a380900
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Could Concorde Fly Transatlantic Subsonic Flight?

Mon Aug 09, 2004 4:27 am

Would flight mixing subsonic over land and supersonic over sea have been possible with concorde without reducing the range too much? Could it have gone supersonic twice during the same flight without burning too much fuel?

My question is in fact related to a possible new SST business jet. If it cannot fly supersonic overland, it will have to have good subsonic flight capabilities for flights mixing sea and ground flying. Is it a possible engineering achievement? How was the Concorde doing in this respect?

[Edited 2004-08-08 21:34:46]
 
DfwRevolution
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RE: Could Concorde Fly Transatlantic Subsonic Flig

Mon Aug 09, 2004 4:34 am

Possibly, but the Concorde would be even less fuel efficent if that is possible. Braniff tried to opperate the Concorde subsonically between DFW-IAD then onto LHR at one point, crusing at Mach .9 over land, but the economics were terrible. I think when BA/SQ tried LHR-SIN, they had to opperate a stage over India subsonically because the booms were spooking sheep heards.

Point is, the Concorde was not designed for subsonic flight. The wing profile is not very efficent at low speeds and the engines are very-low bypass which does not help fuel burn-

http://www.concordesst.com/history/events/sia.html
http://www.concordesst.com/history/events/braniff.html
http://www.concordesst.com/concordeb.html
 
LHR27C
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RE: Could Concorde Fly Transatlantic Subsonic Flight?

Mon Aug 09, 2004 6:09 am

Concorde's engines are as efficient as you can get on supersonic flight in terms of fuel used per mile. The Olympus/SNECMA 593s were designed very carefully to be very efficient turbojets at supersonic speeds.

However in subsonic flight the efficiency is very much lowered, due mainly to the drag experienced by the delta wing shape and the low lift/drag ratio. I think the fuel consumption per mile is (or was  Sad) almost 10 times on final approach what it is in supersonic cruise, so I doubt whether it would make it.

A newly designed SST might well be able to make it, one of the key features of the Concorde B project was the increase in fuel efficiency.
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spacecadet
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RE: Could Concorde Fly Transatlantic Subsonic Flig

Mon Aug 09, 2004 7:13 am

There's work going on right now in "silent" supersonic travel - ie. supersonic without the sonic boom. That seems like a better answer than trying to create a plane that can travel at both sub and supersonic speeds efficiently.
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bill142
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RE: Could Concorde Fly Transatlantic Subsonic Flight?

Mon Aug 09, 2004 9:56 am

How do you go supersonic without a boom?
 
gigneil
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RE: Could Concorde Fly Transatlantic Subsonic Flight?

Mon Aug 09, 2004 12:03 pm

How do you go supersonic without a boom?

Modern math proves it to be impossible, however, the boom can be redirected away from the ground, and the one that does reach the ground will be minor.

N
 
B2707SST
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RE: Could Concorde Fly Transatlantic Subsonic Flight?

Mon Aug 09, 2004 12:06 pm

How do you go supersonic without a boom?

It involves reshaping the aircraft, especially the nose, to weaken the shock wave. You can never completely eliminate the shocks, but they might be reduced enough to become tolerable -- quieter and more like distant rolling thunder than a single sharp bang. NASA has tested a design that reduces boom strength by 40% on fighter jets, but I have my doubts that large supersonic airliners will ever be able to break the sound barrier over populated areas: a 50,000 pound fighter is a far cry from a 750,000 pound SST.


RE the initial question, Concorde's subsonic range was about 3,300 miles, if memory serves. GDB would know for sure. Being pure turbojets designed for supersonic cruise, the Olympuses were not great performers in subsonic cruise and were quite inefficient (loud and gas-guzzlers) at takeoff and landing.

Could it have gone supersonic twice during the same flight without burning too much fuel?

Probably not. The acceleration and climb from 30,000 feet and Mach .9 to 50,000 feet and Mach 2 consumed an enormous amount of fuel: remember that the afterburners were lit until Mach 1.7. I doubt Concorde would ever have had enough fuel onboard to do it twice in a normal flight.

Is it a possible engineering achievement?

Possible, yes. Economical, not yet. Off the top of my head, there are two significant design elements that will boost subsonic efficiency:

- Variable-bypass engines act like high-bypass turbofans at takeoff, subsonic cruise, and landing, reducing noise and fuel consumption, and then "change gears" to act like pure turbojets or low-bypass fans at supersonic cruise to provide the necessary exhaust velocity.

- Variable-sweep wings adjust the aerodynamic profile to fit subsonic and supersonic requirements more closely. Delta wings are fine at supersonic speeds, but create enormous drag at slow speeds and aren't wonderful at subsonic speeds. Folding the wings back into a delta or arrow configuration at supersonic speeds achieves the best of both worlds.

Both elements are heavy, expensive, and very complex, but could bring an SST within striking distance of some subsonic airliners for cruise efficiency over land.

--B2707SST
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NWA757
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RE: Could Concorde Fly Transatlantic Subsonic Flight?

Mon Aug 09, 2004 12:23 pm

How do you go supersonic without a boom? The answer to the question, yes Concorde could travel subsonicly over land but it would not be fuel efficient.
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Bellerophon
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RE: Could Concorde Fly Transatlantic Subsonic Flight?

Mon Aug 09, 2004 9:20 pm

A380900

…Would flight mixing subsonic over land and supersonic over sea have been possible with concorde…

Yes. This was done on charter flights such as LHR-CDG and LHR-FCO and on scheduled flights such as LHR-BAH and IAD-MIA.

…Would flight mixing subsonic over land and supersonic over sea have been possible with concorde ...without reducing the range too much?...

No. If Concorde stayed subsonic, her range would begin to reduce. In very general terms a completely subsonic flight would only achieve around 70% of the range of a supersonic flight.

…Could it have gone supersonic twice during the same flight…

Yes.

…Could it have gone supersonic twice during the same flight ...without burning too much fuel?...

No. Every transonic acceleration, from M0.95 to M1.7 using re-heat, would burn an extra 6 to 10 tonnes of fuel, depending on ambient conditions.

There were quite restrictive time limits on the total use of re-heat during any one flight, and these were always a factor to be considered before deciding whether one could do a second acceleration to supersonic flight.

Regards

Bellerophon

 
ConcordeBoy
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RE: Could Concorde Fly Transatlantic Subsonic Flight?

Tue Aug 10, 2004 3:50 am

IAD-MIA

IINM, IAD-MIA did go supersonic off the coast.

I think GDB wrote about it as well, when expressing his feeling that it should've been nonstop to LHR instead.
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Bellerophon
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RE: Could Concorde Fly Transatlantic Subsonic Flight?

Tue Aug 10, 2004 5:41 am

ConcordeBoy

...IINM, IAD-MIA did go supersonic off the coast...

No, you're not mistaken, that is what I've just said.

However, what she couldn't do was to mix subsonic and supersonic flight without incurring a fuel penalty and consequent loss of range.

Regards

Bellerophon
 
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Starlionblue
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RE: Could Concorde Fly Transatlantic Subsonic Flight?

Tue Aug 10, 2004 6:01 am

Flying with a decreased boom signature will probably involve:

- Reshaped fuselage, probably with a bulbous nose
- Increased dihedral on the wing in order to make the noise travel from the plane more sideways instead of downwards
- Smaller wing=smaller boom

[Edited 2004-08-09 23:01:34]
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cancidas
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RE: Could Concorde Fly Transatlantic Subsonic Flight?

Tue Aug 10, 2004 11:01 am

why not just buy some B-1Bs from the USAF, cut holes in the fuselage for windows and paint them in some livery? maybe that would work?
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nudelhirsch
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RE: Could Concorde Fly Transatlantic Subsonic Flight?

Tue Aug 10, 2004 1:45 pm

Concrode actually mixed subsonic and supersonic. She went subsonic over land and did not accelerate before being away from the coastline, due to the super sonic boom. Then reduced speed early enough.
So actually, she did mix.
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XXXX10
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Bellerophon

Fri Aug 13, 2004 2:26 am

Wasn't there once a time when the maximum time on the reheats was elapsed before M 1.7 was reached. Not sure what happened
 
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Starlionblue
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RE: Could Concorde Fly Transatlantic Subsonic Flight?

Fri Aug 13, 2004 3:07 am

why not just buy some B-1Bs from the USAF, cut holes in the fuselage for windows and paint them in some livery? maybe that would work?

I'd love to fly in one but they're not exactly quiet. Also, military jets often have maintenance regimes which would be prohibitively expensive for a civilian operator. Maybe this is the reason the BC-17X never "took off".

"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
aireuropeuk733
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RE: Could Concorde Fly Transatlantic Subsonic Flight?

Wed Aug 18, 2004 8:34 pm

With regard to reducing the supersonic boom couldn't the techy guys try to produce an inverse boom to cancel out the original - just like the anti-noise and vibration technology used in the new Dash 8?

Please note that I am not an engineer and don't know a huge amount about it. Just an uneducated thought!

Mike
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Starlionblue
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RE: Could Concorde Fly Transatlantic Subsonic Flight?

Wed Aug 18, 2004 9:34 pm

I'm not an engineer either but putting out more noise to cancel the original noise creates it's own problem. The energy has to go somewhere. Heat?
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
Klaus
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RE: Could Concorde Fly Transatlantic Subsonic Flight?

Wed Aug 18, 2004 9:55 pm

There is a second, inverted boom, already! ("bow" and "tail" shockwaves)

The trouble is that nobody has found a practicable way to have them cancel each other out so far...

You´d basically have to "persuade" the air to compress only locally when the nose parts the still air and to quietly decompress locally again at the tail. The problem is that the shockwaves separate from the moving system, so the energy is lost and can´t be recovered.

As far as I understand, a large portion of the engine´s power goes into the shock waves - so eliminating the shockwaves (and the boom) might also help increasing the overall cruise efficiency of a supersonic transport. Now we only have to find a way...  Wink/being sarcastic
 
B2707SST
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RE: Could Concorde Fly Transatlantic Subsonic Flight?

Thu Aug 19, 2004 8:29 am

With regard to reducing the supersonic boom couldn't the techy guys try to produce an inverse boom to cancel out the original - just like the anti-noise and vibration technology used in the new Dash 8?

I'm not an engineer either but putting out more noise to cancel the original noise creates it's own problem. The energy has to go somewhere. Heat?


As Klaus indicated, the problem is more complex than sound waves, which can be cancelled by an opposing signal. As an aircraft moves forward, air is displaced around the fuselage and wings. At subsonic speeds, the air ahead of a plane can "feel" its approach and begins to move ahead of the actual aircraft. You can see this personally when light objects like snow or leaves are deflected by the airflow around a car without actually touching it. The displaced air then flows back together as the plane passes, like water flowing around a ship into its wake.

At supersonic speeds, the plane is moving faster than the speed at which pressure disturbances are transmitted through air. The first "warning" of the approaching aircraft is the nose itself shoving air molecules out of its path. The pressure wave occurs as a shock around the nose and other protruding parts of the aircraft (wings, engines, antennae, etc.). A second set of shocks form at the trailing edge of the wings and fuselage as the air returns to normal pressure.

Shocks forming around a supersonic T-38:



The two sets of shock waves usually coalesce into an overpressure shock at the nose and an underpressure shock at the tail. These create the double-boom heard when an aircraft flies supersonically. The pressure distribution over time looks like an N, hence the term "N wave" for sonic boom shocks:



As far as I know, there is no conceivable way to eliminate sonic booms entirely. An aircraft will always displace some amount of air, and as long as it travels supersonically, shocks will form. The current avenue of research is to break apart the shocks and prevent them from forming two sharp booms (in other words, "depeak" the N-wave). In the image above, a modified NASA fighter achieved some reduction in boom intensity with a modified overpressure shock. This might be audible as a rumble or series of muted thuds instead of a single boom.

I have my doubts that boom intensity can be reduced enough to allow supersonic flights over populated areas. A 750,000-pound aircraft moving at Mach 2 or 2.4 moves an awful lot of air, and studies have shown that a socially acceptable boom would have to be many times quieter than we can achieve now. A 10-seat business jet might be able to pull it off, but a 300 passenger SST -- probably not, at least in the near future.

--B2707SST
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Starlionblue
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RE: Could Concorde Fly Transatlantic Subsonic Flight?

Thu Aug 19, 2004 8:41 am

So we're left with the suborbital model instead, which would solve the boom issue by going around it.
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SimProgrammer
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RE: Could Concorde Fly Transatlantic Subsonic Flight?

Thu Aug 19, 2004 9:38 am

Suborbital SST is technically quite feasible but the problems are political.

Quite a few theories have been privately punted around for some years now and its the engine thats also a stumbling block. The most recent one is a quad delta wing with an inverse dihedral design where engines 1 and 4 are subsonic for gaining the altitude to above FL460 (approx) and engines 2 and 3 produce the supersonic thrust into sub orbit. The a/c is affectively and accurately 'catapaulted' and its momentum carries it until it drops below FL450 and becomes subsonic prior to approach.

There are lots of other theories knocking about, but this one caught my attention the most.
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Starlionblue
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RE: Could Concorde Fly Transatlantic Subsonic Flight?

Thu Aug 19, 2004 9:58 am

Does sound like something I put forward in another thread. Dual propulsion seems easier than designing engines optimized for two so disparate flight regimes..
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
Bellerophon
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RE: Could Concorde Fly Transatlantic Subsonic Flight?

Thu Aug 19, 2004 10:55 am

XXXX10

...Wasn't there once a time when the maximum time on the reheats was elapsed before M 1.7 was reached...

This happened several times over the years, caused by unusually warm outside air temperatures, in the order of ISA +20ºC, between FL280 - FL430.

There was a time limit of 15 minutes on the use of re-heats for the transonic acceleration, and under these conditions this limit could be reached before M1.70 was achieved.

...Not sure what happened...

The re-heats were turned off, and the main engines then took her the rest of the way to M2.00, albeit more slowly than normal.

Regards

Bellerophon
 
bennett123
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RE: Could Concorde Fly Transatlantic Subsonic Flight?

Fri Aug 20, 2004 5:57 pm


Silly question

Why would you WANT to fly the Atlantic subsonically.

There are plenty of aircraft that could do that.
 
fritzi
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RE: Could Concorde Fly Transatlantic Subsonic Flight?

Fri Aug 20, 2004 8:17 pm

Bennet,

This thread is talking about flying supersonic over water and subsonic over land, in order to eliminate the sonic boom which is very noticable from the ground.
 
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Starlionblue
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RE: Could Concorde Fly Transatlantic Subsonic Flight?

Fri Aug 20, 2004 10:36 pm

Suborbital would neatly bypass all the problems. Let's do that instead. Pretty please with sugar on top.

As Ian douglas pointed out in "Semper Mars", the airline could give Astronaut Wings to the pax!
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
GDB
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RE: Could Concorde Fly Transatlantic Subsonic Flight?

Sat Aug 21, 2004 9:52 am

A B-1B would be no good for pax, wrong shape fuselage, too much equipment there, besides, it or the B-1A, could not even approach Concorde's performance with regards to sustained supercruise.

From 1984-91, the IAD-MIA sectors were supersonic, as Bellerphon can tell you, supercruise was allowed over Canada for some BA charters, indeed G-BOAG's very last flight to BFI from JFK, included this, or as a colleague who was a pax on board put it, 'we scared some moose'.

The creeping restrictions that steadily blighted the LHR-BAH-SIN sectors were more political, including supersonic overland over the Mid East.

 
MD-90
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RE: Could Concorde Fly Transatlantic Subsonic Flig

Sun Aug 22, 2004 12:05 am

This thread is talking about flying supersonic over water and subsonic over land, in order to eliminate the sonic boom which is very noticable from the ground.


Well, the thread title is "Could Concorde Fly Transatlantic Subsonic Flight"



The real trick is to go slower. Boeing could build a huge WIG, be much more comfortable for pax (even if it was a little slower), and offer honest-to-goodness cabins for first-class pax. That ought to trump the A380.

But ain't nothing going to trump Concorde any time soon.
 
KingGeo3
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RE: Could Concorde Fly Transatlantic Subsonic Flig

Sun Aug 29, 2004 11:43 am

A B-1B would be no good for pax, wrong shape fuselage, too much equipment there, besides, it or the B-1A, could not even approach Concorde's performance with regards to sustained supercruise.

Plus the passengers probably wouldn't appreciate the very fast and efficient and laser guided precision of deplaning via the forward, intermediate and aft doors (read bomb bay doors) on a B1. But the three weapons bays would provide for a three class layout!  Wow!

-KG3

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ba97
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RE: Could Concorde Fly Transatlantic Subsonic Flight?

Sun Aug 29, 2004 11:57 am

Supersonic over land. I flew on the last BOAG flight to Toronto and we rocketed to a point about 300 miles from Toronto. I have a nice picture of me standing at the display at Mach1.29 as we passed over a place I camp. Moose, bears, ducks, fish and everyone below knew we were there.
:D
there is economy class, business class, first class...then Concorde..pure class

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