Conversely, a hypersonic aircraft traveling at Mach 6, or roughly 4,600 miles per hour, could fly from New York to Boston in under five minutes, and make the same New York to LA flight in about half an hour.

The road to SR-72 production began in 2018

As Sandboxx News has previously reported, 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. 

By September 2017, eyewitness accounts of this Flight Research Vehicle flying over Palmdale, California, where Skunk Works is headquartered, began to surface.

Aviation Week took these SR-72 FRV reports to Lockheed Martin’s Orlando Carvalho, executive vice president of aeronautics, at the time, who did not deny the reports. 

“Although I can’t go into specifics, let us just say the Skunk Works team in Palmdale, California, is doubling down on our commitment to speed,” Carvalho said. 

In February 2018, another senior Lockheed Martin official, Vice President of Strategy and Customer Requirements in Advanced Development Programs Jack O’Banion, told the American Institute of Aeronautics and Astronautics SciTech Forum that the SR-72 FRV was already flying; he then told the Wall Street Journal, “The aircraft is also agile at hypersonic speeds, with reliable engine starts.”

But just as the SR-72 hype train was leaving the station, Russian President Vladimir Putin delivered an address that has since come to be known as the onset of the modern hypersonic arms race, in which he announced a slew of new Russian “doomsday weapons” were entering service, including two different Mach 5+ missile systems. 

Almost immediately after Putin’s speech, Lockheed Martin stripped any mention of its highly-touted SR-72 program from its website and the parade of quotes from senior executives promptly stopped. The company did not announce the cancellation of the effort or any reason for a hiatus. It simply went about its business, at least publicly, as though the SR-72 had never existed. In our previous coverage, we posited that this dramatic shift may have been the result of the Pentagon stepping in with classified lines of accounting and a renewed need for secrecy following Putin’s announcement. 

We now know that, behind closed doors, something big was brewing. By the end of the following year, Lockheed Martin had broken ground on the massive new factory that would become Building 648, and the hiring bonanza to staff this new facility had started even earlier than that. 

The SR-72’s growing paper trail

In the second quarter of 2022, Lockheed reported a $225 million pre-tax loss on a classified Aeronautics program that had just completed a comprehensive review. Three months later, however, Lockheed Martin filings indicated that the customer for this effort had signed a “memorandum of agreement” to modify the scope and price of the contract. This implies that there is indeed a contract in place (seemingly a fixed-price incentive-fee contract), and that Lockheed Martin is unlikely to have to swallow these cost overruns on its own. With continued budgetary overruns now reaching $335 million, it stands to reason that the program’s overall budget is significantly more. 

But that’s not the only evidence pointing toward a highly secretive aircraft being developed for the U.S. Air Force. In fact, there’s a fair bit of evidence to suggest that this program has matured beyond development and pre-production tooling, and is likely beginning a full production run. In particular, there’s the construction of a massive new production facility at the Skunk Works headquarters in Palmdale, California, dubbed Building 648 – along with the hiring of thousands of new personnel tasked with building… something inside. 

Construction on Building 648 was completed in August 2021, with Lockheed Martin touting the massive 215,000-foot structure as an “intelligent, flexible factory” aimed at reducing the significant investments of both time and money required to stand up new production lines. This is accomplished, Lockheed Martin explained, through the use of advanced artificial intelligence, augmented reality, and large, broadly capable robots known as Combined Operation: Bolting and Robotic AutoDrill systems, or COBRAs.

As Skunk Works revealed at the time, they had already demonstrated the functionality of these new robots in the production of the technology testbed that would lead to the X-59A Quiet Supersonic Transport testbed, or QueSST, but based on other publicly available information, Skunk Works is up to much more than building one or two technology demonstrators inside Building 648. 

Hiring an army for ‘advanced development programs’

Between February 2018, when the SR-72 went dark, and September 2023, Lockheed Martin increased the size of the advanced development programs unit, a subsidiary of their aeronautics division, by a whopping 75 percent, hiring more than 2,300 new employees over five years, with hundreds of openings still advertised on their careers page. 

There are also statements from Skunk Works officials that highlight that low-rate production of something is underway. 

“I think it’s fair to say that there is low-rate production going on in the Skunk Works,” Skunk Works General Manager John Clark told the press in 2022. “We’ve got our hands in a myriad of activities, so I feel comfortable saying that because you won’t be able to factor in specifically what it might be to then create security problems for me. But yes, there are low-rate production activities going on in Palmdale.”

Clark went on to say that, while the Skunk Works may be renowned for its rapid prototyping capabilities, the secretive organization has always been a manufacturing center for advanced airframes like the SR-71 and F-117, once again emphasizing that his team at Skunk Works wasn’t dedicated solely to fielding exotic prototypes, but high-end operational aircraft as well. 

“I’ve really tried to reinforce that mindset that we do more than just a one-off X-plane,” Clark said. “It has given me a lot more freedom with the aeronautics executive leadership team to let me grow Skunk Works the way that it historically would have been grown.”

Will the SR-72 break cover soon?

In an episode of the Defense & Aerospace Air Power Podcast late last year, Vago Muradian, the editor-in-chief of the Defense & Aerospace Report, brought up the RQ-180 – a high-flying stealth reconnaissance aircraft so secretive the U.S. government has yet to even acknowledge its existence, despite it being photographed in flight several times in recent years. The high-flying RQ-180 (the platform’s actual name is unknown) is expected to replace America’s venerable U-2 Spy Plane, as well as the RQ-4 Global Hawk, in the coming years.

But Muradian didn’t stop there.

“There is another program, however, which is for a much more capable reconnaissance aircraft that is the product of the Skunk Works and it is Lockheed Martin aircraft. There are articles that have already been delivered but that there have been challenges with that program,” he said.

“My understanding is that the program was re-scoped because it is that ambitious a capability that [it] required a little bit of re-scoping in order to be able to get to the next block of aircraft,” Muradian added.

Thus far, there has been no further confirmation of Muradian’s claims, but many see him as a credible source, and his proposed timeline seems to coincide with both the unanticipated costs Lockheed Martin has since had to swallow and what we know about the firm’s expansion. 

Rumors of Lockheed Martin’s SR-72 program may have once been dismissed as nothing more than flights of fancy within the aviation community, but in the years since this effort began, the technology required to make this aircraft fly has gone from verging on science fiction to the sort of thing a plucky group of upstarts can pull off in an industry park. And that’s not hyperbole — as we speak, Atlanta-based startup Hermeus is continuing to ground test its Quarterhorse Mk 1 flying technology demonstrator with the platform’s first true flight test expected to occur any day now. 

This uncrewed aircraft has hypersonic aspirations of its own, and intends to achieve them using a similar approach to propulsion. Hermeus’ Chimera turbine-based combined cycle engine, made up of a J85 turbojet followed by a ramjet, demonstrated its ability to transition from turbojet to ramjet power inside a highspeed wind tunnel nearly two years ago. The company has already begun work on the much larger Chimera 2, which swaps out that small J85 turbojet for a much larger F100 turbofan; notably, one of the engines Lockheed Martin identified as the turbine basis for their own, similar engine design.