Register here

Author Topic: IRST V F-22/35 and other stealthy aircraft  (Read 636 times)

Offline kcran567

  • CLEARANCE: Top Secret
  • ***
  • Posts: 663
IRST V F-22/35 and other stealthy aircraft
« on: March 30, 2019, 05:53:40 pm »

Early Fighter jets (Voodoo) IRST and others...has an F-22 ever been tested against some of these IRST systems? Maybe even against some Mig-29s and Su-27s at groom lake?

F-4, F-14 (Legion pod based on f-14D IRST) etc.

Legion IRST sensor—Lockheed's IRST21 based on an upgraded version of the AN/AAS-42 IRST that equipped the F-14D

Wonder how effective these systems are against F-22/35 and especially newer systems such as on the Gripen.

Offline stealthflanker

  • CLEARANCE: Secret
  • **
  • Posts: 250
Re: IRST V F-22/35 and other stealthy aircraft
« Reply #1 on: March 30, 2019, 09:25:06 pm »
The greatest problem to define effectiveness is that there are no real set of generic parameter to agree with.

As seen each manufacturer use different kind of targets, say Russian used either "Mig-29" or "Su-30" type targets while US and EU are even more vague with only listing (sometime) detection range and tracking capacity. Let alone any "standard" condition where the measurement is made.

There is a method i proposed for simple assessement but no real feedback.

General consensus however suggest that IRST might offer comparable performance to radar in high altitude and against high speed target where they experienced natural kinetic heating. 

In lower altitude performance may decrease due to denser atmosphere. Another difficulties with IRST is that they are unable to accurately or directly measure target range.

Offline lastdingo

  • CLEARANCE: Top Secret
  • ***
  • Posts: 564
  • Blogger
    • Defence and Freedom blog
Re: IRST V F-22/35 and other stealthy aircraft
« Reply #2 on: March 31, 2019, 07:48:43 am »
IRST can be used for cooperative ranging (two aircraft triangulating).

IIR sensors do not make use of doppler effect, so it's tough to filter out a moving object from a similar background.
It's not impossible, but it's demanding.
Target aircraft will be detected more easily if they fly higher, or are heated-up by air friction (from supersonic travel).

All that I've seen points at IRST being promising against non-afterburning targets at 40 or 50 km or so, under rare conditions maybe 80 km.

IRST may thus become the decisive factor if two VLO aircraft attempt to detect each other. IRST won't change that a F-22 detects a Su-35 or Gripen first if said target is in the forward 120° or the F-22 is turning enough for all-round scans.

Offline sublight is back

  • Senior Member
  • CLEARANCE: Top Secret
  • **
  • Posts: 686
Re: IRST V F-22/35 and other stealthy aircraft
« Reply #3 on: March 31, 2019, 07:55:26 am »
There was some Air Force general that made the off hand comment they could detect the aircraft by its wake.

Offline LowObservable

  • Senior Member
  • CLEARANCE: Top Secret
  • **
  • Posts: 2154
Re: IRST V F-22/35 and other stealthy aircraft
« Reply #4 on: March 31, 2019, 02:18:06 pm »
Stealthflanker is right to point out that there is no equivalent of RCS in the IR regime. This is an inherent problem given that your IR emissions will depend on speed and sunlight and propagation will depend on atmospheric conditions.

IRST can pick up IR signals at very long range - the problem is always that of picking out real targets from the background and getting decent range combined with low false alarm rates. Selex/Leonardo wrestled with this for a long time in the Typhoon program - where IRST was initially regarded as an anti-jamming device working cooperatively with the radar - and did well enough for the Swedes to find space for a derivative system on the JAS 39E. I would suspect that the Leonardo systems are more advanced than anything in the US, which is mostly derived from F-14D work.

Offline JeffB

  • CLEARANCE: Confidential
  • *
  • Posts: 81
Re: IRST V F-22/35 and other stealthy aircraft
« Reply #5 on: April 02, 2019, 03:25:19 pm »
Doesn't the F-35 have active skin cooling?

I seem to remember that there was an effort made dump systems heat into the fuel tanks.

Offline Dragon029

  • CLEARANCE: Top Secret
  • ***
  • Posts: 634
Re: IRST V F-22/35 and other stealthy aircraft
« Reply #6 on: April 02, 2019, 03:35:26 pm »
It does not (unless there's some classified system that's yet to be exposed). F-35s (and jets like the F-22 and Super Hornet) do dump heat heat into their fuel (which is then air cooled via radiators / heat exchangers), but that's not really for IR stealth purposes. Rather the F-35 just utilises coatings, the insulative qualities of its composite skin, exhaust nozzle design (the chevrons mix hot / cold air faster, reducing the IR output of the exhaust plume), it's relatively high military power thrust (vs AB), and the burying of the engine behind S-ducts, weapon bays and a ram-air cooled engine bay.

Offline Steven

  • CLEARANCE: Confidential
  • *
  • Posts: 85
    • AIAA at UCLA
Re: IRST V F-22/35 and other stealthy aircraft
« Reply #7 on: April 10, 2019, 03:00:40 am »
I recall reading a report a while back that the F-22 uses active cooling for the leading edges due to extended supersonic operations, though I'm not sure if this is done for the leading edge flaps (which also houses some antennas).
Do not go gentle into that good night.
Rage, rage against the dying of the light.

Offline Avimimus

  • CLEARANCE: Top Secret
  • ***
  • Posts: 1873
Re: IRST V F-22/35 and other stealthy aircraft
« Reply #8 on: April 10, 2019, 09:09:09 am »
We could see high altitude clear weather combat driven by IRST and extended range BVR weapons... under the right conditions one might even be able to get the initial firing information from looking at the wake of heated air (if I recall correctly)?

But there are also poor weather conditions... clouds... where one would think radar would be critical to combat - where combat would happen at closer ranges, with less reliable interception and enemy contact... and would be much more dependent on the quality of the radars and how the radar data is processed.

So there could be a lot of asymmetries in combat. The infrequency of combat between modern aircraft also means that most testing for radar/missile systems is based on encounters with export models of surface to air missiles... so there must be a lot of uncertainty about real world performance of radars and datalinks against a modern foe... which means falling back on the high-altitude IRST strategy is a good option to have.

One thing I don't know is about the potential role of improvements in far infrared imaging (which can see through a certain amount of water vapour at short/medium ranges)... which might impact the above equation.

Any thoughts? Am I thinking along the right lines?