I flew on Concorde once. I remember its rocket-like climb out of Heathrow, the stillness of cruising at 60,000 feet above the Atlantic, and the dark blue sky out of the window. Then the cabin monitor showing Mach 2, and the thrill of joining an elite flying club, before the nose-elevated descent into New York three and a half hours after take-off.
So, it was with a tingle of nostalgia that I read news of United Airlines placing an order for 15 Overture aircraft being developed by Boom Supersonic in Denver, Colorado. They are intended to enter passenger service as early as 2029: if I wait a few more years, I may be able to relive the excitement of travelling faster than sound.
「We believe in a world where more people can go more places, more often,」 Blake Scholl, Boom』s founder and chief executive, told a Congressional committee in April, and put like that, it sounds good. Having been marooned at home or inside national borders by the pandemic, some might fancy a high-speed jaunt from San Francisco to Tokyo in six hours, instead of 11.
Despite the temptation, I wonder whether supersonic commercial flight will really return, and if it should. Technology has advanced since Concorde』s final commercial passenger flight in 2003, following a fatal accident in Paris in 2000, the September 11, 2001 terrorist attacks and waning demand, but some things are hard to change.
One is that supersonic jets make a lot of noise. I also experienced Concorde from the outside, growing up on the Heathrow flight path in west London and coming to know the deafening roar of its engine afterburners. The Overture will be much quieter than Concorde at subsonic speeds and around airports, but will create a similar sonic boom when in full flight.
Those with military privileges or great wealth can break the sound barrier now. Fighter jets are very loud, as are the rocket craft that are due to take the billionaires Jeff Bezos and Richard Branson to suborbital space. But making such a racket is out of bounds to most: supersonic flights across the US were barred in 1973.
Boom says the Overture will only fly at supersonic speed over oceans, which rather cramps its style. Concorde』s London and Paris to New York routes suit it well, although even those had issues. A morning flight from Europe that arrived in the US early in the day appealed to go-getting executives, but chopping three hours off an overnight return flight held distinctly less appeal.
Crossing the Pacific presents a second challenge for supersonic jets — their limited reach compared with long-range subsonic aircraft. The Overture would have to land for half an hour in Alaska to refuel on its way from San Francisco to Tokyo, and in Tahiti en route from Los Angeles to Sydney. Passengers might be tempted to get off and refuel in Tahiti too.
Supersonic pioneers pin some hope on the US eventually relaxing its ban, at least along some air corridors (Kansas is to test the idea). But it is unthinkable that Europeans would tolerate up to 200 sonic booms per day from air traffic, including jets flying into and out of Heathrow, one scenario for 2035 projected by the International Council on Clean Transportation.
Then there is the broader environmental impact. Supersonic jets tend to be thirsty, and the ICCT estimates that flying on conventional jet fuel, they would emit five to seven times as much carbon dioxide per passenger as comparable subsonic jets. As the airline industry tries to become more ecologically responsible, it risks being carried in the reverse direction.
Scholl assures me that the Overture will burn far less fuel than this, only equivalent to a business class passenger in a conventional jet. It will also be able to fly solely on sustainable aviation fuel, as made by companies such as BP from cooking and waste oil. But all this remains to be proved: Boom』s first test flight of its demonstrator jet will only take place later this year or next.
Aerospace projects of such ambition tend to get delayed, or not to be completed at all. Boeing never made its concept high-speed Sonic Cruiser and Aerion, a US company developing a supersonic business jet, collapsed in May when it ran out of funding. The longest journey is reaching take-off.
Meanwhile, the convenience formerly offered by Concorde to the most elite class of traveller has been partly replicated by long-range business and private jets. For those who can afford it, hopping across the Atlantic on a Gulfstream from a private terminal saves as much time as going supersonic from Heathrow, and is sleeker.
People flying around on many small jets rather than fewer large ones is not very good for the environment, either. But the crisis has encouraged it: the research group WingX expects business jet travel to regain pre-pandemic levels later this year, while airline schedules remain disrupted.
One day, a successor to Concorde might take off again, offering the same speed and excitement, but this time more quietly and sustainably. If that happens, I will take a trip; until then, I have memories.