AHC: Successful Supersonic Airliners

Your challenge is to make supersonic airliners, either concorde or something else somehow successful enough that their future is certain and nobody believes that they are a waste of money. Extra challenge of making them as much as a fixture of aviation as the B737.
 

Archibald

Banned
Not possible. Sonic boom is too much a nuisance. Best hope is the 2707 finding a niche on Los - Angeles / Tokyo, somewhat like Concorde.
 
Not possible. Sonic boom is too much a nuisance. Best hope is the 2707 finding a niche on Los - Angeles / Tokyo, somewhat like Concorde.

This is more of a aviation/physics question. Can a sonic boom be mitigated if the aircraft flies higher and in thinner air? My logic is going along the lines of thinner air offering less of a "boom". Can higher flying aircraft do so supersonically?
 

Archibald

Banned
Nope. It doesn't work that way. Your theory make sense, and there were serious hopes (in 1960) that flying above 70 000 ft would kill the sonic boom. So they flew F-104s, B-58s and the XB-70 all over Oklahoma (in 1964) as high as they could, but it doesn't worked. At all. People just went nuts. Windows broke all over the place.

It took me a while to figure that, but even the Space Shuttle makes sonic boom when it lands. And it comes from 200 miles high ! I mean that the shuttle confirmed the fact that, however high you fly (supersonically) in the atmosphere, there is a sonic boom heard on the ground.

NASA has been working on lowering the sonic boom since 15 years, but progress has been very slow. They flew a modified F-5 Tiger, then a F-15. They have resumed research recently.
 
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Ho hum!

It is sad listening to alt history types stagnated in 50-year-old dogma.

We expect better from alt history types.

NIMBY lobbyists used noise pollution as an excuse to ground Concordes. Most amusing was all the noise complaints phoned in (to American airport administrators) every time a Concorde was scheduled to land. Complaints continued to pour in even on days when Concordes stayed on the ground .... on the far side of the ocean.

Alt history types would be wise to read up on recent research about reducing sonic booms. Google "Boom airplane."
 

Archibald

Banned
Dogma my ar$$e. Or you should complain about volcanic eruptions PODs being considered ASB. sonic boom is a law of physics, or maybe the thread should be moved to ASB.

Alt history types should better read the end of my post, where I mention NASA research on sonic booms.

Concorde survived only because the sonic boom was tolerated... over oceans.
 
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Some ideas:

NASA research on diminishing the sonic boom yields results (it hasn't yet) decades ago. I'm not even sure how possible it is.
Earlier rise of China/East Asia and integration with the USA pacific coast, so there is bigger demand for flights between the East Asia and California - that's another (long) over-water route.
Faster check-ins at airports, so flight time becomes a more significant part of total flight time (otoh, this may already be the norm among the first class fliers who would be the ones capable and willing to pay for supersonic seats anyway)
Restricted land routes where supersonic passenger planes can fly at supersonic speeds. I'm not sure how feasible they are, as they have to be along uninhabited terrain. But if one route between the New York and LA can be designed, another between Western Rusia and the Far East and a third one along the Middle East that allows the rich Arabs to fly supersonic from the Persian Gulf to Majorca (no way supersonic flight is allowed in the more densely populated Europe, I guess) there might be enough demand to keep supersonic airliners in the market.
 

Archibald

Banned
https://www.nasa.gov/press-release/nasa-begins-work-to-build-a-quieter-supersonic-passenger-jet

16-022-supersoniccontract_0.jpg


Not only that thing is supremely ugly, I'm not even sure it could fly without FBW.
 

Wimble Toot

Banned
Extra challenge of making them as much as a fixture of aviation as the B737.

No Yom Kippur War, no OPEC oil price increases/'energy crisis' = bigger sales for Concorde, with JAL, Qantas, Pan Am, TWA, American Airlines not cancelling their orders.
 

Archibald

Banned
Even without sonic boom, going supersonic burns far more fuel. Admittedly, 737 and concorde have same numbers of passengers (130) but Concorde is twice as long and twice as heavy.

a fixture of aviation as the B737

This is not possible. There are thousands of 737, no way Concorde can replace them in similar numbers. Not only because of the sonic boom, but also because supersonic flight is a fuel black hole, an endless pit. No airline can afford that.
 

Wimble Toot

Banned
There are thousands of 737, no way Concorde can replace them in similar numbers. Not only because of the sonic boom, but also because supersonic flight is a fuel black hole, an endless pit. No airline can afford that.

And if Concorde and/or the US Supersonic Airliner outsells subsonic wide body airliners, air travel remains an elitist activity.

Supersonic flight drives airline ticket prices up. 300/400 seat airliners drives them down.

The British Airways Concordes were bought for £1 EACH, the U.K. government subsidising the entire cost of their part of the project.
 
No Yom Kippur War, no OPEC oil price increases/'energy crisis' = bigger sales for Concorde, with JAL, Qantas, Pan Am, TWA, American Airlines not cancelling their orders.
Exactly.
If there's a hundred of them in service before oil prices jump, they're likely to stay in service. With only 2 airlines iOTL, running essentially the same kind of service, there was little innovation in marketing and service. If several other airlines jump in, someone might find a formula/market that can survive the rise in oil prices that will eventually happen.

If the oil price rise is more gradual, that might help, too.

If there are more sold, the idea of putting a Concorde B into service becomes more practical, and that opens up a lot more Pacific routes.

OTL, there's now a handful of companies planning on making supersonic business jets, for instance. Repurposing a Concorde from a 100 passenger all first class machine to an executive shuttle with, say 40 spaces, might be a plausible market for London/NYC and/or London/DC, even if nowhere else.

Flying over land's going to be a distinct problem.
 
I certainly know that sonic booms are a real thing, having lived next to interceptor bases most of my childhood. But also that they are startling and the ones we tolerated were from fighters in the 20-40 tonne ranges; a jetliner would be heavier. The boom is related to the basic fundamental physics of how aerodynamic lift and drag work at supersonic speeds; I can believe clever design can reduce it but never eliminate it. There are other issues also--for instance drag overall is inherently much higher and so more thrust is needed versus subsonic speeds; also, the proper shaping of aircraft for the best efficiency we can get at supersonic speeds is very different from what is optimal subsonic, and so performance in the slower regime, vital for takeoff and landing, is compromised--and to keep it from being dangerously so so is supersonic performance!

Aside from those two issues of boom and compromised two-regime aerodynamic optimization, and the third issue of heavy thrust requirements (higher fuel consumption is offset by lower flight times, but overall higher demand of fuel per revenue passenger-mile does prevail) we have compression heating. As speeds rise well above the speed of sound, air is ram-heated by compression, and the added heat rises to oven-like temperatures and beyond; Concorde was limited to Mach 2 by desire to mainly rely on traditional aircraft aluminum and even so some surfaces had to be made of heavier, less familiar and harder to work with steels. The ambitious US SST plan was to cruise at Mach 3 or more where aluminum would be useless and the whole plane would have to be made of steel or titanium at much greater cost. Sonic booms get worse with higher speed too.

British aeronautical savant Sir Barnes Wallis of Vickers therefore proposed in the early jet age that designers should first concentrate on lower Mach factors. Speeds just above the speed of sound would be bad because in the "transsonic" region around Mach 1 some additional problems occur that make operations very tricky and drag very high, but pushing past to around 1.2 or more gets past them. He recommended early designs stop right there, Mach 1.25-1.5, and take advantage of relatively little drag, relatively simple engineering, using the familiar metals that could take the modest heating--at the right speed, the very cold stratospheric air is heated just to temperatures familiar on the ground, so standard aluminum alloys should work well there too.

But even this is not so easy. Designers were developing planes that could manage extended dash at such speeds in the mid-50s, but these were fighter aircraft with tricky handling. Convair developed the B-58 "Hustler," a cool and wicked looking delta wing in some sense a grown-up version of their successful F-102/-106 design which my father described as magnificent to fly, being clean and able to surge smoothly up to high speeds and even, on rare occasions when he could get away with it, cruise for hours above sonic speed. But normally he'd cruise slower, below Mach 1, in part because people did object to the sonic boom, and mainly because it had superior range there despite a design that pushed for supersonic performance very hard. The delta wing carried over to the Hustler but the bomber had four jet engines in pods below, or perhaps even 8 in double engine pods as on the subsonic high-range B-52. And these had a nasty tendency to suddenly backfire and fail, throwing the plane into spins. This was largely because of the aerodynamics of supersonic air flow. Proposals to convert it to a passenger liner were made but with such unsafe flight characteristics it was unthinkable to proceed. Indeed the rate of loss of planes and crews was quite high, under high performance USAF handling. And while it could dash at supersonic speeds a considerable distance it could not sustain such speeds for an operational strike mission very far; like my Dad's "6" it was necessary to cruise long distances subsonic. Heating problems were serious enough already to demand honycomb insulated skin at considerable cost in many areas too. The Hustler was operational from the very late 50s until the late 60s; the true supersonic cruise B-70 Valkyrie was tested but abandoned when it was realized that its high speed would heat it up so as to be readily observable and despite high speed and altitude Soviet missiles could shoot it down, while ICBMs would deliver bombs even more quickly with no possibility of being intercepted.

Meanwhile by the mid-60s Concorde was already under development evolved from both British and French proposals; the US SST project aimed to leapfrog the anglo-french project which would go at Mach 2 by 50 percent, to Mach 3. With everyone assuming these were all bound to succeed, it would have seemed futile to go for something more modest than either, and yet arguing that a suitable passenger liner as opposed to warplane designed for Mach 1.5 or less could be successfully made in the 1950s seems to be a stretch--especially considering that the DeHavilland Comet, introduced early in the 50s as the first commercially purchased jet liner turned out to be flawed, with a design that did not allow for the unknown problem of metal fatigue arising from routine changes in pressure; who knew what further issues supersonic flight might bring?

If it had been possible, it is possible that the objections to sonic booms might have been overriden in the name of progress and people forced to endure them and the damage they did. (Aside from unnerving people, breaking glass and upsetting sleep patterns, it was realized at some point that humans are not the only creatures who get upset and woken up--there is a real possibility of ecological disruption due to animals becoming deranged as well.) It is possible early success with low-Mach supersonics might even eclipse the development of high speed subsonic planes like the Boeing 707.

But even aside from boom related issues, unlikely. The slower planes would be remarkably cheaper to produce and operate, and much more easily adapted to high density big models. When the oil price surge hit, even modest speed supersonics would struggle to remain in the black financially.
 
But would a match 1.25 airliner be a commercially viable airplane? The distance between NY and London is roughly 5,400km. If airliners went from 0 to top speed as soon as they depart from the airport, a subsonic match 0.9 airliner takes 6 hours to arrive to destination while a match 1.25 match would take 4h20m to arrive... but the actual flight will be longer, because it will take time for the airplane to accelerate to top speed and it will also have to slow down to fly over the UK. Now add the time it takes to check in and out at the airports plus the time it takes to reach the departing airport and to travel from the destination airport to the actual destination (ie, hotel). Passengers wouldn't be saving too much total traveling time, but they would have to pay a premium because of the extra airplane cost (less units sold means fixed and potentially higher development costs are spread among fewer planes), the additional fuel consumption due drag and probably the fewer seats per plane due the slimmer shape to reduce drag. It looks like supersonic commercial flight is a matter of "go big or go home".

And on cooling, as an armchair engineer with no knowledge whatsoever on the issue, I wonder if it's possible to actively cool the aircraft skin from the inside. A separate cooling mechanism with, for instance, liquid nitrogen should be out of the question just on the extra weight alone (and that, assuming I'm not proposing something stupid to begin with), but the SR-71 used it's fuel to cool the airframe. Leaking fuel on the airfield and retorting to in air refueling isn't viable for commercial flight, but is it possible to use cryogenic fuels like liquid methane (hydrogen is too bulky) as fuel and also to cool the aircraft skin?
 
Your challenge is to make supersonic airliners, either concorde or something else somehow successful enough that their future is certain and nobody believes that they are a waste of money. Extra challenge of making them as much as a fixture of aviation as the B737.

According to an old article in Flight International - no I don't remember the date, but Regan or Bush the elder was your president I think - long enough range to handle all the over water routes would be needed. SST's would have to dominate these routes to have a significant market. Also cutting cruising speed back to Mach 1.8 would be needed to allow the fuselage to be built more like a regular airliner and less like the battleship Bismark - their words, not mine - which they said would have positive effects on fuel consumption and sonic boom.

Apparently the original idea - for Concorde - was to cruise at Mach 2.2, which is a fast as Aluminium can be pushed without softening from friction heating. The need for extra rigid structure, combined with the metal being on the edge of softening, meant the plane was massively overbuilt. And they cut speed back to Mach 2.0 anyway apparently, but the massive structure remained.

The overland 'boom corridor' is not going to be acceptable for routine commercial airlines. People complain about the occasional boom from military aircraft, which do not fly supersonic very often or for very long. Overland commercial flights would have people below subjected to 'Boom Boom', 'Boom Boom' so many times an hour. What people reluctantly accepted for national security during the Cold War would not be acceptable that often every day for commercial planes.
 
Summoner wrote:
This is more of an aviation/physics question. Can a sonic boom be mitigated if the aircraft flies higher and in thinner air? My logic is going along the lines of thinner air offering less of a "boom". Can higher flying aircraft do so supersonically?

Archibald wrote:
Nope. It doesn't work that way. Your theory make sense, and there were serious hopes (in 1960) that flying above 70 000 ft would kill the sonic boom. So they flew F-104s, B-58s and the XB-70 all over Oklahoma (in 1964) as high as they could, but it doesn't worked. At all. People just went nuts. Windows broke all over the place.

Actually the higher up the less likely the boom is to survive to reach the ground. This is highly dependent of course on the size of the aircraft since this determines the size of the 'boom' and its footprint. As the chart here shows the SR-71 flying at 80,000ft has less than half the footprint (pressure) of the Concorde flying at 50,000ft. (https://aviation.stackexchange.com/...oom-produced-at-60-000-be-heard-on-the-ground) Above 100,000ft a sonic boom will rarely touch the ground, usually only when certain conditions and atmospheric effects are in place. And smaller airframes could avoid "sonic booms" by flying slower, (but still supersonic) and higher over populated country.

Note on the Oklahoma tests; None were above 50,000ft and most took place between 30,000ft and 40,000ft in order to cause ground pressure (booms) equivalent to those of the proposed Concorde (and its assumed American counter-part) with much smaller aircraft. (Tests ONLY used the F-101 and F-104 aircraft which were vastly smaller than the proposed SST designs) SSTs were assumed to fly no higher than 60,000ft and speeds of only Mach-2. The Oklahoma tests made no attempts to mitigate or reduce the sonic booms but specifically were designed to have the booms impact the ground in Oklahoma City eight (8) times a day for the whole test period with the assumption there would be that many (at least) over-flights per day, every day for transcontinental air routes. The aircraft did not fly "as high as possible" since the sonic booms would be barely detectable from that altitude due to the small size of the fighters used. They in fact flew BELOW nominal supersonic 'safe' altitude of the day which required supersonic flight only over 50,000ft or over 'cleared' (low or non-populated areas) BECAUSE they were trying to create ground level sonic booms.

It took me a while to figure that, but even the Space Shuttle makes sonic boom when it lands. And it comes from 200 miles high ! I mean that the shuttle confirmed the fact that, however high you fly (supersonically) in the atmosphere, there is a sonic boom heard on the ground.

Not correct as the Shuttle's sonic boom cone above Mach-3 is too narrow to impact the ground normally so you don't 'hear' it till it drops below Mach-2 and about 80,000ft to 60,000ft where the cone spreads out enough to actually impact the ground. Those how have heard the Shuttle passing over head usually hear the secondary or reflected sonic booms which sound like a low rumble rather than the sharp "boom" people are used to. Where you DO hear the Shuttle is around 10 minutes from landing as it drops to around Mach-1.5 and about 60,000ft.

And no you don't hear EVERY supersonic flight as both altitude and speed along with atmospheric conditions play a part in propagation or non-propagation of the sonic boom.

NASA has been working on lowering the sonic boom since 15 years, but progress has been very slow. They flew a modified F-5 Tiger, then a F-15. They have resumed research recently.

Actually they've been 'working' the issue since the mid-50s with the effort and support varying greatly over time :) They've known for quite a while that the airframe shape had a lot to do with sonic boom propagation and combination, (most sonic booms are not one boom but the combination of multiple booms generated by the aircraft nose, body, wings and other surfaces combining as they propagate) but getting something to fly supersonic consistently has taken priority over boom mitigation till recently. They have also modified and flown an F-16XL and F-8 in attempts to modify or reduce sonic booms. There were a couple of modification proposed for their SR-71 they had for testing but not enough confidence in the outcome to risk. And that's actually the main issue in that they need a supersonic LARGE airframe to test how well the theory works. As the only models available to test with (Concord and the Russian SST) were unable to accept large changes or modifications they have been limited in what they could actually do.

Dogma my ar$$e. Or you should complain about volcanic eruptions PODs being considered ASB. sonic boom is a law of physics, or maybe the thread should be moved to ASB.

While sonic booms are the resulst of the laws of physics they are not inevitable nor are they uncontrollable. And what Riggerbob is pointing out there was a LOT of hysteria and hype over both the effects and damage generated by the SSTs, especially the Concord. (He's not kidding about the amount of media and legal hyper that would occur for ANY Concord flight whether it happened or not)

Alt history types should better read the end of my post, where I mention NASA research on sonic booms.

NACA, the military and NASA all researched at various times, means to reduce or eliminate sonic booms for various reasons. But it wasn't till after the FAA tests in Oklahoma in 1964 that the public and researchers were significantly made aware of the effects of multiple long term exposures. And this itself wasn't followed up by more in-depth studies until the early to mid-70s where the actual results were still significantly exceeded by the "claimed" consequences.

Concorde survived only because the sonic boom was tolerated... over oceans.

And yet you still had groups and individualts claiming that Concorde flights TO the US were responsible for curdling milk in Virgina and causing earthquakes in California when they landed in New York :) Claims of being able to 'track' a Concord flight over the Atlantic by boats being damaged by over-flights was also never proven, or ozone depletion or fishery collapse which were also claimed to be all about the Concords sonic booms. It was in fact rare for anyone at sea to actually hear a sonic boom unless they were directly under the Concorde and even then it was more often than not a 'rumble' rather than a boom. Why? Surface and atmosphereic conditions and high humidity tended to dampen the shockwave significantly.

The Concorde was a first generation SST and showed it in performance and capability but you also needed that learning curve to transition from the over-optimism of the 50s to the reality of the 60s and move on through the 70s to an operational design.

To get a successful SST design you need to have researchers more aware of the actual problems and the public and media less hyper over the 'supposed' effects so that by the mid-70s you can start to design more economic, capable, and quieter air-frames. With time those would come as they have for smaller supersonic aircraft. Today to break into the market you have to have similar 'performance' (economics and passenger capacity) to the aircraft or significantly superior, (and Mach-1 or 2 won't cut it) performance in one or more areas.

Randy
 
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