Key Points and Summary – What happens if the “Son of Blackbird” never leaves the nest? The SR-72 promises something we don’t have: a reusable, hypersonic ISR/strike jet that can cross continents in minutes and hit time-critical targets before they scatter.
-Killing it would save money in a budget already strained by F-35s, B-21s, and NGAD—but it could also stall U.S. leadership in turbine-to-scramjet propulsion, high-temp materials, and rapid mission timelines.
SR-72 Darkstar Image by Lockheed Martin on X.
-Critics counter that modern war prizes magazine depth and survivability, not speed—and that stealthy UAVs and bombers cover most missions.
-The choice is stark: pay now for a niche advantage, or risk ceding it for years.
What If The SR-72 Is Canceled? What Does The US Stand To Lose?
Lockheed Martin’s highly secretive Skunk Works is working on the SR-72, also known as the Son of Blackbird (SOB). Despite going over budget by $335 million, the SOB appears close to entering production.
At least, for now, that’s an educated guess.
The Skunk Works’ SR-72, a Mach 6+ intelligence, surveillance, reconnaissance, and strike aircraft, utilizes advanced turbine-based combined cycle engines, allowing unprecedented speed and global reach within minutes.
The SOB is the successor to the SR-71 Blackbird, which was retired in 1999. New production facilities at the Skunk Works have led many to believe that either production has already begun or will soon begin for the SR-72.
However, there are several arguments against moving forward with the project. Some argue that the US wouldn’t actually lose much if the project were to be shut down.
SR-72 from Lockheed Martin Image
The question then becomes, is the SR-72 a vital, needed asset for the possibility of combat with China and Russia, or is it a program that isn’t as vital for US national security interests?
Many aviation analysts argue that if the SR-72 program were to be canceled, the United States would lose its most advanced and immediate path to a new, reusable hypersonic intelligence, surveillance, reconnaissance (ISR), and strike platform. This would result in significant losses in military capability and technological leadership.
What are the arguments against building the SR-72? And if it is canceled, what kind of capability is lost as a result? Some analysts believe that the SR-72 program “is incoherent.” Is the SR-72 truly needed?
The Enormous Financial Burden
The SR-72’s development and production come with massive, secret costs. With ongoing expenses for other high-priority programs, such as the F-35 and B-21 bomber, funding the SR-72 becomes a challenge.
As Lockheed Martin has already made public, the program is already $335 million in the red. What are other issues that will undoubtedly crop up with a new aircraft?
The Air Force, which already has several new projects underway, including the F-47 stealth Next Generation Air Dominance (NGAD) fighter and the B-21 Raider stealth bomber, and is continuing to fund more F-35 aircraft, could the SR-72 program be cut?
SR-72 Darkstar. Image Credit: Creative Commons.
It Is A Different World Than The SR-71 Operated In
Critics argue that the SR-72 is not well-suited for modern attritional warfare. And trying to recreate the SR-71’s legacy will fail due to the improvements made in air defenses. Cheaper unmanned aerial vehicles (UAVs), such as the RQ-180, and bombers might offer more persistent and cost-effective capabilities.
Technical Challenges With Building a Mach 6+ Airframe
The SR-72 faces significant engineering hurdles, and while Lockheed Martin has stated that it has found answers to the complex combined-cycle engine, substantial hurdles remain to be overcome, including thermal management at hypersonic speeds and maintaining structural integrity.
Some aviation critics argue that the SR-72 could become more of a “vanity project” that risks dangerous escalation without guaranteeing survival against advanced countermeasures. The speed might not be as invincible as claimed, especially with the development of counter-hypersonic technologies.
Is The War The SR-72 Is Designed For One To Avoid?
National Security Journal aviation expert Andrew Latham wrote that the SR-72 is built for a conflict that the US is seeking to avoid, rather than one in which it wants to get involved.
He asserted that the SR-72 is built to fight a war like the one it is designed for: “a short, sharp, high-tech blitz in which speed, surprise, and precision decide the outcome in days.
“But that’s not how peer wars play out anymore. The future is attritional, defined by magazine depth, logistics, and redundancy. The Chinese aren’t going to fold because one hypersonic plane made it to Chongqing and back. If anything, such a platform tends to tempt escalation.
“The SR-72 is a large, fixed-base-dependent aircraft with a massive logistics footprint. In the opening phases of any war with China or Russia, airbases will be under immediate threat. We’ve already seen in Ukraine what modern missile and drone strikes can do to concentrated infrastructure. The SR-72 may never get off the ground.”
Latham’s other argument is a compelling one. If China sees an SR-72 streaking across the sky toward its homeland, it will blur the line between ISR and a first-strike capability. How would they respond? How would the US react in a similar situation?
What Do We Know About the SR-72
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. Although it is strictly a film reference, the “Darkstar” name, used in several articles, is a really cool nickname.
Lockheed, the original developer of the SR-71, proposed an informally named replacement aircraft, the SR-72. The SR-72 was to be an entirely new plane powered by both 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.
But while the SR-72 would be blistering fast and nearly invisible to the naked eye, is the program economically feasible, and even needed? Or is it a throwback Cold War platform that lacks a proper role in the modern air battlefield?
One argument is that many aviation enthusiasts and professionals sometimes get overwhelmed by the sheer speed of what promises to be a fast, sleek, and menacing bird capable of providing intelligence and removing the threat deep inside of China’s A2/D2 defense network.
The Debate Over Speed May Decide Its Fate
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.
A2/AD Defenses Have Vastly Improved
However, the counterargument to this is that speed isn’t the decisive variable in high-end conflict. Today, unlike the Cold War, a Mach 6 aircraft doesn’t guarantee survival.
Hypersonic sensors and interceptors – like Russia’s S-500 or China’s expanding counter-space architecture – can detect and potentially engage even the fastest platforms. And then there’s the problem of thermal signature, which for an SR-72 is expected to be huge.
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.
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, which would allow the aircraft to achieve speeds in excess of Mach 5 or Mach 6. This would protect the aircraft without any stealth features.
During its unparalleled run as the world’s best spy aircraft, 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 refer to as a “turboramjet.” The SOB’s engine will have to be even more powerful to meet the airframe’s expectations.
What Would The US Lose If the Program Is Cut?
Reduced Time-Critical Strike Capability: A high-speed, unmanned SR-72 would provide a rapid and survivable means to conduct time-sensitive strikes on high-value targets deep within hostile territory. The cancellation would remove this “first responder” capability, increasing the time it takes to neutralize threats like mobile missile platforms or command centers before they can be relocated.
Gap in ISR coverage: The SR-72 was conceived as a successor to the legendary SR-71 Blackbird, providing an unparalleled ability to gather intelligence in contested airspace. Canceling the program would leave a gap for a reusable, hypersonic ISR asset. While other programs, such as the RQ-180 stealth UAV, exist, they do not offer the speed and survivability of a hypersonic platform.
Loss of Hypersonic Speed Capability? In the immediate aftermath of the program’s cancellation, we would also lose the opportunity to utilize its hypersonic speed capabilities. However, those capabilities aren’t necessarily lost. Lockheed Martin could still use them on later projects or even to augment existing platforms.
They have already stated that their prototype for the NGAD program, which lost to the F-47 from Boeing, will be used to enhance existing airframes, such as the F-22 and F-35, or, as they likened it, a “super” F-35.
However, the SR-72’s capabilities can also be used as a hypersonic test bed for future aircraft and weapons. The counterargument to this is that if the program is cut, the knowledge gained from its research and development can be lost if a multi-year gap occurs before a similar program is initiated.
The SR-72’s lessons, including advances in propulsion, materials, and digital design, could still augment other aerospace programs; however, losing overall vehicle development would be a significant setback.
The SR-72 is designed to exceed Mach 6; it serves as a valuable testbed for determining what works and what does not at hypersonic speeds. Things that could be tested include aerodynamics, cockpits, construction materials, shapes, and more. If this sounds like Boom Supersonic’s XB-1, it is good because the XB-1 is intended to test new aerodynamics, cockpit technology, construction materials, and more.
The joint Lockheed-Aerojet Rocketdyne engine will be a true game-changer if it works as they have claimed. That could be the basis for several next-generation fighter and bomber aircraft.
Should the US Cancel The SOB?
There are compelling arguments both for and against building the SR-72. Is it a viable aircraft that will enhance the Air Force’s (Space Force?) ability to win in a modern war scenario, or is it just a shiny hood ornament that is living on in the Cold War minds of many?
The technology is available, but is the finished project the solution to the US’s future war scenarios, or is it a high-tech project that is unnecessary in a modern battlefield?
About the Author: Steve Balestrieri
Steve Balestrieri is a National Security Columnist. He served as a US Army Special Forces NCO and Warrant Officer. In addition to writing on defense, 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.
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