Infrared Signature of the F135 engine?

[Corsair1963]

We now know the F-35 in fact has a lower RCS than the F-22. My question is that also true of the Infrared Signature?

I started to wonder after looking at the design of the F135's exhaust nozzle. Which, appeared far more complex than the one on the F119 from the Raptor. Then after reading more on the design. (based on F-16 LOAN Program) I see it has a number of features not found on the aforementioned. Which, includes things like special coating, internal cooling system, longer travel of hot exhaust gases, etc. etc.

[hornetfinn]

IMO, IR signature is practically impossible to guess. There are features in F-35 and F135 that could make it very possibly have lower IR signature.

1. Higher bypass ratio means there is more cool air available to cool the engine and exhaust
2. Longer length meaning that hot parts of engine are further away from exhaust giving somewhat more time and space to cool the exhaust gases and even out the heat
3. Being developed directly from F119, it's likely there are lessons learned from it and improved in F135. This includes also IR signature.

IMO, F-35 very likely has lower IR signature flying subsonic due to these factors and F-22 very likely has lower IR signature supersonic due to supercruise ability.

[popcorn]

Also, 2 x F119 vs 1 x F135.

[Corsair1963]

Seems very logical.....still trying to find sources to support at least some of those conclusion.

[charlielima223]

interesting tid bit...

https://www.youtube.com/watch?v=FIKZjARXcos

this would lead me to believe that the different nozzle designs of BOTh F-22 and F-35 would have a slightly lower IR signature when compared to more conventional exhaust nozzles you see on other aircraft. Also at certain angles the engine nozzles of both Raptor and Lightning seem to be less visible.







just me making a guess.

[Dragon029]

For the purpose of comparing nozzle diameters:

[hornetfinn]

This is pretty good document about fighter aircraft infrared signatures:
http://www.dtic.mil/cgi-bin/GetTRDoc?AD=ADA566304

Page 34 describes the main components of IR signature from different aspect angles:

Tail: Engine hot parts
2. Rear Quarter: Hot parts and exhaust plume
3. Beam to Forward Quarter: Airframe and exhaust plume
4. Nose: Airframe and intakes

F-35 and F-22 engines have both pretty well buried hot parts. For example F135 has unusually long exhaust pipe which narrows down the viewing angles where hot parts are visible. AFAIK, both have active cooling measures for airframe and exhaust nozzle and also exhaust gases. As seen in those pictures, both also have exhaust nozzle and also hottest part of exhaust gases well hidden behind tail components from most viewing angles. Of course all jet fighters can be easily seen by IR sensors from behind due to massive amount of heat generated by the engine. However the most important part is frontal and beam aspect angles. One important thing is solar reflections from canopy and airframe which are large contributors in IR signature of regular aircraft. Both F-22 and F-35 likely have very well suppressed solar reflections due to coatings used.

Here is also one interesting document about stealth features:
http://www.dror-aero.com/lectur/rcs3.pdf

I doubt you will find anything much more specific than those documents about signature reduction used in any specific aircraft.

[eloise]

Another option is to dazzle or damage enemy's optical sensor by your LFR , the interesting part is imaging infrared sensor are easier to damage by laser compared to ancient conical reticle IR sensor

https://books.google.co.uk/books?id=bBb ... &q&f=false

DIRCM (2).jpg (164.4 KiB) Viewed 361218 times

[Corsair1963]

Would TVC have any advantages in lowering the Infrared Signature???

[eloise]

Would TVC have any advantages in lowering the Infrared Signature???

No

[archeman]

Would TVC have any advantages in lowering the Infrared Signature???

No

Well...

It was an oversimple question and that probably prompted the oversimplified answer here.

There are widely different implementations of TVC, most have some effect on Infrared Signature. Some TVC solutions make the IR signature far greater than none at all.

Check out the X-31 'paddles' hanging out about 5' beyond the exhaust exit. An extreme example of exposing hot metal for all to view. (EDIT) Not metal really, "Made of carbon-carbon, the paddles could sustain temperatures of up to 1,500 degrees C for extended periods."

https://en.wikipedia.org/wiki/Rockwell- ... anding.JPG

[checksixx]

We now know the F-35 in fact has a lower RCS than the F-22.

Do we now?? LoL

[Corsair1963]

We now know the F-35 in fact has a lower RCS than the F-22.

Do we now?? LoL

Are you saying you don't believe the F-35 has a lower RCS than an F-22???

[charlielima223]

Are you saying you don't believe the F-35 has a lower RCS than an F-22???

I remember when the USAF made the statement that the F-22 is has an RCS of metal marble and the F-35 of a metal golf ball. It was pretty much wildly accepted and somewhat debated. Most saying that those RCS figures were at their most optimum of angles (or something like that). Than skip a few years later and you have a USAF General saying that the F-35 is stealthier than the F-22 when before we were all lead to believe the F-22 is the "cream of the crop".

http://breakingdefense.com/2014/06/gen- ... -starts/3/

The F-35’s cross section is much smaller than the F-22’s, but that does not mean, Hostage concedes, that the F-35 is necessarily superior to the F-22 when we go to war

The F-35 is geared to go out and take down the surface targets,” says Hostage, leaning forward. “The F-35 doesn’t have the altitude, doesn’t have the speed [of the F-22], but it can beat the F-22 in stealth.” But stealth — the ability to elude or greatly complicate an enemy’s ability to find and destroy an aircraft using a combination of design, tactics and technology — is not a magic pill, Hostage reminds us.

IMO this makes me think that the F-35 at multiple angles (not just at the most optimal) has the lower overall RCS. Of course the Gen. Hostage does mention design, tactics, and technology. This makes me think again that with the F-35's more comprehensive sensor fusion and wider array of sensors; the F-35 has a better time at staying undetected longer than the F-22 can. Essentially it can see and know more. My own opinion on how I understand and interpret what the General said of course.

[sferrin]

We now know the F-35 in fact has a lower RCS than the F-22.

Do we now?? LoL

'cuz you know more than the General right? LoL This from the same guy who nearly burst a blood vessel in denial about radar blockers in the exhaust on the F-22.

"The F-35’s cross section is much smaller than the F-22’s, but that does not mean, Hostage concedes, that the F-35 is necessarily superior to the F-22 when we go to war

The F-35 is geared to go out and take down the surface targets,” says Hostage, leaning forward. “The F-35 doesn’t have the altitude, doesn’t have the speed [of the F-22], but it can beat the F-22 in stealth.” But stealth — the ability to elude or greatly complicate an enemy’s ability to find and destroy an aircraft using a combination of design, tactics and technology — is not a magic pill, Hostage reminds us."