Boom Supersonic’s XB-1 demonstrator has broken the sound barrier, marking a major milestone in the effort that hopes to lead to a larger 55-seat supersonic airliner design known as Overture. Overall, the program could have significant implications not only for commercial aviation but also for the military.
The aircraft was flown to a speed of Mach 1.1 by former U.S. Navy aviator and Boom test pilot Tristan “Geppetto” Brandenburg, from the Mojave Air & Space Port, California. For the majority of its flight, the XB-1 was accompanied by two other supersonic jets, an ATAC Mirage F1 flown by A.J. “Face” McFarland, serving as primary safety chase, and a T-38 Talon performing photo chase duties. During the flight, the XB-1 entered the supersonic realm three times, landing safely at Mojave after a flight of a little over 30 minutes duration.
The XB-1, which had previously reached a fastest speed of Mach 0.95, performed its historic sortie in a portion of airspace known as the Bell X-1 Supersonic Corridor, named after the X-1 rocket plane, in which Charles E. “Chuck” Yeager, arguably the world’s most famous test pilot, became the first human to break the sound barrier in October 1947.
The XB-1 becomes the latest supersonic platform to take to the air over ‘Test Flight Valley,’ building on the historic first flights performed here by types including the X-1, the North American X-15, and the Lockheed SR-71 Blackbird.
Ultimately, XB-1 is expected to have a top speed of around Mach 2.2 (1,687.99 miles per hour).
The XB-1, also known as the “Baby Boom,” is a one-third-scale technology demonstrator for the Overture. It made its first flight at Mojave on March 22, 2024, as you can read about here. During that flight, the XB-1 was flown at speeds up to 238 knots (273 mph, or Mach 0.355), achieving an altitude of 7,120 feet. On that occasion, Chief Test Pilot Bill “Doc” Shoemaker was at the controls, while the flight was monitored by “Geppetto” Brandenburg, flying a T-38 Talon chase aircraft.
A video showing the first flight of the XB-1, on March 22, 2024:
Boom Supersonic rolled out the XB-1, which carries the U.S. civil registration code N990XB, on Oct. 7, 2020. The company first said it was developing this demonstrator in November 2016, some eight months after announcing its plans for the Overture.
While we have outlined the key aspects of the XB-1 in the past, the aircraft is 62.6 feet long and its elongated delta-wing planform has a wingspan of 21 feet. It makes extensive use of sophisticated technologies, including carbon-fiber composites, advanced avionics, and digitally optimized aerodynamics.
It also has an unusual propulsion system to propel it into the supersonic regime. This comprises three General Electric J85-15 turbojets, which together provide more than 12,000 pounds of thrust. The widely used J85 also powers, among others, the Northrop F-5 and the T-38. Since the XB-1 was rolled out, another three-engined aircraft has broken cover, the Chinese advanced tailless combat aircraft tentatively known as the J-36.
Compared to the XB-1, the Overture will be 201 feet long and is planned to achieve a cruising speed of Mach 1.7 (1,304 miles per hour) and a maximum speed of Mach 2.2. The company anticipates it will have a maximum range of 4,500 nautical miles.
Achieving the Mach 1 mark is a huge achievement for the company and an important statement of intent for the future Overture supersonic airliner.
Aimed to make supersonic travel more affordable to greater numbers of travelers — a goal in which no other operator has succeeded in the past — the Overture is planned to carry a total of 64-80 passengers. Intended to drastically shorten the duration of transoceanic routes, the aircraft is “designed … to be profitable for airlines at fares similar to first and business class,” the company’s website notes. The last time this kind of performance was available to paying passengers was aboard the Anglo-French Concorde. A seat on this iconic airliner cost multiple times that of an equivalent business-class fare, and it was retired from commercial supersonic flight in late 2003.
The Concorde was preceded into service by the Soviet Tupolev Tu-144, which became the world’s first commercial supersonic transport aircraft, beginning operations in 1975. However, it completed only around 100 commercial flights, with roughly half of them carrying passengers, before being quickly relegated to cargo-carrying duties. It saw out its career as a supersonic research aircraft, including on behalf of NASA.
Boom has claimed in the past that each Overture aircraft will cost $200 million to produce. It further states on its website that “Overture’s order book stands at 130 orders and pre-orders,” with commitments from American Airlines, United Airlines, and Japan Airlines.
Boom says it is slated to roll out the first Overture in 2026, with test flights to commence in 2027, and type certification expected by 2029. All this remains highly ambitious, with plenty more hurdles to negotiate, and we shouldn’t be surprised if that timeline fails to be met.
Outside of the commercial market, potential military applications of the Overture shouldn’t be overlooked.
Since 2020, Boom has been working with the U.S. Air Force with a view to a potential version of the Overture for high-speed executive flight. While moving government officials around at supersonic speed would be a unique and highly prestigious capability, the Overture design also offers potential for the rapid transit of cargo, as well as personnel, capabilities the Air Force has also been eyeing.
In July 2022, Northrop Grumman and Boom announced a collaboration to develop a variant of the Overture specifically for the U.S. and allied military forces. At the time, Boom noted that a military variant would be ideal for “rapid-response missions.”
A pilot’s eye view of XB-1’s tenth test flight, narrated by Chief Flight Test Engineer Nick Sheryka:
“Fitted with specialized capabilities, the aircraft could be used to deliver medical supplies, provide for emergency medical evacuation, or surveil vast areas faster than conventional aircraft,” the company said. “The special mission Overture variant could also be used to coordinate other aircraft and ground assets in a variety of scenarios.”
Since then, there have been more efforts to progress the development of “defense variants” of the Overture. In September 2023, Boom announced the launch of its Defense Advisory Group, building on its collaboration with Northrop Grumman. The group aims to help identify unspecified “national security missions” the aircraft could be used for.
But like the commercial applications of the Overture, the prospect of getting a militarized version off the ground is also fraught with difficulties.
Back in 2017, Lockheed Martin announced that it was working with Aerion to develop the AS2 supersonic business jet — a primarily commercial aircraft that could have military applications. At the time, we outlined the various ways in which its capabilities could be harnessed by the U.S. military, only for Aerion to go out of business in 2021.
Ultimately, despite the undoubted military potential of the Overture — or developments of it — it will be the commercial marketplace where the program succeeds or fails. The history of prior programs demonstrates just how difficult it is to make commercial supersonic flight a reality, especially an affordable one. That, however, remains Boom’s primary aim.
For now, however, it’s very much worth reflecting on Boom Supersonic’s achievement of breaking the sound barrier with its XB-1. Whatever the future has in store for this ambitious program, the exotic test jet is sure to capture imaginations like the supersonic pioneers that came before it.
Contact the author: thomas@thewarzone.com