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[Rolepgeek]

I need to ask a question that'll make you think I'm stupid. That's because I'm stupid.

Is a low heat conductivity more important than high melting point? What if I layered something beneath the armor to absorb the heat?

If your armour conducts too much heat through it, whoever is inside it will get cooked. If its melting point is too low, it wont prtect much at all. You want both...

Absorbing the heat, if you have no way to dissipate it in some way, will lead to cooked wearer syndrome. The easiest way to dissipate it would be to conduct it away, presumably into some kind of heat sink system.

Alternately, top layer of armor conducts heat very well, next layer of armor does not conduct it very well at all, and is furthermore a heatsink. Melting point for the top layer only needs to be as high as the heat conductivity is low. In atmosphere, conducting the heat through the outer layers of armor will let it dissipate into the air. Superconductors. That's where it's at.

[Amperzand]

Is there such a thing as a thermal superconductor? If so, I was not aware of this, and believed the phenomenon only applied to electrical conductivity, usually at very low temperatures.

[Rolepgeek]

Modern superconductors only act as superconductors at very low temperatures. The requirement for a lot of sci fi techs to be effective includes room-temp superconductors. And yeah, it applies as much to heat as electricity. It's just usually used for the one and not the other.

[Amperzand]

I see. Presumably because of the low-temperature thing.

Well, that would certainly help with getting heat input to a sink. Maybe a grid of superconductive material suspended in more traditional armor? Most heat follows the path of least resistance to a sink, and presumably the thing's also grounded to help protect from the kind of electric shock that serves a threat to metal armor.

[Rolepgeek]

Really, if it's superconductive over the entire outer plating, you don't need a heatsink. It'll dissipate over the entire surface of the armor.

[HAMMERMILL]

Really, if it's superconductive over the entire outer plating, you don't need a heatsink. It'll dissipate over the entire surface of the armor.

The guy wants to talk about laser weapons against infantry, if it was some superconductive plate in an infantryman's armor it'd just cook that person, ignite his clothing and it'd be just as lethal as if it penetrated.

On an armored vehicle it'd be the same situation. You'd want materials designed to deflect, block or insulate against thermal energy as much as possible.

If you are a target of laser weapons you want materials that are good insulators, not good conductors of thermal energy. Ceramic, used in bodyarmor and armored vehicles already for other properties is a better choice than plates of synthetic lanthanum-based cuprate perovskite or something.

[Rolepgeek]

One layer of superconductive armor plating. Possibly wires or joints connecting different armor plates. If you're talking about laser weapons strong enough to be able to 'cook' someone when the heat's spread out over their entire chestplate, through multiple other layers of armor, then discussions of armor are pointless, which is why I'm presuming we aren't talking about weapons that powerful. You have a layer of conductor over a layer of insulator. Composite armors are a thing, guys.

[Amperzand]

Usually best taken to mean super-speshul-space pottery.

[wierd]

Basically, a ceramic is a thermally fused, low solubility salt.

Usually, this is a salt of a light transition metal, silicon, hydrogen and oxygen-- but not always. The major features are:

Thermally fused- EG, amorphous atomic arrangement. (Not a crystal.)
Non-metallic (Does not exhibit metal-like properties, like electrical conductivity, attack by acids, or ductility)
comprised of a metal (or metaloid) atom, and non-metal atoms.

Noteworthy industrial ceramics include:
silicon carbide (Silicon is a metaloid, carbon is a nonmetal)
Titanium Nitride (Titanium is a metal, Nitrogen is not.)
Mullite/Aluminium silicate (Aluminium is a metal, Silicon is a metaloid, and oxygen is a nonmetal.)
Silicon dioxide (when in "clay" form, not vitreous glass or crystal form) (Silicon is a metaloid, Oxygen is a nonmetal)
Rare earth magnets, like neodymium magnets (made from neodymium, silicon, oxygen, and pals)
Titanium Oxide ceramic (Heat fused titanium dioxide)
and various others.



Basically, it's dirt (even if it is special dirt) that you heat up in an oven, or a thermally deposited amorphous layer produced through high temperature/high energy chemistry (in the case of Titanium Nitride)

[Tack]

Don't even know what 'Ionic' or 'Covalent' mean.

Basically ionic is weaker and covalent is stronger iirc.
There's a third kind I forgot, google tells me it's called "polar" and my interest immediately dies.
---
So basically ceramics are non-metallic stuff made out of metallic compounds?
That's really cool when it's completely made inaccurate.

[wierd]

The most interesting ceramics are the ones that exhibit mysterious and wonderful properties under extreme conditions.

Take for instance, Yttrium-Barium-copper-oxide.  The so called "Shake and bake" superconductor. That stuff exhibits very unique changes in valence electron configuration when cooled sufficiently. At room temperature, it is about as conductive as a large hunk of rubber.

https://en.wikipedia.org/wiki/Yttrium_barium_copper_oxide

[Tack]

I like the idea of chaff as a defense against lasers.
Physics weeps, but something which instantly atomised and formed a laser-retardant cloud would be a cool idea ceramics-wise.
Y'know, as long as you're also wearing a rebreather.

Edit: sublimation was the word I was looking for.
Something with a high melting point, low thermal conductivity, but vaporises as soon as it gets hot enough- the better to dump the excess heat away from the soldier.
(This somehow not resulting in a prospective fighter having- rather than a small, cauterised hole in them- a superheated cloud of gas around them.)

[wierd]

You dont need that. You just need a properly formulated smoke bomb.

Not all particulates will be radio-opaque to all frequencies. That's why smoke screens went out of favor after the invention of IR imaging. However, with the blessing of modern chemistry, most frequency bands best suited to transmitting large sums of energy to a target can be selectively chosen for, and particulates of appropriate absorption bands can be suspended with such aerosols.

See laser weapons? Out go the smoke canisters. lasers bloom out long before reaching the target.

Here's a pretty good video explaining what I mean.  Your typical plastic garbage bag is completely transparent to near infrared. In the visible spectrum, it is nearly completely opaque.

http://www.youtube.com/watch?v=6mV4ecEbV1s&t=2m43s

Likewise, to some of the frequency bands suited to being weaponized lasers, particles invisible in the normal human visible spectrum will be obscuring, and will disrupt the beam, causing it to bloom.

A good mix of such particles over the most likely bands, would be an effective and cheap countermeasure.

[Tack]

...
Meaning that everyone's weapons are suddenly changed into scatterguns?
... That makes for an awesome scene.

[Amperzand]

Less "scattergun." more "sudden fireball".