The Future of Supersonic Flight

In a hurry? Much faster jets may be here sooner than you think.
A little more than a decade after the Concorde made its last flight, faster-than-sound travel may be poised for a comeback. Several airframers have plans to field supersonic business jets within five to 10 years that will cut flight times by about half or, in one case, much more than that. This benefit, they believe, will have customers happily paying the hefty prices these airplanes will command. Everyone in aviation knows the rocky road to even conventional aircraft certification is littered with designs that fell short of their destination. But there are those with dreams to match their high-flying designs.

Aerion Corporation, thought to be the most likely player to bring a supersonic aircraft to market, has taken a huge financial step toward that goal: it just joined forces with Airbus, corporate successor to the original Anglo-French consortium that developed the Concorde. The partnership “puts us solidly on track toward our objective of certifying the world’s first supersonic business jet in 2021,” says Robert M. Bass, chairman and principal investor of the Reno, Nevada-based company. Bass is also the founder of Oak Hill Capital Partners, an investment unit with a $12 billion portfolio. 

Aerion expects its AS2 jet to be capable of traveling at speeds between Mach 1.4 and 1.6 and to carry up to 12 passengers. While the Concorde’s supersonic design made it impractical to cruise at slower-than-supersonic speeds, Aerion’s strategy calls for the AS2 to be able to fly efficiently at just under Mach 1, allowing it to legally fly over the U.S. and any other country with a ban on supersonic flight. Constructed largely of carbon-fiber composite for low weight, the wings of the AS2 are relatively straight, wide and very thin, to facilitate optimal airflow. The result: reduced drag and fuel consumption, which optimizes range and efficiency. With Aerion providing research, design and software tools and Airbus contributing technical and certification support, the two companies expect to receive certification in 2021 and have the jet in service in 2022. It will sell for an estimated $110 million.

Much earlier in the developmental process, Boston-based Spike Aerospace is working on the Spike S-512, which it expects will carry 12 to 18 passengers. Spike’s innovation is its windowless passenger cabin, with screens embedded in the interior walls that can be used to display images from exterior-mounted cameras. Without the structural complexity of windows, “the range is better, the fuel consumption is less and the manufacturing costs are much lower,” according to Vik Kachoria, Spike’s president and founder. He says the jet will sell for $80 million and fly at Mach 1.6, and he’s hoping the first ones will be ready for buyers in 2020. 

Kachoria—who believes that even faster flight will be possible in the not-too-distant future—thinks supersonic aircraft could change the world. “Investors will be able to develop distant regions and bring them into the current era,” he notes.

North Carolina-based HyperMach is among the most ambitious of the supersonic contenders with its plan for the SonicStar, a jet being designed to fly at speeds up to Mach 4.4. For perspective, consider that the Air Force’s SR-71 Blackbird reconnaissance jet—currently the world’s fastest “airbreathing” manned aircraft—has a top speed of Mach 3.3. 

HyperMach CEO Richard Lugg, who hopes the SonicStar will enter service in 2023, acknowledges that it is coming a little later than others. “We’re kind of in the other realm,” he says. “With the higher Mach numbers, there’s a longer time to mature technology and there’s higher risk and higher cost, but the payoff is higher as well.” Intended to be able to fly from New York to London in all of 71 minutes, the SonicStar is expected to cost $220 million.

One large difference in HyperMach’s design is the engine. For seven years now, the company has been working on what Lugg calls a “revolution in jet propulsion.” The planned HyperMach engine is a hybrid, using both jet fuel and electricity, which Lugg says means the aircraft will be able to fly farther than competitors. Lugg believes that increased distance, the higher Mach speed and a cabin capable of fitting 24 to 36 people will make his airplane a contender.

Some industry experts, however, question whether a market exists for any supersonics. Gulfstream Aerospace floated and then abandoned a supersonic design several years ago, but retains a “modest” research-and-development program dedicated to sonic-boom mitigation, for example. However, a spokesperson for the company notes that it “does not believe there’s a business case for a supersonic business jet at this time due to the ban on supersonic flight over land.”

Even Kachoria of Spike allows that it could take 15 or 20 years to change the paradigm of allowing supersonic flight over land. And Jens Hennig, vice president of operations for the General Aviation Manufacturers Association, notes that the U.S. is clearly a key market for the these aircraft and “it would be difficult to make an investment in a supersonic business jet that can’t be used in the main market of the industry.”   

The Sonic Boom Problem

In a recent NASA press release, Peter Coen, manager of NASA’s High Speed Project, said, “There are three barriers particular to civil supersonic flight: sonic boom, high-altitude emissions and airport noise.” Sonic boom is the biggest barrier.

When an aircraft travels faster than the speed of sound (Mach 1), the sound waves it creates can’t get out of its way, so they coalesce together, creating a rolling “boom” capable of shaking buildings and shattering windows. It was this sonic boom that meant the Concorde was limited to overwater operations and couldn’t overfly many countries at its supersonic cruise speeds, most notably the U.S. But engineers at several companies are experimenting with designs that would reduce the sound to a manageable level. NASA has also been working on aircraft design and believes supersonic flight with an acceptably low sonic boom will be technically and politically possible in less than 10 years.

Not all sonic booms are alike, and a variety of factors determine the makeup of an aircraft’s signature, ranging from the shape and position of the airframe components to the propulsion system’s characteristics. As a result, a boom signature can be shaped to minimize loudness, according to several NASA engineers, who presented their research findings at a conference last June in Atlanta. They noted that most current concepts include a needle-like nose, a sleek fuselage, and a delta wing or highly swept wings.

The companies developing supersonic jets, meanwhile, are finding other ways to quiet the sonic boom. Aerion, for example, says its aircraft might be able to fly as fast as Mach 1.2 over land in much of the world, because a phenomenon known as “Mach cutoff” will prevent its boom from ever reaching the ground. Conditions like temperature and winds determine Mach cutoff, and Aerion’s technology can measure prevailing atmospheric data to calculate the exact speed that will cause the sonic boom to bounce upward off the Earth without ever reaching the ground. Of course, current laws prohibiting all supersonic flight would have to change for the company to put this plan into action.

HyperMach CEO Richard Lugg, meanwhile, says, “We utilize a large amount of electricity to lessen the shockwave at the nose of the plane.” Basically, the company’s plan is to charge the atmosphere in front of the aircraft. It will carry the charge just long enough to change the pressure around the nose, lessening the boom by 60 to 70 percent at Mach 4. HyperMach has plans to test the theory in a few years. 

Alexandra Kay is a New York-based freelance writer.