A new era of superfast flight is taking shape as several planemakers are developing supersonic aircraft that would match the speed of the legendary Concorde—while reducing the supersonic boom that hampered that plane’s success.
“It would be reasonable to expect a first generation of supersonic airliners in the 2030s.” said Mike Mancini, chief financial officer and executive vice president at Aerion—one of the companies in the race.
But this promising new market needs to overcome two significant obstacles: reducing the problem of the sonic boom, and making supersonic flight commercially and environmentally viable—which the Concorde couldn’t do.
Solving the Sonic Boom
When an aircraft reaches Mach 1, the speed of sound, the compression of air around the vehicle creates shockwaves that trail the aircraft like the wake of a boat. When those shockwaves hit the ground they sound like a loud crack—hence the term “sonic boom.”
The Concorde’s boom was so disruptive that the U.S. and Europe implemented regulations limiting the jet to transoceanic flights. The International Council on Clean Transportation (ICCC) estimates that supersonic jets could double the size around airports exposed to significant noise pollution relative to existing commercial aircraft. Canada, the U.S. and several countries in and near Europe would feel frequent sonic booms—up to between 150 and 200 incidents per day.
One solution is to design the aircraft differently to reduce the shockwave. A long nose and highly swept wings could to reduce the impact of the sonic boom by creating weaker shockwaves when the aircraft breaks the sound barrier. NASA’s experimental X-59 prototype, to be built by Lockheed Martin, is taking this approach. Computer models indicate that it would make the boom sound more like closing a car door.
Image courtesy of Spike Aerospace
Spike Aerospace’s S-512 will feature the company’s proprietary Quiet Supersonic Flight technology, which would optimize the vehicle’s aerodynamic design to minimize its sonic boom. The planemaker anticipates the sonic signature of the aircraft will be under 75 PLdb (perceived loudness level) on the ground—making it background noise. The Concorde’s PLdb, by comparison, was 105.
The S-512 is an 18-passenger aircraft, and Spike is planning a 40 to 50-seat variant. At Mach 1.8 it could fly from London to Hong Kong nonstop.
Boom Supersonic is also designing its aircraft to reduce the sonic boom. The XB-1 test aircraft will form the basis of its Overture commercial jet—a 55-seat Mach-2.2 supersonic plane.
Image courtesy of Boom Supersonic
The Overture will feature a carbon fiber composite fuselage, and three General Electric J85-15 engines adapted by Boom for Mach-2.2 operation.
Aerion, on the other hand, is taking a different approach with its AS2: preventing the boom from hitting the ground at all. At speeds up to about Mach 1.2, the plane will deflect the boom upwards off warmer layers of the atmosphere. Aerion is developing cockpit technology to accurately measure atmospheric conditions ahead of the aircraft so it can maintain supersonic speed without rattling the windows in communities it passes over.
The AS2 will begin flight testing in 2023 and enter service in 2025 as a 12-seat business jet while flying at Mach 1.4. Earlier this year Aerion partnered with Boeing, which will provide engineering, manufacturing, flight-test resources and other support.
Green Supersonic Flight?
The other challenge for plane developers need to overcome is the large carbon footprint that supersonic flight creates—and the increasing market and regulatory demand for greener flight options such as electric airplanes.
According to ICCC, supersonic jets are inherently inefficient. Their high speed, limited passenger and cargo space and refueling requirements make them five to seven times as carbon intensive per passenger as conventional aircraft.
The ICCC predicts that a supersonic jet fleet (which it projects to be 2,000 planes by 2035) would emit about 96 million metric tons of CO2 per year—roughly the same as the combined fleets of American, Delta, and Southwest Airlines in 2017.
But advances in aerodynamic design, materials and propulsion show promise for the supersonic flight sector.
Boom seems to be leading the way in this area. The XB-1 and Overture have already been tested with environmentally friendly and sustainable alternative fuels. Boom claims its planes will have operating costs 75 per cent lower than the Concorde’s, making them viable for more than 500 routes across the planet.
Boom is also exploring converting atmospheric CO2 into liquid hydrocarbon and then into fuel.
Another player focusing on green supersonic flight is… China? The country recently unveiled its own design concept for an ultra-fast plane, reportedly being developed by the state-owned China Aeronautical Establishment.
Xu Yue, a deputy chief engineer from the group, said researchers had mastered several core technologies. While details of the plane’s carbon abatement technologies weren’t revealed, China has prioritized developing a low-carbon-footprint supersonic civil aircraft, according to the China Association for Science and Technology.
“We hope that, through our own technological development and continued scientific investment, we can launch our own supersonic civil aircraft prototype in around 2035,” said Xu.
Xu also said the design team was capable of giving precise predictions of the sonic boom.
So the race is on to get a successor to the Concorde into the air--with new entries like Hermeus joining the fray. And now that the FAA has proposed to loosen restrictions on supersonic air travel to open the door to testing the aircraft, that future could be getting closer—at great speed.
“Naturally, there are questions about ‘who’, ‘how’ and ‘when’,” said Boom founder and chief executive officer Blake Scholl. “But there's no longer any discussion about ‘if’.”
Read more about next-generation supersonic aircraft at NUMECA Partners with Boom Supersonic.