Rolls-Royce has ended its involvement in a project by Boom Supersonic to develop a faster-than-sound passenger airliner, leaving unclear the powerplant options available to Boom.

“We are appreciative of Rolls-Royce’s work over the last few years, but it became clear that Rolls’ proposed engine design and legacy business model is not the best option for Overture’s future airline operators or passengers,” Boom said on 7 September.

“Later this year, we will announce our selected engine partner and our transformational approach for reliable, cost-effective and sustainable supersonic flight.”

Overture clouds

Source: Boom Supersonic

Boom this year revised Overture to have four, not two, powerplants

Earlier in the day, news broke that R-R had backed out of the Boom project. “We’ve completed our contract with Boom and delivered various engineering studies for their Overture supersonic programme,” the UK engine manufacturer says. 

”After careful consideration, Rolls-Royce has determined that the commercial aviation supersonic market is not currently a priority for us and, therefore, will not pursue further work on the programme at this time. It has been a pleasure to work with the Boom team and we wish them every success in the future.”

Boom, with offices in Denver, has been developing a supersonic aircraft called Overture that it says will carry up to 80 passengers and cruise at Mach 1.7. It initially intended for Overture to have two engines, but recently changed to a four-engined design.

The company has been targeting first flight of Overture in 2026 and first delivery in 2029.

“Overture remains on track to carry passengers in 2029, and we are looking forward to making our engine announcement later this year,” Boom says.

The company had also said it would fly a demonstrator supersonic aircraft called XB-1 in 2021, though that aircraft’s first flight remains unfulfilled.

News of R-R’s retreat comes as the aerospace industry faces immense pressure to cut carbon emissions.

Supersonic aircraft are less efficient per passenger than subsonic types, though Boom has countered that Overture will burn sustainable aviation fuel, offsetting its carbon footprint to “net zero”. Still, real uncertainty exists about the availability and environmental benefits of such alternative fuels. 

Despite environmental concerns, Boom’s concept has the caught attention of major carriers, including United Airlines and American Airlines, which agreed to purchase the jet.

Boom has also been working to secure more funding for the incredibly expensive work of bringing a new jetliner to market.

Michel Merluzeau, an aerospace analyst with consultancy AIR, describes Boom’s project as an imperfect fit for R-R.

He calls Boom an “expensive and risky endeavour” that faces regulatory hurdles, and says R-R is best served deploying its resources to safer, more-lucrative projects, such as developing engines for the next commercial airliner from Airbus or Boeing.

R-R and Boom disclosed their partnership in 2020. Boom said R-R would “explore” pairing an engine with Overture. The companies would form teams to study various options, including those using existing engine architectures.

“The goal of the new agreement is to work together to identify the propulsion system that would complement Boom’s Overture airframe,” it said in 2020.

R-R has history of making engines for supersonic jets. Decades ago it partnered with Snecma – now Safran Aircraft Engines – to produce the Concorde’s Olympus 593 powerplants.

With R-R out, Boom’s propulsion options for Overture are unclear. The company could potentially attempt to partner with GE Aviation.

That engine maker had been developing its Infinity engine to power a supersonic aircraft under development by a company called Aerion. In May 2021, however, Aerion folded amid financial issues.

GE Aviation did not immediately respond to a request for comment.

Updated with comment from Rolls-Royce.