Possible technologies to greatly mitigate sonic boom in supersonic planes

I came across this reply in a dead Supersonic Travel thread.

If TL;DR, the statement says that fears about sonic booms were too hyped, as at high altitudes, the sonic boom's intensity would be very low. The user basically says that had knowledge about sonic booms been discovered earlier, people would have been more well-informed and not be too scared of SSTs and that efforts to lessen the sonic boom to tolerable levels would have been made, and thus they would have been widely used*. IMO, this also is a good case to make that had knowledge about sonic booms been discovered earlier, the SSTs would also have been widely used between inner cities as well.

*That is, if there were many SSTs before the 1973 Oil Crisis, or there were no 1970s Oil Crises at all, which would make SST travelling much cheaper

With that, what innovative technologies could have been available in the 1960s to mitigate sonic boom levels to extremely tolerable ones*2, so much that SSTs are the dominant form of travel not just in Continental and Transatlantic flights, but also, for intercity flights, e.g. between cities in the continental US like LAX-JFK?

*2 Even then, as the reply below said, the sonic boom, without much regulation, would even just be a low rumble if the SST flies at high altitudes.

Summoner wrote:


Archibald wrote:


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.

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.

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.



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)

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.

And yet you still had groups and individuals 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
 
Even if the Sonic-boom was not mitigated at first then the super-sonic planes could perhaps still be used for flyover above sparsely populated areas. In the meantime reserach could be made into how to mitigate the sonic-boom. One advantage of this is that it would give some revenue, but more importantly it would give scientists more data(or the possibility to gather more data).
 
Even if the Sonic-boom was not mitigated at first then the super-sonic planes could perhaps still be used for flyover above sparsely populated areas. In the meantime reserach could be made into how to mitigate the sonic-boom. One advantage of this is that it would give some revenue, but more importantly it would give scientists more data(or the possibility to gather more data).

Indeed, IMO they could have done that overland, but they didn't. That's why if I were to create a scenario based on that, I'd have a sitting US President be an avid supporter of the SST, and the POTUS will debunk myths and help rally the SST cause in Congress, thus allowing it to be used overland by traversing sparsely-populated areas. It was certainly doable in the West but harder in the Northeast with the more closely-located cities, esp. in the Northeast, but it's certainly doable.

Even then, as the above quote in the OP said, the SST booms at around 50,000-60,000 feet would be barely heard and would not gravely affect people. So your proposition really, really helps in making SSTs the dominant form of transportation in the present day.

How did sonic-booms impact non-human lifeforms(Whales, Walrus, Birds, Fish, Domesticated Animals, etc)?

Apparently, save for avian species, i.e. birds, the effect is minimal

Another study says the startle response in humans and animals dissipates quickly

And another study says the sonic boom's effect on animals is somewhat minimal, and the animals that do go deaf are just rodents and some birds. Even then, the boom simulations were at high decibels at the order of around +150 dB, and I doubt sonic booms would be that loud
 
And @Hvalrossen, I'm also thinking that had the growth of American suburbs been slowed, i.e. the majority of Americans still live in big cities, then it would be much easier for supersonic planes to avoid populated areas, since the growth of the suburbs greatly expanded the area in which Americans were living in, so it became harder to avoid sonic boom over populated areas.
 
Indeed, IMO they could have done that overland, but they didn't. That's why if I were to create a scenario based on that, I'd have a sitting US President be an avid supporter of the SST, and the POTUS will debunk myths and help rally the SST cause in Congress, thus allowing it to be used overland by traversing sparsely-populated areas. It was certainly doable in the West but harder in the Northeast with the more closely-located cities, esp. in the Northeast, but it's certainly doable.

Even then, as the above quote in the OP said, the SST booms at around 50,000-60,000 feet would be barely heard and would not gravely affect people. So your proposition really, really helps in making SSTs the dominant form of transportation in the present day.



Apparently, save for avian species, i.e. birds, the effect is minimal

Another study says the startle response in humans and animals dissipates quickly

And another study says the sonic boom's effect on animals is somewhat minimal, and the animals that do go deaf are just rodents and some birds. Even then, the boom simulations were at high decibels at the order of around +150 dB, and I doubt sonic booms would be that loud
Walrus are quickly frighened and when they get scared a stampede can occur. This stampede can runover other Walrusses, especially young Walrus risk death and/or damage. Perhaps the super-sonic-plane will have to avoid areas with Walrus populations?

Trans-sea(Trans-Pacific, Trans-Atlantic,etc) flights might be the most appropriate.

It would likely help the SST technology if it were not given up on as early as it were. Then there would be more interest in researching SST technology.

Rodents reproduce quickly so they might not be the lifeform most impacted.
 
Walrus are quickly frighened and when they get scared a stampede can occur. This stampede can runover other Walrusses, especially young Walrus risk death and/or damage. Perhaps the super-sonic-plane will have to avoid areas with Walrus populations?

Trans-sea(Trans-Pacific, Trans-Atlantic,etc) flights might be the most appropriate.

It would likely help the SST technology if it were not given up on as early as it were. Then there would be more interest in researching SST technology.

Rodents reproduce quickly so they might not be the lifeform most impacted.

You can say that on walruses. Certainly, it has to avoid their habitats. Not hard as they're mostly located in far-off areas near the poles.

I agree that they would best be useful for transcontinental and transatlantic routes, even though as you said the planes can be used over land by taking routes over sparsely-populated areas. No affected population centers over sea > Not-that-affected population centers over land.

Yes, I kinda think they should have pushed forward, though with the turmoil of the 1960s and overhyped fear over it, funding for the SST program was greatly reduced :(
 
Indeed, IMO they could have done that overland, but they didn't. That's why if I were to create a scenario based on that, I'd have a sitting US President be an avid supporter of the SST, and the POTUS will debunk myths and help rally the SST cause in Congress, thus allowing it to be used overland by traversing sparsely-populated areas. It was certainly doable in the West but harder in the Northeast with the more closely-located cities, esp. in the Northeast, but it's certainly doable.

Even then, as the above quote in the OP said, the SST booms at around 50,000-60,000 feet would be barely heard and would not gravely affect people. So your proposition really, really helps in making SSTs the dominant form of transportation in the present day.



Apparently, save for avian species, i.e. birds, the effect is minimal

Another study says the startle response in humans and animals dissipates quickly

And another study says the sonic boom's effect on animals is somewhat minimal, and the animals that do go deaf are just rodents and some birds. Even then, the boom simulations were at high decibels at the order of around +150 dB, and I doubt sonic booms would be that loud
By making supersonic travel the form of air travel you just reinvented the jet set. Regardless of whether there was an oil crisis or not it still is going to use a lot more fuel which is going to raise the cost of flying. I think what you would see is two classes of air travel Super Sonic and non Super Sonic. I'm not against the SST and I also wonder if the death rate per million miles we go up with supersonic if you have a engine problem and you're at 30000 ft a lot easier to solve the problem then if you're at 70,000 feet you crash and it is if you're with an Super Sonic
 
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By making supersonic travel the form of air travel you just reinvented the jet set. Regardless of whether there was an oil crisis or not it still is going to use a lot more fuel which is going to raise the cost of flying. I think what you would see is two classes of air travel Super Sonic and non Super Sonic. I'm not against the SST and I also wonder if the death rate per million miles we go up with supersonic if you have a engine problem and you're at 30000 ft a lot easier to solve the problem before you crash and it is if you're with an Super Sonic

Hi, can I ask, what do you mean by reinventing the jet set?

Yeah, supersonic planes will be more expensive than subsonic planes. And you're saying it's easier to solve an engine problem with a supersonic plane?
 
Hi, can I ask, what do you mean by reinventing the jet set?

Yeah, supersonic planes will be more expensive than subsonic planes. And you're saying it's easier to solve an engine problem with a supersonic plane?

Back in the late 50s in the 60s until the 747 came out there was The Limited capacity on the 707, DC 8 Etc so tickets for very expensive so the term for people who could afford to fly was the Jet Set. And that ends today's lesson of ancient slang.

I chose the engine as an example but it's basic physics if you have brake failure in your car do you want to be doing 35 miles an hour or 75 miles an hour. There's higher stresses the point that the first generation Concord one of the major reasons it crashed the one that ad is that a strip of metal that wouldn't affect your tire cars got thrown up into the wing on take off. So any problem you have is going to be magnified by how high you are and how fast you're going. A good example was beginning of the jet age of commercial transportation 707, dc-8, Etc had a much higher rate of accidents and fatality then they do today. The Concorde gave slight Edge to Future supersonic travel by finding some of these little errors but ask DeHaviln <sp>the devil's in the details.
 
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I’m quoted? :)

Something to keep in mind for SST travel is that sonic booms are really only part of the problem especially early on. Supersonic aircraft of the 60s and early 70s for the most part have VERY loud engines which due to sound mitigation regulations were no longer ‘acceptable’ at most airports by the early 70s. The climb-out and landing pattern noise for the proposed US-SST was exceedingly loud and would be found to be unacceptable over any city population. And since that’s where these things would fly in and out of…

Also keep in mind that the ‘effective’ utility of an SST has a great deal to do with its climb-to-altitude/speed capability which arguably before the advent of more efficient engines in the late-70s and early 80s is questionable. (On anything less than coast-to-coast routes you don’t have time to climb-out from takeoff to altitude/speed before you are entering the landing pattern of the destination. For example some of the most ‘productive’ routes such as LA to Las Vegas are too short to benefit from supersonic transit. Similarly Boston to New York has that issue plus most of the flight is over heavily populated areas)

Early on it was quite clear that air-frame shape had a lot to do with sonic boom propagation as well as creation. For example the B-58 is a very ‘boomy’ air-frame whereas the XB-70 was somewhat less. Finally there is aspects of the flight profile which can also be used to mitigate the boom and noise issue BUT are dependent on VERY different flight protocols and procedures. For example a direct takeoff and then extreme, (70 degree AoA for example) climb to supersonic speed and high altitude, (60K+ft) actually reduces you sonic boom foot print since it’s mostly at an extreme angle to the ground but it require VERY powerful engines and clear climb corridor. And while passengers can probably get rapidly used to such a climb-out arguably you’d have a similar ‘drop-down’ on landing and passengers won’t be as willing to accept what ‘feels’ like “diving-into-the-ground” angle of attack on coming in :)

This book helps give a pretty good picture of both early and later mitigation research:
https://www.nasa.gov/sites/default/files/files/QuietingtheBoom-ebook.pdf

It shows that around 1963 it was becoming clear that the initial idea of front and back, (bow and tail) shocks being the main contributors to the sonic boom weren’t accurate and that many other features, (again the B-58 was a big contributor to this data as its engine-pods, wing surfaces, weapons pod and even canopy was found to contribute to its sonic foot print) on an air-frame contributed to the extent and magnitude of a sonic boom. (Page 17 shows a ‘shock’ model of an X-15 and looking closely you see over a half dozen ‘shocks’ coming off the basic body and wings!) At the same time planning for the US SST was focused on designs that, frankly, had the highest sonic boom issues literally ‘built-in’ with podded engines, variable sweep wing surfaces and separate ‘flying’ tail surfaces.

Oddly enough some of the earlier work showing that specific shaping of the body and air-frame could probably mitigate sonic booms ran headlong into the ‘fact’ that such modifications tended to be “less appealing” to consumers and passengers which is still today a problem. (The “Pelican” F-5E SSBD demonstrator is in fact a very effective shape… Try applying that to an airliner though and most ‘customers’ will worry about paying passengers not wanting to ride on something that ugly :) Oddly enough I seem to recall a vaguely similar concept at some point during the XB-58 evolution but the ‘nose’ fell away with the expendable bomb-pod… Supposedly to ‘clean’ up the design for a dash home… Missed opportunities )

In the end it would probably take more modern design AND materials to make a really viable SST available, see:
https://www.machinedesign.com/motion-control/next-nasa-x-plane-born-boom

Randy
 
I’m quoted? :)

Something to keep in mind for SST travel is that sonic booms are really only part of the problem especially early on. Supersonic aircraft of the 60s and early 70s for the most part have VERY loud engines which due to sound mitigation regulations were no longer ‘acceptable’ at most airports by the early 70s. The climb-out and landing pattern noise for the proposed US-SST was exceedingly loud and would be found to be unacceptable over any city population. And since that’s where these things would fly in and out of…

Also keep in mind that the ‘effective’ utility of an SST has a great deal to do with its climb-to-altitude/speed capability which arguably before the advent of more efficient engines in the late-70s and early 80s is questionable. (On anything less than coast-to-coast routes you don’t have time to climb-out from takeoff to altitude/speed before you are entering the landing pattern of the destination. For example some of the most ‘productive’ routes such as LA to Las Vegas are too short to benefit from supersonic transit. Similarly Boston to New York has that issue plus most of the flight is over heavily populated areas)

Early on it was quite clear that air-frame shape had a lot to do with sonic boom propagation as well as creation. For example the B-58 is a very ‘boomy’ air-frame whereas the XB-70 was somewhat less. Finally there is aspects of the flight profile which can also be used to mitigate the boom and noise issue BUT are dependent on VERY different flight protocols and procedures. For example a direct takeoff and then extreme, (70 degree AoA for example) climb to supersonic speed and high altitude, (60K+ft) actually reduces you sonic boom foot print since it’s mostly at an extreme angle to the ground but it require VERY powerful engines and clear climb corridor. And while passengers can probably get rapidly used to such a climb-out arguably you’d have a similar ‘drop-down’ on landing and passengers won’t be as willing to accept what ‘feels’ like “diving-into-the-ground” angle of attack on coming in :)

This book helps give a pretty good picture of both early and later mitigation research:
https://www.nasa.gov/sites/default/files/files/QuietingtheBoom-ebook.pdf

It shows that around 1963 it was becoming clear that the initial idea of front and back, (bow and tail) shocks being the main contributors to the sonic boom weren’t accurate and that many other features, (again the B-58 was a big contributor to this data as its engine-pods, wing surfaces, weapons pod and even canopy was found to contribute to its sonic foot print) on an air-frame contributed to the extent and magnitude of a sonic boom. (Page 17 shows a ‘shock’ model of an X-15 and looking closely you see over a half dozen ‘shocks’ coming off the basic body and wings!) At the same time planning for the US SST was focused on designs that, frankly, had the highest sonic boom issues literally ‘built-in’ with podded engines, variable sweep wing surfaces and separate ‘flying’ tail surfaces.

Oddly enough some of the earlier work showing that specific shaping of the body and air-frame could probably mitigate sonic booms ran headlong into the ‘fact’ that such modifications tended to be “less appealing” to consumers and passengers which is still today a problem. (The “Pelican” F-5E SSBD demonstrator is in fact a very effective shape… Try applying that to an airliner though and most ‘customers’ will worry about paying passengers not wanting to ride on something that ugly :) Oddly enough I seem to recall a vaguely similar concept at some point during the XB-58 evolution but the ‘nose’ fell away with the expendable bomb-pod… Supposedly to ‘clean’ up the design for a dash home… Missed opportunities )

In the end it would probably take more modern design AND materials to make a really viable SST available, see:
https://www.machinedesign.com/motion-control/next-nasa-x-plane-born-boom

Randy
How does the Sonic booms relate to the b-58's ability to get to its Target without being exposed to additional Danger from the enemies defenses?
 
How does the Sonic booms relate to the b-58's ability to get to its Target without being exposed to additional Danger from the enemies defenses?

Really you can 'track' a supersonic target with a series of ground based sound/seismic sensors and part of the rationale of developing such sensors as were later used to study sonic booms was for this reason. In the USSR's case they had issues with getting accurate radar coverage over a lot of the Northern Tier territory so deployed as sound/seismic system but it never worked very well. The US doubled down on radar and put up a series of ''lines" instead. Interestingly the early sonic boom studies pointed out that the boom itself could do damage and it was one of the reasons the PLUTO/SLAM was designed to fly so fast so low :)

Randy
 
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