Blame it on particle accelerators, 114 Mbps-enabled downloads, Hyperloops or the Bugatti Chiron, but fast is becoming faster. Humanity is no longer content to stab the horizon in Aventador SVs and Trains à Grande Vitesse—or, apparently, aircraft that travel below the speed of sound. On February 29, NASA announced it was awarding $20 million to aerospace firm Lockheed Martin to develop a supersonic aircraft prototype, called QuesSST. The gauntlet thrown at the contractor’s space boots: Break the sound barrier without creating the livestock-spooking, window-shattering atmospheric fart known as a boom.
The challenges of boomless supersonic flight have long stuck in NASA’s craw. Engineering firms ultimately have to tackle the headaches of implementation, scale, and commercial viability of a quiet supersonic aircraft, but NASA is the tireless pusher. The agency has spurred many of aviation’s greatest innovations, whether through challenges—like the one seized on by Lockheed Martin—or by developing its own proofs of concept (uh, winglets, anyone?). Indeed, NASA has led on countless aeronautical features that never once left our atmosphere. The agency’s latest challenge suggests that the U.S. is getting serious about commercially viable supersonic flight.
Good intentions, however, have a way of going “boom” in the night.
The Drive caught up with Dr. Bob van der Linden, chairman of the aeronautics department at the National Air and Space Museum and a self-described “total car nut,” to discuss the viability of muted supersonic flight. If the weight of human endeavor has ever pressed down on your shoulders inside the museum’s “Milestones of Flight”hall, it’s thanks in part Dr. van der Linden’s efforts.
The takeaway from our conversation is this: We really should content ourselves with hurtling through space at speeds below 767 mph. Also, Concorde—the best-known commercial supersonic, or SST, ever produced—didn't make much money for its operators. But for background on the good doctor’s reasoning, please read on.
You’ve written about the Bell X-1, the first officially recognized supersonic aircraft. What would a new era for commercially viable supersonic flight mean to you?
I’d love to see it happen. Breaking the sound barrier was amazing, and it ushered in the Supersonic Age. But the problems of flying supersonically are still the same. The fuel costs are enormous. Most supersonic-capable military aircraft fly subsonically for that reason. Yes, the Bell X-1 went supersonic, but that was over desert.
What contributes to sonic booms, and how can the damn things be mitigated?
I’m not an aerodynamicist, but basically, it’s a factor of the size of the aircraft. The footprint of the sonic boom is going to be wide if the aircraft is wide. When you’re breaking windows with the boom, that’s when you’ve got a problem. You don’t have to break a lot of windows to get a public outcry.
So far they haven’t figured out a way to mitigate booms. But if the sonic boom is no longer a problem, it would allow supersonics to fly over land. That was a big problem for Concorde; you were restricted from half of the world’s routes.
Between its start and the first orders being taken, the Concorde’s development lasted about a decade. Is that a reasonable timeline for a boomless, next-gen SST?
The development period of very sophisticated aircraft can last 20 years. It can take decades. Good luck to Lockheed Martin, because NASA has been working on sonic boom mitigation for decades.
What can this new program learn from Concorde?
It’s nothing they wouldn’t know already. Basic things. For one, flying supersonically is very, very expensive. The fuel costs are enormous. To maintain speed, you have to burn a lot of fuel. And the more fuel you have to carry means the less cargo or passengers you can accommodate.
The Concorde could just—just—make it across the Atlantic. Between London and New York, O.K., but between Paris and D.C., it couldn’t carry a full payload. Concorde required one ton of fuel per seat.
But the Concorde came together in the Sixties. Aren’t we, like, smarter now? Can we be more clever about it?
You could argue that the technology’s changed, but the physics haven’t. There’s significant drag as you approach Mach .4, Mach .5. Sure, the drag does go down after you’ve gone supersonic, but it’s still significantly higher than in subsonic flight.
What if a next-gen SST used a less expensive fuel stock than jet or rocket fuel?
Let’s presume you make a huge advancement in powertrain technology for SSTs. Well, what’s stopping you from adapting that to subsonic aircraft, which are already proven to be more efficient and profitable?
It’s NASA’s job to push the envelope, to push companies where they don’t necessarily want to invest. The slope is very steep here, though.
And that’s why Concorde is no more?
Nobody bought it. The state airline of Britain and the state airline of France bought them. For matters of national pride, they had to do it. [Concorde was produced jointly by Britain and France—Ed.]. Pan-Am was one of the first to have options on it, and back then they were all about being on the cutting edge of technology, but as soon as they saw the numbers, they said, ‘Thanks, but no thanks.’
To their credit, the Concorde’s developers knew they were building a far more expensive proposition, and they expected first-class fares to make up that cost. That wasn’t the case. You know, the sole purpose of a commercial aircraft is to make money for the airline that operates it. That easily gets lost in these conversations.
What else is standing in the way of supersonics’ commercial viability?
With the [Boeing] 787 [Dreamliner] and [Airbus] A350—these large, wide-body jets—they’re light, they’re efficient, they’re comfortable, and their seat/mile costs are extremely low. I just don’t see a next-generation SST, even one that could quietly break the sound barrier, competing with them. You’ve got to build 500 or 600 planes just to turn a profit. I just don’t see that ever happening with SSTs.