Does supersonic transport have a future?

Does supersonic transport have a future?

To make fast planes great again, we need to rethink rules against overland sonic booms

Matthew Yglesias

Jun 9

Last week, United Airlines entered a conditional agreement to buy 15 planes from Boom Supersonic and become the first airline to offer commercial faster-than-sound travel since the Concorde stopped flying in 2003.

The deal is highly provisional. United is buying 15 of Boom’s Overture planes, but the Overture does not exist, per se, at the moment. Boom claims they will be able to deliver them around 2029, but United’s agreement to buy planes is conditional on that actually happening first and the aircraft passing safety tests and such. If it works out, and if the planes prove themselves to be commercially viable as well as technically feasible, United has the option of buying 35 more.

Of course, in the end, it might not amount to anything. But Boom is a pretty exciting company that’s been gaining momentum for years now and this is definitely another step forward for them. It’s exciting in part because fast planes are cool.

But really what makes it interesting is the founder, Blake Scholl. He has a computer science degree from Carnegie Mellon and for most of his career, he was a software guy working for Silicon Valley companies. He left in 2014 to go to Colorado and start Boom with the idea that advances in computer-assisted design made it possible to tackle a big, difficult physical engineering problem in a new way. And fundamentally, that’s the kind of thinking the country needs. We’ve had tremendous progress in the specific zone of computers and internet stuff. But thus far in its history, all that digital technology has been a serious disappointment in terms of raising economy-wide productivity and living standards. Applying digital advances to solve big physical problems is what could change that. But to really make that work, we’re probably going to need to make regulatory changes that say “yes” to progress.

Flight of the Concorde

The Concorde was an impressive technical achievement, but the basic problem is that the operating costs were much too high. It’s true that it would get you to your destination faster than a conventional jet, and that’s worth paying extra for. But the cost in terms of extra fuel was just really, really high.

And once you get into a world of high operating costs, you end up in a compounding series of problems.

A key goal in commercial aviation is not to fly too many empty seats. Ideally, you sell an expensive seat for a lot of money. But failing that, selling it for a little money is better than flying empty. But if you discount your unsold inventory too much, you make people feel like suckers for paying full price. Working this out is hard, and that’s why airlines invest a lot of money in yield management experts and software. But a basic issue is that the higher your operating costs, the thornier all those yield management issues become, because the gap between full price and $0 becomes cavernous.

Another problem with the high operating costs is that even on busy routes — Concorde flew New York to London and New York to Paris — there’s not that much demand for a niche product. So while there are planes departing London that are bound for New York at all kinds of times, there were never a lot of Concorde flights. So depending on your schedule, the super-duper-fast plane might not actually be the most convenient option.

Last but by no means least, while manufacturing planes is expensive, there’s also an enormous cost in developing a new plane type. To be viable, you can’t just sell a few planes — you need to sell lots and lots of planes to amortize your development costs. And with plenty of orders, the plane can be constantly in production so airlines can swap in new models and there are plenty of spare parts around. Once it became clear that there were never going to be a lot of Concordes, the whole thing kind of unspooled.

Boom’s current plans solve some of these problems and give them at least a fighting chance to solve the rest.

The modern landscape

The actual future of aviation turned out not to be faster planes but more fuel-efficient planes. Today’s flights actually tend to go a little slower than the conventional flights of the time when Concorde first launched, because that turned out to be more optimal. Then a lot of work went into building better engines, lighter planes, tweaking wings, etc. to bring fuel costs down.

Beyond that, we’ve had a lot of innovation in seats. It turns out that making the coach product worse was good for business. In a lot of scenarios, it turns out that customers want the cheapest possible way to get from Point A to Point B, never mind how cramped the seats are. Then you can upsell the pickier/richer clientele on “premium economy” seats with more legroom.

But on long-haul flights, the fanciest seats also got better. A transatlantic flight these days is no faster than it was before the Concorde, but international business class turned into an arms race for lay-flat seats and direct aisle access. Concorde’s idea was that a rich businessman would pay extra to get to New York faster. What’s turned out to work is that a rich businessman pays extra to get to New York in a more comfortable hard product.

The basic Boom calculus is that these trends have come together in a way that creates an opportunity:

On the one hand, engineering lessons about fuel efficiency can be applied to supersonic flight to create a vehicle that is much more fuel-economical than the Concorde was — in particular, it won’t use afterburners, which make planes go fast but use tons of fuel.

On the other hand, the arms race to giant seats has made international business class less fuel-efficient. Boom wants to give passengers a nice, armchair-style seat like you see on domestic first class, rather than the giant lay-flat pods that dominate today’s international business class. That seat difference, they hope, will close the operating cost gap.

Basically, the proposition is that you can fly a plane full of armchair-style seats for the same price airlines currently charge for lay-flat seats as long as you can make it a lot faster. Boom’s Overture design is also planned to be smaller than the Concorde — seating between 65 and 88, rather than 92, so that you don’t need as much demand to operate profitably.

On some routes, this makes a lot of sense

Concorde’s best route was London to New York, and the Boom value proposition makes a lot of sense at that distance. The current standard flight time of six and a half hours is enough to be an annoying amount of time to spend on a plane, but really not enough time to take advantage of the modern international business class concept of sleeping in an approximation of a comfy bed.

But most important of all, New York to London is not only suited to that mode of travel, but there’s also a shitload of people flying between those two cities. If you lump Newark in with JFK, it’s the number one route in the world in terms of passenger-kilometers flown, and there are five different airlines flying it.

And yet despite the competition, there’s very little actual differentiation in the product across the various airlines. On that particular route, introducing just a different way to pay a lot of money for an international business flight is very promising.

What’s not really clear to me is how many routes there are that fit that bill. On the Boom website, they list Tokyo to Seattle in 4.5 hours rather than 8.5 as an example. That sounds nice. But there’s just structurally way less Tokyo-Seattle air travel demand than there is on the London-NYC route. That means you’d need a much higher market bar to clear. In a really big market, idiosyncratic variation in preferences is a good enough reason to think some luxury passengers would prefer the supersonic option. In a lower demand market, you really need to be clearly superior, especially because airlines are still going to want to serve economy passengers.

So when introducing a whole new plane technology that is going to have to involve all-premium flights, a big question is how many high-demand routes are there really?

After all, right now most of the world’s busiest city-pairs are short routes in Asia:

Asia gets very high transportation demand because the countries are so densely populated. People had a lot of questions about my “One Billion Americans” idea, but at Korea’s population density, we would have 4.9 billion Americans. Short routes through dense countries are ideal markets for high-speed rail. The reason Seoul to Jeju and Tokyo to Sapporo are the two biggest routes in the world is that Jeju and Sapporo are on islands, so you can’t take the train (though Japan is working on extending the Shinkansen that far).

And at this range, it’s just not clear to me that a faster plane is something anyone is going to want to pay a lot for. Flying from Mumbai to Delhi or from Hanoi to Ho Chi Minh City takes about two hours, and since it takes time to reach maximum cruising speed, you’re just not going to be able to speed it up all that much.

The other thing you see here is that the busiest routes tend to be domestic, and Hong Kong to Taipei is an “exception that proves the rule” sort of situation. But there is an appropriate-distance route out of JFK airport that is even more popular than London — it’s just that it’s currently illegal to fly it with a supersonic plane.

Overland domestic SST is commercially promising

The most popular city pair to fly between in the United States is New York to Los Angeles, which pre-pandemic attracted about 1.8 million annual passengers out of JFK and another 900,000 out of Newark. San Francisco had a million each from Newark and JFK.

The very popular LA-SF route is probably too short for there to be a huge supersonic edge. But the roughly five-and-a-half-hour distance that it takes to go from New York to Los Angeles is just begging for a faster plane. These are intensely competitive routes, and there’s already an arms race among airlines to provide what they call “premium transcontinental” service — i.e., similar products to what you get on international business class — with the huge lie-flat seats and the whole deal. But it’s only a five-and-a-half-hour flight, so it’s not like you’re getting restful sleep no matter what kind of seat you get. And there are planes departing at all times of day when people aren’t going to be sleeping anyway. This is what airlines are offering their highest-paying customers because it’s the best thing they have on hand to offer them, not because it’s actually the most appealing premium product.

What would be most appealing would be to pay extra and in exchange fly faster — a supersonic plane.

The problem is that you’re not allowed to fly a supersonic plane over land ever since a 1973 FAA rule banned them due to sonic boom concerns. Back in the 1950s and 1960s, supersonic transportation (SST) was the subject of active government-funded research in the U.S., U.S.S.R., and Europe. The United States sonic boom testing was done around Oklahoma City, and this 1969 report from the Public Health Service had a largely negative verdict:

The effects of sonic boom on man's physical and mental health are presented. Sonic booms have marked effects on behavior and subjective experience as exemplified by startle reactions and attendant feelings of fear. Such intrusions disrupt sleep, rest and relaxation, and also interfere with communications. These forms of sonic boom interruption generate annoyance which is perceived greater when indoors, and which is judged equal to that experienced by residents living around busy airports. In this regard, indications are that sonic boom disturbances produced by commercial SST aircraft now being designed will not be deemed acceptable by at least 25 percent of the population regardless of habituation. From the psychological viewpoint, greater public acceptance of SST booms will be largely contingent on determining and prescribing overpressure limits below which startle reactions are minimal, posing no problems to performance or risk of personal injury. Of equal importance will be an identification of the limits of sonic boom levels that will allow undisturbed sleep. Special cases such as insomniacs and persons peculiarly sensitive to noise disturbance must be given consideration in defining limits here. Social surveys note that complaints to sonic booms rest on beliefs that property has or can be damaged by such occurrences. Aside from establishing damage threshold levels for sonic boom loads on structures, effective methods for pacifying, if not, altering these beliefs must be developed and used to gain better community acceptance. Other factors important to facilitating community accommodation to sonic booms, both acoustic (e.g., background level) and nonacoustic (e.g., community tolerance to other public irritants), require further investigation. A discussion of the mechanics of sonic shock waves and a comparison of sound pressure levels between sonic boom and some better known sounds are presented.

In 1971, the American SST program was shut down by Congress over the objections of the Nixon administration. At that point, allowing sonic booms over land would create benefits primarily for the Franco-British consortium that made the Concorde, so there was no real political pressure to do it, and in 1973, the FAA adopted the ban.

Flash forward to 2018 and it’s American startups who are most invested in the idea of creating a new generation of SST, and as part of a larger bipartisan bill, Congress directs the FAA to reconsider this rule by the end of 2020. This doesn’t actually happen, though. It’s apparently common for Congress to direct agencies to do this or that and then for the agency not to do it, since the mandates don’t come with extra funding to do the legwork or modify the Administrative Procedure Act in a way that would make it easier to do. So the only way for it to actually get done is if political appointees prioritize the work over something else. What did happen is that on January 6, 2021, when most of us were paying attention to other events, the FAA put out a rule allowing supersonic test flights.

Toward a better sonic boom rule

The actual noisiness of a sonic boom is a function of more than just the speed of the plane; its shape and cruising altitude also make a difference.

The Concorde had various shortcomings as an aircraft design, but it also had a big meta-shortcoming which was that all the design work was done with 1960s technology. That meant that to test anything, you had to build physical objects — there was no way to do computer-assisted design and modeling. Concorde was really pushing the limits of the possible along a number of dimensions — it created lots of heat from friction, and it required an angle of attack so steep that the pilot couldn’t actually see the plane land, which in turn required the kludgy solution of making the nose of the plane droop downward. The people working on this today don’t just have better engines and material to work with, but they have a much cheaper and faster design and testing process. So with more degrees of freedom to try stuff out, they can make quieter planes.

But how much quieter?

This is the problem with the FAA’s current rule. The Concorde generated booms of about 105 decibels, which is almost as loud as a jackhammer. A lawnmower operates in the 85-90 decibel range. During the daytime at least, we tend to consider that an acceptable level of noise for someone to inflict on their neighbors.

The FAA’s current attitude is basically that if you come to them with a plane that’s quieter than the Concorde, they will look at the case for allowing it. But in a paper they did a few years ago for the Mercatus Center, Eli Dourado and Samuel Hammond argue that’s not really how investment or engineering works. If you tell people that a boom of 88 decibels (matching a motorcycle) will be allowed, then that unlocked a lot of financial and engineering resources dedicated to trying to hit that target. If you’re like “well, give it a try and ask me later,” that’s a much more difficult sell. And it’s especially difficult since the incumbent players in airplane manufacturing have a vested interest in not allowing a competing product.

I agree with the basic argument here — developing a domestic market for faster planes is at least as socially valuable as motorcycles and lawnmowers, and we should apply a reasonable daytime regulatory standard. That would unlock the giant LA-NYC and SF-NYC markets as well as a market for business jets. Beyond that, there are no guarantees, but one would hope that competition and learning-by-doing could start to generate cheaper planes and even better designs that would be useful on the many other coast-to-coast routes. Overland SST is also useful in other countries, of course, but America’s geography is genuinely a bit special in that we have a bunch of big cities that are way too far apart to realistically link by train.

Does this matter?

I mostly try to write about issues that I think are very important (or about McDonald’s), and in this case, I’ll admit to you that I’m not sold on the stakes here being super high.

In a lot of ways, the arguments mostly seem symbolic. Kate Aronoff did a piece in The New Republic dumping on the idea of the Boom Overture, ostensibly from an environmental point of view, but really if you read it, just expressing an all-around negative affect toward technology. Obviously, the climate impact of the aviation industry is not great. Aware of that fact, Boom has committed to operating its plans carbon neutrally. In practice, I think that means paying for direct carbon air capture the way that Stripe does. Of course, a big question around direct air capture is what do you do with the CO2 after you capture it, but one leading idea is you make jet fuel out of it. Now is that pledge for real or is it vaporware? It seems kind of vapor-y to me. But compared to what? It’s better than any pledge the big incumbent airlines have made, and it’s not like the world is on the verge of outlawing jet travel and getting around in airships.

After Greta Thunberg sailed across the Atlantic as a kind of low-carbon publicity stunt, she thanked the team that sailed her and said “we can’t require from everyone to rely on people like this to sail you across an ocean, that is absurd.”

I think she’s clearly right. We should put appropriate taxes on the pollution externalities of jet fuel, should invest money in carbon capture and alternative fuels, and as better technology is developed, we should require its use. But the idea that stigmatizing innovation in the aerospace sector will make the climate problems with aviation go away is ridiculous.

It’s just a kind of anti-technology posturing.

Conversely, to me, the biggest stakes in supersonic flight are in some ways the tech-positivity symbolism. One of the most visceral symbols of the slowdown in technological progress is that in the 1970s, we went to the moon and traveled faster than sound, and today we don’t. You can go to the Udvar-Hazy Museum and see the Concorde on display alongside biplanes and all kinds of other things. But the reason we don’t fly biplanes anymore is we built something better. With Concorde, we stopped making progress and it proved uneconomical to keep operating such a small fleet. That’s sad. I don’t think faster airplanes are going to be a huge economic game-changer. But the fact is that we have made progress in engines and progress in materials and progress in computer-assisted design that should allow us to solve the problems that bedeviled Concorde. Then, in the future, people will look at it in the museum and say “this was a cool plane that got superseded by something better.” And that’s how the world should work.

But to get there, we need to realign our regulations. Since Congress has already voted to do this on a bipartisan basis, it shouldn’t be too much of a political lift. It’s more a question of Joe Biden and Pete Buttigieg deciding they want to make a big deal about it and get it prioritized in a world of competing demands. I think it would be in Democrats’ interest to strongly seize the brand of being forward-thinking, pro-technology people, and this would be a good way to do it.

Comment

Share

This post is only for paying subscribers of Slow Boring .

Like & Comment

© 2021 Matthew Yglesias Unsubscribe

548 Market Street PMB 72296, San Francisco, CA 94104

Publish on Substack