Masking armored vehicle infrared signiture (from above)?

[VariousRen]

Originally Posted by BraselC5048

I've got a "massive conventional warfare between TL 8+ major powers" setting, and one thing I'm wondering about is the practicality of (mostly) reducing the infrared visibility of a tank, at least from above. Mainly to help hide the tank from hostile aircraft and helicopters., so infrared signatures from the side are far less of a problem. The first obvious possibility is to have the exhaust from the engine (the main heat source) directed downwards or downwards and to the side or rear, instead of out the top. Air intakes for the engine (likely gas or diesel, possibility gas turbine) would be from above but on the sides, with a 90 degree turn to get to the engine compartment. Finally, the main signature would be reduced by a layer of insulation over the engine compartment. And possibly a poor-heat-conducting layer of composite as or above the top armor.

Mostly I'm wondering about the practicality of it, and how effective it would be at avoiding easy aerial IR detection, and at best reducing the hit rate of IR-guided (air launched) weapons. From ground level, simply visually seeing a big old tank wouldn't be any harder then IR detection.

In terms of thermodynamics, the heat that would be picked up by IR has to go somewhere. If you just vent the engine exhaust below the tank you'll end up with a tank shaped cold spot surrounded by a plume of hot air, instead of a plume of hot air coming out the back of the tank. Probably about the same difficulty to hit with a missile.

The approach then would be to have heat sinks that can store the heat inside the tank, and dump it when it's more convenient (read: when there's not a missile coming towards you). I'm not sure how you would do this, but some thing like disposable metal slugs that you drop (perhaps as IR decoys) would be interesting.