Lockheed Martin’s super-secretive Skunk Works is actively working on a super-secretive aircraft, the SR-72 Darkstar. And despite going over budget by just a smidgen ($335 million), the Darkstar seems ever closer to reality.
Kelly Johnson, the man behind building the Skunk Works, was a legend in the aircraft industry. He is akin to what John M. Browning was to arms designers. The Skunk Works has been working on the SR-72, a Mach 6+ intelligence, surveillance, reconnaissance, and strike aircraft. This aircraft utilizes advanced turbine-based combined cycle engines, allowing unprecedented speed and global reach within minutes.
SR-71. SR-71 photo taken at the National Air and Space Museum. Taken by 19FortyFive on 10/1/2022.
The Darkstar is the successor to the SR-71 Blackbird, which was retired in 1999. Some aviation experts call it the “Son of a Blackbird, or SOB.” New production facilities at the Skunk Works lead many to believe that either production has already begun or soon will begin for the Darkstar. Yes, it is coming.
What is known about the SR-72 So Far
The original Blackbird’s J58 afterburner engines could push it up to MACH 3.2 (2,400 MPH) at an altitude of 85,000 feet, with a range of more than 3,300 miles. The SR-72 plans on doing double that speed.
In 2013, Aviation Week & Space Technology published an article, “Meet the Son of Blackbird,” on Lockheed Martin’s plan to develop a new high-speed multirole aircraft.
Lockheed, the original developer of the SR-71, proposed an informally named replacement aircraft, the SR-72. The SR-72 was to be an all-new plane powered by a turbine and a scramjet. It would take off and land from runways under turbine power but transition to the scramjet once airborne.
The aircraft would travel at Mach 6 (4,600 mph), or twice as fast as the SR-71. Unlike the SR-71, whose air-to-ground attack capability was never realized, the SR-72 would be capable of reconnaissance and strike missions from the outset.
Two questions remain: What could hold back the program?
And what kind of engine will power the Darkstar?
The Engine Is Completely New
In June 2017, Lockheed Martin’s executive vice president and general manager for Skunk Works, Rob Weiss, told the media that testing was complete on the turbine-based combined cycle hypersonic propulsion system for the SR-72 and that they were “getting close” to beginning work on what he described as an SR-72 Flight Research Vehicle (FRV).
This single-engine technology demonstrator was said to be “about the size of an F-22 Raptor” and was meant to demonstrate the platform’s ability to take off under conventional turbofan power, accelerate up to supersonic speeds, and then transition from turbofan power to a much more exotic dual-mode scramjet that would allow the aircraft to achieve maximum speeds well above Mach 6.
“Hypersonic aircraft, coupled with hypersonic missiles, could penetrate denied airspace and strike at nearly any location across a continent in less than an hour,” Brad Leland, Lockheed Martin’s hypersonics manager, said in a Lockheed Martin press release that has since been taken down.
“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 battlespace today.”
Lockheed Martin is collaborating with Aerojet Rocketdyne (an L3Harris company) on a turbine-based combined cycle (TBCC) propulsion system that will enable the aircraft to achieve a cruise speed of Mach 6 (~7,300 kilometers per hour), twice that of the SR-71 aircraft.
The TBCC system’s subscale ground tests were conducted by integrating a small off-the-shelf turbine engine with a dual-mode ramjet/scramjet with an axisymmetric inlet and a nozzle.
The Skunk Works developed the Hypersonic Technology Vehicle 2 (HTV-2), a rocket-launched aircraft, as part of the Defense Advanced Research Projects Agency (DARPA) Falcon project.
The Falcon HTV-2 is an unmanned, rocket-launched, maneuverable aircraft that glides through the Earth’s atmosphere at incredibly fast speeds—Mach 20 (approximately 13,000 miles per hour).
At HTV-2 speeds, flight time between New York City and Los Angeles would be less than 12 minutes. The HTV-2 vehicle is a “data truck” with numerous sensors that collect data.
The HTV-2 project was created to gather data on aerodynamics, guidance, navigation, control, and aerothermal effects. The vehicle took its first flight in April 2010 and its second in August 2011. It achieved a maximum speed of Mach 20. The knowledge and data obtained from the HTV-2 are now being used to develop better designs for the SR-72.
The Airframe Has Its Own Challenges
The SR-72’s airframe will get Space Shuttle hot when going at Mach 6+, and it will need to withstand those temperatures. Traveling at Mach 6 or 4,603.61 mph will generate tremendous heat for the airframe.
SR-71 Blackbird. Image Credit: Creative Commons.
SR-71 Spy Plane. Image Credit: Creative Commons.
SR-71 Spy Plane. Image Credit: Creative Commons.
Front view of Lockheed SR-71A (Blackbird, s/n 61-7972, A19920072000) on display at the National Air and Space Museum’s Steven F. Udvar-Hazy Center, Chantilly, Virginia.
Maya Carlin wrote recently, “At speeds greater than Mach 5.0, the resulting high temperatures can melt conventional metallic airframes. To rectify this, engineers are researching alternate composites including high-performance ceramic, carbon, and metal mixes.” The heat would reach more than 500 degrees Fahrenheit on the aircraft’s external surfaces.
The surfaces of this unmanned aircraft will be built from carbon, ceramic, and some metal particles to withstand the heat from air friction. They plan an ISR version (intelligence, surveillance, and reconnaissance) and an armed version that can carry hypersonic missiles.
It’s All About Hypersonic Speed
The speed generated by conventional turbofan power accelerates up to supersonic speeds. Then, the aircraft transitions from turbofan power to a much more exotic dual-mode scramjet, allowing the aircraft to achieve speeds in excess of Mach 5 or 6. This would protect the aircraft without any stealth features.
During its unparalleled run as the best spy aircraft in the world, the SR-71 was fired at by more than 4,000 missiles, none of which hit it. The Blackbird could fly at Mach 3.56 (2,731.478 mph).
The original SR-71 was powered by the Pratt & Whitney J58 turbojet engine, which aviation experts often call a “turboramjet.” The Darkstar’s engine will have to be even more powerful to meet the airframe’s expectations.
Lockheed Lets The Cat Out of the Bag … Sort of
In 2023, Lockheed posted on Twitter or “X” that set tongues wagging.
The first, with an image of the SR-71, reads, “The SR-71 Blackbird is still the fastest acknowledged crewed air-breathing jet aircraft,” implying an even faster aircraft out there.
Another tweet, posted to celebrate the success the latest Top Gun film enjoyed, featured an image of the high-speed aircraft featured in that film. Interestingly, Lockheed Martin said, “To celebrate, we are sharing some Maverick-worthy images of real aircraft.”
Cost Is The One Thing That Could Set It Back
The SR-72’s first flight is predicted to be sometime in 2025. The design work, composite materials, new engines, and construction of one aircraft are expected to cost slightly less than $1 billion. Yikes.
However, the fact that Lockheed Martin ate the $335 million cost overrun tells me that the Air Force or the Intelligence agencies have already decided they need this aircraft. Given its speed, the SR-72 can spy on our adversaries with impunity. If there is a war between the US and our adversaries, the SR-72 can then engage the targeted area with hypersonic missiles.
The twin-engined SR-72 is expected to be operational by 2030. Tally Ho.
About the Author:
Steve Balestrieri is a 19FortyFive National Security Columnist. He served as a US Army Special Forces NCO and Warrant Officer. In addition to writing for 19FortyFive, he covers the NFL for PatsFans.com and is a member of the Pro Football Writers of America (PFWA). His work was regularly featured in many military publications
