Personal Thermal Camouflage

[KerikBalm]

Here on Earth, as in space, your heat signature makes you easy to detect in most combat scenarios. However, on Earth the background temperature is generally above 270 K, as opposed to 3K in space. Radiation of heat can be done via convection, and its easy to obtain material to use as a heat sink. Additionally, there are some directions in which you could radiate heat with a low probability of detection

... that said, I have my doubts that stuff like this really works in combat:

 

 

 

It seems to me that sure, when you first put on such a suit it can block the IR radiation, but heat will build up underneath the suit, and surely after a while it too will start to glow in IR. They claim the suits allow you to stay cool, but I doubt those claims. I'd bet it gets extremely hot inside one of those suits rather quickly.

If there was a lot of convection with the air, without having skin directly exposed, you could make your thermal signature more diffuse... but I highly doubt any suit designed like this will be as effective as these pictures imply for more than a few minutes. Your basic body metabolism is releasing a certain amount of energy, and that energy doesn't just disappear, and black body radiation in the IR spectrum at these temperatures cannot be stopped.

 

Am I missing something? do these suits actually work or are they a gimmick that lasts a few minutes?

[Green Baron]

Well, for those who like it in "combat scenarios" ....

Good question, where does the heat go if it can't radiate ? And what about sweat ? I hope the battle is over before it gets too warm inside ....

I'd rather continue to stay out of trouble :-)

 

[monophonic]

1 hour ago, Green Baron said:

Well, for those who like it in "combat scenarios" ....

Good question, where does the heat go if it can't radiate ? And what about sweat ? I hope the battle is over before it gets too warm inside ....

I'd rather continue to stay out of trouble :-)

 

Convection most likely. You can see the person in "ghost suit" is still recognizable as just a tad warmer than ambient. As long as that gradient is sufficient for the suit to convectively transfer its heat into surrounding air and it is opaque to the blackbody radiation from layers underneath the advantage stays.

In those images, in the open and at very close range it may seem like what's the point. After all both guys are still visible. But combat rarely if ever happens under such a situation. Put some distance and a thin brush between you and them, then you'll see how one guy blends into the background while the other is still visible. Same basics of camouflage that work in the daylight visual still work in thermal views.

[wumpus]

42 minutes ago, monophonic said:

In those images, in the open and at very close range it may seem like what's the point. After all both guys are still visible. But combat rarely if ever happens under such a situation. Put some distance and a thin brush between you and them, then you'll see how one guy blends into the background while the other is still visible. Same basics of camouflage that work in the daylight visual still work in thermal views.

At that point you needn't bother looking for the guy in the suit:  aim for the white-hot rifle and the guy firing it will be nearby.  If you have time before  they shooting starts, you still have time to find the [presumably optimal] guys in the marketing pictures.

[KerikBalm]

The difference with thermal and normal, is that vision is based off of reflected light, not emitted light.

I'm not even thinking "whats the point" for close range, I'm thinking about that attack Helo 2km away with a 30mm gun slaved to its FLIR view, or the jet flying overhead with a FLIR targeting pod that can get your coordinates and drop a bomb in your vicinity.

Wrapping yourself in a thermal blanket will surely work for a while, but its not something you'd be wearing for hours on end before you know when the fighting will start. Its not something you'd be wearing as you move several km on foot as part of an operation...

As long as that gradient is sufficient for the suit to convectively transfer its heat into surrounding air and it is opaque to the blackbody radiation from layers underneath the advantage stays.

Transfering heat to another object rather than just direct IR emission doesn't help so much, because that heat will be re-emitted.

Granted... if your body is at 37 C, and you have a high airflow so that air passing by only warms from 25 to 26 degrees, then it will be much dimmer and shifted to a lower wavelength... but I really really doubt that there's going to be enough airflow to keep the wearer cool for an extended period of time/after a few minutes of physical exertion.

I've seen claims that some suit is still cool enough... but I've never seen a demonstration that makes it clear that the person has been wearing the suit for more than a few minutes... I think for such a suit to be practical, you'd really need to be able to wear it for at least an hour while doing moderate physical activity - but I don't know if that is the case

[kerbiloid]

Opponent's POV.

Spoiler

Also they will have a rear vent, pumping the steam outside.
Enemy will see only columns of smoke.

In a desert they will carry a huge white-hot radiator with fan, to move the heat out rather than in.
In winter... Well, just hard to imagine.

Edited May 13, 2017 by kerbiloid

[andrewas]

7 hours ago, wumpus said:

At that point you needn't bother looking for the guy in the suit:  aim for the white-hot rifle and the guy firing it will be nearby.  If you have time before  they shooting starts, you still have time to find the [presumably optimal] guys in the marketing pictures.

I think this is more for attackers - when setting an ambush or positioning snipers you might expect the defenders to be using thermal vision, but they are unlikely to be particularly alert at 2 am after weeks of no action. Unshielded guys stand out like a sore thumb on thermal, this makes you that much less likely to be picked up. Sure, when the shooting starts your gun gives you away, but at that point the enemy has other problems. 

Edited May 13, 2017 by andrewas

[55delta]

It's not a bad idea, even if this thermal camo isn't perfect. In an area with enemy vehicles that could use thermal systems, like tanks, attack helicopters, and AC-130s, something that would cut a thermal profile to less of a human-shaped bright spot is actually pretty handy.

[kerbiloid]

4 hours ago, 55delta said:

In an area with enemy vehicles that could use thermal systems, like tanks, attack helicopters, and AC-130s

A combined assault of tanks and ninjas.

Spoiler

They even can hide a tank sitting on top.

 

P.S.
Thermocamouflage in a desert.

Spoiler

 

Edited May 14, 2017 by kerbiloid

[Xeorm]

Haven't looked particularly at this video or their claims. Much too late for that right now, but...

Don't confuse thermal imaging with actually seeing the heat of objects. Objects only tend to emit IR on the same levels as most other objects. If most objects in the same area emit IR similarly based on temperature, it can become a way to see heat, but get something that works a little differently and you'd get bad readings. Assuming the fabric did have a different emissivity that's enough to fool sensors, then you're set. You don't need to do anything with the heat, so it could be cool and lightweight. Theoretically.

[YNM]

You can always do the following :

- Hide behind a glass

- Hide behind a metal cover (preferably those used as heatsink)

At human body temperatures, the earlier blocks IR while the later reflects incident IR. Although, both can't be touched by the heat-emitting object to ensure they works.

Edited May 14, 2017 by YNM

[Codraroll]

I don't think this would work very well for combat. As stated previously, a rifle would appear as a white-hot dot after a single shot.

But for spotters for artillery, or recon units, I could see it being useful. Those guys whose mission is considered a failure if they ever have to fire their rifles. They lay around in the bushes with binoculars and radios, hoping to never draw the attention of the enemy (such as by shooting at them). Then somebody else, far away, takes care of the shooting part.

[magnemoe]

15 hours ago, 55delta said:

It's not a bad idea, even if this thermal camo isn't perfect. In an area with enemy vehicles that could use thermal systems, like tanks, attack helicopters, and AC-130s, something that would cut a thermal profile to less of a human-shaped bright spot is actually pretty handy.

This, its not about invisibility its about reduced profile. 
And I don't really get how this works, as I understand its not insulation who would not work, the fabric breathes. but don't give of much of an thermal signature somehow. 
Did not knew it was possible, yes an shield would have its own temperature and thermal signature who would not be heathen up but this is something else.
 

[Shpaget]

Metals are reflective in IR, so a bare metal object will not show its own temperature when viewed with a thermal camera, but the temperature of its surroundings. Basically it acts just like a mirror.

I don't know if this think works on this principle, but it looks like i might.

[p1t1o]

12 hours ago, Shpaget said:

Metals are reflective in IR, so a bare metal object will not show its own temperature when viewed with a thermal camera, but the temperature of its surroundings. Basically it acts just like a mirror.

I don't know if this think works on this principle, but it looks like i might.

A metallic object will still radiate its black-body signiture, surface finish is of no object, but it will also reflect incident radiation as well (not 100%, some is always absorbed, proportion dependant on material properties).

RelatedFunFact: What colour is the sun? Its black. It just glows white/orange because its hot.

***

Anyone know anything about the frequencies detected by IR cameras? Is it possible that IR camoflage is working, rather than just blociking IR radiation, by shifting emissions to a frequency not as readily detected by common IR CCDs?

[Green Baron]

23 minutes ago, p1t1o said:

 

Anyone know anything about the frequencies detected by IR cameras? Is it possible that IR camoflage is working, rather than just blociking IR radiation, by shifting emissions to a frequency not as readily detected by common IR CCDs?

IR is a much wider spectrum than visual. What the chips read depends mainly on filtering. In the far infrared exposure times could get longer, but far infrared is not very interesting on earth.

http://starizona.com/acb/ccd/advtheorycolor.aspx

That whole radiation thing with the suit is somewhat dubious. Fact is, a human body radiates and not little. That energy must get away, our skin takes care of that to keep the temperature in a convenient area. Depending on activity, humidity and temperature, the skin can starts to evaporate water to cool the inside but the vapour needs to escape and take the energy away. Humans can't survive long in a 45°C humid environment, they'll overheat, proteins start to decay and the body functions come to a halt.

If, like implied by the photos, no radiation escapes the suit then the inhabitant will soon die as the body temperature exceeds 40°C and humidity from sweat and insulation from the suit prevent getting rid of the energy. So i believe that they used a filter to narrow the sensitivity of the camera to a wavelength where the suit indeed might be impermeable while steaming more heftily on other wavelengths. Or they retouched the pictures. Or the victim model put it on, they took the photo and then it threw away the clothes.

Make a test with a full neoprene suit with a hood in room temperature. You'll be surprised how warm it gets inside :-)

 

Edited May 15, 2017 by Green Baron

[kerbiloid]

How to hide a 70 W bulb under cloak and stay invisible. Or up to 700 W if breathing hard.

[monophonic]

1 hour ago, Green Baron said:

That whole radiation thing with the suit is somewhat dubious. Fact is, a human body radiates and not little. That energy must get away, our skin takes care of that to keep the temperature in a convenient area. Depending on activity, humidity and temperature, the skin can starts to evaporate water to cool the inside but the vapour needs to escape and take the energy away.

Yes, human bodies can keep cool in a few ways. Radiation is one, but not that efficient as a heat transfer method at our preferred body temperature. Human body can radiate at up to 100W, or a little over half of our heat production at rest. Convection in the form of respiration is of course another one, like you mention, and very efficient when the surrounding environment permits the sweat to evaporate. But it is reserved for real need - people in general are not sweating while taking a stroll in a park.

The one you forgot to account for is conduction: The thermal vibration of the outer atoms on our skin - or whatever we are wearing - directly transfers energy into the atoms of surrounding air. Which being a gas tends to expand and move up and away when warmed. Letting cooler air again come in to contact with our outer surface. (Of course this works in the opposite direction when air is hotter than us.) Neoprene has quite a low thermal conductivity, thus it is very good for e.g. wetsuits and other clothes meant to keep you warm. I would be very surprised if I didn't get hot just sitting in a suit made from it. If you had a suit made of steel fabric - not very comfortable, but it will definitely keep you cool. Of course we as a species haven't really had a need for thermally conductive fabrics, so those are harder to come by - NASA has a method that utilizes carbon nanotubes: http://www.techbriefs.com/component/content/article/ntb/tech-briefs/materials/14234

2 hours ago, p1t1o said:

Anyone know anything about the frequencies detected by IR cameras? Is it possible that IR camoflage is working, rather than just blociking IR radiation, by shifting emissions to a frequency not as readily detected by common IR CCDs?

Industrial IR cameras tend to have a temperature range of over 1000 Kelvins while having resolutions of dozens millikelvins or better. This may be one of the very few cases where industrial requirements are greater than military requirements. Basically though you can forget about trying to trick the system by messing with the wavelength.

On 5/14/2017 at 11:57 AM, Codraroll said:

I don't think this would work very well for combat. As stated previously, a rifle would appear as a white-hot dot after a single shot.

A rifle shot is very conspicuous even in broad daylight - not to mention in darkness - to the old Mk1 eyeball. If you leave your rifle and yourself visible after taking your few rapid or single well aimed shot you deserve every bullet that's coming your way. Thermal sights or not.

[Hannu2]

3 hours ago, p1t1o said:

A metallic object will still radiate its black-body signiture, surface finish is of no object, but it will also reflect incident radiation as well (not 100%, some is always absorbed, proportion dependant on material properties).

RelatedFunFact: What colour is the sun? Its black. It just glows white/orange because its hot.

***

Anyone know anything about the frequencies detected by IR cameras? Is it possible that IR camoflage is working, rather than just blociking IR radiation, by shifting emissions to a frequency not as readily detected by common IR CCDs?

Black body is by definition a body which does not reflect any incoming electromagnetic radiation. The Sun can be usually approximated as a black body at visible and most IR range, but metals are more complex. Emissivity is a factor which tells how much a surface radiates compared to black surface. Practical emissivities varies much depending on temperature and surface properties, but very low values (<0.1) are common for glossy metal surfaces at human body temperature.

https://www.omega.com/literature/transactions/volume1/emissivitya.html

Thermal imaging use wavelengths around 10 µm. It is not practical to convert low intensity radiation to other wavelengths. Those camouflages are just good insulators which have surface temperature near the ambient value. Heat must be somehow transferred into air, which does not radiate effectively. I think that those clothes must be quite hot in warm environment, but probably work well in recon missions at lower temperatures. Normal winter clothing and animal's hair reduces also thermal emission significantly.

Probably such camouflage is usable at special situations, but it is not perfect solution for every situation, like not any other weapon or defense. Probably it does not work well on empty plains, but significantly reduced IR trace and broken body shape may be very difficult to distinguish from wild animals and other disturbances in forest environment.

 

[p1t1o]

26 minutes ago, Hannu2 said:

Black body is by definition a body which does not reflect any incoming electromagnetic radiation. The Sun can be usually approximated as a black body at visible and most IR range, but metals are more complex. Emissivity is a factor which tells how much a surface radiates compared to black surface. Practical emissivities varies much depending on temperature and surface properties, but very low values (<0.1) are common for glossy metal surfaces at human body temperature.

https://www.omega.com/literature/transactions/volume1/emissivitya.html

Thermal imaging use wavelengths around 10 µm. It is not practical to convert low intensity radiation to other wavelengths. Those camouflages are just good insulators which have surface temperature near the ambient value. Heat must be somehow transferred into air, which does not radiate effectively. I think that those clothes must be quite hot in warm environment, but probably work well in recon missions at lower temperatures. Normal winter clothing and animal's hair reduces also thermal emission significantly.

Probably such camouflage is usable at special situations, but it is not perfect solution for every situation, like not any other weapon or defense. Probably it does not work well on empty plains, but significantly reduced IR trace and broken body shape may be very difficult to distinguish from wild animals and other disturbances in forest environment.

 

"A black body" yes, is a hypothetical totally non-reflecting object. However, "Black body radiation" or what I referred to as "black body signiture" is something everything emits, even a shiny, metallic object. No real object is a perfect "black body" due to material properties such as those you mention for metals. So depending on what an object is made of, it might not have an emission spectra exactly matching "a black body" at its temperature, but its wrong to suggest that a shiny metallic object will only reflect incident radiation and won't emit any of its own IR radiation.

 

[Shpaget]

7 hours ago, p1t1o said:

A metallic object will still radiate its black-body signiture, surface finish is of no object, but it will also reflect incident radiation as well (not 100%, some is always absorbed, proportion dependant on material properties).

Take a look at this video of a thermal camera filming an aluminium heatsink.

 

In order for the camera to register the temperature of the metal, the guy needed to put some sticky tape on it. The bare metal is just reflecting the temperature from ambient objects, or the room itself.

So, if the camo suit is some sort of IR mirror that reflects the ambient temperature, it would be hard for a thermal camera to spot anyone wearing it, regardless of the actual temperature of the material.

[Hannu2]

17 hours ago, p1t1o said:

"A black body" yes, is a hypothetical totally non-reflecting object. However, "Black body radiation" or what I referred to as "black body signiture" is something everything emits, even a shiny, metallic object. No real object is a perfect "black body" due to material properties such as those you mention for metals. So depending on what an object is made of, it might not have an emission spectra exactly matching "a black body" at its temperature, but its wrong to suggest that a shiny metallic object will only reflect incident radiation and won't emit any of its own IR radiation.

 

Surface reflectivity works to both directions. Reflective surfaces do not emit thermal radiation as much as black surfaces. Lowest emissivities in that table was 0.02. Such a body emits only 2 % of black body emission. Infrared thermometers do not work with glossy metal surfaces. If you want to measure temperature from such surface you have to put something more black, like piece of tape. Some surfaces, for example black anodized aluminium heatsinks, may be black at visual wavelengths but reflective at thermal IR wavelengths.

[-Velocity-]

The best possibility I can think of is if you can make your IR camouflage out of a material with very low IR emissivity at 3 um to 5 um and at 8 um to 12 um.  Basically not every surface is going to emit like a blackbody, in fact, no surface will exactly emit like a blackbody, and that's where the concept of IR emissivity comes from- emissivity is basically how well does a surface emit at a specific wavelength.  Anyway, 3 um to 5 um and 8 um to 12 um are the spectral ranges that thermal imaging systems operate at due to high atmospheric transparency in these spectral windows.  So "all" you need to do is make your camouflage out of a material that has very low IR emissivity at 3 um to 5 um and 8 um to 12 um.  The side effect will be that whatever is inside your camouflage will have to heat up some so to that it emits more strongly in wavelengths outside of 3 to 5 and 8 to 12.

This is exaclty how more CO2 creates more global warming, by the way.  The more CO2 that goes into the atmosphere, the higher and higher in altitude you must go before any IR radiation is able to escape within CO2's IR absorption bands.  Since the temperature drops as you go higher and higher in altitude, that means that less and less IR will be emitted into space within CO2's absorption bands the more and more CO2 is put into the atmosphere.  Therefore, the Earth must heat up enough so that the extra IR emitted in other wavelengths equals the amount of IR NOT emitted within CO2's absorption band.  Energy in must equal energy out, but because more CO2 makes Earth a slightly less efficient heat emitter, the Earth must get hotter to emit the same amount of energy back into space as it receives from the Sun.

[kerbiloid]

And then 3-5 and 8-12 um spectral ranges will be used by thermoscopes to ensure if this is somebody in thermal camouflage, but not just a tourist in a sleeping bag..

Edited May 30, 2017 by kerbiloid

[sevenperforce]

On 5/15/2017 at 4:48 AM, p1t1o said:

A metallic object will still radiate its black-body signiture, surface finish is of no object, but it will also reflect incident radiation as well (not 100%, some is always absorbed, proportion dependant on material properties).

RelatedFunFact: What colour is the sun? Its black. It just glows white/orange because its hot.

Uselessly pedantic note: technically it glows white; it only appears orange because the atmosphere scatters higher-energy wavelengths, filtering out blue and violet light and leaving behind a nice warm orange glow. The sun is white when viewed from space.