Most of us travel subsonically, but that might change before too long—at least for a wealthy few. Last month, the Aerion Corporation announced an impending technological collaboration with Airbus to manufacture and certify the AS2, a supersonic passenger jet.
The company's chairman and principal investor, Robert Bass, called the collaboration a "major step forward for Aerion [that] puts us solidly on track toward our objective of certifying the world's first supersonic business jet in 2021." Among the new airplane's design features, Aerion is touting its use of supersonic natural laminar flow as its main new development.
Getting laminar (uninterrupted and smooth) airflow over an airplane's wing is sort of the holy grail in terms of airplane design. Smooth airflow means your airplane is more aerodynamic, allowing you to fly faster with less fuel.
The problem is, it's nearly impossible to create a wing uniform enough for laminar flow to exist. Wings are riveted together and have control surfaces like ailerons, leading edge slats, and trailing edge flaps. These things interrupt smooth airflow to create small pockets of turbulent air, causing drag that slows down your airplane. When you fly supersonically, that turbulence can become a shockwave, which is more disruptive to your aerodynamics—as well as disruptive to anyone living below a flight path.
The Concorde, the world's first supersonic passenger jet, which debuted in the 1970s and retired in 2003, was designed to be more aerodynamically efficient than other passenger aircraft, which balance aerodynamics with passenger-carrying efficiency. This aircraft featured a slender delta wing and a slim, tubular fuselage, a design decision that took mineralized potential flow theory into consideration. It was, simply, a very aerodynamic design, one that is quite popular in the quest to reduce the booms of supersonic flight.
The Concorde's wing, too, was designed with laminar flow in mind. Between trim controls, flaps, and slats, traditional aircraft can have dozens of moving parts in a wing. The Concorde had just six trailing edge elevons—that is, surface on the rearward part of the wing—that gave its pilot pitch and roll control. It was a very clean design.
The Concorde's delta wing was great for the time, but ultimately limited. The biggest technological development that promised to go beyond the Concorde's wing was the development of designs that could support supersonic natural laminar flow, which would allow air to pass cleanly over a wing at supersonic speeds, but just didn't exist in the 1970s.
But, according to Aerion, the company has figured out one solution to the elusive supersonic natural laminar flow design. It's been a dozen years in the making; between high-speed tests and wind tunnels, the company has says it's developed a large, proprietary database on the new technology. In 2013, a test with NASA yielded the first full-scale wing capable of sustaining supersonic natural laminar flow.
Aerion's wing isn't a delta wing, but it does share the Concorde's smooth and thin profile. It's an unswept but tapered design with sharp leading edges and a slightly curved profile that reduces friction drag by nearly 50 percent. This translates to a total airframe drag reduction of about 20 percent, a large enough reduction to make supersonic flight practical for regional and intercontinental travel, or so Aerion argues.
And of course, there are other aspects of the AS2 that make it a design to be reckoned with. Its composite airframe made of titanium, aluminum, and carbon fiber makes it extremely lightweight, and its long ovoid fuselage with a tapering cross section gives it what engineers call the ideal "fineness ratio" to reduce drag.
The AS2 should also get closer to boomless supersonic flight than anything we've seen in awhile. Any aircraft flying above Mach 1 creates a pressure wave that in turn creates a sonic boom, and generally, the larger the aircraft, the louder the boom. But there's a phenomenon called "Mach cutoff" that affects the volume of a sonic boom.
Depending on atmospheric conditions like temperature and winds, sonic boom sound waves can refract and bounce upwards. Taking advantage of the Mach cutoff phenomenon, the AS2 could potentially fly at supersonic speeds over land in some parts of the world, which previously has been impossible because of noise concerns. According to its design specifications, the AS2 will be able to cruise at Mach 1.4 for almost 5,800 miles.
The Concorde met its demise thanks to a combination of low passenger numbers and high maintenance costs. It will be interesting to see if the developments Aerion promises to bring to the AS2 will spare this aircraft the same fate.
It assuredly won't be cheap, but as it's a business jet targeting the wealthy, it may not have to deal with the same economic realities as even the Concorde did. For a lot of the world's super rich, being able to travel faster than anyone, and doing so in style, is worth any price. It's not hard to see how this plane could revolutionize air travel, but we'll have to wait to see if it can actually take to the skies.