Boom’s Quest to Make Supersonic Flights a Reality (Again)

Denver-based startup Boom already has orders for its commercial supersonic planes. But is supersonic travel really the future, or best left to nostalgia?
Image may contain Transportation Vehicle Aircraft Airplane Warplane and Landing
Photograph: Boom

ONBOARD MY FIRST plane in well over a year, since the start of the pandemic, I settle into seat 20F of United Airlines 1450, nonstop Newark to Denver on a twin-engine Boeing 737-900. There’s a covalent sensation of nostalgia and novelty, like seeing a familiar place with fresh eyes, rebooting muscle memory grown soft from disuse. As the familiar patter crackles over the PA system—“flight attendants, stand by for all-call and prepare for cross check”—my eyes are drawn to the monitor on the seat back in front of me.

To the rambunctious beat of hip-hop duo WEARETHEGOOD’s “Boom,” the words “SUPERSONIC IS HERE” flash across the screen, followed by the striking image of a blindingly glossy, impossibly svelte white plane (“JOINING THE UNITED FLEET”), with a pronouncedly pointy nose and arcing delta wings undulating backwards and outwards from the midsection. “CUT FLIGHT TIME IN HALF,” the ad continues, with an eye-catching series of itineraries: San Francisco to Tokyo in six hours, Newark to London in three and a half. That latter trip, it’s worth noting, would be shorter than my currently scheduled domestic flight, which, owing to an elongated flight path due to “weather” in the Midwest, ends up being four hours and 32 minutes, at a speed of 900 kph. By the time I was over Nebraska, in a supersonic world I could have been across the Atlantic.

Supersonic is not—as of yet—actually here, despite the seductive geometry and messaging of the advertisement by United, which has signed on to buy 15 planes that have not yet been built (but have generated a fair amount of positive media attention in an otherwise disastrous year). Where it is, at least putatively, is propped up on a platform inside the headquarters of Boom Supersonic, a low-slung building adjacent to Centennial Airport in the suburbs of Denver, Colorado. Inside a sprawling hangar, filled with racks of parts and clusters of desks, overlooked by a banner high on a wall declaring “THE FUTURE IS SUPERSONIC,” rests the XB-1 Supersonic Demonstrator, a two-thirds scale version of the larger plane, named Overture, that Boom hopes will one day take to the skies—at 1.7 times the speed of sound.

When I first meet Blake Scholl, Boom’s cofounder and CEO, on the morning after my subsonic flight to Denver, he tells me I’ve come at a propitious moment. “This is actually a really big week,” he says as we don safety hats and glasses, “because we powered up the airplane for the first time this week. And then fuel goes onboard the airplane for the first time on Sunday. And then we’re just a few weeks away from running the engines.”

At some point down the road, on a test strip in the Mojave Desert, the XB-1 will have a taxi test, and, at some point after that, a flight test. Loaded to the hilt with sensors, it is a virtual flying probe. Scholl predicts that “an enormous amount of learning will come out of this plane.”

Early on—because, as Scholl explains, you “design the cockpit around the pilot”—Boom tapped two test pilots: Bill Shoemaker, a Navy pilot and Stanford University astrophysicist who, prior to coming to Boom, was chief test pilot at Zee Aero, the seminal Larry Page–funded startup working on electric Vertical Takeoff and Landing (VTOL) aircraft; and Chris “Duff“ Guarente, who flew F-22s for the US Air Force and whose previous role was chief test pilot for Scaled Composites, the legendary experimental aircraft company founded by Burt Rutan. “We’ve got a Navy rockstar and an Air Force rockstar,” says Scholl. “They’re going to have to arm wrestle to see who gets to bust the sound barrier.”

There is, of course, nothing new about flying supersonic. US Air Force legend Chuck Yeager did it in 1947, before American households even had color television, comparing it to a “poke through Jell-O,” and there’s an inevitable Back to the Future air about Boom’s enterprise. To the casual observer, the profile of the XB-1 recalls a petite version of the iconic mothership of supersonic flight, the Concorde, one of only two supersonic passenger aircraft to have ever flown (the other being the Soviet Union’s Tupolev Tu-144).

But this, says Scholl, is not your grandfather’s supersonic plane. While the planes of Boom, as the name would indicate, will share with Concorde the signature sound of crossing the sound barrier, in many other ways they will diverge. The most noticeable difference is the absence of the downward-angled nose that was Concorde’s signature visual feature. “That had nothing to do with aerodynamics,” Scholl says. “It was about the ability to see the runway.” Subsequent advances in technology mean that Boom’s pilots will do most of their viewing through a “virtual window”—a high-resolution display powered by what Boom says are thousands of sensors. Similarly, advances in computing power and simulation technology—“virtual wind-tunnels”—mean that while Concorde, Scholl notes, “had about a dozen wind-tunnel tests,” today, “you can do hundreds or even thousands of iterations in simulations.” 

Where Concorde was made out of aluminum alloy, the XB-1 is built from a lighter carbon-fiber composite. Where Concorde employed inefficient afterburners to generate sufficient thrust, Boom has quieter, more efficient turbofan engines at its disposal. And while Concorde burned conventional jet fuel—more than a ton of the stuff just to get to the runway—Boom says its planes will run on 100 percent sustainable aviation fuel (SAF), made from renewable wastes ranging from fatty acids to “forest cover” fuels made from fallen trees, leaves, and other biomass. (While SAF is touted as providing up to an 80 percent reduction in lifecycle carbon emissions—and, as reported in a recent study in the Nature journal Communications Earth and Environment, a 50 to 70 percent reduction in contrail formation, which itself is believed to lead to climate warming—there are real questions about how much of the stuff there will be. As the International Council on Clean Transport notes: “We estimate that there is a resource base to meet approximately 5.5 per cent of the European Union’s projected 2030 jet fuel demand using advanced SAFs.” And that’s the optimistic projection.)

And while only 14 Concordes were ever produced, United has already ordered 15 Overture jets for its fleet. “When we talk about an order,” Scholl says, “what we mean is industry standard terms, including nonrefundable, meaningful upfront cash payments.” Which makes it, he says, “the first true order of supersonic airplanes since the 1970s.”

Blake Scholl, cofounder and CEO of Boom

Photograph: Chris Crisman

THE LAST ERA of supersonic passenger flight ended, yes, with a sonic boom, but also a whimper. By the time the last Concorde, British Airways Flight 002, departed New York’s John F. Kennedy Airport on October 22, 2003, the rarefied market for civilian supersonic air travel had been in retreat. “Nobody will think about whether it was a commercial success or not,” said Lord Sterling, one of the boldfaced names onboard the celebrity-packed final flight. “They will say this is another frontier which the human race has broken through.”

And indeed, despite the air of glamour, the exquisite Raymond Loewy–designed cutlery that Andy Warhol implored passengers to steal, and the fact that, as Lawrence Azerrad notes in his book Supersonic, the plane flew so fast—16 km in the time it took to pour a glass of champagne—that it actually stretched during flight, there was always the lurking sense the Concorde existed simply as proof that it could. That idea came at a huge expense in government subsidies, so much so that it birthed the economic concept known as the “Concorde fallacy,” which, as defined by the Cambridge Dictionary, means: “the idea that you should continue to spend money on a project, product, etc., in order not to waste the money or effort you have already put into it, which may lead to bad decisions.”

Concorde had been the result of a decades-long fever dream of supersonic civilian flight, buoyed by postwar technological and economic optimism and fueled by Cold War competitiveness (the Soviets got there a few months earlier). But the sound barrier was only one constraint. “Because of economic and political factors,” argues Lawrence Benson in his book Quieting the Boom, “developing such an aircraft became more than a purely technological challenge—and thus proved to be in some ways even more of a technological challenge than sending astronauts to the Moon.” NASA, after all, didn’t have to worry about finding paying passengers, or bothering people under its flightpath. Throughout the 1960s, Benson notes, the US Air Force, along with the Federal Aviation Administration, conducted large-scale tests on the effect of sonic booms: on buildings, on people, on incubated chicken eggs. In one test, the National Park Service even tried to use the shock waves of F-106 fighter jets to spark controlled avalanches in Montana. In the end, the FAA banned civil aircraft from traveling faster than Mach 1 over land. Boom, like Concorde, will have to go subsonic over land. But Scholl insists there “are hundreds of routes on the planet where you can give passengers an enormous speed-up flying supersonic over water and high subsonic over land.”

Even after Concorde’s demise, the idea of supersonic civilian flight stayed alive, nurtured by deep-pocketed dreamers. In 2004, Fortune magazine observed that the market was “starting to get excited about a new generation of hot little jets that would warp the very fabric of space-time while meeting noise and environmental regulations.” Brian Foley, an aviation consultant who for many years worked for French aerospace concern Dassault Aviation (which, he says, “looked at supersonic”), says that over the past few decades, two things have remained constant when it comes to civil supersonic transport. “The first is that no one denies there’s a market for supersonic jets,” he says. “The other thing is that manufacturers keep saying it will be within 10 years.” 

But those goalposts, as with self-driving cars, keep getting pushed out. Projects have come and gone; earlier this year, Reno, Nevada–based startup Aerion, founded by billionaire investor Robert Bass and backed by Boeing, gave up on its quest to build an eight-to-10-passenger supersonic business jet. Still in business are a number of rivals, including Boston-based Spike and California-based Exosonic; unlike Boom, they are working on “quiet boom” planes that would theoretically pass regulators’ restrictions and thus be able to fly supersonic over land (another company, Atlanta-based Hermeus, with funding from the US Air Force, is working on an aircraft designed to hit Mach 5). No one is as far along as Boom in terms of having a near-flyable demonstrator. “Progress,” says Foley, “goes at the speed of money.”

And so why might Boom, which Scholl likes to say is “the only private supersonic company on the planet funded all the way through to flight test,” be able to succeed where so many have failed?

Engineers working on the XB-1

Photograph: Chris Crisman

ONE REASON MIGHT be Scholl himself. Supersonic air travel is, he admits as we tour Boom’s facilities, a “non-sequitur on [his] résumé.” His zest for entrepreneurship started in high school, when he built an internet service provider in his parent’s basement. After getting a degree in computer science at Carnegie Mellon University, he started and sold a few companies, and did stints at Amazon and Groupon (of the latter, he jokes: “There’s nothing like working on internet coupons to make you want to work on something you love”).

And that something was aviation. He started flying in college, finally got his license in 2007, and when he sold his first company, he was going to buy an airplane. Instead, he started an airplane company. Like many Silicon Valley executives, he can come across like a walking pitch deck, veering between techy details on afterburners and grand statements tinged with techno-optimism. “If you look back,” he says, “we haven’t had a World War since we’ve had jets.” He deflects very real hurdles—like the fact that a supersonic plane doesn’t have the fuel capacity to go from, say, Sydney to London—with the assured, there’s-an-app-for-that optimism of the serial entrepreneur. “LA to Sydney today is a 15-hour flight,” he says. “We’ll be able to do it in eight, and that includes stopping for fuel in Tahiti.” He compares refueling to a race-car pit stop. “You won’t get out of your seat. The flight attendants will give you a cocktail. You’ll be on the ground for less than a half-hour.” The plane, he notes, will have four high-pressure fueling points: “It’s designed for that use case.” But there’s no denying the passion, the almost boyish enthusiasm, as he walks me through a progression of XB-1 scale models, zeroing in on the minor iteration changes (“the sweep of the wing is too aggressive”) with unreserved zeal.

Scholl argues there’s a sort of “bystander effect” that can happen with innovation. “Sometimes,” he says, “the most obvious problems with the most obvious solutions get ignored” because everyone assumes they must have already been tried. He says his insight was simple: “Let’s give people a nice seat, speed up the flight, let people sleep in their beds at home instead of on an airplane, and let’s make the economics click without any fundamental unobtanium.”

Why wouldn’t a big player like Boeing or Airbus already have done it? He cites business theorist Clayton Christensen’s famous “innovator’s dilemma,” by which incumbent players in established markets make only incremental improvements to a product—until a “disruptor” comes along and changes the category. “If you look at Boeing,” Scholl says, “they’ve got their cash cows, the 777, the 787. If you’re the CEO of Boeing and you can only do one big program every 15 years, why do you want to build a supersonic plane? It’s only going to undermine the business case for the airplanes that are your cash cows.” Boom’s gamble is that all the technological advancements since Concorde—in materials, computer-assisted design, engines, fuel—won’t simply make it Concorde redux. “Concorde was a very strong technological advancement,” says Boom’s senior vice president Brian Durrence. “But it was focused on speed, and speed at all costs.”

For much of its seven-year life, Boom has been running iterations through simulated wind tunnels. “There’s not a straight line on this aircraft,” Scholl says. The art of designing a supersonic jet, he says, is that it’s really two planes in one: fast and efficient like a bullet, but safe and stable for slower speeds and landing. Adding to the complexity, Durrence tells me that the “high transonic phase”—that moment of moving from subsonic to supersonic—is one of the most challenging environments to design for. After endless virtual testing, resulting in changes to the wing contour and the fuselage that Scholl says “aren’t really visible to the human eye,” Boom thinks it is ready. “We feel very calibrated.”

Learning how to build the plane, Scholl says, wasn’t the hard part. “It was learning how to tell the story, finding the right people, building the right culture.” He’s enlisted people like Durrence, a longtime executive at Gulfstream Aerospace, to take up the quest. “I started looking at the amount of runway in front of me,” Durrence says, “and I knew I probably only had one more big aircraft program in me. I really wanted to do something special.” Boom has also partnered with Rolls-Royce, engine supplier for the Concorde. Simon Carlisle, the company’s director of strategy for civil aerospace, praises Boom’s vision and says for a startup to get to the point where it has a demonstrator aircraft to fly represents a “huge achievement.”

Boom test-pilot Bill Shoemaker in front of the XB-1 simulatorPhotograph: Chris Crisman

Reading about supersonic aviation, it’s not uncommon to come across the lament that in the entire history of the passenger jet, average speeds have barely changed (with the footnoted exception of Concorde, of course). It’s not as if jets can’t go faster. Durrence notes that it’s not uncommon for small jets to go supersonic during testing—“just to hit the required points for certification.” Why, I ask Scholl, can’t we simply aim to have commercial jets fly just under the speed of sound, avoiding the boom and still gaining a time advantage? “The juice isn’t worth the squeeze,” he says. One reason, he suggests, is scheduling. Of the roughly six-hour New York to London route, “it’s long enough that people want to fly it overnight as a red eye and sleep on it,” he says. “If you shrink that flight by a little bit, you’ve actually made it worse.” You need a big leap forward, not a little one. But a more overriding issue is fuel consumption. Richard Aboulafia, an aviation consultant with Teal Group, notes that while speeds may not have budged much over the more than half-century of jet transport, “the fuel burn has gone down by 70 per cent.” Boom says it will use sustainable airline fuel—the novel biomass-derived source currently used on less than one percent of commercial flights in the world—but, no matter what, it will be using more of it than it would if it were flying slower (by some five to seven times, according to an estimate from the International Council on Clean Transportation).

The addition of internet connectivity to planes has, argues Aboulafia, changed the meaning of time (and that’s assuming, in this Zoom-driven pandemic age, you’re even flying to begin with). “In Concorde’s day,” he says, “you were a prisoner”—albeit one being fed terrine de foie gras and Château Gruaud Larose Bordeaux. “You got off the plane and went straight to a phone and said, ‘Hey, what’s going on?’” Now, you can be connected throughout. “You have a wonderful office in the sky, and they’re serving you delicious meals”—at least at the front of the plane. “Why are you rushing?” The sentiment is not unfamiliar. 

When I rode the inaugural Newark to Singapore route, then the longest flight in the world, on Singapore Air—in business class—I caught up on films I hadn’t seen, ate Singapore noodles, slept and ate again. I was only dimly aware of the passage of time, certainly not enough to pay a premium to go faster. Which raises the question of how many people would. “Perhaps my greatest frustration is that everyone says Concorde was killed by regulations and the sonic boom,” Aboulafia says. “No, Concorde was killed because there weren’t enough people willing to pay $12,000 roundtrip.”

Scholl counters that time spent on an airplane is a tangible source of consumer pain: “You don’t see any evidence in the market today that people like time on airplanes.” When a direct route is introduced to a market that was previously only served by a connecting flight, fares go up and passenger volumes go up. He does recognize that Concorde, for all its associated glamour, was, as a pure passenger experience, less than optimal. “You’ve got this bird that looks like it’s from the future, but you step on board and your first impression is that this is cramped.” To that end, Boom has enlisted the prominent design firm IDEO to create Overture’s interiors. “We’re doing things like taking the overhead bins out of the airplane,” Scholl says, “so the whole cabin feels more spacious.” The goal, he says, “is that when you leave the airplane, you should feel better than when you got on.” It’s an admittedly enticing thought: arriving somewhere earlier than when you set out, a sort of temporal and metaphysical reset.

The rear of the XB-1, where its three jet engines output enough thrust to push the vehicle to supersonic speed

Photograph: Boom

AS ITS COMPANY name would indicate, the airplanes of Boom, should they ever take to the skies, will produce the eponymous sound associated with the displacement of air-pressure waves—not just when they go supersonic, but along the continuity of their supersonic flight path—greatly constraining where they can fly. Scholl says that overland, Boom will fly 20 percent faster than current jets—just under the boom threshold.

What if they produced no boom, or, more plausibly, a sound that was more akin to the soft closing of a car door? This is the premise of NASA’s X-59 QueSST, a single-seat demonstrator plane currently being built at Lockheed Martin’s Skunk Works in Palmdale, California. As Peter Coen, a mission manager with the program, describes it, it is the culmination of decades’ worth of research, largely theoretical and dating back to the 1950s, oriented around the idea of changing the nature of the sonic boom and thus its aural signature. It’s not so much noise-canceling, he explains, in which headsets create a kind of anti-sound, as it is shifting the shape of the wave that produces the sound. “If you’re quiet enough,” he says, “you can fly overland supersonic.” As Air and Space notes, where the Concorde’s supersonic waves exerted an average of 10 kg per square meter of atmospheric overpressure on the human eardrum, the X-59 comes in at a mere 1.4.

In 2018, NASA carried out two weeks of tests in which F/A-18 Hornet jets, carrying large speakers, flew over Galveston, Texas, producing a simulacrum of what an actual X-59 might sound like. “Nobody’s done a community test for supersonic overflight sound since the 1960s,” Coen says. Some Galvestonians compared the flight noise to a dustbin lorry, others to distant thunder, others said they heard nothing—reinforcing the point that while the physics of sound are a constant, human perception of sound is not.

The plane, after being assembled in Palmdale, is scheduled to be shipped to Fort Worth for structural testing in late 2021; after that, Coen says, it will go back to Palmdale for “final system checkouts.” The first flight tests will happen in 2024, with data from community tests to be sent to the Federal Aviation Administration by 2027. “NASA is not building an airplane,” notes Coen. “We are building a technology solution and something that can contribute to research, trying to understand what it would take to fully open up the market by enabling supersonic travel over land.”

Boom, of course, isn’t waiting for that moment. Back in the hangar, Scholl is talking about the XB-1 as more than a massively instrumented, super sleek assemblage of carbon fiber, but as a vital proof of concept. “There’s two places in the world you can see a civil supersonic airplane: a museum, and right here,” he says. That he treats this as-yet-unrealized ambition as a fait accompli either reflects unfettered optimism and gritty determination, an Icarus-like entrepreneurial hubris, or some measure of both.

Updated 12/26/2021, 3:00 pm EST: A previous version of this story incorrectly stated that British Airways Flight 002 arrived in London earlier than it had departed New York on October 22, 2003. This feat is only possible when flying supersonic from east to west.

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