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Why is there no mention of IR (heat) radar? As far as I know, its impossible to hide a jet engine heat signature. Thermodynamics 101. This is especially true wh

Why is there no mention of IR (heat) radar? As far as I know, its impossible to hide a jet engine heat signature. Thermodynamics 101. This is especially true when you are looking up and the thermal background is pretty much black space.

tropo 7y ago
It's possible. The heat signature is well-hidden on the B-2, YF-23, F-117, and A-10. Yes, from the perspective of ground-launched IR-seeking missiles, the A-10 is actually stealth. The tail wraps around the engines as seen from many angles on the ground. Generally, it also helps to fly toward the enemy. This is a bit of extra incentive to not wimp out and flee. :-) The F-35 is a bit of a failure with the heat signature. The tail heats up from the engine exhaust. There are prohibited maneuvers that damage the tail due to heat. Aircraft don't have to be perfect about heat signatures. They aren't in a cold vacuum, and the enemy isn't flying the James Webb Space Telescope.
Majromax 7y ago
> Why is there no mention of IR (heat) radar? As far as I know, its impossible to hide a jet engine heat signature. The heat signature of what, the exhaust? That's very low density, so emissions from the exhaust itself will be negligible. The plane itself will emit black-body radiation, but that is based on the skin temperature, not the temperature of any interior engine parts. In the meantime, all of this is for passive detection, so at a distance you'd be asking for the detector to pick an at-best-tiny signal out of the entire sky. Moreover, clouds are opaque.
- nyc_pizzadev 7y ago
  The heat signature of the engine, which in part is connected to the entire plane. Burning that much jet fuel produces a tremendous amount of energy. You literally have a glowing ball of energy streaking thru a vast void of no to low energy. Clouds have heat, but not at the huge concentration a fighter jet has. I guess you have flares, but now its an "AI" problem of choosing the right target.
  - jazzyjackson 7y ago
    I'm no expert at this but I think the efficacy of infrared detection would depend entirely on the elevation of the plane and its size in arc seconds. What's the resolution of your detector? Is the time it takes for the plane to move from one pixel to the next shorter than the time it takes for photons to gather on the sensor above threshold? Don't forget the inverse square law of light, by the time the energy reaches a detector on the ground, the signal has weakened considerably. Skimming wikipedia for infrared stealth gives me "Infrared Search and Track" systems which are plane-mounted, which makes a bit more sense to me -- if you're closer to the targets altitude and velocity you'll get much cleaner data https://en.wikipedia.org/wiki/Infrared_search_and_track https://en.wikipedia.org/wiki/Infrared_search_and_track
outworlder 7y ago
Because the sort of aircraft that cares about radar that much will also have taken steps to minimize the heat signature.

tropo 7y ago

It's possible. The heat signature is well-hidden on the B-2, YF-23, F-117, and A-10. Yes, from the perspective of ground-launched IR-seeking missiles, the A-10 is actually stealth. The tail wraps around the engines as seen from many angles on the ground. Generally, it also helps to fly toward the enemy. This is a bit of extra incentive to not wimp out and flee. :-) The F-35 is a bit of a failure with the heat signature. The tail heats up from the engine exhaust. There are prohibited maneuvers that damage the tail due to heat. Aircraft don't have to be perfect about heat signatures. They aren't in a cold vacuum, and the enemy isn't flying the James Webb Space Telescope.

Majromax 7y ago

> Why is there no mention of IR (heat) radar? As far as I know, its impossible to hide a jet engine heat signature. The heat signature of what, the exhaust? That's very low density, so emissions from the exhaust itself will be negligible. The plane itself will emit black-body radiation, but that is based on the skin temperature, not the temperature of any interior engine parts. In the meantime, all of this is for passive detection, so at a distance you'd be asking for the detector to pick an at-best-tiny signal out of the entire sky. Moreover, clouds are opaque.

nyc_pizzadev 7y ago
The heat signature of the engine, which in part is connected to the entire plane. Burning that much jet fuel produces a tremendous amount of energy. You literally have a glowing ball of energy streaking thru a vast void of no to low energy. Clouds have heat, but not at the huge concentration a fighter jet has. I guess you have flares, but now its an "AI" problem of choosing the right target.
- jazzyjackson 7y ago
  I'm no expert at this but I think the efficacy of infrared detection would depend entirely on the elevation of the plane and its size in arc seconds. What's the resolution of your detector? Is the time it takes for the plane to move from one pixel to the next shorter than the time it takes for photons to gather on the sensor above threshold? Don't forget the inverse square law of light, by the time the energy reaches a detector on the ground, the signal has weakened considerably. Skimming wikipedia for infrared stealth gives me "Infrared Search and Track" systems which are plane-mounted, which makes a bit more sense to me -- if you're closer to the targets altitude and velocity you'll get much cleaner data https://en.wikipedia.org/wiki/Infrared_search_and_track https://en.wikipedia.org/wiki/Infrared_search_and_track

outworlder 7y ago

Because the sort of aircraft that cares about radar that much will also have taken steps to minimize the heat signature.