Hacker News Reader

Comment by goodcanadian | Hacker News Reader

A very cool development, but . . .

I wonder about its long term potential as camouflage. By reducing its infrared emissivity, it can make a hot object look cooler, but might it not also prevent that hot object from shedding heat thereby causing its temperature to go up? Invisible soldiers aren't much good if they literally cook to death.

View on HN

It has nothing to do with the thermal qualities of the object and everything to do with being able to alter emissivity. Thermal cameras are only accurate for a given emissivity and high end thermal cameras allow you to tune emissivity to get accurate readings [1]. By altering the emissivity of the material at will, you can camouflage your object against a camera assuming constant emissivity.

[1] http://en-us.fluke.com/training/training-library/measurement...

That's a great page! I only recently started learning about black body radiation namely due to investigating lighting for my house and photography lighting.

It will prevent objects from shedding heat through radiation, but it does not seem that it will in any way prevent them from shedding heat through conduction, convection, or evaporation. If the film were on the outer layer of a garment, as long as the inner layers still allowed the soldier's sweat to evaporate they would still be able to keep cool.

I suspect it will be most useful when you have a reasonable suspicion of where the camera will be, deploy this between you and said camera.

This is the main problem of stealth in every wavelength - it's easy to be stealthy in a certain direction. For example, fighter planes are only "really" stealthy when an enemy is approaching them from the front. If an F-35 turns after releasing missiles, it can suddenly be targeted easily.

Going back to the original topic - optical camouflage is possible, but only toward one observer, or to be more specific, from a single angle.

True, though I imagine there's plenty of use for vehicles, aircraft, and buildings.

Reply on news.ycombinator.com