Practicality of Invisibility cloak?

[m74z00219]

Hi all,

A cloak that guides the entire optical band around it seems very useful, but what about the radiant spectrum of a person? Couldn't anyone with infrared googles spot an individual? Perhaps a cloaked individual would be harder to spot during the day? Perhaps, even the radiant light could be guided out of the cloak in a preferred direction (less the wearer be be cooked alive).

Any thoughts?

Thanks,
M74

[sarongsong]

...Any thoughts?

Editing.

[Sharlos]

An invisibility cloak that could hide your visible spectrum would also be capable of hiding your infra-red spectrum.

[m74z00219]

Editing.

Thanks for your valuable reply.

An invisibility cloak that could hide your visible spectrum would also be capable of hiding your infra-red spectrum.

Could you elaborate please?


m74

[Noclevername]

An invisibility cloak that could hide your visible spectrum would also be capable of hiding your infra-red spectrum.

Visible light is reflected from outside, heat is radiated from within. All an invisible cloak has to do is change the way light flows around you, but you can't stop being warm unless you're dead, and thermodynamics says that heat has to go somewhere. A cooling system with a large heat sink might provide temporary thermal invisibility, assuming it doesn't leak, but it's not going to be very stealthy-- like walking around with a refrigerator on your back.

[m74z00219]

Visible light is reflected from outside, heat is radiated from within. All an invisible cloak has to do is change the way light flows around you, but you can't stop being warm unless you're dead, and thermodynamics says that heat has to go somewhere. A cooling system with a large heat sink might provide temporary thermal invisibility, assuming it doesn't leak, but it's not going to be very stealthy-- like walking around with a refrigerator on your back.

Great imagery!

[mugaliens]

I have a wonderful invisibility cloak in the closet, but it only works on moonless nights...

[Romanus]

Much easier than an invisibility cloak (and probably within current means) would be a simple adaptive camouflage that could be adjusted for a variety of environments--like say, pushing a button to switch from desert to jungle pattern, or from jungle to snow white.

[mugaliens]

We have that now, but only in limited bands of the EM spectrum.

A true cloak would require that one remove nearly all of the signature with cooling, say, the release of pressurized nitrogen to cool a metallic skin, then cover that skin with layers absorbent across the EM spectrum from radio through X-ray, before applying adaptive camoflague throughout the same bands.

To top it off, the emitted signal would have to be fairly detailed, down to the cm range under close observation, and highly directional to accurately depict the background.

By comparison, point sources, such as an aircraft at a distance, need only emit light in roughly the same intensity and color as the background to fool the eye.

[eburacum45]

I'm told that phased array optics could acheive something like invisibility;
http://en.wikipedia.org/wiki/Phased-array_optics
http://www.phased-array.com/
(particularly this chapter)
http://www.phased-array.com/1996-Book-Chapter.html
.
.

[m74z00219]

I have a wonderful invisibility cloak in the closet, but it only works on moonless nights...

Sir, I will invest in your cloaking technology.


@Romanus
I really this idea. Instead of transforming incoming light. Just project a fitting pattern! Genius

@eburacum45
Looks interesting, but I don't have time to read it at the moment. I will later.

Thanks,
M74

[Romanus]

^
Tanks, but it wasn't really my idea; I first came across it in Haldeman's The Forever War. Scooped by 35 years.

[publiusr]

We have that now, but only in limited bands of the EM spectrum.

A true cloak would require that one remove nearly all of the signature with cooling, say, the release of pressurized nitrogen to cool a metallic skin.

Wouldn't a sphere be the best shape for this type of craft, a cocoon that might be shed by a deep space craft?
This might be great covering for the so called ENZMANN Starships shown here http://www.ricksternbach.com/real1.html http://www.ricksternbach.com/port1.html