BBC Inside Science – How is air travel returning to supersonic speeds? – BBC Sounds.

Fifty years ago, on January 22nd, 1976, two Concorde jets simultaneously embarked on their inaugural commercial flights from Paris and London, marking a new era of luxury and speed in air travel. For decades, Concorde stood as the epitome of high-end aviation, a marvel of Anglo-French engineering that could transport passengers across the Atlantic in under three and a half hours, defying the sound barrier. Yet, nearly half that time has passed since the iconic supersonic jet made its final journey, landing for the last time in Bristol, UK, its birthplace, in 2003. This poignant anniversary prompts a crucial question: what is Concorde’s enduring engineering legacy, and will the dream of supersonic speeds ever again become a reality for air travellers?

The BBC Inside Science episode delves into this fascinating return to supersonic ambitions, with presenter Tom Whipple embarking on a journey back aboard the retired Concorde, now a preserved exhibit at Aerospace Bristol. Here, he meets John Britton, Concorde’s former Chief Engineer, whose insights illuminate the groundbreaking innovations that defined the aircraft. Concorde wasn’t just fast; it was a technological leap. Its distinctive delta wing design provided both stability at high speeds and sufficient lift for landing, while its four Rolls-Royce/Snecma Olympus 593 turbojet engines, equipped with afterburners, generated the immense thrust required to push past Mach 2 (twice the speed of sound). The aircraft’s famous ‘droop nose’ allowed pilots improved visibility during take-off and landing while maintaining an aerodynamically sleek profile during supersonic flight. These features, coupled with advanced materials capable of withstanding the extreme temperatures generated by air friction at Mach 2, made Concorde a testament to human ingenuity and a benchmark for aerospace engineering.

However, Concorde’s reign was not without its challenges, ultimately leading to its retirement. Its operational costs were astronomical, largely due to its prodigious fuel consumption. With a capacity of just 100 passengers, the economic model was precarious, catering exclusively to an elite clientele who could afford the premium price for speed. Regulatory hurdles, particularly restrictions on supersonic flight over land due to the disruptive "sonic boom," severely limited its routes to transoceanic crossings. The devastating crash of Air France Flight 4590 in 2000, though attributed to external debris, profoundly impacted public confidence and exacerbated economic pressures. The subsequent downturn in air travel following the 9/11 attacks delivered the final blow, rendering Concorde commercially unviable.

The path back to supersonic travel is fraught with the very engineering complexities that challenged Concorde, as highlighted by Dr. Kshitij Sabnis, a lecturer in Aerospace Engineering at Queen Mary University of London. The primary hurdle remains the sonic boom – the shockwave created when an object moves faster than the speed of sound, which can be heard as a loud thunder-like clap on the ground. Modern research is focused on mitigating this phenomenon, moving beyond simply restricting overland flights. NASA’s X-59 QueSST (Quiet SuperSonic Technology) demonstrator, for instance, is designed with a sleek, elongated fuselage and carefully sculpted surfaces to spread out the shockwaves, aiming to reduce the intense boom to a mere "thump" or even render it imperceptible on the ground. This "low-boom" technology is critical for unlocking overland supersonic routes and expanding market potential.

Beyond the sonic boom, the environmental footprint of supersonic flight presents a significant challenge in an era increasingly focused on sustainability. Supersonic jets inherently burn more fuel per passenger-mile than their subsonic counterparts. Addressing this requires radical advancements in propulsion systems, materials science, and fuel technology. New engine designs must be more efficient, quieter during take-off and landing (another persistent noise concern), and capable of operating with sustainable aviation fuels (SAFs). The aerospace industry’s commitment to net-zero emissions necessitates that any new supersonic aircraft not only perform well but also contribute responsibly to environmental goals. This includes exploring lightweight composite materials that can withstand high temperatures while reducing overall aircraft weight, thereby improving fuel efficiency.

Despite these formidable obstacles, a new generation of aerospace innovators is determined to revive supersonic air travel. Among the most prominent is Blake Scholl, founder and CEO of US start-up Boom Supersonic. Scholl’s vision, as shared in the BBC Inside Science episode, is ambitious: to make supersonic air travel not just a luxury, but genuinely accessible to a broader demographic. His company’s flagship aircraft, the Overture, aims to cruise at Mach 1.7, faster than any commercial aircraft today, but slightly slower than Concorde’s Mach 2.04. This difference in speed is strategic, allowing for design optimisations that enhance fuel efficiency and reduce the sonic boom’s intensity.

Boom Supersonic’s approach to overcoming Concorde’s limitations is multi-faceted. They are focusing on a design that incorporates advanced aerodynamics, new composite materials, and engines optimized for both supersonic performance and quieter subsonic operation near airports. Critically, Boom has committed to making Overture compatible with 100% sustainable aviation fuel (SAF) from day one, aiming to address the environmental concerns head-on. By leveraging modern manufacturing techniques and digital design tools, they hope to achieve a more cost-effective production and operational model compared to Concorde. Their target market includes business travellers and premium leisure passengers, but Scholl’s long-term goal is to bring ticket prices down to a level comparable with today’s business class fares, a significant departure from Concorde’s ultra-luxury pricing.

The re-emergence of supersonic ambition isn’t limited to Boom Supersonic. Other companies like Hermeus, focusing on even higher Mach numbers for defence and executive travel, and Spike Aerospace, with its quieter supersonic jet designs, are also contributing to this burgeoning field. NASA’s ongoing research, particularly with the X-59, plays a pivotal role in providing the foundational data and demonstrating the feasibility of low-boom flight, which could pave the way for updated regulatory frameworks. The Federal Aviation Administration (FAA) and European Union Aviation Safety Agency (EASA) will be crucial in defining the new standards for noise, emissions, and safety that will govern the next generation of supersonic aircraft.

The question of whether supersonic speeds will ever be a reality for air travellers again hinges on a complex interplay of technological breakthroughs, economic viability, and regulatory evolution. Concorde’s engineering legacy provides an invaluable blueprint, offering lessons in both what is possible and what challenges must be overcome. The current wave of innovation, driven by companies like Boom Supersonic and supported by research from institutions like Queen Mary University of London and NASA, suggests a future where faster air travel is not just a nostalgic dream but a tangible goal. The focus on sustainability, noise reduction, and operational efficiency marks a departure from Concorde’s era, reflecting a more environmentally conscious and economically pragmatic approach.

The journey from Concorde’s magnificent, yet ultimately unsustainable, reign to a new era of supersonic flight is a testament to the relentless spirit of scientific inquiry and engineering ambition. It’s a narrative of learning from the past, embracing new technologies, and striving to connect the world faster, smarter, and more responsibly. As the aviation industry looks towards the mid-21st century, the prospect of crossing continents in a fraction of the time, without the drawbacks of the past, moves closer to reality.

To discover more fascinating science content and delve deeper into the cutting edge of research and innovation, listeners are encouraged to visit bbc.co.uk, search for BBC Inside Science, and follow the links to The Open University. This episode, presented by Tom Whipple, produced by Tim Dodd, Kate White, and Clare Salisbury, and edited by Martin Smith, with production coordination by Jana Bennett-Holesworth, serves as a compelling exploration of this exciting frontier.