The Concorde, one of only two faster-than-sound aircraft to ever carry paying passengers, was one of mankind’s greatest aeronautic achievements. For those wealthy enough to afford the five-figure round trip ticket, a journey aboard Concorde was the closest they might get to flying on a rocket. The aircraft still holds the Guinness World Record for fastest commercial flight across the Atlantic, clocking in at a blistering 2 hours, 52 minutes, 59 seconds. (The passengers aboard the 1996 London-to-New York flight only learned of their involvement in aviation history upon landing.)
Today, the Concorde that set that record is sitting idle on Manhattan’s Pier 86 beside the U.S.S. Intrepid, an aircraft carrier turned aviation museum. While the Concorde’s speed and on-board luxury captured the world’s imagination, it couldn’t outrun economics. High maintenance costs and the drop in air travel after September 11, 2001 made flying the Concorde increasingly inefficient from a business perspective. (A fiery June 2000 crash that killed all 109 aboard didn’t help.) Eventually, the airlines that operated Concorde realized they could make more money by putting high-paying passengers in first class on subsonic jetliners. The Concorde last flew in November of 2003.
The Concorde faced problems beyond high costs. Any aircraft traveling faster than the speed of sound creates what’s aptly called a “sonic boom.” The house-ratting noise can be terrifying. When a military jet caused one such boom in New Jersey earlier this year, social media lit up with reports mistaking it for an earthquake or explosion. To avoid this problem, the Concorde was limited to subsonic speeds while flying over land. That meant it could only exercise its prime advantage over other aircraft while traveling on trans-oceanic routes.
Now, NASA Commercial Supersonic Technology Project Manager Peter Coen thinks his team can solve the sonic boom, potentially opening the door for a new era of faster-than-sound commercial travel. NASA in February awarded a roughly $20 million contract to Lockheed Martin for preliminary work on a new supersonic aircraft that could travel quickly and quietly, the holy grail of supersonic aeronautics. TIME spoke with Coen, a 55-year-old Queens native and 33-year NASA veteran, about the project. Our conversation has been edited for length and clarity.
TIME: Tell us about what your team is up to.
Coen: We like to say we’re working on breaking down some of the barriers to successful commercial supersonic flight. Those include environmental barriers, like sonic booms, which we consider the new sound barrier. But we’re also working on takeoff and landing noise, high-altitude emissions . . . we’re working on reducing fuel burn by addressing propulsion and airframe technologies to make the operating economics better.
We’re also working in conjunction with our airspace technology programs to make sure the airspace system is compatible with having fast airplanes trying to use their speed to the maximum extent they can, but also when it comes to takeoff and landing and terminal operations and integrating with the sub-sonic traffic.
Why is it important to make a quieter supersonic jet?
In recent years we’ve been focusing more on the sonic boom effort, because we feel that’s the key barrier to opening the market. You can’t fly supersonic over land, there may be a niche market you could fill with a business jet or something like the Concorde, but if you’re going to really get airline-type operations with a supersonic aircraft, the airlines have to be able to use the aircraft on a variety of routes, and that includes overland routes.
What is Lockheed Martin working on exactly?
We have developed some technology which can change the nature of sonic booms quite significantly. We got to the point where we understand the physics — we’ve developed configurations that, or at least computer studies of configurations, that incorporate that technology. The next step is really to demonstrate it in flight.
There are two reasons for doing that. One is, you need to make sure that the technology works as advertised. We . . . really need to get flight data in the real atmosphere that helps us answer some questions about the interaction between the signal and the atmosphere.
But the really big reason for building a demonstrator aircraft is to get community response data to this low-noise signal. The Federal Aviation Administration and the International Civil Aviation Organization have said they will consider developing a noise standard for supersonic overland flight. But they can’t set a certification level without having community response data. So we did some conceptual studies where we asked, “is it feasible to do a relatively low-cost X-Plane type of program, where you would be able to get that answer?” And the answer from those studies came out “yes.” So we had a competition to do the preliminary design of the X-Plane, and that was awarded to Lockheed.
It has always amazed me that we, humanity, have had the capability of doing supersonic commercial travel for decades, but one of the things that killed it was noise, of all things.
You’ve heard sonic booms? It’s funny, because we’ve demonstrated them for lots of people. There are essentially two camps of people. One that says, “Oh, that’s pretty cool,” and they’re impressed by the technology. And the other camp goes, “Are you kidding me? We can’t live with that.”
Personally I’m a technologist, and I like aircraft. Concorde was a fascinating thing to me. But I truly believe that four or five or more Concorde booms per day in your backyard would really make your life pretty miserable. I don’t think we as technologists can essentially decide that we’re going to affect people’s lives in that way.
If you look back . . . in the 50s, it was technology for technology’s sake. In the 60s, the environmental movement was starting, it was in its infancy, but I really think the idea of sonic boom exposure was a driver that essentially, people began to say, “Wait a minute, just because it’s a good technology for somebody, doesn’t mean it’s a good technology for everybody.” I really think that moving forward, as technologists, we really need to look at things in a more holistic and global sense.
That’s why I’m really excited about what we’ve done. Literally, I’m trying to take “sonic boom” out of my vocabulary. It’s not a boom that we can create from aircraft using this new shaping technology. It’s really kind of a soft thump. We’ve used “heartbeat” in some of our promotional material, and that may be a little bit too much, but I’m quite sure in some circumstances this noise will go completely unnoticed if there’s background noise.
Pretend I have little-to-no understanding of aerodynamics. How would you explain sonic booms to me?
Essentially, sound is a variation in pressure. An aircraft, when it’s flying, is creating a pressure wave that moves out in front of it. I’m not talking about the noise from the jets. I’m just talking about, the air is flowing around the aircraft which causes a change in pressure, which, although you can’t hear it, is a sound. And that sound travels out from the airplane in all directions at the speed of sound.
When you’re flying faster than sound, that pressure can’t get out in front of the airplane. So all pressure changes related to air flowing around anything traveling at supersonic speeds occur as shockwaves, instantaneous pressure changes. So the Concorde, and any supersonic aircraft to date, if you look at the pressure distribution up close to the airplane, you would see all these shockwaves. One from the noise, one from the canopy or windshield, one from the wing, the engine nacelles, almost anything that sticks off the airplane creates a shockwave. They’re all different strengths, and they occur at all different positions along the length of the airplane. Because they’re different strengths, they tend to pile up on each other. They move at slightly different speeds . . . and so in a very short distance from the airplane, all those shockwaves have combined into just two. A strong shock at the nose of the pressure signal, and a strong shock at the tail of the pressure signal. And that travels in all directions, but we’re most interested where it travels down and intersects the ground. And so when that pressure disturbance sweeps over you, you hear that sharp bang bang sound that most of us who have experienced a sonic boom are aware of.
So the trick to taking the annoyance out of sonic booms is to take those shockwaves from coalescing and piling up into those two signals. If you can do that, each little shockwave now is minimized by the long distance that it travels. Instead of being a sharp pulse, it becomes kind of a rounded, more gradual pressure rise. So at the ground, instead of those two sharp rises, you get kind of a gradual pressure increase. If you drew it on a piece of paper, it would look more like a sine wave than an N-wave.
I imagine the challenge would be designing an airplane that accommodates those physics as well as what a paying passenger might expect from a commercial jet.
Precisely. The math was developed in the early 70s. In the 80s and 90s, we started being able to design practical airplane configurations that produced certain types of shaped waveforms on the ground. But in recent times . . . the computers improved, the analysis improved, we had some very innovative people.
[Eventually] we broke free from the original math, which only allowed certain shapes of ground signals, to enable us to say, alright, what we want is the lowest noise signal that we can get. So we evolved our design target and the shape of the airplane at the same time. That does two things. It allows us to achieve a lower noise on the ground, and like you said it allows you to design an airplane that has a low-noise sonic boom, but you can also put a reasonable passenger cabin in it. And it does all the other things that an airplane needs to do well. It can have good takeoff and landing performance, it’s efficient at cruise, it’s stable, it’s safe, it’s structurally viable, and all of those things. That’s really been the breakthrough. We’ve been able to go from a nice mathematical solution, which you really couldn’t design an airplane to meet, to the point where we’ve got a good practical solution for low noise that we can meet with a practical airplane design.
So is this about the human desire to break barriers like the speed of sound, or is it more about practicality for you?
From a practical perspective, people want to spend less time in the air when they’re traveling. They would love to get there faster. I really think that what most people are looking for is just reduced travel time. And whatever technology it takes to enable that for them.
I don’t know if there’s any particular fascination with going faster than sound in the broader sense. For those of us that are interested in the technology, one of the things is, why are we stuck? Why is this — it’s not really a sound barrier anymore, but what is this barrier that has kept us at Mach .85 for the last 40 years, and what does it take to overcome that? But for most people it’s, “Hey, I can get there twice as fast. That’s a real time saver for me. That gives me a much better quality of life if I have to travel for a living, say.”
I’ve read that you’re planning to have a working aircraft using this new design by 2020. Is that accurate?
That’s correct, yes. Right now, Lockheed has been given a contract for preliminary design, which essentially sets the shape of the airplane. We’ll do analysis and wind tunnel testing to verify the performance. We should be through with that by the middle of next year, 2017. Then after that we’ll award another contract, if the program goes forward — there’s always government funding to be considered. But we would award another contract, which would be the final design and the fabrication phase. I like to say we’re looking forward to a first flight at the end of 2019, early 2020. And by 2021, we would be conducting our first community overflight testing.
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