Seventy-one years ago last Sunday, Chuck Yeager strapped on a hand-modified leather football helmet and strapped into his Bell X1, which he flew faster than sound for the first time. While honoring the past, this year’s NBAA-BACE has been abuzz with talk about the future of a supersonic business jet—and maybe more. While there are a few contenders working to bring an SSBJ to market, Aerion with its AS2 has the floor to itself here in Orlando, and has taken advantage of the biggest stage in business aviation to tell its story.
The big news is the engine. Partner GE Aviation has stepped up with a program to design and build its Affinity line—the first purpose-built civil supersonic engine platform in 55 years. Built around the same GE core found on the CFM56 (GE designed it as part of a consortium with Safran), the Affinity will be optimized for efficiency in both subsonic and supersonic flight.
It will be the highest-bypass supersonic engine ever, according to GE. Though that will penalize supersonic range, the new engine will meet Stage 5 noise limits and comply with international emissions standards. “The AS2 will be welcome around the world,” said Aerion v-p of marketing and communications Jeff Miller.
Arguably even bigger news is that Aerion envisions larger and faster follow-on aircraft, though those plans are in very early stages, starting with assessing market needs. The AS2 is a two-zone cabin, and he said that’s as far as Aerion can go with the power it has available.
Larger, faster versions would have to wait for further engine development, said Miller. Aerion envisions a future AS3 with a three-zone cabin, with ultimate plans for a possible airliner-size version. The middle-tier aircraft could fall into an all-first-class airliner configuration. He pointed out that the economics of an airliner are significantly different from those of a business jet: “[Airlines] have to make money.”
Together with its development team—which includes Lockheed Martin, GE Aviation, and Honeywell—Aerion’s next steps involve exploring further Tier 1 suppliers. They need to source the contractors who will build the AS2's fuselage, wings, and control surfaces, as well as major components such as the landing gear.
As an indication of how supersonic fever is spreading throughout the industry, UTC's Aerospace Systems reports it has recently invested more than $100 million in R&D, with a portion dedicated to the areas of noise and high temperatures associated with supersonic flight. The company has a history in supersonics, having been one of the suppliers on the Concorde program. UTAS also has experience with some the technologies in subsonic applications, such as its titanium liquid interface bonding process on its fan case for the Rolls-Royce Trent 900.
“We firmly believe that the next big step in aerospace is to go into supersonics,” said Gary Reynolds, UTAS v-p of regional and engine systems.
While bar patrons at Pancho Barnes’s Happy Bottom Riding Club didn’t seem bothered by sonic booms over the high desert of California’s Muroc air base in 1947, today’s environmental concerns over noise are a formidable hurdle in the path of future supersonic flight. Mach busting is still forbidden over land in the U.S., though the recent five-year FAA reauthorization includes funding for research into the possibility that technology could mitigate booming to acceptable levels.
Strategies for reducing booms include aerodynamic measures that would reshape and disrupt the so-called N-wave generated by the initial shock created by the nose of the jet followed almost immediately by a similar shock wave from the tail. Aerodynamics can reshape the wave to turn the double sharp booms into more of a low rumble, according to the Aerion spokesman.
Up to a certain speed known as Mach cutoff, the N-wave itself does not extend all the way to the ground. Atmospheric conditions also play a role in determining Mach cutoff, and Honeywell is researching “boom mapping” software that could ultimately take the form of a flight deck display similar to weather radar that can show pilots when the boom is getting too low for comfort (5,000 feet above ground level is thought to be a sufficient buffer).
Developing boom-mapping software is dependent on enhancing and refining atmospheric data available to the onboard equipment. That effort involves a combination of increasing the type and amount of amount of data uploaded from external ground- or satellite-based sources, as well as developing more robust onboard sensors.
“Networked and datalinked crowdsourced weather will be [required] for things that go fast," said Carl Esposito, Honeywell Aerospace president of electronic solutions. "We have a lot of the fundamental building blocks, based on [our] military technology.”
Aerion partner Lockheed Martin is also researching boom effects with its X59 program. That effort was specified in the FAA funding bill, and the research would involve establishing a test range in a remote area where a sample of people would be asked to evaluate sonic booms under varying test conditions—atmospheric and aerodynamic.
Developing the first supersonic business jet is a competitive exercise. “It’s a race,” said one Aerion executive. Spike Aerospace is also developing its program, and Boom has designs on the airline industry. Also, some are intrigued that Gulfstream, which had long ago back-burnered its own supersonic development program, recently reserved trademarks on the model names G1100 and G1200, fueling speculation that it could be reviving plans to get back into the Machbuster race.