The SR-71 Blackbird had been utilized by the United States from 1964 until its retirement in 1998. Aside from its duties as a spy plane and being able to do things such as take photographs of the Soviet Union, the SR-71 also set numerous speed records, such as its still-standing record of 2,193mph from 1976. When it was retired, it seemed that the U.S. had no more need for spy planes, and that such duty could be carried out with satellites. It wasn’t until November of 2013 that it was announced the Blackbird would finally have a worthy replacement: the SR-72.
Despite the impressive records set by the SR-71, the engineers at the Lockheed Martin’s Skunk Works are envisioning an aircraft that would have the capability to fly twice as fast as the SR-71. Nicknamed the “Son of Blackbird”, the SR-72 is planned to be able to fly at Mach 6 at speeds of roughly 3,500 mph, while the SR-71 was only able to reach speeds of Mach 3. And while the SR-71 was only intended as a spy plane, the SR-72 is planned on being able to fill more roles.
According to Brad Leland, the program manager for hypersonics at Lockheed,
“Hypersonic aircraft, coupled with hypersonic missiles, could penetrate denied airspace and strike at nearly any location across a continent in less than an hour. Speed is the next aviation advancement to counter emerging threats in the next several decades. The technology would be a game-changer in theater, similar to how stealth is changing the battlefield today.”
The major change in development with the SR-72 is how the SR-71 was developed during a time period in which aviation engineers utilized pencils and paper, while today’s modern computing technology will allow engineers to design an aircraft whose capabilities far exceed that of its predecessor. Lockheed Martin wants to test the technology on a missile first before utilizing it on the SR-72, hopefully by the year 2018. That missile will be codenamed the High Speed Strike Weapon (HSSW), and is operated by the Air Force Research Laboratory and DARPA (Defense Advanced Research Projects Agency). Essentially, the HSSW will be a smaller version of the SR-72 and of comparable size to the Boeing X-51. After that, it is planned to have the SR-72 operational by 2030 and able to carry out reconnaissance and combat operations. Also unlike the SR-71, which was flown by two pilots, the SR-72 is intended to be an unmanned aircraft.
Of course, this will only be made possible by the engines developed jointly by Lockheed Martin and Aerojet Rocketdyne. The SR-72 will be propelled by a combination of an off-the-shelf turbine and a supersonic combustion ramjet air-breathing jet engine, which is intended to give the SR-72 the ability to go from a standstill to Mach 6. This technology had previously been developed by Lockheed Martin and Aerojet Rocketdyne for an unmanned glider called the Falcon Hypersonic Technology Vehicle 2, or HTV-2. The HTV-2 had been able to fly at 13,000mph or Mach 20, giving it a surface temperature of roughly 3500 degrees Fahrenheit. Unfortunately, the HVT-2 crashed into the Pacific Ocean during its test flight in 2011 after only nine minutes. As Brad Leland stated in regards to the propulsion system,
“The turbine, which works well up to Mach 2, and the scramjet (supersonic combustion ramjet) work well at Mach 4 and above. By making those work together down at Mach 3-below Mach 3-that’s really the key.”
The technology involved in the transition between the turbine and the scramjet (a problematic part of the process) was originally tested in the HTV-3X aircraft project run by DARPA. The HTV-3X, codenamed Blackswift, unfortunately failed due to the lack of a turbine that had the ability to propel the aircraft to Mach 4, where the scramjet could take over.
Unfortunately, as of now the SR-72 only exists on paper, both due to the technical difficulties involved in developing a suitable turbine as well as the extremely high costs involved with such research. In regards to the engines, Brad Leland stated,
“Those turbines just weren’t ready yet. As a result, we couldn’t go forward with the demonstrator program called Blackswift. We couldn’t go forward with that program because the turbine was the one technical weight that was not yet available.”
Despite the appearance that Lockheed Martin is being a bit impetuous with the announcement of the SR-72 and such a long wait for delivery, the are some in the aviation community who are claiming that the SR-72 is related to the rumored Aurora aircraft sightings. There are certainly similarities, as the Aurora was rumored to be able to fly from Mach 4 to Mach 5.2, was sometimes rumored to be unmanned, supposed to be able to carry out both espionage and combat missions, and was always described as a triangular design. The Aurora was also believed to be under development at the Lockheed Skunk Works.
It’s unknown as of now exactly how long it will take to fully develop the SR-72, although Lockheed Martin and Aerojet Rocketdyne are clearly taking the initiative in developing the next and possibly most advanced aircraft in the world. Only time will tell if and when the SR-72 is developed, and whether or not the records set by the SR-72 will last as long as those set by the SR-71.