjet airbreathing jet engine in which combustion takes place in supersonic airflow. As in ramjets, a scramjet relies on high vehicle speed to compress the incoming air forcefully b ...
(Mach 4), as typical turbine engines cannot accelerate sufficiently for a scramjet to take over. The NASA-Lockheed Martin study explored options such as a higher-speed turbine engine or a scramjet operable within a turbine's slower flight envelope; the DARPA HTV-3X had demonstrated a low-speed ramjet (DMRJ) functional below Mach 3. Existing
turbofan A turbofan or fanjet is a type of airbreathing jet engine that is widely used in aircraft engine, aircraft propulsion. The word "turbofan" is a combination of references to the preceding generation engine technology of the turbojet and the add ...
engines from jet fighters and experimental designs were considered for modification. If successful, NASA planned to fund a demonstrator to test the DMRJ in a flight research vehicle. On December 15, 2014, NASA's
Glenn Research Center NASA John H. Glenn Research Center at Lewis Field is a NASA center within the cities of Brook Park, Ohio, Brook Park and Cleveland between Cleveland Hopkins International Airport and the Rocky River Reservation of Cleveland Metroparks, with a s ...
awarded Aerojet Rocketdyne a $1,099,916 (~$1.47 million in 2025) contract to support mode-transition research. The two companies were reportedly collaborating on the TBCC propulsion system, aiming to begin development of the SR-72 hypersonic demonstrator in 2018, with an initial flight targeted for 2023.


2015 to 2016

In May 2015, the SR-72 was reported to be envisioned as an ISR and strike platform, though no specific payloads were identified—likely because existing payloads would be inadequate for an aircraft traveling at Mach 6 and up to altitude, requiring hundreds of miles to turn. New sensors and weapons would likely need to be developed specifically for such speeds. In March 2016, Lockheed Martin CEO Marillyn Hewson announced that the company was on the verge of a technological breakthrough, enabling the SR-72 to reach Mach 6 and permitting a hypersonic demonstrator—roughly the size of an F-22 stealth fighter—to be constructed for under $1 billion.


2017 to 2018

In June 2017, Lockheed Martin announced that the SR-72 would enter development by the early 2020s, with a top speed exceeding Mach 6.
Executive Vice President A vice president or vice-president, also director in British English, is an officer in government or business who is below the president (chief executive officer) in rank. It can also refer to executive vice presidents, signifying that the vi ...
Rob Weiss remarked, "We've been saying hypersonics retwo years away for the last 20 years, but all I can say is the technology is mature, and we, along with DARPA and the services, are working hard to get that capability into the hands of our warfighters as soon as possible." In January 2018, Lockheed Martin
Vice President A vice president or vice-president, also director in British English, is an officer in government or business who is below the president (chief executive officer) in rank. It can also refer to executive vice presidents, signifying that the vi ...
Jack O'Banion delivered a presentation attributing advancements in additive manufacturing and computer modeling to the SR-72's feasibility, noting that building the aircraft five years earlier would have been impossible and that
3D printing 3D printing, or additive manufacturing, is the construction of a three-dimensional object from a CAD model or a digital 3D model. It can be done in a variety of processes in which material is deposited, joined or solidified under computer ...
enabled embedding a cooling system in the engine. In February 2018, Orlando Carvalho, executive vice president of
aeronautics Aeronautics is the science or art involved with the study, design process, design, and manufacturing of air flight-capable machines, and the techniques of operating aircraft and rockets within the atmosphere. While the term originally referred ...
at Lockheed Martin, refuted reports of the SR-72's development, stating that no such aircraft had been produced. He added that hypersonic research was driving weapons development: "Eventually as that technology is matured, it could ultimately enable the development of a reusable vehicle. Prior to this we may have referred to it as a 'like an SR-72', but now the terminology of choice is 'reusable vehicle'" In November 2018, Lockheed Martin reported that a prototype of the SR-72 was scheduled to fly by 2025 and would be equipped to launch hypersonic missiles. The SR-72 could enter service in the 2030s.


See also

* Aurora (aircraft) * Boeing X-51 * DARPA Falcon Project * MD-22 * AVIC WZ-8 * AVIC Dark Sword * Prompt Global Strike * Reaction Engines Scimitar * Tupolev Tu-360


References

{{US reconnaissance aircraft Aircraft with retractable tricycle landing gear Hypersonic aircraft SR-072 Low-wing aircraft Proposed military aircraft of the United States Scramjet-powered aircraft Strategic reconnaissance aircraft