The T-50 (PAK-FA) Thread

[Vekkinho]

The Raptor's design cuts the visible area of the immediate exhaust by ~30-40% from directly aft, and by a huge amount when viewed from a small off-angle. That could be a significant difference in rear-hemisphere detection. I could imagine IR acquisition denial or delay as well, which could mean the difference between death or a fighting chance when talking about a high HCA/AOT IR missile shot.

 

Great selection of pictures, though, Weta43.

 

It's not just the nozzle and heat that comes out of it...

 

Look at the difference in exposed parts of the engine. F-22 has only few sq feet of nozzles protruding out of the fuselage, compression and combustion parts of the engine are hidden within it and coated in heat insulating materials.

 

Now look the T-50...

[Pilotasso]

I fail to see how the nozzles have anything to do with IR detection range.

 

Heat signature usually is hidden by the tail fins, not by nozzle design.

 

Also IR signature is degraded by moisture in the air. You seldom have the perfect weather to match brochure specs, and even at that they only tell you fictional ones since the real figures are classified.

[aaron886]

Not sure how else to describe it, Pilotasso. Lower visible surface area of the strongest IR emission on the airplane.

[Vekkinho]

I fail to see how the nozzles have anything to do with IR detection range.

 

 

Try touching them on a working engine and you'll understand.

 

 

Read my post again and note that I said it's not just the nozzle that radiates heat than look at this vid:

 

Jet engine has a cold end:

- inlet and compression sections

and a hot end:

- Combustion, turbine and nozzle (exhaust).

 

Combustion and turbine part are exposed on a T-50 and hidden under livery of a F-22.

 

As you can see in the video above, not only thrust but all exposed hot parts of the engine are visible on thermal camera but hot parts of the engine which are "hidden" under the nacelle do not glow in the cam.

[Vekkinho]

There's even better example:

 

compare F-16 and F-22 heat signature...

[GGTharos]

They look pretty similar when they both have burners on. Perhaps I missed it, but I didn't see an F-16 out of AB.

[Namenlos Ein]

 

 

[Invader ZIM]

Keep in mind, with the thermal views these aircraft are being watched at public airshows at very close spitting distances.

 

Trying to find an aircraft 50 plus miles out not on afterburner for a thermal camera can be a real challenge depending on the resolution and detector material of the array, as well as the cooling method and supporting electronics. The aircraft at such a distance might only be a single pixel in diameter for the detector for instance.

Edited January 31, 2014 by Invader ZIM

[Vekkinho]

Keep in mind, with the thermal views these aircraft are being watched at public airshows at very close spitting distances.

 

Trying to find an aircraft 50 plus miles out not on afterburner for a thermal camera can be a real challenge depending on the resolution and detector material of the array, as well as the cooling method and supporting electronics. The aircraft at such a distance might only be a single pixel in diameter for the detector for instance.

 

Single pixel or no pixel is a 100% difference.

[Invader ZIM]

Very true, and a low contrast thermal target versus a high contrast heat target can be the difference between locking on and not being able to, despite seeing him.

[Pilotasso]

Try touching them on a working engine and you'll understand.

 

 

Its the plume, not the nozzles ;) and that holds true just the same for F-22, you cant cool the exhaust just like that. You can only hide it with the twin fins and that's limited to some angles.

 

These days the heat source for all aspect IR missiles is friction on the airframe. That's far worse than nozzles because you cant hide fuselage friction heat with aspect.

Edited January 31, 2014 by Pilotasso

[OutOnTheOP]

Its the plume, not the nozzles ;) and that holds true just the same for F-22, you cant cool the exhaust just like that. You can only hide it with the twin fins and that's limited to some angles.

 

Well, you can't magically disappear all that heat, but you CAN use nozzle design to mix it with cooler bypass air; a very broad, thin nozzle using bypass air mixing will have a cooler plume.

[aaron886]

Its the plume, not the nozzles ;)

 

Wrong. Although that is true to some extent, the jet core cools rapidly and is wrapped in cooler bypass air. The engine exhaust nozzle surface will be far, far brighter.... and the goal is not elimination of IR signature, just reduction.

[AlexHunter]

http://www.fips.ru/cdfi/fips.dll/ru?ty=29&docid=2502643

 

 

http://www.findpatent.ru/patent/227/2271964.html

[ФрогФут]

These days the heat source for all aspect IR missiles is friction on the airframe.

It's pretty cold on subsonic, there is more use for part of plume, that's not covered by airframe. It can be seen even in front hemisphere.

Single pixel or no pixel is a 100% difference.

Even on very high distance the aircraft would be seen as a diffraction spot on the receiver and it would make sense and make it big enough to cover at least one pixel, even if the centre of it is between them.

[Pilotasso]

You can see the fuselage glowing on the nose and leading edges with IR radiation after airshows aerobatic demos, and those planes never went supersonic.

 

 

Wrong. Although that is true to some extent, the jet core cools rapidly and is wrapped in cooler bypass air. The engine exhaust nozzle surface will be far, far brighter.... and the goal is not elimination of IR signature, just reduction.

 

The bypass ratio on these engines is very low, you still have hundreds of degrees at the plume, not only that but the core exhaust radiation has no problem at all crossing the colder bypass wrap (they only mix with ambient air much further at the back). No miracle about it.

[RIPTIDE]

You can see the fuselage glowing on the nose and leading edges with IR radiation after airshows aerobatic demos, and those planes never went supersonic.

 

 

 

 

The bypass ratio on these engines is very low, you still have hundreds of degrees at the plume, not only that but the core exhaust radiation has no problem at all crossing the colder bypass wrap (they only mix with ambient air much further at the back). No miracle about it.

As missiles advance they'll be looking more at the optical side of things to pick out a preferred part of the airframe to intersect with, anyway.

[Pilotasso]

AIM-9L/M's have no trouble locking on to aircraft during exercises in subsonic regimes. Yes they can be easily decoyed but that's another championship.

[Vekkinho]

They look pretty similar when they both have burners on. Perhaps I missed it, but I didn't see an F-16 out of AB.

 

Exactly! No footage of F-16 in MIL power range which answers the other raised question of heat being similar with burners on.

 

It's a pure proof of how really powerful F119 are, F-16 needing an AB for most of it's turns and F-22 using it for vertical acceleration only.

 

Bear in mind that there are 2*F199 on average Raptor and the general thrust (and heat) is beyond that of a single F100.

Edited February 1, 2014 by Vekkinho

[Vekkinho]

 

These days the heat source for all aspect IR missiles is friction on the airframe. That's far worse than nozzles because you cant hide fuselage friction heat with aspect.

 

Heat as a result of friction during subsonic travel is venial...On the other hand You'll have trouble engaging a SR-71 travelling M3.0 with a 'winder...

[Vekkinho]

Interesting Wedge:

 

Faster it goes less direct airflow on compressor blades thus hiding a great deal of RCS...

[ФрогФут]

You can see the fuselage glowing on the nose and leading edges with IR radiation after airshows aerobatic demos, and those planes never went supersonic.

Compared to plume - it is pretty cold.

[Vekkinho]

AIM-9L/M's have no trouble locking on to aircraft during exercises in subsonic regimes. Yes they can be easily decoyed but that's another championship.

 

Avenger or ASRAD has no trouble locking Iraqi cars idling at the red traffic light...No friction there but engine's hot.

[NOLA]

Interesting Wedge:

Intake ramps are nothing new... It didnt make MiG-25 stealth. There will be another device inside of the intake dealing with hiding of compressor blades.

[Namenlos Ein]

 

T-50-5 "Blue Shark".

 

 

 

http://michaeldec.livejournal.com/33943.html

 

Edited February 6, 2014 by Namenlos Ein