Back in June 2021, as aviation hobbled with financial losses, carrier closures, irregular connectivity and near-complete loss of revenue, news of supersonic travel’s return shook up the world. Eighteen years after the last supersonic passenger flight had touched down in Bristol’s Filton Airport, United Airlines raised hopes of common travellers influenced for years by a steady diet of Concorde lore. The leading American carrier had signed a $3-billion deal with the start-up Boom Supersonic for 15 passenger aircraft to be made part of the United fleet.
Of course, fans of full-throttle flying have been expecting it for a while. In 2017, Japan Airlines had invested $10 million in Boom for a pre-order that could go up to 20 airplanes. In hot pursuit, Aerion Supersonic announced a 12-seater jet that would reach Mach 1.4, and a few partnerships. In 2020, Virgin Galactic claimed to have halved the existing supersonic flight time with a 19-passenger aircraft that could fly from New York to London in 90 minutes.
United’s investment (the pre-order consignment has one aircraft more than the Concorde’s entire fleet in service), has a provision for 35 more aircraft in addition to the pre-ordered consignment. If this did work out, dreams of flying to the U. K. for a business meeting and being back in New York by evening would come true. The current 11-hour flight from San Francisco to Japan would come down to six hours. Phil Collins could replicate his 1985 mega-concert and perform in North America and Europe on the same day.
There are a few caveats, though. The frenzy of express intercontinental travel aside, any scenario where it becomes realistically possible could potentially conflict with the urgent climate change demands being made of the airline industry. Even as air travel emissions continue to rise unprecedentedly, with the U. S. alone accounting for a fourth of the global total, accommodating the demands of supersonic travel and the objectives of COP26 might end up too tall an order. Supersonic aircraft are thirsty fuel-guzzlers owing to the requirements of speed and cruising altitude, and use several times greater amounts of fuel per passenger.
Whether corporate claims—of net-zero carbon, better aerodynamics for reduced drag and thus improved fuel efficiency, a carbon composite make over an aluminium one, and use of Sustainable Aviation Fuels (SAFs)—will hold, is yet to be seen. At the moment, the engine that Boom needs for its fuel efficiency projections is nowhere in sight.
Much of the scepticism around supersonic travel’s carbon footprint is addressed with the perceived efficacy of SAFs as a one-stop solution. This patchwork of multi-generation biofuels has been proven to cut emissions by 80 per cent, but it’s a bit premature to treat them as a panacea. The costs required to scale production up and the renewable energy needed for the conversion of raw feedstock to liquid fuel will still prove a roadblock.
The supposedly ground-breaking aspect of supersonic flying, this time around, is greater affordability. Carriers have indicated that flight tickets would cost almost the same as business class, thereby opening up the experience and convenience to a greater demographic of travellers. Business travel, which has plummeted to almost nil during the pandemic years, is also expected to be a niche market for supersonic air travel. However, at this stage, there’s no estimating the inflation in green fuel costs a decade from now. Who’s to say what percentage of the engines will eventually run on SAFs to ensure cost recovery and return on investment?
The same magnitude of waiting time and costs is expected for the realisation of usable hydrogen fuel. The ultimate green travel unicorn, hydrogen-powered planes are estimated to be still two decades away, and that is if support from governments follows through in earnest. That is independent of the fact that the costs of hydrogen fuel will mean far fewer trips for travellers, not to mention a significant transformation in aircraft design. The lack of energy density in liquid hydrogen could altogether rule it out for supersonic aircraft, which are known for their sleek and streamlined build.
One of the major pain points with the Concorde was the notorious sonic boom, which modern companies are apparently actively working to iron out, even at the cost of a compromise in speed. In fact, with its work-in-progress X-59 QueSST aircraft, Lockheed Martin claims to have achieved a significant reduction in decibel levels. Much was expected of Aerion’s ambitious ‘boomless cruise’ technology and afterburner-less flight concept, but the company shut down last year after a long struggle with funding.
If aviation wants to go beyond the usual, coast-to-coast transatlantic routes, sonic booms will have to be eliminated or significantly reduced. That is a major factor if considerably large fleets and 65-88-seater planes as part of elaborate supersonic flight services have to be economically viable. Even if concerns around sonic booms are hypothetically circumvented, the availability of sufficient feedstock for biofuel and renewable energy for synthesising the large quantities of SAFs that the larger aviation industry will require, remains a conspicuous impediment. There are also persistent fears about safety, arising mostly from the devastating Air France 4590 crash of 2000, not to mention the short-lived glory of the flashy and faulty Russian Tupolev Tu-144.
A lot needs to be answered before sustainable supersonic travel can cease to be a flight of fancy. For now, travellers are staring optimistically at a black box.
The feature appeared in the print edition of National Geographic Traveller India, January-February 2022.
Prannay Pathak dreams about living out of a suitcase and retiring to the island of Hamneskär to watch films in solitary confinement. He is Assistant Editor (Digital) at National Geographic Traveller India.