IR Camouflage at TL 0 - 1 - Page 2

thulben · 05-01-2012, 07:04 AM

How did Arnold do it in Predator? He lit up some torches to "blind" that sense and covered himself in mud.

vierasmarius · 05-01-2012, 07:16 AM

Quote:

Originally Posted by thulben

How did Arnold do it in Predator? He lit up some torches to "blind" that sense and covered himself in mud.

The Mythbusters tested using mud to bypass a thermal sensor (at around 5 minutes in this clip). It didn't work very well. For a cinematic action hero though, it could work.

Jovus · 05-01-2012, 07:18 AM

I'm surprised nobody's mentioned, "Live somewhere the ambient temperature is comparable to your body heat."

vicky_molokh · 05-01-2012, 07:23 AM

Quote:

Originally Posted by Jovus

I'm surprised nobody's mentioned, "Live somewhere the ambient temperature is comparable to your body heat."

Not helpful. You still emit a different spectral picture ('IR colour') than other stuff.

whswhs · 05-01-2012, 07:31 AM

What IR vision detects is radiated heat. If you can avoid radiating in the IR spectrum, you can avoid being spotted by IR vision. That seems to me to say that you need to have a high albedo in the IR; blackbodies are both good absorbers and good emitters of electromagnetic radiation, and if you are a poorer absorber you are also a poorer emitter, at least as a first approximation. To me that says that you would look for materials that looked "white" to your own IR senses, or even better metallic (silvery surfaces have higher albedo than white).

Of course, you'd also have to deal with getting rid of heat by nonradiative methods: conduction or evaporation, mainly, since you can't count on having moving air to provide convection. Air doesn't conduct heat well, so you'd either have to lie on the ground, or else sweat or pant heavily. But you'd have to balance your thermal books somehow.

Bill Stoddard

Jovus · 05-01-2012, 07:34 AM

Quote:

Originally Posted by vicky_molokh

Not helpful. You still emit a different spectral picture ('IR colour') than other stuff.

Really? Do you have any research I can look at for that?

I'm not disbelieving you; I'm just curious, because this is something I haven't heard before, and so I want to see how and why it works that way.

vicky_molokh · 05-01-2012, 07:36 AM

Quote:

Originally Posted by Jovus

Really? Do you have any research I can look at for that?

I'm not disbelieving you; I'm just curious, because this is something I haven't heard before, and so I want to see how and why it works that way.

Not anything I can link to on demand, but generally, bodies don't emit energy equally across all spectra. They emit (or reflect) more or less in different frequencies. I once found a picture which mapped different IR frequencies to different RGB colours. It was weird and fascinating.

Jovus · 05-01-2012, 07:41 AM

Quote:

Originally Posted by vicky_molokh

Not anything I can link to on demand, but generally, bodies don't emit energy equally across all spectra. They emit (or reflect) more or less in different frequencies. I once found a picture which mapped different IR frequencies to different RGB colours. It was weird and fascinating.

...yeah, this is a case of me being stupid and confusing IR with other methods of heat dissipation.

Still, I suppose it pushes back my answer to, "Live somewhere the ambient temperature is comparable with your body heat and cover yourself with local vegetation."

'tain't perfect, but it's something.

Purple Haze · 05-01-2012, 11:57 AM

The biggest problem is that the IR detector needs to be cooler than what it is trying to detect, otherwise it loses any image in it's own thermal noise. So if they are seeing each other with IR, their eyeballs must be much colder than their body temp, and I doubt that doing the testical trick with eye stalks is anywhere near enough difference.

vicky_molokh · 05-01-2012, 12:09 PM

Quote:

Originally Posted by Purple Haze

The biggest problem is that the IR detector needs to be cooler than what it is trying to detect, otherwise it loses any image in it's own thermal noise. So if they are seeing each other with IR, their eyeballs must be much colder than their body temp, and I doubt that doing the testical trick with eye stalks is anywhere near enough difference.

How do vampire bats work? They have some sort of insulation between their IR sensors and the rest of the body, or something like that.

05-01-2012, 07:04 AM	#11
thulben Join Date: Sep 2006 Location: SF Bay Area, CA	Re: IR Camouflage at TL 0 - 1 How did Arnold do it in Predator? He lit up some torches to "blind" that sense and covered himself in mud.

05-01-2012, 07:18 AM	#13
Jovus Join Date: Sep 2008	Re: IR Camouflage at TL 0 - 1 I'm surprised nobody's mentioned, "Live somewhere the ambient temperature is comparable to your body heat."

05-01-2012, 07:31 AM	#15
whswhs Join Date: Jun 2005 Location: Lawrence, KS	Re: IR Camouflage at TL 0 - 1 What IR vision detects is radiated heat. If you can avoid radiating in the IR spectrum, you can avoid being spotted by IR vision. That seems to me to say that you need to have a high albedo in the IR; blackbodies are both good absorbers and good emitters of electromagnetic radiation, and if you are a poorer absorber you are also a poorer emitter, at least as a first approximation. To me that says that you would look for materials that looked "white" to your own IR senses, or even better metallic (silvery surfaces have higher albedo than white). Of course, you'd also have to deal with getting rid of heat by nonradiative methods: conduction or evaporation, mainly, since you can't count on having moving air to provide convection. Air doesn't conduct heat well, so you'd either have to lie on the ground, or else sweat or pant heavily. But you'd have to balance your thermal books somehow. Bill Stoddard

05-01-2012, 11:57 AM	#19
Purple Haze Join Date: Jul 2006	Re: IR Camouflage at TL 0 - 1 The biggest problem is that the IR detector needs to be cooler than what it is trying to detect, otherwise it loses any image in it's own thermal noise. So if they are seeing each other with IR, their eyeballs must be much colder than their body temp, and I doubt that doing the testical trick with eye stalks is anywhere near enough difference.