By combining a large mister* with a microwave emitter one can create an unmoving ceiling of hot water vapor over an arbitrary area.
This would have the advantage of hiding or distorting heat emissions without the requirement of a physical roof for rapid deployment.
*"mister" means mist-making machine. we all see the unavoidable pun.-- Voice, Sep 19 2011 Would this work? http://www.uq.edu.au/news/?article=2008 [2 fries shy of a happy meal, Sep 19 2011] "OK guys, you see that big mist cloud on your IR? Put your stores down right in the centre of it, and see what pops. Oh, and someone put a radar-seeker down on their microwave emitter with a bit of luck, it might take out the generators and fuel trucks as well "-- 8th of 7, Sep 19 2011 To loosely paraphrase Monty, the major problem with hiding anything from the enemy is that the enemy will know you're hiding something.
Ever hear of wired camo netting? With today's battlefield technology, it would have more or less the same effect, with the added benefit of also visually obscuring the object.-- Alterother, Sep 19 2011 If this is, as claimed, faster to deploy than conventional techniques, then it might be suitable for a shell game with multiple IR screens, most concealing nothing.-- mouseposture, Sep 19 2011 Rapid deployment has all but replaced large-scale camoflage on the modern battlefield. The shell game has become 'where will it be' instead of 'where is it'.-- Alterother, Sep 19 2011 Interesting idea +. This is probably good for covering large areas quickly.-- rcarty, Sep 20 2011 Covering them with what? Slightly irradiated water? Perfectly visible and somewhat damp military equipment?-- Alterother, Sep 20 2011 An IR distortion field. This idea goes well beyond my requirements for a halfbaked idea. Sciency, cool title, works in theory, probably not in practice.-- rcarty, Sep 20 2011 Agreed. No bun, though.-- Alterother, Sep 20 2011 random, halfbakery