How to make a supersonic transport viable

[Dr Jekyll]

The noise level of Concorde wasn't out of line with most other airliners at the time it was introduced, some US airports looked at tightening noise regulations to keep Concorde out but found it would keep their existing customers out as well . Incidentally if Concorde had remained in production the very next airframe onwards would have dispensed with afterburners.

[Mave]

Dr Jekyll said:

Incidentally if Concorde had remained in production the very next airframe onwards would have dispensed with afterburners.

That's not really true is it? I assume you're referring to Concorde - B, that was a totally different aircraft which didn't get beyond concept studies.

[Eric Mc]

Also, by the time Concorde WAS introduced into service (1976), the move to quieter high bypass turbofan powered airlines was already well underway. Louder old technology engined airliners were still in service, but their days were numbered

[Dr Jekyll]

Mave said:

Dr Jekyll said:

Incidentally if Concorde had remained in production the very next airframe onwards would have dispensed with afterburners.

That's not really true is it? I assume you're referring to Concorde - B, that was a totally different aircraft which didn't get beyond concept studies.

We are talking second order hypotheticals here as to when exactly it might have been produced if Concorde production had continued. But it was planned to be the next off the line, and it wasn't a to be totally different aircraft, it was just to have a few aerodynamic mods and a modified engine and would use most of the same production tooling, In any case the point I was making was that it clearly would be possible in principle to have an SST without afterburners.

[Mave]

Dr Jekyll said:

Mave said:

Dr Jekyll said:

Incidentally if Concorde had remained in production the very next airframe onwards would have dispensed with afterburners.

That's not really true is it? I assume you're referring to Concorde - B, that was a totally different aircraft which didn't get beyond concept studies.

We are talking second order hypotheticals here as to when exactly it might have been produced if Concorde production had continued. But it was planned to be the next off the line, and it wasn't a to be totally different aircraft, it was just to have a few aerodynamic mods and a modified engine and would use most of the same production tooling, In any case the point I was making was that it clearly would be possible in principle to have an SST without afterburners.

I think the allocated 5 years development programme is more than just a few aerodynamic mods

Nevertheless, what I can't find is any reference to the numbers where they actually show how to go supersonic without reheat. The increased flow gives more sea level power, but you can see that the power increase is reducing as they get to transonic speeds - courtesy of that extra turbine stage dragging the exhaust pressure ratio down, and the benefits will continue to drop as the aircraft accelerates.

I'm not aware of any aircraft which has actually got up to supercruise without reheat (unless they were planning to do a climb > dive + accelerate > climb manoeuvre) and i don't really see that using reheat is a huge problem for the acceleration phase anyway as 1) jet noise isn't a huge problem in cruise, and 2) you really want to get to cruise speed and altitude ASAP as that's where the aircraft and engine is most efficient.

I'd love to see what the intake / engine / exhaust system was expected to be doing during the acceleration and climb phase.

Edited by Mave on Thursday 10th June 20:37

[Arnie Cunningham]

I thought concorde could get to super cruise without reheat, but it just took longer and ended up burning more fuel, so using reheat was actually more efficient to get there?

[Teddy Lop]

Arnie Cunningham said:

I thought concorde could get to super cruise without reheat, but it just took longer and ended up burning more fuel, so using reheat was actually more efficient to get there?

It was so much more efficient at its cruise altitude that turning it all to 11 and blasting straight there made more sense IIRC.

[Mave]

Arnie Cunningham said:

I thought concorde could get to super cruise without reheat, but it just took longer and ended up burning more fuel, so using reheat was actually more efficient to get there?

Interesting, I didn't realise it could actually do that. I thought the basic engine size would have been set at cruise, with the reheat used to get over the transonic / supersonic bump in the drag curve.

I suppose with the high takeoff speed, takeoff could have actually been the sizing case, with the engine then slightly oversized at cruise.

[Dr Jekyll]

The model B proposal included a modified engine design expected to be 25% more powerful, so more powerful without afterburner than the existing engines were with.

[Eric Mc]

Is there any aeroplane today capable of achieving supersonic flight without the use of afterburners? I'm not talking about "supercruise" - which Concorde could do (as well as some modern supersonic fighters).

[Evanivitch]

Eric Mc said:

Is there any aeroplane today capable of achieving supersonic flight without the use of afterburners? I'm not talking about "supercruise" - which Concorde could do (as well as some modern supersonic fighters).

Without a dive?

[Eric Mc]

Evanivitch said:

Without a dive?

Yes - I was ignoring gravity assist and really talking about level flight, or even climbing.

Diving an airliner to achieve supersonic flight would be rather pointless - although it has been done.

[annodomini2]

Super cruise is where it can sustain supersonic without re-heat but the transition from subsonic to supersonic still requires re-heat.

To date I don't think anyone has publicly created a propulsion system that can do it without re-heat.

[Eric Mc]

That's what I understood too. You need that extra kick to overcome transonic drag as you pass from subsonic to supersonic. Once "on the other side", Concorde (and a small number of other aircraft) can go back to non-afterburner thrust and still maintain supersonic cruise.

[Krikkit]

Eric Mc said:

That's what I understood too. You need that extra kick to overcome transonic drag as you pass from subsonic to supersonic. Once "on the other side", Concorde (and a small number of other aircraft) can go back to non-afterburner thrust and still maintain supersonic cruise.

Still amazing when you look at the list of supercruise-capable aircraft that it's a) very short and b) Concorde happily sits in there! I know all of us nerds in this sub know it, but a great reminder of what a tremendously advanced piece of engineering it was.

I wonder if the Su-57 would be able to cross the sound barrier without afterburner, 2x 93kN engines at full dry thrust.

[nikaiyo2]

Eric Mc said:

That's what I understood too. You need that extra kick to overcome transonic drag as you pass from subsonic to supersonic. Once "on the other side", Concorde (and a small number of other aircraft) can go back to non-afterburner thrust and still maintain supersonic cruise.

I always thought the F22 could attain and sustain supersonic flight without ever using afterburner? Isnt that why it won out over the F23.

[Eric Mc]

Don't know to be honest.

[Kawasicki]

Slower is safer and more environmentally friendly.

In the past progressive development was about going faster, now it's about going slower.

[Eric Mc]

Not TOO slow - especially in an aeroplane.

[Kawasicki]

Eric Mc said:

Not TOO slow - especially in an aeroplane.

Good point.

Of course the most progressive decision would be to keep 99% of them permanently on the ground.