DailyDirt: Flying Faster Than The Speed Of Sound (Again)

from the urls-we-dig-up dept

The Concorde jet flew for nearly 30 years before it went out of service. And now, the time airline passengers spend in security lines wastes far more time than a supersonic jet could make up in the air (depending on the journey, of course). Still, traveling fast is cool, regardless if it’s done by air or in an evacuated tube — as long as it’s fast. Perhaps there’s some analogy to the Skyscraper Index where supersonic transportation designs arise right before an economic recession… so maybe hold off on buying a high-speed ticket to London.

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Comments on “DailyDirt: Flying Faster Than The Speed Of Sound (Again)”

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Anonymous Coward says:

Re: Concorde

They became too expensive to fly. At its core, the Concorde is a 1970’s vintage aircraft that uses inefficient, fuel thirsty turbojet engines and afterburners to achieve its speed. With the increases in fuel costs over the past two decades, the market just was not able to bear the cost of flying the Concorde.

In fact, Concorde would not have flown in the first place without massive subsidies provided by the British and French governments.

That’s the problem with supersonic transport: It’s devilishly expensive to travel at supersonic velocities for long distances. I can see an SST being useful for an executive jet, where reducing the travel time is more important than the expense. I don’t see supersonic commercial flight coming back on a large scale until there is a breakthrough in the technology that will allow a fuel efficient supercruise on a large aircraft.

John Fenderson (profile) says:

Re: Re: Concorde

“I can see an SST being useful for an executive jet, where reducing the travel time is more important than the expense.”

I have problems seeing even that use case. Perhaps there may occur some rare emergency requiring the physical presence of an executive on a rush basis, but what would such an emergency even look like?

Anonymous Coward says:

Re: Re: Re:2 Emergency transit of experts

My colleagues and I have experienced several situations such as this. I will share my experience, in generalities.

A widget that I had some experience with was failing lot acceptance tests. It was made up of two widgets, one supplied by the company performing the test (call them company A) and one supplied by another company (call them company B). Separately, they both tested fine by their respective manufacturers. However, the widget made by company b was cutting edge technology, and the application requires both a high degree of safety and reliability with good confidence. The decision was made to test widget A and widget B coupled together, like they would be when installed in the final product.

So, that was how the lot acceptance test for company B was carried out. The two widgets were attached together and then the whole subsystem was tested. This was done successfully for a number of production lots. However, within a timespan of a few months, there were multiple failures (this is a subsystem that was touted to have greater than 99% reliability at greater than 95% confidence, we would not expect to see this number of failures). A tiger team was assembled to figure out why these widgets were failing the test, and to correct the problems found. I was selected to be on the team.

Coming to the point now: Tests like the ones that we were doing are devilishly expensive. We were limited to the test site that was being used during the lot acceptance tests, and availability on that sites was sparse (the test site had to support a number of product lines, we were one of the smaller lines working with this test site). We had to get several days worth of testing time to hope to find what the problem was and attempt to correct it. Furthermore, the team had to be at the test site in person (as an engineer working with physical product, I find that I do not get the quantity or quality of information via telepresence that I get in person. This can be the difference between figuring out the problem and floundering around in the dark) The team was spread across the US, so scheduling time for the test sequence generally meant bumping other tests that needed to be done on the same equipment at the same site (difficult to do with a small production run). If we had the means to travel quickly cross country, we could make use of small and hard to predict gaps in the test schedule to run additional diagnostics and tests while reducing the cost of the failure investigation.

I think that it is in that role where SST will be most useful. Unless design and production are colocated, you have to have a way of getting the expertise of the design team, the production team, and the test team together at a given site quickly in order to resolve problems in a timely manner. If the product has enough priority, or is worth enough, I think that there would be a market (however small) for supersonic flights.

Andrew D. Todd (user link) says:

Re: Re: Re:3 Emergency transit of experts

Well, the thing is that, due to the sonic boom issue, you can only fly a SST over water. The sonic boom issue is real. It is not something you can wish your way out of. The sonic-boom track at high altitude is fifty miles wide. Over land, it is practically impossible to find a route which does not annoy millions of people. Say, a million people, filing claims for a thousand dollars each, that is a billion dollars. Read the Shurcliff book. Among other things, it has a transcript (ch. 6) of two high federal officials (an Undersecretary of Transportation, the Administrator of the FAA) being grilled by an angry congressman. I assure you that the present uproar about the drones is trivial by comparison. Anonymous Coward #13, I don’t know who you are, of course, but I doubt that you are that much of a big shot.

At one point, the Air Force was using sonic booms as weapons of cold war against Cuba. They would deliberately fly SR-71’s at Mach 3 over Havana, so that windows would be smashed, and the explosion-like noise would panic the population, who would be diving for the bomb shelters in the belief that the Air Force was about to bomb them back to the stone age.

There have been cases of people on the ground being killed by sonic booms, when the shock waves triggered the collapse of buildings, and suchlike. In the early 1960’s, air forces tended to show off with sonic booms. They managed to stoke a cumulative public anger, and mass-protest movements.

Anonymous Coward says:

Re: Re: Re:4 Emergency transit of experts

The sonic boom issue is not a technical problem, but an engineering problem. It is most likely a straightforward engineering problem, and I will tell you my reasoning behind this.

#1: Air is a terrible medium for propagation of shock waves. For one, shock waves propagate in a sphere, and drop off proportional to 1/r^3. Air is also compressible, which means that shock is not transmitted very well. An example of this effect is the german stielhandgranate of the second world war, which was constructed with a thin steel case that did not produce fragments. This was designed to produce an overpressure (similar to a sonic boom, detonations are supersonic after all). Data collected during the war showed that, unless the weapon was used indoors where there was some containment of the shock, it was not very effective.

#2: NASA did some studies using a modified F-5 to determine if shaping of an aircraft can be used to reduce the sonic boom signature. They were successful in reducing the intensity of the boom, though it did stretch out the duration a little.

#3: We now have complex aerodynamic simulation utilities. These are used to make the complex shapes required for a diverterless supersonic inlet (see F-35). This can be used to refine the effects of the NASA empirically derived shock attenuation data into a practical SST.

I think that careful shaping, derived from computer simulations backed by empirical data, coupled with extreme high altitudes (e.g. 70K feet) would sufficiently attenuate the sonic boom as to make it unnoticable from ground level. The problem then becomes the extreme expense of flying to those altitudes and speeds.

Sonic booms are not as intense as you think. There is a military air base near where I live/work, and they occasionally fly fighters overhead at supersonic velocities and high altitudes. If I was not told it was happening, then I would never have known. Additionally, I don’t think the thunderscreech killed anyone, though it was undoubtedly unpleasant to be around. My recollection of an SR-71 overflight was a few rattled windows.

The last time that I heard of windows being broken around here was back in the 70’s when a pilot flew over town at about 500ft AGL going supersonic. That broke out a few windows, and seriously pissed off the base commander. It also earned the pilot the callsign “boomer”.

A colleague of mine tells a story of when he was driving home and an F-104 flew over at about 50 feet AGL at supersonic velocities (there was a low-level supersonic corridor running along that road). It didn’t damage his car, but it did cause him to inhale his seat.

I will admit that I am most decidedly not a big shot. I’m just an R&D engineer with delusions of grandeur. However, if the project has enough priority, the unobtainable can be obtained and mountains can be moved (I’m thinking of the Manhattan project as an example). Either that, or pilots wanting to get back in time for happy hour.

Andrew D. Todd (user link) says:

Re: Re: Re:5 Emergency transit of experts

Of course, you would be talking about a much bigger aircraft than an F-5, and operating at a much higher Mach number. You notice that Airbus is talking Mach 4-5, because that is what they would need to achieve a substantial improvement in net speed, inclusive of ground travel, airport delays, climb to altitude, etc. No one is really interested in a twenty percent improvement in effective speed. It has to be a hundred percent faster or two hundred percent faster before it enables new uses.

My source for the Cuban overflights– you will recall that there was a thaw in relations during the Carter administration, and a sub-official representative from the State Department was sent to Havana. He subsequently wrote his memoirs, and admittedly, I am going by memory. I think I read the memoirs about 1990.

I know that in West Virginia, coal mine operators get away with a lot of stuff by pointing out that their activities create jobs. As you will be aware, most air bases are in the hardscrabble rural South or Inter-Mountain West. The employment factor has to be taken into account. That doesn’t mean that you could get away with flying like that over Chicago on a regular basis. Again, quoting Shurcliff (ch. 4), a series of 49 supersonic flights over Chicago in 1965 resulted in “7128 complaints, 3156 damage claims, and 1,464 payments aggregating $116,229.” Say, about a million dollars in modern money, and the mental climate was different. People were more reluctant to complain, on the other side of the Vietnam War. In the more extensive Oklahoma City tests in 1964 (1,254 flights at 1.3 psf over five months) there were more than 15,452 complaints in a population of 324,000. Figuring that the complaints were actually on behalf of households rather than individuals, that would have been a complaint rate on the order of 20%. When twenty percent of the population is complaining, that becomes a political fact. The local congressman is forced to declare open season on the relevant officials. The congressman who so vigorously interrogated the two high government officials was Sidney R. Yates (1909-2000, served in the House, Dem, IL., 9th district, 1949-63, 1965-99). His constituency was on the North Side of Chicago. He had obviously gotten a clear and unmistakable message from his constituents. No politician can tollerate a more or less discretionary government program which actively antagonizes twenty percent of the population.

I don’t know that the Manhattan project is a valid comparison. Apart from anything else, by modern standards, both Gen. Leslie Groves and Robert Oppenheimer would be facing homicide charges in the death of Louis Slotin, a junior scientist who got a fatal does of radiation while initiating a fission reaction on the lab bench in front of him by pushing two chunks of uranium together with a screwdriver. When the screwdriver slipped, Slotin was obliged to pluck the chunks of uranium apart with his bare hands. Bosses can be prosecuted for industrial accidents of that order of recklessness.

Anonymous Coward says:

Re: Re: Re:6 Emergency transit of experts

Actually, most test flights occur near population centers, and that includes supersonic test flights. The USAF tests its aircraft at Edwards AFB, just north of Lancaster/Palmdale (suburbs of Los Angeles). NASA Dryden research center (where the testing with the F-5 was done) is colocated at Edwards AFB. The SR-71 was built in Palmdale, and routinely flew supersonic from there back in the day. The Navy has NAWS China Lake just north of Edwards, and NAS Patuxent River 60 miles south of Washington DC.

I’m sure that supersonic flights piss off a number of folks in the overflown paths, given the right conditions. If atmospheric conditions are right, you can get stronger propagation of sonic booms. That, coupled with pilots flying a lower altitude, make for a bit of a racket. That is why most supersonic flights are conducted at high altitudes (above 30K feet) on days where the weather does not support good propagation conditions. Flying a commercial plane at 70K feet will result in approximately 16x more attenuation than flying at 30K feet.

I personally was thinking an aircraft on the order of a 6 passenger gulfstream G100. Those aren’t that much bigger than an F-18.

As for Slotin, you really don’t know the whole story. The experiment that he was performing was informally called “tickling the dragon’s tail,” and was understood to be highly dangerous. It involved lowering a neutron reflector onto a core of Plutonium. There was a special tool to do this operation, but Slotin decided to use a screwdriver instead. When the screwdriver slipped out, a burst of prompt neutrons was released. Slotin was able to slap the assembly apart within a short time. His actions saved 5 others who were in the room with him. He was a damned hero.

Andrew D. Todd (user link) says:

Re: Re: Re:7 Emergency transit of experts

It depends on what you consider “near.” I don’t consider the Edwards/Mojave Desert area to be near Los Angeles, and there’s an impressive mountain range between them. It is only comparatively recently that Los Angeles suburbia has breached the mountains.

My understanding was that Airbus was proposing a good-sized aircraft, with large engines and fuel tanks, and only a small passenger compartment, an asymptotic approach to the ideal of a aircraft consisting of engines, wings, fuel tanks, and nothing else.

The point about Slotin is that you are supposed to have a safety officer, whose job is to prevent young hotshots like Slotin from doing reckless things which subsequently require them to become heroes. This does slow the work down, of course, and, under wartime conditions, safety standards slipped. Calling someone a hero is often a kind of convenient absolution for the people ultimately responsible. Mine owners do it all the time to refer to miners who have been killed through the mine owners’ greed.

There is evidence that in 1964-68, over-pressures of 1.3 psf provoked widespread resistance. A lot of things have gone on since then, and people simply are not as docile in the face of authority as they used to be. I suspect that you will find that the current acceptable figure is much lower.

Anonymous Coward says:

Re: Re: Re:8 Emergency transit of experts

I suppose my definition of near is different from other folks. I count near as being within an hour and a half by car.

I’m going to review the Airbus design. I originally was merely offering my opinion on what the optimal use for an SST, which will dictate the form factor for an SST. From the use case of an executive transport, with a top speed of about Mach 2.5 (speed limit determined by the materials, concorde showed that Mach 2.5 is about the limit for 2000/7000 series aluminum alloys, any higher than that and you need to go to titanium [SR-71] or stainless steel [MiG-25]) and a passenger capacity of 6-9 people. That is within current manufacturing capability, if we can get the engines/fuel system to work efficiently enough. I suppose that my viewpoints are informed by a previous life as a systems engineer, where we go from requirements to form factor. The airbus design seems to be a solution in search of a problem, particularly with how expensive the craft will be to operate and its limitations to oversea routes.

I am familiar with safety. Try reading the safety manuals for fuzing sometime (MIL-STD-1316, MIL-STD-1901, both available on assist.dla.mil). They’re (almost literally) written in blood, nearly every disallowed practice is because there was an accident that was caused by that practice sometime in the past.

Oddly enough, you mentioned something that I was thinking of when I mentioned the Manhattan project earlier. Los Alamos had a bit of a reputation for being lax with safety. Groves thought they would blow themselves up if tasked with building the bomb (they were only able to produce a few lens assemblies, most of which were used up at Trinity). Parsons mentioned that China Lake was producing aerial rockets in vast quantities, and could most likely produce explosive lenses. They were also doing work on aerodynamics and prox sensors for the project, so this was a logical outgrowth. Groves okayed the production facility, and the Salt Well Pilot PLant went from open desert, where they didn’t even know how they were going to produce the lenses to full rate production in 115 days. If the priority is there, anything is possible.

Andrew D. Todd (user link) says:

Re: Re: Re:9 Emergency transit of experts

The only plausible use-case for a Mach 5 airliner is to cross the Pacific in a couple of hours, from the United States to China. However, there are massive cultural differences, apart from the language issues. The one place where flying in, barking orders, and flying out again is not going to work, is China.

I think that, in the largest sense of the word, the real issue is that Airbus is getting Backed into the Corner. The situation is more acute for Airbus than for Boeing, because of the way that “native son” markets operate. At a certain level, Airbus’s most fundamental competition is the French SNCF Railroad (Societie National de Chemins de Fer). At the time of the Olympics, I heard a rather curious story: people who could not get hotel rooms in London were staying in Paris, and taking the high-speed “chunnel” train over to see the games, using the high-speed train as a commuter train, in effect. Last time I checked, the railroad had a 75% market share between London and Paris. And obviously, this is just the beginning. When people whom you might normally regard as stable and sensible get Backed into the Corner, they suddenly start doing crazy things, and one has to make allowance for this. The same goes for Lufthansa, and the recent GermanWings crash.

You have to recognize that someone who is in competition with you, if only at the level of funding, will find a means to operate by remote-control, which is to say, over the internet. You can get into an impossible situation, trying to outrun the internet by physical travel.

Anonymous Coward says:

Re: Re: Re:4 Emergency transit of experts

“The sonic boom issue is real.”

Made so by Boeings department of astroturfing. The protests about this back in the 80’s were just silly. I grew up in Europe during the cold war, and every once in a while some jet jockey needed to get somewhere in a hurry, and you’d hear the double boom. It would rattle a window or two. As a kid I would run outside and see if I could see the plane that did it. Certainly less scary than thunder.

Personally I believe there is a market for a smaller SST, maybe about the size of a CRJ200.

I could totally see connecting Halifax to London with the SST, and then connecting CHI, NYC, DUL to Halifax. Great circle your pretty much flying over Halifax anyway, so all you’re doing is adding a transfer.

But you’d need a few dozen other routes to justify the engineering costs.

Andrew D. Todd (user link) says:

Re: Re: Re:5 Emergency transit of experts

Well, imagine, if you will, a fleet of 200 SST’s on a given route, each plane doing two round-trips a day, and generating 40,000-60,000 round-trip seats a day, with a class of 1-2 million people who fly more or less monthly. Coming and going, that means that 800 SST’s pass over a point en route per day, or one every minute and forty-eight seconds, on average. All day long, all night long, every day, Sundays included. Holidays too. You could see that this might get a bit tiresome.

Andrew D. Todd (user link) says:

Sonic Booms.

The main thing which caused the American SST project to be shut down was the Sonic Boom issue. I refer you to William A. Shurcliff, _S/S/T and Sonic Boom Handbook_, 1970.

I am immensely suspicious of claims to have eliminated the Sonic Boom. The basic physics of the situation are that an airplane has to shove air downward in order to stay up. Second, if the airplane moves faster than the speed of sound, this displacement will be concentrated at one point at a time. A claim to the contrary, without scientific publication to back it up, is rather like Cold Fusion.

In thermodynamics and fluid dynamics, there is a notion called the control volume. You draw an imaginary cube of air surrounding the airplane, and on the surfaces of this cube, the laws of matter conservation, energy conservation, and momentum conservation have to operate. If you cannot show how your airplane is going to stay up without pushing air downwards across the lower boundary of the control volume, it isn’t science. It doesn’t matter what shape the wings are– the basic laws of physics have to operate at the control volume boundaries.

Trains are gradually driving out airliners. A rough rule of thumb is that a train can compete with an airplane whose top speed is about twice the top speed of the train. In Europe and Asia, they are building increasing numbers of railroads fast enough to drive out airliners. This means that once a train gets up to, say 350 MPH, it becomes “economically supersonic,” in the sense that an airplane would have to be supersonic to compete. The French SNCF has achieved 357 MPH in a test run on its newest high-speed track running east from Paris. This means that the airline and aircraft industries are gradually developing paranoid symptoms, and beginning to tell themselves lies.

Another point is that any kind of business travel is immensely vulnerable to a competitor who can figure out how to travel electronically. It’s all very well to get in an airplane, and go five or ten thousand miles, but when you get there, you will probably find that the people speak a different language. If you don’t have someone there, who you can trust sufficiently, and give enough authority to, that you don’t have to send the head honcho for every little thing, then you have already lost.

The kind of travel which is valuable is usually student travel. Rather than zooming the CEO around, you want to put your money into a traveling apprenticeship scheme for newly hired engineers or accountants. You send young people, who are both mentally and physically adaptable, to spend a year or so somewhere, and “absorb the atmosphere,” to gain some personal experience against which they can afterwards test reports at a distance. That sort of thing is best done with a rucksack on one’s back.

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