Supersonic and sustainability are not two words that naturally mesh together. The image of fighter jets screaming across the skies at 1,000 miles per hour is practically the antithesis of carbon reduction efforts on the ground, so the notion that we’ll be hurtling across the Atlantic in supersonic airliners in ten years’ time seems, well, rather 1980s.

The last mass supersonic passenger transport plane to grace our skies was not what one would call sustainable, in any sense of the word. Concorde produced three times more noise, CO2 and NOx than today’s commercial aircraft. It burned over two tonnes of fuel just taxiing from the gate to the runway. And the noise, enough to break windows, made it less than welcome by people living near the airport.

Supersonic transport protest
Photo: Getty Images

As a result, Concorde was often positioned by campaigners as the personification of the fight between environment and technology. Its takeoffs were often attended by well-meaning banner wavers, hoping their ‘ban the boom’ and ‘save the ozone layer’ slogans would tug the heartstrings of just one flyer sitting in the noisy cabin.

But the demand was there. Businesspeople saw fit to shell out five figures for a round trip across the pond, or into Asia. To them, the extra hours to do business, the lack of jetlag and the ability to be home before the pub shut made it all worth the expense. So if the demand was there, why did Concorde fail?

Concorde taking off
The cruising altitude of 60,000 feet was much higher than regular passenger jets. Photo: Getty Images

The problem comes back to a lack of sustainability, and not just in the ‘green’ sense of the word. As well as being incredibly loud, the plane required expensive specialist maintenance, and a lot of fuel to get it from A to B. The crash in 2000 highlighted design flaws that would need rectifying, and the rising oil prices and dwindling passenger traffic following 9/11 combined to make it a thoroughly unsustainable aircraft – financially, environmentally and operationally. The Concorde retired, with no successor… until now.

The next supersonic passenger plane

Clearly a lot has changed since the days of Concorde. Advances in materials, manufacturing and technology mean any successor will be coming to the market much better equipped for the modern age. One company looking to bring supersonic travel back to the masses is Boom, an American startup founded in Denver in 2014.

Boom Supersonic Overture
Photo: Boom Supersonic

The Overture, its first commercial airliner, will seat from 65 – 88 passengers and crew, with a range of 4,250 NM (7,870 km) and a cruise speed of Mach 1.7 – something Boom calls ‘an optimized balance between speed and efficiency’. The XB-1, or Baby Boom, is its testbed, and was rolled out last year with a view to beginning flight testing later this year.

I sat down with Blake Scholl, the founder and CEO of Boom Supersonic, to find out what he plans to do differently to make the Overture a commercial success where Concorde failed. He said,

“I think the world has a little bit of a Concorde hangover. That airplane was not sustainable - we literally don't have it anymore. But there is no reason why high speed flight has to be unsustainable. In fact, what we're going to see in Overture is that in fact the most sustainable airliner is going to be supersonic.”

As aviation faces down its biggest challenge in history – to shake off the image of a polluting, careless, fossil-fueled industry – how can a supersonic airliner possibly lay claim to taking the crown as the world’s greenest plane?

Boom Supersonic Overture
Developed to fly on 100% SAF, Overture promises carbon-neutral flying. Photo: Boom Supersonic

Sustainability strategies

For Scholl, sustainability begins at home. The firm has already committed to becoming carbon neutral, in all areas of its business, by 2025, several years ahead of most other industrial organizations. The company’s recently published Environmental Sustainability Report sets out the roadmap to achieving this, so that the Overture is born from a place that has a demonstrable environmental consciousness.

For the airplane itself, it’s all about embracing the use of sustainable fuels. Scholl explained,

“The overture is the first airliner that's going to run on 100% sustainable aviation fuel for net zero carbon operation. All other airplanes flying today have to blend in fossil fuel, they can't get to net zero. Overture doesn't need those blends. It can run on pure sustainable aviation fuel and that's zero carbon.”

To meet that goal, not only does Boom need to perfect the engine technology for 100% SAF operations, but it also needs to ensure there is a suitable supply of SAF at the potentially hundreds of airports from which the Overture can operate. To stimulate the market, Boom is a member of the Sustainable Aviation Buyers Alliance (SABA), the ASTM International 100% SAF Task Force, and participates in the Roundtable on Sustainable Biomaterials (RSB) and the Commercial Aviation Alternative Fuels Initiative (CAAFI).

Boom Supersonic Overture
Boom is working to stimulate the development of next-generation sustainable fuels. Photo: Boom Supersonic

Scholl knows that, to make SAF a viable option for aircraft like Overture, partnerships are critical. Boom has already announced a partnership with Prometheus, a supplier of next-generation SAF from carbon capture technology – using green electricity to produce liquid fuels using atmospheric carbon - and anticipates more similar partnerships being announced soon. The CEO is convinced in the business case for SAF, explaining,

“When we look closely at the economics, they're incredibly exciting. We’re looking at production energy requirements of 80 to 100 kilowatt hours per gallon of jet fuel, and we've got solar power costs that are dropping below two cents per kilowatt hour in much of the world, so, do the math. Sustainable fuel is ultimately going to cost less to produce than fossil fuel, and that is incredibly exciting.”

If that ambition does play out as Scholl hopes, it would be a massive win for the industry as a whole. Getting SAF to a place where it is not only available but also commercially attractive would be a total game changer for aviation globally, propelling the industry into its next era of connecting the world.

Of course, future operators of the Overture also need to be committed to using 100% SAF. Boom's first customer, United Airlines, has already said it plans to do so on its fleet of 15 aircraft already ordered from the firm.

But what about the boom?

Boom Supersonic is well aware of the downsides of traveling supersonic, and is focused on a better passenger experience. That’s not just for passengers traveling in the plane itself, but also for prospective passengers on the ground, living and working below its flight paths. Scholl noted that Overture already not only meets but actually exceeds the most stringent subsonic standards for community noise, so residents can look forward to the arrival of supersonic travel at their local airport, rather than worrying about broken windowpanes.

Boom Supersonic Overture
The Overture is designed to exceed even the most stringent noise regulations currently imposed on airplanes. Photo: Boom Supersonic

The sonic boom was another reason Concorde won haters. Although there are still some regulatory issues to work around, Boom’s strategy will be to make sonic booms where nobody can hear them – much as Concorde did on its transatlantic routes. That removes that element of noise pollution from the equation, as Blake explained,

“Overland we will fly right under the speed of sound, which still gives us a 20% speed advantage over land. So, 20% faster over land, two times faster over water, and the sonic boom is a non-issue because no one will be able to hear it.”

He noted that, in the long run, he hopes to be able to fly supersonic everywhere. The second iteration of the Overture is targeting the elimination of the sonic boom altogether, although Scholl admits that the technology is not quite there yet.

Boom’s Overture is set to begin flight testing in 2026, and to enter passenger service in 2029. Despite COVID, supply chain issues and the war in Ukraine, Overture remains on target to meet these goals. That’s an impressive achievement and a marker of just how committed to success the team at Boom is.