You are missing an important factor in the baseline here, the cost of time.

Right now, a cheap 7 hour each way round trip between NYC and London is ~500$.

Halve it to 3.5 hours each way with a supersonic plane, saving a total of 7 hours.

Now, the real question is then, what's one hour of your time worth to you or whoever is paying for your flight?

If improvements to subsonic aircrafts bring down the price to 200$ instead of $500, people would still be willing to pay 200$ + 7 * $HOURLY for a faster flight.

Even with a low-ish estimate of $HOURLY = 50, it would make sense to take the supersonic fight if the price was $500, which it could conceivably be brought down to, and the market has already validated to be willing to pay.

That's a reasonable argument for businesspeople, but it doesn't apply for the greater public. Because chances are that except in a minority of situations, they are on holidays and during that saved time they wouldn't be working at all anyways.

People who could perfecty afford a $2,000 plane ticket still fly with $400 ones (as long as they are within reasonable standards), for example because they have a desired budget for a given trip, and the expensive option would blow it away, so they don't mind the extra time.

Even most businesspeople aren't really that hyper-scheduled on trips--especially the ones that can't book whatever class they want.

And to your latter point, I can afford higher-class tickets but it comes back to what I could do with the money instead like a nice dinner. I don't tend to have a budget per se but I do recognize tradeoffs.

Have you ever picked a slightly more expensive nonstop flight instead of one with a layover for a vacation?

This is similar. 3.5 hours vs 7 hours is a pretty good difference.

You can take a 3.5 hours flight in the morning and have energy to see a city the whole day after that. Maybe not after a 7 hour flight unless you are a pretty experienced and motivated traveler who can sleep the entire flight and have the mental energy to enjoy new things after that.

I do actually think you're right, but the counterpoint is that airlines have slowed down all their flights to save money, and no one has come in offering a faster flight in exchange for more money.

Maybe the delta just isn't enough to matter? Or maybe people aren't willing to pay for it.

I’d say the tech isn’t there yet.

Remember we’re still pretty early in the history of aviation.

We know the tech is there. It used to take 45 minutes to fly from LAX to SFO. Now it's 70 minutes. That's not a tech problem, it's a logistics/fuel problem. But if people really valued the difference, they would offer a 45 minute flight for more money.

Or when I leave from Boston to go to the San Francisco, and we leave an hour late but we still arrive on time, it's because they were able to go faster. We certainly have the tech to go faster.

So why can't I buy a BOS->SFO flight that is one hour shorter for more money? Probably because of a lack of willingness to pay.

> Or when I leave from Boston to go to the San Francisco, and we leave an hour late but we still arrive on time, it's because they were able to go faster. We certainly have the tech to go faster.

Catching favorable winds and burning more fuel. It is in the airlines best interest to have the plane in position for the next flight, so they will burn the fuel when they need to. However, committing to a tighter schedule would cause a lot of problems if they were late too often, kinds of problems that means they would make less money than with the current schedule.

> However, committing to a tighter schedule would cause a lot of problems if they were late too often, kinds of problems that means they would make less money than with the current schedule.

There is always a price where this isn't the case. My overall point is that that price is still too high and people aren't willing to pay, and we don't really know if that's the case (but maybe the airlines probably do).

They aren’t going to make that flight time very often so even if it was offered at a premium, they just could not deliver that product consistently.

That depends entirely on how much "slightly more expensive" is. For the vast majority of the travelling public, they'll choose the cheaper option and we know that because that's what they choose already.

If that was the case, most nonstop flights between non-major cities would not exist at all.

Most major airports are at their physical limit in terms of both airfield and gate traffic and are charging extremely high gate fees. I'm not in airline logistics but I would bet my bottom dollar that is the true constraint in having more traffic fly into hubs.

Also, the same plane can now make twice as many revenue flights.

Business passengers aren't out here paying for their own tickets. Their employers are paying for those tickets, so the question is whether or not companies care about the time their salaried employees spend in the air, when those employees can be just as productive on the business-class wifi.

Assuming they're even micro-managing employee productivity to the degree that they really care about working on a plane. Personally, I never purchased plane wi-fi even when I could have expensed it.

Most employers book the most convenient flight for their employees, and not really care much but saving a few hundred dollars.

7 hour to London is actually 10 hours when you factor in the commute to the airport, security, planing, flight, deplaning, shuttle to hotel.

Cutting it to 3.5 hours isn't a 50% overall decrease, because those 3.5 will turn into 6.5 of real time.

So the marginal value of faster flight goes down the shorter the trip is, and these supersonic airplanes can't do the super long Pacific flights because physics.

It's a much smaller niche than is often imagined. But it's still a niche, I guess.

the argument breaks down when the cost of these flights will be at minimum in the range of $10000

Read the article

unrealistic expectations or double decker economy where you can't even sit down. I believe that overvalue their time - there's a lot of things you can do during flights including sleeping and SpaceX providing near gigabit of Ethernet over the Atlantic further reduces the need for these solutions. VR is also being heavily used to review designs 'in person', anyone that genuinely needs to be at the right place at the right time probably has a private jet already.

I might be an outlier as someone who is never in a rush to live their life.

Supersonic is more interesting over the Pacific than the Atlantic. An uncomfortable 7-hour flight becoming a less uncomfortable 4-hour flight isn't really news. A miserable 14-hour flight becoming a tolerable 8-hour flight is, both for passengers and possibly even for the burden on staff. IIRC the old Concorde just didn't have the range, but any improvement in the underlying tech could change that.

I think we’ll eventually have some technology to make this realistic.

Supersonic flights powered by jet/rocket engines might not be it for all we know. IMO we are still pretty early in the history of aviation as a technology.

If you are already mentioning rocket propulsion, then you should know that Gwen Shotwell foresees Starship flying E2E (point to point on Earth) flights with paying passengers, competing with airlines. One hour to anywhere on the planet.

Hopefully we discover some sort of gravity physics/tech that makes chemical rockets obsolete!

I don't see Starship being useful for civilian transport use cases, but for military operations sure! But there's not much to distinguish a starship from a nuke launch during a war, so it remains to be seen whether that risk is worth it.

> One hour to anywhere on the planet.

Anywhere they can take off from, which is a decent distance from a population center. The last (forty?) mile problem bites again.

I can imagine Starship landing on a sea launchpad (in coastal cities), and the last 30 miles can be taken by a speedboat in half an hour. The sea usually isn't as traffic-jammed as land communications, and boats, unlike high-speed trains, don't require that much infrastructure.

Which is nonsense. Not only will rockets never have airplane reliability and safety for basic physics reasons, but that rocket profile looks exactly like an ICBM and nobody wants to let that confusion happen.

Airplane flight trajectories look exactly like a V1 missile, and even modern tomahawks could be made to fly such a profile. Or it could be a subsonic B-1B instead of a Boeing 747. Solutions to IFF have decades of development.

With Starlink and better wifi, the time on board can also be used better. So if you end up on the internet answering mails and so on, you can do that on the plain or in the hotel-room.

> Airlines will always arbitrage toward the lowest energy-per-seat-km for most routes

That's a second order effect from fuel being the primary cost, and thus the primary lever to either make more profit or improve competitivity.

If airlines could triple their profits by doubling their fuel burn they'd happily do that.

Hm... I don't know that I buy your argument, since just as you point out, traditional jets are already very optimized. One would assume there's less slack to pick up.

Traditional jets have a long inventory and regulation cycle but for example retrofitting a A320 to LNG appears to save 20%:

https://repository.tudelft.nl/record/uuid:63b89022-ac68-426d...

Which still puts it behind the 787 let alone the generation that comes next.. But you aren't going to succeed at making any new inventory without every possible efficiency improvement to drive sales and retirement of older inventory.

Fuel is a huge component of the cost of operating an airline, sometimes the largest component. LNG is a much cheaper fuel, so I can see it being adopted for mainstream aviation eventually. Existing jets could technically be converted, though the conservative nature of aviation would demand many years of testing before use on commercial flights.

It's also a pathway to incremental decarbonizing of aviation. LNG releases less CO2 per unit energy than oil, and methane can be produced biologically or synthetically which offers a path to total (net) decarbonization.

> Even if fossil LNG is used, it releases less CO2 per unit energy.

However released methane has a significantly worse greenhouse effect than CO2 (80x over 20 years, 28 over 100, 8 over 500 — this decreases because methane has an atmospheric lifetime of 12 years and decays to CO2). So leakage in the LNG chain is a massive problem.

Jet engines don’t release the methane, they burn it, and they’re very efficient. And jets don’t leak fuel, that would be very hazardous.

LNG is not a nice liquid at room temp, so more use means more in transit and more complicated supply chains, meaning more leaks.

Right, but are leakage rates high enough to make this a concern? Every methane molecule leaked is a methane molecule not burnt, so there's already a strong profit maximisation incentive to leak as little as possible (even before considering loftier goals like workplace safety or externally imposed regulation).

> Right, but are leakage rates high enough to make this a concern?

According to a recent IEA report, 30% of the LMG supply chain’s greenhouse impact is methane leaks.

> there's already a strong profit maximisation incentive to leak as little as possible

That runs against the stronger profit maximisation incentive of doing as little maintenance and being as cheap as possible.

A major difference is: there is an economic incentive to not leak methane since a leak is wasted fuel, while the economic incentive for CO2 is to make more of it.

> A major difference is: there is an economic incentive to not leak methane since a leak is wasted fuel

That economic incentive only goes so far given the entire point of the discussion: LNG is cheap. Per the IEA's recent "Assessing Emissions from LNG Supply and Abatement Options":

> Our analysis estimates total GHG emissions from the LNG supply chain are around 350 million tonnes of carbon dioxide equivalent (Mt CO2-eq) (this excludes emissions from combustion of the natural gas at the point of use). Around 70% of this is in the form of CO2 emissions which are either combusted or vented, and the remaining 30% is methane that escapes, unburnt, into the atmosphere.

> ...

> Globally, the average GHG emissions intensity of delivered LNG is just under 20 g CO2-eq/MJ, compared with an average of 12 g CO2/MJ for natural gas supply overall.

I agree with your market analysis. Private jets are often referred to as "time machines" given how much time HNW / exec travelers can save. There's a market segment that's willing to pay a high premium for reduced travel time.

For most of my trips, a huge % of the travel time is outside the actual flight time. Trip to the airport, security, boarding, waiting to take off, and reverse on the other side (with addition of potentially getting a rental car). This can be solved without supersonic solutions (e.g. flying private), but adoption is low for business travel – is it too expensive?

Separately, I wonder if a lot of the demand is also obviated by in-air wifi.

> adoption is low for business travel – is it too expensive

Yes. Most companies won't even spring for business/first class, which is 10-20% the cost of a charter. Unless your time is both limited and worth 4 digits per hour, it's not worth it.

You might also look at “semi-private” solutions like JSX, if they go where you want to go. Should significantly cut down on the time outside of the flight itself.

Private jets don't go faster. They can just land closer to your destination and make you skip all the annoying airport stuff.

Aeronautical engineering isn't that linear. A technology suited to one application may not be helpful in another. It's one of those "hardware is hard" fields.

Want to reduce the time it takes to get somewhere? Reduce the security circus at airports. This will cut off way more of the travel time for the majority of flights, wothout the downsides of supersonic planes.

You're going to have some security in any case and have since at least the 1970s. And it typically takes me <10 minutes even if I allow some extra time for the potential that it could be longer if it rarely is with pre-check.

Yes but compare it to trains or busses. If I want to take the train/bus I make sure I am at the station 10 minutes before the vehicle departs.

In my experience the good time to arrive before a flight (with luggage to check in) is roughly 1 hour before (and this nearly wasn't enough in some cases).

If we talk about a short flight that can add more than 50% to the flight duration on the ground for (1) putting the luggage somewhere, (2) going through the security funnel and (3) getting to the plane.

Sure I get why things are shaped the way they are, but if I wanted to cut travel time I would first have a long deep look at that.

If you are flying to/from popular destination like Europe in August, you can stuck for two hours just in the luggage drop queue. Extra hour for security check queue and one more for border/customs check queue. Another 20 minutes just to walk to the gate.

Depends on the airport and your luck, of course.

I admit I just avoid Europe at that time of year, although I'd note that Eurostar from the UK to the Continent can be pretty bad too at any time of the year.

TSA in the US is a jobs program

And even then, it is only so premium. As you could have a speedy economy seat on the Concorde or a lie flat bed on a widebody by the time Concorde left service. The speed benefit largely goes away if I can travel while sleeping.

Halving travel times would be really good, the problem is that supersonic never had the range to make the difference meaningful.

JFK-London in 3 hours vs 6 is pretty tolerable if you’re more comfortable for the 6 hours. SFO to Shanghai in 7 hours vs 14 would be a lot more compelling but Concorde could not do transpacific range.

That's the just flight time, but you've also got travel to/from the airport, parking, maybe shuttle bus/monorail, and checking/security/wait time at the airport as well.

So, add an hour for door-door travel to airport, and 2-hr before flight check-in, and now the comparison isn't 3 vs 6hr but 9 vs 12hr, which doesn't sound so worthwhile, although no doubt there are customers for it.

For longer flights it'd be much more attractive, but this is never going to be an affordable service for the masses.

A service where your limo drives out to the aircraft, with all searches and paperwork pre-done, would have about the same time gain as going Mach 1.7 vs. Mach 0.85.

Underrated observation. The low-hanging fruit is all in the office/home-to-takeoff and touchdown-to-office/home blocks on each end, not the time in the air. The commute, checkin, security, airport transit, boarding, and taxiing are the time-sinks worth optimizing.

That's a real service. Some airports, including LAX and London Heathrow, allow a "tarmac transfer", where the limo goes directly to the plane. [1][2] Cost is $200 to $1000. That could save an hour or more at each end.

VIP Terminal Access: Skip the standard queues and enter exclusive VIP terminals where you’ll receive expedited passport control, security checks, and personalized services, all while enjoying luxury amenities. Avoid long security lines with expedited security processing, ensuring you spend minimal time in the airport.

[1] https://limossist.com/tarmac-transfers/

[2] https://airssist.com/airport-tarmac-transfer-service/

private jets already solve these problems.

Which already is a bad signal for the article's argument. We already have a way to significantly reduce that travel time and it's a niche.

Could Boom Supersonic or whoever actually survive selling only to a hundred Taylor Swifts? How are they going to keep the lights on for the 30 years those jets fully saturate the market?

And probably fewer regulatory hurdles (and I don't mean that because they wouldn't be considerable...)

But for the private jet market, the reduction would be huge. They're already paying a premium to save time. The top end will pay an even larger premium to save even more time.

I agree with you that for commercial, anything other than super long haul (which is technically very hard), the time saving advantages are much less compelling.

I actually prefer a 10+ hrs business class flight over a 6-7 hrs flight. At least you can get a full night of sleep

Depends on the time zone change. From Europe to with Africa sure a 12 hour figggt is great. If I travel business London to singapore i get far worse jet lag than if I fly via the Middle East and break my journey for a few hours.

Past like hour 12 it becomes really draining. I used to fly JFK to HKG and that was an ordeal; I can’t imagine the newer super long haul like London to Perth.

Cutting 22 hours Sydney to London to 12 would make a big difference though.

There's no real way to make that much time on a plane bearable even if you had a lie flat bed: that's just a ton of time in the air.

Australian international travel would be the premier market if you wanted to travel supersonic (also our coastal cities mean most departures could accelerate immediately).

The irony is that supersonic jets don't have the range to realize the time savings over such long routes.

Having done Dallas<>Sydney a few times, going from 17 hours to ~8.5 hours would be huge.

Highly depends on the person. Over 6 feet tall with screws and rods holding my spine together, even a lie flat is not very comfortable, and not having to spend my first day or two at my destination decompressing before I actually enjoy the trip would be pretty valuable to me. The only way to achieve that is less travel time, but even so I'm not sure reducing the time in air would be enough when you add in travel to and from the airport, plus taxi time on the runway. It wouldn't be nothing, though, and I'd definitely pay for it if it made a difference.

Problem is broad market trends don't care about me personally. There have to be a lot of people like me with both sufficient injuries and sufficient money and there probably are not.

Some planes used to have lounges and bars and such.

Would maybe have helped? I know I'd pay more for that.

Some planes still do e.g. Emirates A380 has a bar, Qantas' has a lounge (though apparently it's not very good).

Is it actually not very good, or did you read an online review by someone who got miffed for some petty reason so they're magnifying the tiniest things?

That is not quite true. The advantages of LNG are much more important for high supersonic jets (Mach 2.5 and higher) than for subsonic jets. There are disadvantages too, and they are quite significant for all jets, but altogether the tradeoff is worth it at high speed long endurance supersonic jets.

Here's why. LNG offers 2 main benefits. The first is the higher energy density (53.6 MJ/kg vs 43 MJ/kg, so 25% more [1]). Airplanes are subject to the rocket equation, even if they are not rockets. The rocket equation says that the mass of the fueled vehicle is the mass of the vehicle at the end of the trip times the exponential of delta-v divided by the exhaust velocity. For airplanes, it is not exhaust velocity, but "effective exhaust velocity", because they borrow a lot of reaction mass from the atmosphere (the air used as oxidizer, and more importantly, the bypass air). The effective exhaust velocity is very high for subsonic airplanes, and much lower for high supersonic airplanes. The delta-v for subsonic airplanes is lower than the delta-v for supersonic airplanes because of the lower drag (although not as much lower as one would expect, because they need a higher attack angle). Overall, the benefit from the high energy density LNG is much more pronounced for high supersonic jets.

The second benefit is the use of the cryogenic LNG to cool off the engine. For very high speed engines, this is huge. So huge that the famous (but never materialized) SABRE engine was supposed to use liquid hydrogen, which is stored at much lower temperatures.

The disadvantage of LNG is, surprisingly, not the need for cryogenic storage. It is the lower volumetric energy density. It is 22% lower than that of jet fuel. The rocket equation does not care about volumes, only about mass, but larger volumes means bigger airplanes, so more drag.

So, for subsonic airplanes the advantages of LNG are not all that important, while the bulkier tanks are a pretty big downside. For high supersonic jets, the advantages of LNG are so high that they simply open up possibilities that are not there with jet fuel. The fact that the LNG is cheaper is a nice thing to have, but it's really not that important, since the economics of high supersonic jets are more impacted by the construction cost and very high maintenance cost than by the fuel cost.

[1] https://en.wikipedia.org/wiki/Energy_density#Chemical_reacti...

Are you sure the numbers are correct?

Wikipedia lists LNG as 53.6 MJ/kg and 22.2 MJ/L and jet fuel as 43MJ/kg and 35MJ/L.

53.6 / 43 = 1.247

22.2 / 35 = 0.634

Energy density by mass is higher than jet fuel. But it is higher by less than jet fuel's energy density by volume is higher than LNG. And LNG requires heavier tanks.

So all in all, if it's not absolutely needed because of the cooling advantages, LNG can store less energy in the fuel tanks.

You are absolutely right. My 22% was a mistake, the correct number is indeed 36.5% lower volumetric energy density. But that strengthens my argument, doesn't it?

yes i agree with you on it being unfeasible for most applications.

> Historically, faster transport doesn’t replace slower transport wholesale; it creates a premium tier while pushing the mass market down to a lower cost/energy equilibrium.

If that were true, we’d all be taking trains and boats everywhere. We aren’t.

The difference between a supersonic jet and and a subsonic jet is about 2x. Between NY and London that's a 3.5 hour flight vs a 7 hour flight (plus the overhead of security, traveling to and from the airport, boarding, taxiing, etc. which brings down the proportional cost).

By comparison, a boat would take 7-8 days. The disparity in time saved between supersonic and subsonic flight is pretty trivial in comparison to the time saved between a boat and a subsonic plane.

Presumably there are no flights from Paris to Munich then?

There are. A flight is about an hour and a half, a train is about 5 hours. Far more people fly between the two every day than take a train.

A 5x disparity is still a lot more than a 2x disparity. In fact, considerably less than 2x given the overhead time of traveling to the airport, security, boarding, etc.

How many people would pay 8x the ticket price for a 45 minute flight from Paris to Munich (The Concorde was ~8x the ticket price of economy subsonic flight tickets)?

Isn't the flight cheaper as well?

Surprisingly, at least in theory, and probably in practice with better technology, supersonic travel can be as efficient or even more efficient than subsonic flight. Supersonic travel opens up higher altitudes, higher altitudes means less air resistance.

The ultra high altitudes of LEO satellites showcase the steelman example, traveling effortlessly through the vanishingly thin atmosphere at hypersonic speeds with extreme efficiency even though the fuel expenditure to get them there was high.

For more reasonable hypersonic travel, at 100k feet, the “wind” force at 3375mph is only as much as you would feel at 400 mph at sea level… so you can exert the force needed to fly at 400mph, but for that same energy you are going 3375mph.

Of course there is a lot of tech needed to take advantage of these efficiencies, but it’s not a matter of faster = less efficient. As for economies, a jet that can fly LA to NY in 70 minutes, with an hour of turn at each end, could make 10 trips a day, potentially cutting the number of aircraft needed to cover a given route or route rotation by a factor of 4.

Obviously this is not currently practical on so many levels, but there is nothing fundamentally stopping us from achieving that level of service, given enough knowledge and technical capability.

If we ever want to achieve that level of understanding and competence, we will have to work on it when it seems impractical. Remember, it was in a single persons lifetime between flying precariously in glorified kites and supersonic flight.