A Rebirth of Supersonic Flight?
50-years ago we flew to the moon. 42-years ago, we flew from New York to Paris
in 3.5-hours. Isn’t it about time we sped up air travel?
Why is it that non-military air travel has stalled at the speed of sound? When the Concorde SST entered commercial service in 1976, the “personal computer” was in its infancy, with Steve Jobs and Steve Wozniak building primitive kits and Bill Gates a few years away from popularizing MS DOS. Today my Apple Watch has more computing power than early PCs, but the best I can do as a passenger in the air is 710-mph in the Gulfstream G650 ER. That’s 100-mph faster than the average commercial plane, but just a bit better than half the speed of the retired Concorde SST.
It’s clear that flying at 1,354-mph wasn’t simply too fast for business travel. So what happened? It was a combination of high cost, noise and politics, capped with a tragic crash during a takeoff in Paris that ended supersonic passenger travel.
Although there’s little mystery in breaking the sound barrier, we’ve done that since the 1950’s, it involves developing an aircraft that can operate in two very different environments. At subsonic speeds, where virtually all commercial and private planes travel, materials, airframe and wing design and engines are optimized with high bypass turbofan design for efficient cruise and low noise. Past Mach One speed (767-mph), the rules change. Instead of bypass, pure thrust is the requirement along with a slippery shape and wing design that performs at all speeds.
Since engines designed for supersonic flight are noisy, especially during takeoff and climb, there’s a limit to available airports. And while sonic boom during flyover is still an issue (supersonic flight is forbidden over most of North America) it can be mitigated by new design, especially in business aircraft.
Then there’s cost. The estimated price tag for two competing business jet designs is $120-million for an aircraft with about the same passenger and payload capability as a $40-million Gulfstream 450. And like the Concorde, you get an airplane that can only operate at supersonic speeds over oceans. Both Reno-based Aerion Supersonic and Boston’s Spike Aerospace are confident that enough business jet flyers, about 36 a year, are willing to pay that premium for faster time travel.
Aerion Supersonic AS2
Aerion appears to have the leadership position in the supersonic business jet field. The company chairman and principal funding source is billionaire Robert Bass, its CEO Brian Barents is a veteran of Learjet, Cessna and Galaxy Aerospace and noted aerodynamicist Dr. Richard Tracy is Chief Technology Officer.
The Aerion team acquired Palo Alto’s Desktop Aero to refine and develop computer design tools to analyze supersonic airflows and entered a joint venture with Airbus to develop its composite structure. More recently, Aerion has partnered with GE for new engines and Lockheed Martin to develop the AS2. The company has booked 50 refundable orders for the new aircraft with an expected in-service date of 2025.
The AS2 is not overly ambitious about performance specifications, but to strike the right balance of fast subsonic speed of Mach 0.95, supersonic cruise speed of Mach 1.4 and what it calls a Boomless Cruise of Mach 1.2. That last specification is planned for flights over land if Aerion can lobby for realistic rule change that cites noise rather than speed standards. The service ceiling is 51,000-feet, high enough to avoid weather, but not too high to seriously impact the ozone layer.
Spike Aerospace S512
Vik Kachoria, a veteran of NASA and GE Aircraft Engines, is Spike Aerospace’s founder and CEO. An MIT Sloan School MBA graduate with a degree in physics and math, Kachoria followed his government and corporate career nurturing technology startups. Kachoria has put a team of aircraft and science veterans together to help design and build Aerion’s supersonic business jet.
The delta wing S512 is a bit more ambitious in its speed specification with a Mach 1.6 cruise at 50,000-feet. Kachoria asserts that the sonic boom from his airplane will be a modest 75 dB under most circumstances, or little more than a hand clap.
The Spake’s most interesting design feature is the “Multiplex Digital Cabin” with large flat panels displaying views of the outside world or presumably turned off when rest or work are needed. It’s a perfectly sound plan from an engineering standpoint, since eliminating double-pane windows designed for high pressure differentials saves weight and adds strength.
I asked Kachoria how he thought passengers would feel about a video cabin. A few Boeing engineers explored the same notion with the 787 and were quickly rebuffed. Vik responded that his business prospects are tech savvy and would embrace the concept. We’ll stay tuned for that outcome.
If all goes well, we’ll return to supersonic civilian flight, at least for the .001% of the world’s population. If it’s successful and changes decades old rules, supersonic might be in all our futures.