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The fuel costs are a larger concern to the low cost airlines charging $300 round-trip, than to a supersonic service charging say $2500 round trip (this would represent a 75% saving over Concorde). The fuel consumption per seat mile of the Concorde was roughly 3x that of a 747. Concorde used abt 700l of fuel per passenger, each way, IIRC, and today, with turbofans rather than turboject, you might achieve say 500 l. Bear in mind that airlines pay less for fuel than you and I at the pump... about $0.5/litre, today.

As for maintenance costs, I imagine that one can expect a very substantial decrease due to the use of CAD, better materials and improved practices. Cost reductions of >40% per flight hour were achieved in the military for "equivalent" aircraft between 1970's and 2000's, and reductions of >50% per seat-mile were achieved in the same period for commercial aircraft (eg: early B747 vs B777). Maintenance costs for commercial airlines are a fraction of the fuel costs in any case.

Finally, it is worth remembering that the Concorde was a very profitable business for British Airways, with operating profit of ~40% for the Concorde!

> Finally, it is worth remembering that the Concorde was a very profitable business for British Airways, with operating profit of ~40% for the Concorde!

You make some good points, but BA received their Concordes for free. It's easy to turn a profit with a 150 million pound gift. Air France did not have it as easy. Boom's customers will not be getting their planes for free. And a 50% efficiency saving does not translate into 75% cheaper tickets. And my experience is that claimed maintenance savings are never as good as promised, and that goes doubly so for the "A" variant of any plane.

Interesting why was BA gifted their Concordes? Did Air France lose money on their Concorde routes?

My grandfather was one of the first pilots in Air France. He refused to fly the Concorde because he would never fly a plane that would make the company loose money.

Guess he would never have been an astronaut either.

Standard common-sense job security considerations.

According to a NYT article [1] from the 2003, when the Concorde flew it's last flight, the airlines have never disclosed exact numbers for the profitability of the Concorde. Air France said 'Concorde operation was profitable "in some years."' BA said it once was, but not after the AF Concorde crash in 2000.

They specifically mention that both Airlines didn't have to pay for the planes:

> Part of the reason the airlines could claim some profitability on the Concorde was because they did not have to incur capital costs on the planes. [...] The governments of England and France underwrote the costs of building the 14 Concordes, which were then turned over to the two national airlines.

[1] http://www.nytimes.com/2003/10/24/nyregion/for-concorde-econ...

> but BA received their Concordes for free.

Only the last four white-tails were close to free, they cost 1 Franc each.

The original UK Government-borne £115 million contract cost of the BOAC / BA Concordes was being recouped at a rate of 80% of their operating profit until in 1984 BA bought themselves out of the arrangement for £25 million.

> a supersonic service charging say $2500 round trip (this would represent a 75% saving over Concorde)

FWIW Concorde ticket prices were so high because they were expected to be so high. By clients. BA raised their prices significantly in the early 80s to match what customers perceived the prices would be:

> Market research had revealed that many of Concorde's existing business customers had their tickets purchased by their employers, and thought the cost of a journey on Concorde was more expensive than it actually was; thus ticket prices were progressively raised to match these perceptions.

I'm inclined to be skeptical of the prospects of this for all sorts of reasons (airport noise, viability of the "all premium" business concept). But they are now reporting contracts with airlines, including nonrefundable deposits, and the airlines that put money down are presumably familiar with all the costs you mention, and probably had someone go over the math.

I'm sure the airlines know exactly what they are getting. The passengers are going to be the mad ones when they find out they can't afford a ticket. When this happens the demand will plateau for the few high-demand routes that can sustain this price of ticket, and Boom won't get another order past the original 76 pre-orders.

The airlines know what they are getting and the passengers are going to be the mad when they can't afford a ticket?

This doesn't make sense to me. The airline should have a netter idea of what passengers can and cant afford. Is they are confident enough to order planes, I feel its safe to assume the demand is there.

More importantly I'd like to know what the cost and payment down is. If its $100k you might have many taking a high risk punt. If its $20m you've got some real commitment and confidence.

> The passengers are going to be the mad ones when they find out they can't afford a ticket

Business travelers will be buying these. They'll have a travel budget, the trip will be justified, and the company card will pay. It will pass through silently and might eventually show up in a travel policy that states how only executives are allowed to book supersonic flights.

Not only won't the passengers be mad, they might even be more likely to fly given the reduced travel time. It will now be much faster from NYC to London than to the Bay.

Considering the airlines financial history of government bailouts and bankruptcy I wouldn't be so sure.

> But they are now reporting contracts with airlines, including nonrefundable deposits

Partial payments like that are an investment in the chance that Boom will deliver something exceptional; they avoid not being in the first wave if Boom succeeds.

It doesn't mean they think the chances of Boom producing a worthwhile product are > 50%.

And yet again someone on HN spends 5 mins reading about a company and concludes that the company has

forgotten / misunderstood / miscalculated / is hiding

something entirely fundamental to their business model.

Look, this is a company with adults on board. It's not just 2-3 kids doing another CRUD app in a domain they are completely new to. It's engineers with education and long careers in aviation. I think they know better than most of us the size of engines, that planes use fuel and what it cost. I think they know the cost of insurance and maintenance and other cost components that go into flying at supersonic speed.

Right, because marketing speech is never misleading. Say, would you be interested in purchasing some shares on an innovative blood testing company?

If it's run by highly experienced biotech scientists, and not a 20-something Stanford dropout, sure.

There’s a difference between sceptical questioning and “there is no way...” from someone who doesn’t appear to be a domain expert and is flat out guessing.

Concorde used turbojet engines, with afterburners for takeoff and from M0.95 to M1.7

Boom is using medium-bypass turbofan engines which are much more efficient.

As for comparison with the F-22, The F-22 engines are quite reliable. The F119 engine (to my knowledge) has never had a core failure requiring shutdown in flight. The RAM (Radar Absorbent Material) coating on the F-22 is maintenance intensive, but not required for a SST. Almost 50 years of research should provide a paint that can handle the heating of supersonic flight, with minimal maintenance.

It is important to note that afterburners, while they give you extra speed, are pretty much like dumping fuel overboard.

Aircraft fuel efficiency has improved by more than 50% since the 1960s. Most people would call that more than "a few percent".

To be fair, the cost of jet fuel has increased by more than 50% too, and won't be the dominant cost if they are only shipping 70 jets.

But the comparison is with the costs of the Concorde when it was shut down in 2003, not the costs of the Concorde in the 1960s.

According to US census bureau, per capital income in US has increased by 10x since late 60s. Jet fuel prices have increased around 6x, from around 30 cents to around $2. So wouldn’t that make jet fuel more affordable?

Did you account for inflation? $1 in 1970 is worth $6.52 now.

Inflation, the general rate at which the price of goods and services is rising and falling, is literally the calculation made in the post to which you have replied.

That's subsonic fuel efficiency. Supersonic is another thing entirely.

The supersonic wing is also terrible at subsonic speeds, meaning it takes a terrifying amount of fuel to push it up to altitude and supersonic. Military supersonics deal with this by getting a drink from a tanker after takeoff.

Boom are flying with turbofan engines, not the turbojet engines that were common in the 60s.

As for aerodynamics, the F-22 is relatively efficient at high subsonic speed and also doesn't require external tanks like earlier jets do.

Wikipedia says that the F-22 is able to supercruise without afterburner, using turbofan engines. This may be the key.

Supersonic capable turbofans that are able to get the "force multiplier" of using bypass airflow for thrust at supersonic speeds are honestly the key enabling technology here.

So basically a supersonic turbofan is a SCRAMJET behind the first fan?

Not being an expert on supersonic turbofans, I went to the obvious first information source and it was surprisingly illustrative. https://en.m.wikipedia.org/wiki/Turbofan

From a little further reading it seems it seems that supersonic turbofans are actually just the apex of the continued sophisticated work being done on jet engines which has allowed them to push the intake fans of low bypass turbofans up to supersonic airflow speeds.

As is the Typhoon

Why has nobody designed a variable width wing? One that can expand / contract for different speeds?

Naïve question, I know. Just curious...

Concorde has a variable width wing.

I think they mean variable geometry more in the line of the B-1 Lancer or F-14 Tomcat... And the answer is probably cost, complexity, reliability and weight.

All four of those.

They're called flaps and slats.

https://www.grc.nasa.gov/www/k-12/airplane/flap.html

Barnes Wallis developed some interesting designs in the early 50s: http://www.sirbarneswallis.com/Supersonics.htm

"but they need to fix their marketing"... Indeed, why would anyone name a vehicle that catapults you across the Atlantic as the sound of an explosion?

How much time does one actually save? Modern air travel is as much about the airport as the aircraft. You spend almost as much time getting to or from the aircraft than actually flying, even on transatlantic routes. So for far less money they could achieve the same results by attacking the airport ends of the travel time equation.

And what business passenger, by definition someone with a degree of wealth, would cram themselves into a concorde-like seat rather than the epic accommodations of a modern first class cabin? Just to save a couple hours?

I think the possibility of leaving New York for a London meeting and then returning the same day, would have a great appeal for some people. Then cutting long trans-Pacific flight times in half could also be worth paying a premium for. And, like you suggest, these aircraft are likely to be flying from the smaller airports that private jets use that can get you on the plane quick. Like London City Airport.

Or Luton Airport which has a lot of private jets

I imagine it's a huge upgrade being able to design with computer modeling. I honestly can't fathom how they calculated supersonic airflow when designing the Concore.

I doubt they could with much precision, which is probably why they just gave the Concorde a ton of thrust and huge flight control surfaces.

Even into the 90s, numerical simulation of naiver-stokes was pretty minimal (I worked with the NASA Numerical Aerodynamic Simulation folks at Ames at the time) and yet up to then the SR-71, X-1B, Valkyrie etc were all designed, built and flown, not to mention some spacecraft too that you might have heard of :-).

There was some computational modeling, but mostly it was old fashioned engineering: slide rules, models, and as someone else remarked, some over-engineering. The same way people built bridges 150 years ago when that was a black art.

There's a wonderful/sad picture at the Hiller museum on 101 in San Carlos. It shows the day the Boeing SST program† was shut down. In front of the mockup (which is also at the museum) are wooden workbenches with vices attached.

It made me realize that not only were they designing everything with slide rules, but people then built all the parts by hand from drawings a draftsman (not draftsperson in those days unfortunately) also produced by hand from hand-sketches and notes by and engineer. Honestly this blew my mind when I realized that the ME-262, SR-71 and LEM were produced in the same way.

And I should have known: at MIT I took Unified the last year (1983) that the practical work was done entirely on old WW II surplus machine tools. In the next room, not yet unpacked, were early CAD systems.

† I still wonder if Boeing was every really serious about passenger SST.

In 1971 my mother worked for Caltrans[1] with the title of 'delineator'. The title was originally 'draftsman' in 1965 or so when she was hired.

When it ruins your life, it's a vice. When it holds your work together, it's a vise.

[1] California Dept of Transportation

Reminds me of my Mech eng BTEC thermofluids course the college had a load of ww2 surplus lathes to.

Though on my course we only had 1 person who worked at a traditional engineering firm the rest of us worked in RnD at the RAE ARA or on campus at CIT.

The engine development from 80's/90's (e.g. F404) to the modern variants (F414) basically allows 20% more thrust at the same size/weight of engine. Supercruise isn't that exotic now in the military realm. Quite a few modern fighters have supercruise now that the most modern engines support it.

Of course, supercruising in a fantastically expensive small fighter is not the same as supercruising in an airliner. And a military fighter being sold as "cheap to operate" such as the Gripen E is not the same thing as being able to sell seats in it at commercial prices. 75% less sounds like a LOT, but I'm not sure how much of the Concordes prices consisted of fuel, and how much consisted of other things (expensive development, expensive maintenance?)

The Concorde's design was finished in 1960, when almost all computers still used vacuum tubes. Computational aerodynamics definitely made a huge improvement in design, especially for supersonic flight.

I think most of the computers used were actually humans back then.

Concorde had analogue fly-by-wire, including autostabilisation and autothrottle. Information about it is scattered all over this pprune megathread: http://www.pprune.org/tech-log/423988-concorde-question-78.h...

"I wish Google the best of luck, but there is absolutely no way that their index will cover a billion pages. It takes a massive amount of storage to maintain coverage…"

This is the standard "engineers other than software are idiots" type HN FUD. For the record, Boom is staffed by aerospace veterans from the likes of Scaled Composites, P&W, Adam Aircraft, SpaceX and Boeing. https://boomsupersonic.com/about/ They might know thing or two about cost analysis.

I am listening, I'd like to know more from them.

>This is the standard "engineers other than software are idiots" type HN FUD

What? I don't think that has anything to do with it at all, and the distinction between types of engineering seems irrelevant. I think he's pointing out that they're trying to make a profitable business without understanding the necessary costs. Given the nature of startups to overpromise and underdeliver (as that's a common tactic to help raise money), his skepticism seems reasonable to me. I see just as many criticisms of software businesses on this site (actually many more, since there are far more articles about software companies here than hardware companies).

I have very little aerospace experience so I do not claim to be an expert, and while like to see people tackling big problems eventually succeed, his points seem salient to me.

This has nothing to do with a software engineer looking down on other types of engineering, since I'm not a software engineer. My post was all about Boom's marketing mouth making claims that it won't be able to back up, or possibly making half-truths that are going to leave people disappointed.

I'm also an "aerospace veteran" and have seen more projects cancelled than succeed (most recently the Lear 85). Designing a new plane is capital "H" Hard. That goes doubly so for planes that are big departures from the previous experience of the company. Cessna makes great light business jets. They are currently trying to design a line of bigger jets and are finding it very hard. Lear can't figure out how to make anything without mechanical flight controls. It takes a couple generations of design to figure things out. So a bunch of engineers from Scaled and Boeing aren't going to help. How many ex-Concorde engineers have they hired?

>How many ex-Concorde engineers have they hired?

All right, when you said you are an aerospace veteran I was prepared to take you seriously, but this cancels that out completely. Firstly any Concorde engineers would, if they started their career right out of college on Concorde, be about 80 years old by now. Then this plane is using different and much more modern engine technology, different control systems and different materials. Almost nothing learned from Concorde would be up to date and relevant to this plane, from an engineering perspective.

Indeed. It's much easier to criticize a new effort. It's not that the components of the criticism itself is necessarily wrong, but the conclusion that what the new endeavor is doing is impossible is purely based on armchair quarterback.

We should remain skeptical whenever someone says they will do great things that hasn't been done before, but immediately going to the conclusion of "it's impossible because I can't imagine how to make it work" is just plain arrogance - a true skeptic should be skeptical of his/her own judgement.

In fairness, HN usually assumes software engineers are idiots too. The general sentiment is more "engineers other than me are idiots".

Not here. My sentiment is 'I have no idea what I am doing'

It's more like "engineering is simpletons' work; not anything like the deep mathematics of computer programming that I do."