Masking armored vehicle infrared signiture (from above)?

[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.

[Nereidalbel]

Poland has some ideas on this.

[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.

[Anthony]

The best way to reduce infrared signature is to produce less heat in the first place -- more efficient engines, more efficient drivetrains, simply not moving as much, and so on. EVs and hybrids running on batteries have much lower heat production than a conventional automobile, for example.

Most of the ideas you suggest will either make the exhaust system less effective (resulting in the vehicle overheating) or just won't do anything useful. Your best bet might be just mixing the exhaust with a lot of air, thus spreading the heat out, but that could wind up overly obvious for other reasons.

[BraselC5048]

Oh, OK then. One related question - how much does several of miles of atmosphere interfere with infrared, and what about clouds, particularly thick clouds? (assuming looking down from 100,000+ feet to low orbit.)

It's mostly for spacecraft sensors designed for detecting other spacecraft, mot things on the ground. Radar/microwave frequencies are pretty much useless looking through rain, since they lack circular polarization (which real-world air defense and ATC radars have, but would require different equipment then looking for spacecraft.)

Wasn't there also something called "hot smoke," a smoke discharger or grenade that interfered with IR (presumably by either being composed of particles that absorb IR, or alternately simply being very warm)? A simple smoke decoy would probably be more effective and far cheaper, whenever it's obvious hostile aircraft are about to attack.

[benz72]

There are a few things you can try to reduce signature.

1) Cool exhaust priore to release - using the intake/ehxaust streams as counterflow heat exchangers can do this but the flow restrictions will affect efficiency. At the very least consider using a bypass on such a scheme so it isn't affecting engine performance when speed is more important than stealth. You could also circulate cooling water around your exhaust.

2) Minimize the difference in temperature between the tank and the surroundings - if you have good computer controlled sensors they can auto-adjust the signal for better resolution but I am guseeing your early IR missiles aren't that sophisitcated. Operate in very hot environments, set fires nearby that generate lots of hot air, &c.

3) Give the incoming missile a new target - If it is a true IR seeker throw a flare off to one side and have it steer towards the decoy. Alternatively, launch one up a few hundred feet and have it parachut down slowly. Let the missile detonate at altitiude instead of against the armor.

[Racer]

Perhaps use the whole bottom of the vehicle as heat sink ? Some modern diesels use tough ceramic plates rather than radiators to get rid of heat . Far easier to armour & much tougher to totally put out of action than pipes , tubes and fans etc . As said before hybrid and battery power plants could also use this to it's advantage .

[shawnhcorey]

If the exhaust is aimed downward, it will leave a heat trail, like this kitten.

Aircraft use flares to try to draw off heat-seeking missiles. I think some tanks also have them.

[Sir Tifyable]

If you're not looking for a real-world answer, here's one that would add a bit of 'we're not in Kansas any more'. Give the tanks a trailer on a long hitch so it rides ten yards or so back from the tank. Run a highly insulated exhaust pipe along the hitch which vents from the trailer. The first IR-guided missile will take it out rather than the tank. The remainder of the insulated pipe will then trail along the ground, gradually getting closer to the tank as succeeding missiles blow the back end off. If they're lucky, they might get two or even three near-misses instead of direct hits.

The same principle was used on the Crocodile Tanks amongst Hobart's Funnies: Cromwell tanks with flamethrowers. To avoid strapping huge reservoirs for the flamethrower to the tank with consequent risk to the crew if it was hit, the reservoir was fitted to a trailer pulled behind the tanks.

[jason taylor]

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.

It's harder then it sounds. Historically tank warfare has hinged on the difficulty of seeing. For one thing there are usually terrain wrinkles even in the desert let alone Europe(though Poland is kinda flat for Europe but not that flat). For another, tanks are cramped places hard to see in. While tank crew poking their heads out of hatches are as vulnerable to sharpshooters as anyone putting their heads up. So whether or not one puts one's head up is a nice point of tactics. One, for instance, that military historians of the Arab-Israeli wars made a comment on when the IDF started ordering every tank in a unit to have a man with a head up instead of just one man.

Having an effective IR allows the option of keeping head down more often. Furthermore the IR(and any other kind of artificial sensor) can be artificially wired into a processor as a human cannot making a different kind of intelligence possible.

Tank warfare is like the legendary old west duels that almost never took place in real life in one sense; that it hinges on getting off the first shot. Because of this, any information that can be gotten is necessary because being the first to spot is usually being the first with a chance to shoot.