# What are the barriers to feasibility of stratospheric cruising for commercial air travel? (i.e. Concorde?)

In 2003, British Airways retired the Concorde for a few reasons.

1. Rising maintenance costs
2. Lack of demand due to safety concerns
3. Further decrease in demand due to 9/11 attacks

additionally, due to lack of competition, the Concorde was never properly maintained. Because no other airline had such a plane, British Airways kept the analog cockpit from 1970 up until the planes retirement.

Well, we live in a world where safety in aviation is continuing to increase, and the technology we have to utilize the world around us constantly gets better.

What engineering breakthroughs will allow commercial aviation to use the upper atmosphere and supersonic cruising speeds?

--EDIT--

I don't mind if you downvote my question, but it certainly annoys me if you downvote and you don't leave a comment telling my why. I've tried to make this question as objective as possible, if you're going to take the time to downvote, take the time to explain yourself, and I would be happy to try and mitigate your concerns.

• Re "proper maintenance" and "keeping analogue flight decks". Production ceased in 1979. By 2003 there were 9 Concordes in operation. Has any airline or manufacturer ever retrofitted a new design of flight deck of existing 25 year-old commercial airliners? What would be the cost of designing and getting approval for a new flight deck for only nine aircraft? Isn't it only the military that repurpose old airframes in this way? May 8, 2014 at 22:21
• This seems to be almost entirely opinion-based. May 9, 2014 at 0:13
• @DavidRicherby while I think it's possible you could consider this as an opinion based question, I also think there are a lot of facts that influence the answer. I suppose I could reword the question to ask about the cost effectiveness of concord travel, if the costs are reducing, etc. Also when considering that safety is a factor, I think there is a lot more than just an opinion based answer here May 9, 2014 at 0:21
• I really think this question can only lead to broad speculation. The number of possible reasons for or against is...large, to say the least. So I've voted to close the question. If you want to ask a questions about the particular issue you raise, that might be the better way forward. Maybe use this as a place to find evidence to build a case for or against rather than asking that the case simply be decided in one go. May 9, 2014 at 18:26
• While this question might be a great topic for a blog post, or an editorial, or the Stack Exchange Aviation chat... it strikes me as way too open-ended for us to really answer concretely here.
– egid
May 9, 2014 at 18:50

I would argue that the Concorde was from the beginning economically unfeasible and instead served as a prestige technology for the British and French governments. Even the name Concorde, indicates that the two governments working together to produce the aircraft seemed the most important aspect of it.

Both British and France at the time had completely nationalized airlines and almost all their major aviation companies as well. Americans were going to the moon so Britain and France were looking around for a prestige technology of their own. Bigger and faster airplanes had been the rage for twenty years so the Concorde seemed like a cool thing to do. The Soviets came to the same conclusion.

In the US, civilian airline development was still wholly private so when when Boeing , Douglas et crunched the numbers they saw little value in supersonic transport with it's non-linear cost. US supersonic transport never made it off the ground, but in Europe, the politically driven Concorde did because the people making the decisions weren't paying the bills.

As noted by others, the Concorde was essentially a military aircraft, produced by political compromise with the primary goal of expressing the technical powers of the governments involved. It was more an art project like building the Pyramids than it was a piece of mobile transportation infrastructure.

Edit: (May 14, 2014)

Some sources on the economics of the Concorde:

The Atlantic August 1977:

Already Britain, and France spent £1.46 billion \$2.3 billion to reach this (and a London political economist has recently argued that the true cost is roughly three times this amount)... ...In May 1976, Professor David Henderson, newly appointed professor of political economy at University College, London, argued that the government's figure of £1.46 billion shared between Britain and France was a drastic underestimate. It had been reached by adding the yearly expenditure on the project at the current prices. If these were adjusted to 1975 prices, and interest charges of 10 percent added, then the cost of Concorde was not £1.46 bilion but £4.26 billion (\$6.82 billion at the present exchange rate of \$1.60). That would be$22 billion US (2014 dollars.) Just to get the thing into the air.

They built 26 of the aircraft, 20 of which that actually flew paid flights. So, around 1.1 billion per plane, roughly the cost of a B2 stealth bomber. I can't find any hard numbers on operating cost but with 1.1 billion per plane sunk capitial cost, it's clear it would never operate at a total profit.

I believe the plane only flew for 20+ years because the British government essentially gave it away, eating the billions of in development and deployment cost and leaving the plane to just have to cover operating cost. I'm not clear that it even really did that.

Considering how much money was thrown at the problem, not particularly elegant or interesting.

Edit 02:

In rereading the parent, I realized I didn't make my answer explicit to the original question. He wanted to know what it would take to bring a Concorde like plane back.

1. My answer was really just saying, "the Concorde itself had no economic foundation so firstly, you'd have to find an economic niche for SST."
2. There was never an economic demand for the Concorde's speed of travel and there doesn't seem to be one now, either.
3. Technologically, you'd probably need something hyper radical like a nuclear powered air spike so the plane wouldn't burn tons of fuel and could fly over land masses without sonic booms or destroying smaller aircraft. (Seriously, it would have to be that advanced.)
4. In our current luddite era, it would be saner to think about inventing anti-gravity drives than think that the political regulators would let that type of radical technology fly, even if it existed.
• @GdD got any citations for your 'scaled up fighter' claim?
– egid
May 9, 2014 at 18:51
• "Concorde was essentially a military aircraft"? May 10, 2014 at 5:38
• @shortstheory - I would argue rather emphatically that system, no matter how technologically nifty, which doesn't fulfill its core design goal has failed. In this case, the design goal was (notionally at least) to create an economically self-sustaining civilian airliner. I'm pretty sure that, while it did operate profitably some years, it never paid off its entire life cycle cost. Looked at another way, if all airliners had the life cycle cost pattern of the Concorde, we wouldn't have an airline industry at all. That's a design failure in my book. May 14, 2014 at 17:40
• @TechZen "It was also 'military' in the sense of..." Neither of those two things is a defining characteristic of what is military. Governments create all kinds of things; unless (roughly speaking) those things are designed for use in war, they are not military. Concorde was not designed for use in war. May 15, 2014 at 15:46

Concorde was a viable SST aircraft and was initially looking like it would sell quite well. Then US airports started banning it due to concerns over the sonic boom, which were really just sour grapes because US companies had failed to develop their own SST aircraft. That killed most of the orders.

It's worth noting that Russia flaw it's supersonic passenger jet for years quite successfully too. It had technical issues but, like with Concorde, the sonic boom issue turned out to be of little real concern.

A lot of research has gone into lessening sonic booms, but it isn't clear if this will actually help. Given the attitude of the US commercial flight industry it seems likely that unless Boeing's name is on the aircraft they would resist it anyway. I think it is more likely that such an aircraft would be developed and used mostly in the far east. China might do it, or Japan.

• Haha, successful is a huge overstatement for the Tupelov Tu-144/Concordski. It barely made any revenue, had pathetic efficiency, was plagued by hundreds of technical issues in only 50ish flights, and pax couldn't stand the sound of its engines. May 10, 2014 at 5:37

It's all about cost. Concorde stopped flying because it wasn't making money. The crash actually didn't mean that much economically, it's that it happened in the time of an economic downturn and executives couldn't be seen to get on a Concorde when they'd just laid off thousands of people. The airlines and airbus had had enough keeping it alive, so they are now all in museums.

Tickets were fantastically expensive. Concorde was basically a scaled up fighter jet with fighter jet engines. It used afterburner for some segments of the flight, which requires vast amounts of fuel.

Another reason SST failed is the sonic boom made it practically impossible to fly any land routes. They tried a few times but it was just unworkable.

Will it ever come back? I'm sure it will one day once they solve certain problems. You have the fuel consumption issue for one. There are engines that do "supercruise", giving high power without afterburners but they aren't exactly efficient. Either lowering fuel consumption or fuel costs is necessary. Second, you have the sonic boom. There are some promising designs out there which use specially shaped wings and fuselages to change and reduce sonic boom noise.

Personally I think that rather than supersonic travel things will jump to hypersonic, super-high altitude travel. Once you are in the really thin air you don't have to worry about sonic booms, and you have much less air resistance.

No matter how you cut it it's about cost though. If they can figure out a way to have supersonic travel with a cost enough people are willing to pay then they may build it, if not you'll never have it.

• Minor point but Concorde did not use afterburner all the time. Only for takeoff and for acceleration from transonic to about Mach 1.7. It then "supercruised" on conventional thrust only. May 9, 2014 at 0:21
• @flyingfisch It definitely was an engineering marvel in many ways. This answer is right about the cost and other reasons but it sure was sad to see it retired. May 9, 2014 at 1:55
• "On average Concorde made [an] operating profit of £30-50 Million a year for British Airways in the boom years [...] British Airways reportedly received £1.75 Billion in revenue for Concorde services against an operating cost of around £1 Billion." ... "the Airlines are not making back the money spent on the safety modifications and other upgrades. With some other big costs coming up, BA need to write off £84M now, rather than £150M in 3 or 4 years. Air France will write off a large sum of money too." - concordesst.com/retire/faq_r.html May 9, 2014 at 8:53
• There are many things factually wrong about this answer. As others have pointed out, Concorde did not use afterburners for the whole flight. Also, saying it was a scaled up fighter jet with fighter jet engines is misleading. It has a delta wing, which many fighters do, simply because that's the design which is efficient for supersonic flight, not because it was scaled up from something. Its engines were developed specifically for Concorde, but were partially based off of engines from a light bomber. May 9, 2014 at 18:14
• "When the air france one crashed it took a sizable portion of the customer base with it" is completely wrong as well. That flight was a charter full of German passengers on their way to a cruise. These were not their normal business customers who flew back and forth between Paris and New York or DC. According to British Airways, Septermber 11, 2001 had substantially more to do with why the Concorde was retired than the AF crash. Please, if you're going to speculate about something, at least get the facts straight. This answer needs some substantial editing. May 9, 2014 at 18:14

Airframe heating is a big barrier to any airframe design and in consequence the fuselage needs to be able to grow longitudinally. The pressure hull needs to be encased inside a flexible, expandable sleeve-like skin. It requires the use of a great deal of heat resistant titanium and you can't use normal tools on the titanium.

Various issues could be overcome but you would need to develop a supersonic inlet with variable geometry surfaces to close and slow down air entering the engines at supersonic speed, or open to allow maximum airflow at subsonic speeds.

The development cost would be huge which is why I think the economics actually require a people mover rather than a VIP airframe with a limited market.

The market is definitely trans Pacific and trans Atlantic. Concorde never had the range for trans-Pacific. If you had the backing of say Singapore Airlines, Japan Airlines or a Big Chinese airline as a launch customer to operate trans Pacific then you would have some prospect of launching a new design.

For the Chinese in particular this would be a spectacular prestige product.

• I agree that the golden market for a SST is trans-Pacific. However, the passenger profile necessary to sustain a SST is the high end business traveler. My company gags at the cost of Business Class on a transpac route right now. They won't be putting the likes of me on a super-premium aircraft where the ticket cost is several multiples of the standard Business or First class ticket. That's just the way it is. So unless there is a technological revolution, or a new source of low cost fuel, the odds of success for a SST on the transpac route are low. May 16, 2014 at 14:00

Economics. Some innovations in engine technology that promise to lower fuel consumption for an SST can be applied to subsonic airliners keeping subsonic airliners ahead financially.

There's also the question of speed. Aluminum is sufficient for an aircraft up to Mach 2.2. Beyond that requires steel or titanium.

So, a plane with a max speed of Mach 2.2 is less than 3 times as fast as today's jetliners. Counting taxiing, acceleration, and climb, this makes the SST's time advantage for the trip even less.

The SST will have a lower lift over drag ratio in all parts of the flight envelope compared to a subsonic airliner. It will have greater parasite drag due to the greater speed.

If a plane with speed over Mach 2.2 is built, it will be heavier and therefore burn more fuel. It seems there is no sweet spot for SST speed. The sweet spot seems to be Mach .85 or hypersonic where the craft can exit the atmosphere.

Could it happen? Yes. Anything could happen.
Is there a realistic chance of it happening at some point in the future? Yes, quite likely, if there's an incentive to develop the technology that would make it economical.

Is that moment likely to arrive during my lifetime? I seriously doubt it, especially given the lead times for such projects which are measured in decades, and I don't have centuries to live (which suggest of course that I don't envision the technology that makes such an aircraft economically feasible to become available within the next few decades).

There's no theoretical reason to assume that supersonic air transport can never be achieved. We know it's possible, it has been done. In fact it has been done several times.
Concorde, Konkordski, there was even (or so I've read) plans to create a transport version of the B-58 Hustler at some point, think a supersonic VIP and priority cargo transport for the US Air Force. There was an attempt to create a supersonic business jet by Sukhoi that was abandoned (I think) a few years ago.
So we know it's possible, it's just not economical.
But who knows what may become economical in the future? If there's a large enough group of people who value their time more than the price of admission, there's a market. Right now that market isn't there, but it might emerge (the death of Concorde may have led to an increase in sales in long range business jet, if aviation laws get stricter, making it harder to use those, those owners might once again get interested in buying tickets on supersonic airliners and start asking airlines and governments, and aircraft manufacturers, to look into building them).

Or maybe there will be some revolution in aircraft design that makes it so cheap to build supersonic airliners that it just makes no sense to build anything else.

Of course that's all theoretical. There's no crystal ball anyone can look into and say definitely whether it will happen or not. But it might.

• "during my lifetime", well how old are you? I'm 18, so that leaves a ton of possibility May 9, 2014 at 13:53