How good would Aluminum armor be?
 

If I make a breastplate out of aluminum, how much DR would it give? If you need numbers, assume a DR 6 medium plate breastplate, only made from aluminum (same thickness, it would obviously be lighter, 2.7g/cm^3 vs 7.8g/cm^3). I'm rolling with the idea of early aluminum refining from Fantasy Tech and seeing where it takes me.

Re: How good would Aluminum armor be?
 

Probably DR 2 if you're keeping volume the same. Most aluminum alloys are way too soft for armor.

Re: How good would Aluminum armor be?
 

This is almost a FAQ, though I doubt it has a good answer, by the time aluminum could be made in quantities suitable for plate no-one wore plate. It's probably 1/3 weight, DR 2-3 (possibly DR 2, 3 vs crushing), and TL 6.

Re: How good would Aluminum armor be?
 

Pound for pound it should be a lot worse than steel. Otherwise aluminium would have been used for armour today.

Re: How good would Aluminum armor be?
 

Technically, it has been used for vehicular armor (Vietnam-era M-113 if nothing else).

Only in light roles, moslty for anti-fragment level protection and due to aluminum's predilection for catching fire it's no longer used for such purposes.

Re: How good would Aluminum armor be?
 

Isn't aluminium oxide a pretty common ceramic for body armor inserts?

There seem to be a few aluminium alloys that are DoD approved for vehicular armor. Don't ask me for which vehicles, though… (Edit: Seems at least some Bradley CFVs use 'em)

Re: How good would Aluminum armor be?
 

We do use aluminum armor today: the M113 and the M2 Bradley AFVs both use aluminum, specifically because it gives the same protection as steel at a slightly lighter weight. I'm sure other light AFVs do the same.

I can't find any specific cites in a quick web search, but I expect aluminum has a bulk issue that makes it impractical for personal body armor: at the thicknesses you can actually move in while wearing it, it doesn't provide enough protection compared to the same volume of steel, though it is lighter. So pound for pound, it's roughly equivalent, but per cubic inch it's much, much worse. If you're armoring a light tracked vehicle or a thin skinned warship, that's not a big deal, since you can just use thicker slabs. If you're armoring a person or a heavy tank, you run into size constraints. Aluminum also looks to be at least twice as expensive (per pound) as armor grade steel.

So for body armor (or other volume limited applications), I'd expect something like 40% of the weight of steel, about 1/2 the DR, and the same cost. If you can increase the thickness, 90% of the weight of steel, same DR, and twice the cost is reasonable.

Ninja'd by Fred!

Re: How good would Aluminum armor be?
 

It has been used for armor, but it underperforms high strength alloys that are available at the same basic TL as aluminum, at least against bullets (crush protection is probably better). That doesn't mean it isn't competitive with TL 3-4 wrought iron. The big problem with aluminum armor is that aluminum is fairly soft and bulky.

Re: How good would Aluminum armor be?
 

"Bends easily" is actually a pretty good thing when you're up against bullets and tank shells. Not so good against bludgeoning weapons.

Re: How good would Aluminum armor be?
 

If you have the ability to anodize, I could see a pretty effective laminate made from aluminum. Aluminum oxide is pretty hard stuff, although raw aluminum is very soft.

I suppose the ideal would be the ability to do type III anodizing. That gives you the best hardness and thickness for durability, but requires temperature control and current control. It's probably beyond the means of any sub-kevlar technology base. Heck, steel is probably a more practical even-lower-tech alternative.

Re: How good would Aluminum armor be?
 

I said 'soft', not 'flexible'. Aluminum isn't all that flexible, and at the same weight is generally less flexible (due to being thicker), but it's soft, which means you can cut it with a blade.

As for anodizing, if you can produce aluminum at all you can handle anodizing it. The only way you'd be unable to do that is if for some reason you have a supply of found aluminum, and any such aluminum will have been manufactured, it simply doesn't occur in pure or semi-pure form in nature.

Re: How good would Aluminum armor be?
 

Way back when I designed the M113, I was told aluminum armor has 1/3 the DR for the same thickness (or in this case, weight):

http://forums.sjgames.com/showthread.php?t=64749

Re: How good would Aluminum armor be?
 

Transparent aluminum is stronger then tempered wire reinforced bulletproof glass

en.wikipedia.org/wiki/Transparent_ceramics

so it should at least have superior DR/weight to tempered wire reinforced glass (or if somehow being used for body armour, better then glass with the shatterproof spell on it).

Re: How good would Aluminum armor be?
 

That's a ceramic composite. It's not metallic aluminum. It's only called that because of The Voyage Home.

Re: How good would Aluminum armor be?
 

What you reference is most certainly not transparent aluminum. It is transparent alumina (among other things) - very different.

Luke

Re: How good would Aluminum armor be?
 

Yeah, the only way to make transparent metallic aluminum is by having it extremely thin (aluminized mylar) or having holes in it (wire mesh screens).

Re: How good would Aluminum armor be?
 

Aieeeee! Fetch the torches and the pitchforks! The undead arwe among us!

Re: How good would Aluminum armor be?
 

Which has always struck me as strange when you could just as legitimately sell it as Sapphire, which you'd think would have a broader market appeal.

Re: How good would Aluminum armor be?
 

Then you lose the "How do'ye know he didna invent the ting?" jokes. I suspect the inventors are geeks.

Re: How good would Aluminum armor be?
 

...Aluminum and steel have radically different densities. It may have 1/3 DR by thickness, or 1/3 DR by weight, but it cannot possibly have both.

Re: How good would Aluminum armor be?
 

I know that helmets made from aluminum make you immune to mind control, especially if they are pyramid shaped.

Re: How good would Aluminum armor be?
 

At least that's what they want you to believe.

Re: How good would Aluminum armor be?
 

Indeed. Aluminium blocks proper orgone flow.

Re: How good would Aluminum armor be?
 

I use 3/16" 6061 T6 aluminum for my SCA armor. It deals with rattan bludgeoning weapons nicely. Maybe not against a flanged mace or something like that, but it would give some DR... 2 or 3 seems reasonable.

Re: How good would Aluminum armor be?
 

I believe you mean tin foil hats. Making people mistake tin for aluminum so often people assume you mean the second when you say the first is all a part of "their" plan.

Re: How good would Aluminum armor be?
 

Aluminum armor in the field has turned out to be not-a-good-idea since 1965. It fragments a lot worse than steel, so a small hole becomes a small hole plus a lot of shrapnel. It also has a marvelous tendency to catch fire. I was in a squadron that had a plane deployed on a carrier in the Med when the Belknap caught fire. It had a mostly-aluminum superstructure. It burned so hot that our guys on the carrier almost got cooked just being close to it!

Re: How good would Aluminum armor be?
 

Nah, it's just old technology. Mind control rays used to use aluminum optics - the famous aluminum pyramid at the top of the Washington Monument for example. Governments haven't used this system since they started deploying mind control satellites in the 1930s, but there are still corporate users. I think the parabolic shape on the bottom of aluminium beer or soft drink cans are focusing elements to concentrate them on your head as you drink from the can.

Re: How good would Aluminum armor be?
 

They let that rumor escape. By tricking you into switching to glass bottles, you have less aluminum handy, not to mention eliminating the beer coozy hat. And you notice there's a parallel rumor that says your beer bottles ought to be brown instead of clear, purportedly to protect the beer. There's a reason they don't want you to be able to see inside of them.

Meanwhile, back on topic, what property is used to evaluate DR for a material? The "aluminum is 1/3 steel" makes me think modulus of elasticity? There are aluminum alloys which can get about as hard as steel.

Re: How good would Aluminum armor be?
 

Which can actually save even more weight over steel. Since aluminum armor of a given weight is thicker and more rigid, aluminum vehicles pass from "frame with armor bolted on" to "vehicle shaped shell" sooner. A steel M113 would have required more extensive internal structure.

Aluminum still has plenty of problems, of course. Probably chief of which is that it burns. Look up USS Belknap for a good example (short version: aluminum superstructure completely destroyed, steel hull in need of new paint).

Re: How good would Aluminum armor be?
 

Apparently the problem is that aluminium collapses under a lower temperature than steel, not that it burns better than steel. It does conduct heat a lot better which can be a problem on ships. Aluminium suffers more from metal fatigue than steel.

Re: How good would Aluminum armor be?
 

I don't think so. Aluminum is the fuel in thermite and iron oxide si the oxidizer. I think that says "aluminum burns better than steel" pretty clearly.

Re: How good would Aluminum armor be?
 

Aluminium is only useful as thermite because the particle size is very small. It doesn't react the same if it is armour plate.

http://www.g2mil.com/aluminum.htm

"Aluminum and Iron will burn as will any other metal, if it has a sufficiently sized particle. For both metals it is a very small size. A single plate will simply react on the outer layers however the outer skin will be covered in ash from the combustion and protect the inner plate."

Apparently, all of the so-called examples of burning aluminium armour have turned out to be the contents of the vehicle burning, not the metal itself.

Re: How good would Aluminum armor be?
 

Or.....

"Aluminum is more reactive than Steel,"

Sometimes you can overthink these things.

Re: How good would Aluminum armor be?
 

It is only reactive until the surface forms a protective barrier of oxide.

Re: How good would Aluminum armor be?
 

Yeah a big differnace, Aluminum Oxide creates a protective barrier, Iron Oxide as a corrosive effect.

Re: How good would Aluminum armor be?
 

On the modern battlefield and on any higher-tech version, aluminum armor is a BAD IDEA.

Low-tech aluminum personal armor is an oxymoron. It isn't available at all until late TL5 and then it's very expensive. The Washington Monument has a cap made of aluminum, which was more expensive than silver in 1884.

Of course, if you want to build a civilization of intelligent cockroaches after the big-oops, all those non-biodegradable aluminum cans provide a practically-endless source of metal. And maybe some smuggler is making a fortune "recycling" old cans to Microworld.

Re: How good would Aluminum armor be?
 

No, the total combustion of some aluminum structures is well-documented and not just the military examples quoted in the article you seem to be ignoring. It's also seen quite commonly in civilian aircraft disasters.

Try this one for a simple example.

http://aviation-safety.net/wikibase/wiki.php?id=22676

The skin isn't just melted, it's burned to ashes. That doesn't happen to the steel body panels of automobiles in simialr situations. The surface layer of aluminum oxide didn't protect it. All aluminum in an oxygen atmosphere already has such a surface layer anyway. Aluminium is _that_ reactive.

Re: How good would Aluminum armor be?
 

The question is whether the aluminum would burn in a fire that isn't already hot enough to completely destroy the structure. It doesn't specifically matter if the aluminum is destroyed in a fire (if it would have been melted anyway, it's not much worse to have it be ash), it matters whether the aluminum is making the fire worse. In your example, it's a fuel fire that consumed the aluminum, not an aluminum fire.

Re: How good would Aluminum armor be?
 

But the aluminum didn't just melt. It did burn. That releases heat pretty much by definition. I have trouble seeing how more fuel and hotter fire doesn't equal more destruction.

Re: How good would Aluminum armor be?
 

Something cannot be more than completely destroyed...

Re: How good would Aluminum armor be?
 

Side note on low tech aluminium:

The process for extracting aluminium from clay is very energy intensive; but not actually using any metallurgical processes above TL2- it's just that no one thought to react bauxite clay with acid, boil off the result, melt in crucible the result of that. That knowledge could have allowed aluminium extraction at TL2ish where it would have been pretty competitive with copper and bronze as a tool/armour/weapon material.

Re: How good would Aluminum armor be?
 

The thing is that we need to be talking TL1-ish. TL2 is the Iron Age and copper and bronze have been reduced to specialty niches.

Re: How good would Aluminum armor be?
 

One reason the question comes up is for fantasy games. Those iron-vulnerable fae need something other than steel. And (as always) magic might substitute for technology.

Re: How good would Aluminum armor be?
 

Until TL6 electric furnaces, all previous methods of refining aluminum were very resource-intensive. The best TL5 was able to do was reduce the cost of aluminum from being more expensive than gold, to merely more expensive than silver. I'm no chemist, but even this appears to have required things like vacuums or pure elemental potassium that will be tough to pull off at TL2 (or if you can do it, you're no longer TL2 in any meaningful sense).

Re: How good would Aluminum armor be?
 

One curiosity to keep in mind with aluminum armor - aluminum reacts ... interestingly ... with elemental mercury. Exposure to mercury can result in even fairly large pieces of aluminum corroding away within hours.

Luke

Re: How good would Aluminum armor be?
 

Bronze. It's more expensive than iron, but it's perfectly good armor.

Re: How good would Aluminum armor be?
 

While your timeline is correct, the reasons are not exact. Aluminum was barely in the range of 'applied theroy' in the 1800s and would not be processed in any reasonable form until the mid 1850s. That processing method (dissolve bauxite clay in a mixture of acid, boil away results, collect aluminum powder) was actually viable (though not nearly as effective as the current electrolytic method) and would represent the drop from 'more expensive then gold and platinum' to 10% of that, it would require either instruction, or a compelling reason to try to isolate the metal inside clay (and knowing that there IS a metal inside clay) to do so at TL2, but there is nothing particularly complicated about the process (labour intensive, but not complicated).

Re: How good would Aluminum armor be?
 

The non-electrolysis process invented in the mid 1850s (Deville's modification of the Wöhler process) required metallic sodium. Metallic sodium was not isolated until 1807 -- via electrolysis (the Wöhler process used potassium, also isolated in 1807). Production of aluminum without electrolysis requires a stronger reducing agent than aluminum, and there are no alkali or alkaline earth metals that occur naturally (carbon can pull oxygen off of iron, but not off of aluminum).

Re: How good would Aluminum armor be?
 

Aluminum has an oxidation number of 3, there are stronger oxidizers (the Group IVA-VIIA metals). Are you saying that they don't occur naturally in any form that would be useable for this? I'm assuming that's the case, or I really don't understand oxidation-reduction (and I really thought I did).

Re: How good would Aluminum armor be?
 

You want reduction potential, not number (on that table, the top is strong oxidizers, the bottom is strong reducers). All of the stronger reducing agents are alkalines or alkaline earths, and do not occur in pure form in nature.

Re: How good would Aluminum armor be?
 

Right, because we are talking about Reduction not Oxidation here. Nevermind. I've got some otherthing going on from the other direction, and got my wires crossed. Yes, using Lithium Hydride or something isn't feasible before TL5.