Why don't passenger jets fly at supersonic speeds?

[silverpig]

Originally posted by: Canterwood
I think the fastest supersonic plane (officially) was the SR71 Blackbird. Now that baby was wayyyyyy ahead of its time, an awesome machine.

I dunno... just strap two of the biggest jet engines you can find onto a plane. Seems pretty simple. 🙂

 

[Mday]

As some of the others have already said, FUEL cost is the primary concern. Fatigue is another due to the stress PRE supersonic.

Also, there is little demand, especially since supersonic can only be done over the oceans due to the sonic boom, even if you design the wings and body to direct the boom in another direction.

 

[everman]

Originally posted by: silverpig

Originally posted by: Canterwood
I think the fastest supersonic plane (officially) was the SR71 Blackbird. Now that baby was wayyyyyy ahead of its time, an awesome machine.

I dunno... just strap two of the biggest jet engines you can find onto a plane. Seems pretty simple. 🙂

I remember a show about the SR71 that was awsome. They were talking to a pilot who flew over Israel during some conflict I don't remember. They could not tell Israel about the spyplane, so they flew it over the battlefield anyways and simply outran all of the missiles which were fired at it.

 

[Evadman]

There have been a few posts that hinted at this, but I am going to say it outright. Flying a non-military plane faster than the speed of sound is illegal in the US. From what I understand the maximum allowed speed is actually Mach 0.92.

 

[unipidity]

I didnt know that. Is it regulated by aircraft type, or is any civilian owned plane subject to the restrictions? I only ask because I know that in South Africa, there is a company that has bought an English Electric Lighnting or two and kept them in prime condition. They sell flights for silly money because people want to see what a jet fighter (albeit a 1960s jet fighter) is like... but I dont know if they go supersonic or not.

Presumably its airspeed, not groundspeed though. Sensible restriction, stop retards crashing due to some urge to try and break the sound barrier in a Gulf V or something....

 

[SonicIce]

So how really disturbing is a sonic boom anyway? How loud is it on the ground and how long does it last?

 

[gsellis]

Originally posted by: SonicIce
So how really disturbing is a sonic boom anyway? How loud is it on the ground and how long does it last?

It depends. When the shuttle goes over, you know it. You hear it inside in Orlando and it is above 50,000 feet. I remember tales of windows being broken by Air Force jets in the 60's before they put a halt to breaking Mach in regular airspace. Don't know how frequent it was. But the boom does interrupt lots of things, frighten animals, etc., ad naseum.

As for duration, it is boom boom. Just like a shotgun.

I do think I remember the FAA cracking down on some business jet pilots for exceeding Mach. It was more than 5 years ago though. My neighbor is a G3 driver and he should remember (he got home from a trip last night.) It may have been Citation X's (max cruise is listed as .92 Mach).

 

[dkozloski]

The advertised top speed of the SR-71 was about 2000 MPH. People in the program for eight years or more have told me that when the planes were rotated between Okinawa and Beale AFB the flight was flight planned at 4500MPH and they were not BSing. The engines on an SR-71 are unique to aviation. They are known as turbo ramjets. The major share of the compression required to operate them comes not from the compressor section of the engine but from the shock wave at the engine intake. The shock wave is formed from a cone that is computer controlled and is continually repositioned to operate properly. If the shock wave is disturbed for any reason it is a very serious situation and requires the system to immediately recapture the shockwave and get it back in the proper position. At Mach 2 and 80,000 feet altitude the total aerodynamic drag of the airframe is about 12,000 pounds but there are 33,000 pounds of thrust available per engine. Project manager Kelly Johnson has stated that if you gave the airplane to another country they could not duplicate any system in it in 100 years. The average temperature of every component part in cruise runs at 450 to 500 degrees F. The fuel is used as a heat sink for the cockpit A/C. The coolest part of the airframe is the interior walls of the cockpit and that measures 180 deg.F. The only thing that keeps the pilot from cooking is the spacesuit he wears. The pilot is subjected to physical examinations that are much more stringent that the astronauts. The successor to the SR-71 is designated by the code word Aurora and runs on a hydrogen fueled hypersonic scramjet. These have been seen flying at several places around the world and are characterised by the strange rumbling sound made and the string of smoke rings left behind. Analysis made of the sound and the video has produced estimates of the speed as at least 12,000 MPH +.

 

[unipidity]

Im sorry, but Aurora is a tin-foil hat type program. NASA's scramjets do not get close to being able to produce a fuctioning aircraft, especially not one that goes at Mach 20 or whatever ridiculous speeds are claimed for Aurora. Whilst you cannot discount the possibility of the development of classified engines, a project of that size would be impossible to hide in finacial terms. The many many billions required just for research, not to mention procurment costs boggle the mind.

Its the kind of thing mentioned on silly-season-all-year-round websites like abovetopsecret, by people who frequently dont have the slightest clue what they are on about.

 

[esun]

Originally posted by: pak9rabid
i think it's the combination of the costs to operate at supersonic speeds and also because of the sonic boom. I guess the airlines figure passengers really don't want to have to listen to a horribly loud boom from point A to B.

whoops, my bad..that's not how sonic booms work. but i could see some room for conflict if the average passenger plane was emitting sonic booms over highly populated areas.

This is correct. It was a combination of air pollution and noise pollution that resulted in the lack of supersonic commercial jets. Or at least that's what the History Channel says (and I trust them).

 

[tinyabs]

Most people choose cheap air ticket. The market dictates it. Expensive supersonic flight would not be an option for air travel companies as the fuel expenses usually take up 40% of the operating cost.

One of the concern is security. A hijacked plane travelling at supersonic speed would be a big threat. The air defence and fighter planes would not have time to react. If an air crash occurs, the debris would spread over a very large area, making recovery job very difficult like the recent space shuttle (Columbia) crash.

 

[systema]

Yeah...terrorists would be more interested in such a plane, which is another negative

 

[unipidity]

Hmm, good point. I wonder is Concorde's days might haev been numbered for that reason, excluding all the rest of the kerfufle. Having said that, I imagine that at low altitude Concorde couldnt have even approached M2.

 

[dkozloski]

unipidity, much the same was said about the SR-71 as is now reported about Aurora. SR-71 flew for years before being officially reported let alone with about double the performance that has been officially acknowledged. Something has been observed and recorded streaking across the sky making a strange rumbling noise and leaving a contrail surrounded by what looks like smoke rings. A good friend of mine who is scientifically grounded has seen the above described sight in southern California. Analysis by scientific professionals that matches the acoustic signature with the smoke ring shaped puffs in the video has put the speed of whatever is producing the disturbance at about 12,000 MPH. These tracks and noises being first reported coincides with the retirement of the SR-71. Logic dictates that something has replaced the Blackbird. As an aside, work of some sort has been going on at the Lockheed "skunkworks" long after the end of the SR-71 and F-117 projects. They aren't turning out hang gliders. Don't sell these guys short, they have a history of turning out one miracle after another.

 

[unipidity]

Uhhh.... the skunkworks have been bust with F-22 and F-35 designs, imo.

I simply do not think that the Blackbird could get even near 4500mph- that is a speed akin to that of a pre-accelerated NASA scramjet which is 95% engine. If something is going at 12,000 mph, it would have to be cacked in a heat-shield of somekind reducing performance enormously. Plans for a hypersonic skipping bomber have been around for donkey's but the engines simply DO NOT EXIST. A mach 4 aircraft using a air-breathing jet engine? Id say unlikely, but not out of the range of existing technology. Mach 20 is a mile from where we are now.

Moreover, the use of Aurora would be severly limited relative to the benefits of designing a trans-stage of an spacecraft around the technology which could revolutionise space travel and deliver all future satellite launches in US hands... worth trillions of dollars. Something that can travel at 12 kmph is in the right ballpark for this use.

Acquisitions are always approved by congress, to the best of my knowledge, even for projects like the B-2 or F-117. Can you imagine the cost of maybe 20 aircraft that far ahead of the prevailing technological bleeding edge? 100 billion? If a B-2 can cost well over a billion for something slow and LO, imagnie the unit cost of somethnig faster than anything else and LO.

Its a fantasy of people with too much time on their hands and a dubious obssesion with military aircraft. Its like someone saying that Nvidia are about to miss out a generation and release the NV65 which gives you 140fps in D3 at 2000x1880 with all options on. Its just not going to happen for a variety of technological and economic reasons.

 

[yhelothar]

Only way for the blackbird to go at 12,000mph is if it went into space, but then it would probably incinerate when it re-entered the atmosphere going at such high speeds.
Blackbird always looked like a futuristic looking spaceship to me 🙂

 

[BespinReactorShaft]

Anyone recall that Mach3 plane from the Soviets?

http://www.aerospaceweb.org/aircraft/fighter/mig25/

 

[dkozloski]

unipidity, The X-15 was flying an official Mach 6.7 in 1967. The heat resistant structure was primarily Inconel a rather common alloy used for exhaust systems and jet engine burner cans. No magic there. Ron Rowland was in the SR-71 program for eight years at both Kadena AFB, Okinawa and Beale AFB, Ca. He says that when a plane was transferred from Kadena to Beale a message was sent as soon as the plane left the ground stating when to expect it. In order for the planes to touch down at Beale when they did they had to AVERAGE 4500MPH. Maybe there was a secret base where some other plane stared out half way. I have worked in the missile and aerospace industry for almost fifty years and in that time I have talked to a lot of people with some remarkable experiences. For your education, look up PDWE engines and Aurora contrails on Google. You have a lot to learn grasshopper. I have heard a drag race between an F-104 Starfighter and a Blackbird described by an eye witness. The Blackbird sat on the end of the runway. As the the F-104 passed over going as fast as it would go at low altitude, the Blackbird began it's takeoff run. As the landing gear of the Blackbird finished the retraction cycle it was in the lead. When the Blackbird set altitude and speed records back in the sixties that haven't been exceeded to this day, Kelly Johnson was asked "What if the Russians top this?" His reply was "There is more under the hood".

 

[AnnoyedGrunt]

Going back to a point mentioned above, both the F-22 and YF-23 (the Northrup Proposal) were more stealthy than the F-117. The only reason the F-117 was angled was because @ the time of development the computers were not powerful enough to generate a smooth shape. With the advancement of materials and computers, the second generation of stealth aircraft were able to be both stealthy and retain the more efficient curved shapes.

I also read a funny anecdote (I can't remember where anymore), that during the radar testing of the F-117 a tech thought his radar was broken because he wasn't picking up any signal from the aircraft. All of a sudden he got a blip, and thought everything was fixed, but in reality a crow had landed on the stationary test aircraft, and it was the crow that was giving the radar signature.

Probably not true, but a fun story none the less.

-D'oh!

 

[Geomagick]

Originally posted by: unipidity
Hmm, good point. I wonder is Concorde's days might haev been numbered for that reason, excluding all the rest of the kerfufle. Having said that, I imagine that at low altitude Concorde couldnt have even approached M2.

You are quite right Concorde could not reach Mach 2 near the ground.

Gaining access to Concorde's flight deck was difficult enough on the ground let alone in the air when the armoured door was locked.
The space on the flightdeck was minimal and to get to the controls one had to go past the flight engineers panel and seat.

Also even if you could successfully get past the flight engineer and into one of the pilots seats most people (pilots of subsonic jets included) would have had real difficulty in flying the aircraft as it flew in such a different way to normal aircraft.

As for the economics of the aircraft between London and New York it used over 80 tonnes of fuel to carry 100 pax. The 747-400 uses just over 50 tonnes to do the same route with about 400pax plus several tonnes of cargo.

The economics for the aircraft just didn't add up and when Airbus announced that they would not longer support the aircraft it became impossible to operate after the cutoff date last year for legal reasons as well as economic ones.

In the current economic climate reducing costs is more important than increasing speed as can be shown by Boeing (scrapping Sonic Cruiser) and Airbus (building the A380 superjumbo).

 

[unipidity]

A second hand indirect observation of the speed of an aircraft that is a mile beyond concievable performance? Yeah, right.

PDE engines have serious conceptual problems, not least of which is the idea that you can have a fuel-air explosion on the skin of an aircraft without melting the damn things. The research state of such engines in offical terms is about nothing- as of 1995 no engines hads been produced.

The fact remains that NASA is still the primary source of aerospace research in the US, and the idea that Lockheed (who have specifically said that Aurora was a budgetry fudge to get more money for the B-2 ski) could do so much primary research at what is in essenece an engineering labs is silly. I cant discount it, but I can say that I would be hugely suprised.

The X-15 is a ROCKET, with all of the excess thrust that implies, launched from 45,00 ft, no 0ft, and utterly different from a hyopthetical non-rocket hypersonic aircraft.

TO sum up; the Aurora is a hypothetic craft with vastly over expanded performance specifications (some places claim that it is optically invisble, which is laughable) and no direct evidence exists of its operation. A lot of old cobblers has been thrown together by people with too much imagination and not enough critical thinking to make it look possible. The Lockheed TAV from '85 looks like a good candidate for something that might have become Aurora.

If the code name ever applied to a stealthy hypersonic aircraft, it has never reached production, and I would not beleive anything that put performance above mach 8.

 

[dkozloski]

unipidity,the invisible airplane is pretty easy to achieve. Another friend described a formation of aircraft wherein the center aircraft would come and go in visibility. It turns out that this was an experiment involving entirely covering the aircraft with LCD panels that would display the input from video cameras pointed in various directions around it. The coming and going was the video source being switched and adjusted. NASA is the visible aeroresearch arm in the U.S. but the military and CIA have their own group home based at Area 51 and Groom Lake. Historically, these guys come up with and develope the ideas and NASA feeds them out to the public. Case in point, the A-12, YF-12, SR-71, all existed for more than 10 years before NASA ever got involved. As far as possibilities for materials for constructing an Aurora type aircraft, there have been a hell of a lot more ceramic foam tiles produced than can be accounted for by sticking them on the outside of space shuttles. Some were used for the exhaust nozzles of the F-117 to reduce the heat signature from above by spreading out the engine exhaust. It is a fine thing to be skeptical but don't also be closed minded. Anything within the realm of the imagination is within the realm of possibility.

 

[unipidity]

LCD panels that are also ceramic tiles, or alternativly are going to function at a few hundred deg. C? Yeah, of cuorse. You could create such a system, and I have seen the odd attempt on a tank, but never a plane. Conformal LCDs, as well, unless you sacrifice masses of performance for no apparent gain and produce a bitch ugly angular box.
Why would a invisible plane be an advantage? It supposedly produces incredibly visible contrails all over the place, and how many missiles guide on sight? Moreover, an Aurora could be blatently visible and at your ridiculous specifications would be able to outrun anythng fired at at.

All of the aircraft you mention used technology that was not a million miles from commercial state of the art. You can design a passeneger airplane that goes Mach2, id be suprised if you couldnt develop a Mach 3.x ramjet powered spycraft. Its engineering, not basic science, which is what Aurora would need to have to get anywhere NEAR those specs. Add to that the fact that Aurora is two decades old and we have had not a sniff of any technology even close to producing such performance.... its a stupid concept.

Im not saying that a project called Aurora has never existed, but if it has, and that point is VERY much up to debate. Its nature is UNKNOWN, and the random speculation, and especailly performance cited in your post, IS RANDOM CRAP.

That last comment was stupid. I imagine a speed of light aircraft with the bomb capacity to blow up the universe. Possible? Hmmm.

 

[f95toli]

As Unipidity points out there is a difference between enginering and basic science and you would need a LOT of new science in order to build something like the Aurora.
Not even NASA does much basic science, their research focus on trying to "move" existing research (e.g a novel material) to the real world (and if it does not work they move on to another material). Most of the basic research is the world is done at universities, not in secret labs.

 

[dkozloski]

I made no statement that the LCD panel aircraft had any exceptional performance except that it appeared to come and go in visibility. it exists for whatever reason and has been obsrved in flight by several [people including my friend. The LCD panels were reported by the aviation press to be flexible plastic. I worked on ramjet powered surface to air missiles in the 1960's that traveled at Mach 3.5 and had a range of nearly 200 miles (Talos). Bendix was the prime contractor and the missiles were used on guided missile cruisers like the U.S.S. Columbus and U.S.S. Chicago. If you go to the Boeing aircraft museum you will find an SR-71 that has a drone mounted between the vertical tail surfaces that has obviously flown at very high speeds judging by it's scorched appearance. The drone appears to be powered by one of the same engines that powers the mother craft. The official designation is GTD-21B. Must I remind you that every system in the SR-71 was totally new technology that did not exist when it was first concieved, from the hydraulic fluid, to the tires, to the fuel, to the titanium structure, to the engines, to the electronics able to operate at unheard of temperatures, to the aerodynamics and it flew for years before anyone was aware of it except for a few sightings by people who were called nuts and liars. All I am saying is that Kelly Johnson's group at the Lockheed skunkworks or someone like them has not been asleep and someday we will know that I am right and you are wrong. I am patient enough to be able to wait for that day quietly instead of running around bleating about someone else spreading crap.