Commercial airliners haven’t broken the sound barrier since the Concorde was retired in 2003. But now some aerospace firms hope to usher in a new era of supersonic air travel. Boom Supersonic, for one, plans to build 1,451-mile-per-hour planes that would be able to make the trip from New York to London in 3 hours and 15 minutes starting in 2023.
Other firms aren’t content with supersonic flight. They’re designing so-called hypersonic aircraft capable of flying five times the speed of sound, or around 3,800 miles per hour. These ultra-fast planes would likely first be used by the military for strike and reconnaissance missions. But experts say hypersonic technology could make its way into commercial jets. It would then be possible to fly anywhere on Earth in under three hours.
“It’s certainly within the realm of possibility,” says Dr. Kevin Bowcutt, senior technical fellow and chief scientist of hypersonics for Boeing Research & Technology. “I think we have the technology now where we could actually do it.”
Building a faster jet
It’s no easy task to create a plane that can slice through the air at hypersonic speed.
A few aircraft have flown that fast, including Boeing’s experimental X-51A WaveRider. But all hypersonic planes built so far have been powered by rocket engines or used rocket boosters. Rockets are powerful but heavy because they have to carry the oxygen needed to burn fuel with them. “Rocket motors are great for going to space and powering missiles, but they’re less than ideal for carrying people,” Bowcutt says.
That’s why Boeing and Lockheed Martin are working to develop jet-powered hypersonic aircraft. So far, information about these incredibly fast aircraft is sparse; Lockheed Martin declined to provide details on their plane.
Boeing unveiled a new design earlier this month at a conference in Orlando, Florida. At low speeds for takeoff and landing, the sleek plane would be powered by a turbine engine, much like a regular commercial plane. But for the main portion of flights, it would switch over to an engine called a dual-mode ramjet that can only operate at speeds above Mach 3.
A regular turbine uses whirling fan blades to suck air into the engine and other blades to compress the air so more oxygen can come in contact with the fuel. But this equipment would melt if used at hypersonic speeds. The ramjet instead uses the shockwaves created by traveling at such high speeds to squeeze incoming air.
Flying at such high speeds creates an incredible amount of friction, so a hypersonic aircraft would have to be made out of heat-resistant materials such as a nickel alloy, Bowcutt says.
A hypersonic aircraft using this technology could be available within 10 to 20 years. What would it feel like to fly on one? You’d be pushed back into your seat as the plane accelerates to take off, just as with a regular passenger jet. “The only difference with a hypersonic plane is that the feeling of takeoff would persist for a few minutes until you got up to speed and altitude,” Bowcutt says. “Then it would feel no different than any other airplane.”
You’d be traveling at 90,000 to 100,000 feet. That’s much higher than today’s airliners, which typically fly at altitudes around 35,000 feet, and high enough to see Earth’s curvature below and the blackness of space above. To strengthen the fuselage, the plane might substitute virtual windows for real ones. Cameras mounted on the plane’s exterior would feed video to the virtual windows, recreating what you’d see if you actually looked out of the plane.
A speedy future
Both supersonic and hypersonic flight face many hurdles before they can be used for commercial air travel. One hurdle will be dealing with the environmental impacts of emissions at such high altitudes. Another will be finding enough of a market for this ultra-fast form of travel; to support its supersonic speed, the Concorde demanded four times as much fuel per passenger as other jets, which drove up ticket prices.
When it comes to hypersonic passenger travel, "It's hard for me to see, at least in the next 15-20 years, that it's going to be so cost competitive that it's going to compel the airlines to take a stab at it," John Plueger, president and CEO of Air Lease Corporation, a company that leases aircraft around the world, told CNBC.
And then there’s the sonic boom that is created by aircraft traveling faster than the speed of sound. Sonic booms can startle humans and wildlife on the ground; to avoid that, the Federal Aviation Administration has forbidden supersonic flights over land. The Concorde used to go supersonic only over the ocean, limiting the routes it could fly.
But engineers are hard at work on ways to quiet the sonic boom. NASA is hoping to create a supersonic plane that can fly quietly enough to convince the FAA to lift its ban, opening the door for airlines to offer supersonic commercial flights over land.
The agency selected Lockheed Martin to create the preliminary design for its QueSST (Quiet Supersonic Technology) aircraft. The plane’s shape would scatter the shockwaves produced at intense speeds so they couldn't combine to form a loud sonic boom. Instead they will create a soft thump, like the sound of a neighbor closing their car door.
“If you were at a barbeque and there’s people out there and you’re chatting and there’s potentially some music, you would never hear it,” says Peter Iosifidis, the QueSST program manager at Lockheed Martin.
Hopefully, this will inspire the FAA to update its rules around 2025, he says, allowing supersonic travel to become widespread within a few years.
Supersonic speed would cut many journey times in half. But hypersonic flight could make commercial air travel still faster and more convenient. International day trips around the world could eventually become routine. You could travel from New York to London in about an hour. Or you might wake up and eat lunch in Los Angeles and then spend two hours flying to Tokyo. “You have a meeting, maybe grab a bite to eat, come home and you sleep in your bed,” Bowcutt says.