How thick is modern MBT armor (DR 2000)?

[BraselC5048]

From another thread, I know that a modern top-of-the-line Main Battle Tank has DR 2000 or so. That's not what I'm looking for. What I'm wondering is how many inches thick it is, physically. Mostly for comparison to my starship armor.

Or to work around it the other way, I want middle-of-the-road starship armor to be DR 2000, same as a MBT. I've also decided what it's made of, for radiation protection, namely layers of carbon composite (I 'think' it was high lithium carbon composite) (for neutrons) and steel (for mass for X-rays). Most of the weapons going against it will be directed energy weapons, as in lasers and nuclear shaped charges, so having to burn through something made of carbon will do a pretty good job of stopping it. Making it out of solid steel, DR 70 per inch, would be something like 2ft 4" think, which seems thicker than what a tank would have, and is too think for my starships. If an Abrams is less than DR 2000, then DR of the starship can go down too.

Perhaps about 8" thick for medium cruisers (armor value 8, DR 2000), and 12" thick for the most heavily protected battleships? (DR 3000?) Or just 1" thick per point of armor value, which ranges from 0 (no armor) to 12?

That would be DR 250 per inch, which seems high, although I don't know what exact kind of composite armor modern western tanks are made of, or what it's DR would be. Then again, it's classified anyway. Maybe 1.5" x armor value thick?

[Fred Brackin]

Originally Posted by BraselC5048

s. If an Abrams is less than DR 2000, then DR of the starship can go down too.

The DR of an Abrams is generally set at about 1680 and double that for Shaped Charge weapons. This is equivalent to 24 inches of Rolled Homogenous Alloy (steel). RHA is DR70 per inch (25mm). The best steel armor is provably 20% better.

Titanium is probably about the same DR per unit of thickness bit only 60% as dense.

You can get higher DRs per unit of weight but most of those armor types are made of materials much less dense than steel. Steel is around 8 gm/cc while a ceramic as dense as glass would only be around 2. Even tough forms of stone are under 3.

Sppacecraft armor might use a lot of spacing too so thickness would be even greater.

If you like your hull thicknesses of 8" to 12"'re going to need a semi-exotic material (and probably just make up your DR numbers). An iridium composite might be about as good as you can get without superscience and iridium has a density around 20.

[BraselC5048]

Originally Posted by Fred Brackin

The DR of an Abrams is generally set at about 1680 and double that for Shaped Charge weapons. This is equivalent to 24 inches of Rolled Homogenous Alloy (steel). RHA is DR70 per inch (25mm). The best steel armor is provably 20% better.

So is the Abrams actually made out of 24" of armor steel, or composite materials that have a higher DR per inch? For that matter, it can't be and still weigh under 100 tons, 24" of steel just weighs too much. And how many inches thick is it, actually?

Originally Posted by Fred Brackin

Titanium is probably about the same DR per unit of thickness bit only 60% as dense.

You can get higher DRs per unit of weight but most of those armor types are made of materials much less dense than steel. Steel is around 8 gm/cc while a ceramic as dense as glass would only be around 2. Even tough forms of stone are under 3.

Sppacecraft armor might use a lot of spacing too so thickness would be even greater.

If you like your hull thicknesses of 8" to 12"'re going to need a semi-exotic material (and probably just make up your DR numbers). An iridium composite might be about as good as you can get without superscience and iridium has a density around 20.

Actually, I already designed the ships using a tonnage-based system. This is just an exercise in figuring out how many inches thick the armor is, and it's DR, which does not matter for starship combat, where the armor value uses its own rules. Also, you actually need enough mass to stop X-rays and avoid getting the crew killed. The armor's biggest design criteria is to stop directed energy weapons, and having to burn through a carbon composite uses up a lot of energy.

I originally went with plain carbon shipbuilding steel for mass along with carbon composite. If you've got something significantly more dense with better properties against kinetic impact, than I'm all ears. Still, most of the thickness is in the carbon composite armor. Using pretty much present-day materials.

The real question here is what kind of DR per inch are we talking about for advanced composite material armor? I would figure it's more than 70. Would 12-18" thick fit better?

[BraselC5048]

Apparently GURPS Vehicles lists the right materials and their DR and weight, but does it give thickness? Or a per square foot and a density, that would enable running some math to figure it out?

[acrosome]

Originally Posted by BraselC5048

So is the Abrams actually made out of 24" of armor steel, or composite materials that have a higher DR per inch?

The latter- you're making the mistake of assuming that the Abrams armor is RHA. It isn't. It's a pretty complex composite using among other things depleted uranium.

[Fred Brackin]

Originally Posted by BraselC5048

So is the Abrams actually made out of 24" of armor steel, or composite materials that have a higher DR per inch? For that matter, it can't be and still weigh under 100 tons, 24" of steel just weighs too much. And how many inches thick is it, actually?

Abrams armor is (probably) made out of a multi-layered "sandwich" of high-grade steel, depleted uranium, ceramic blocks and high tensile strength synthetic weaves. Exact thickness and composition is unknown and probably complicated due to the varying materials.

For a simpler example, the armor belts on an Iowa-class Battleship average 20" thick and probably are made out of RHA.

No, you probably can't work out thickness from the Ve2 armor tables. It might be possible of you had exact compositions and densities but the Ve2 tables are too generic for that.

[Anthony]

The glacis plate on an M1 is apparently about 2" thick, but it's also at an 82 degree angle, so the thickness you'd have to shoot through to penetrate the plate from the front is about 14".

[BraselC5048]

Originally Posted by Anthony

The glacis plate on an M1 is apparently about 2" thick, but it's also at an 82 degree angle, so the thickness you'd have to shoot through to penetrate the plate from the front is about 14".

And Here we have what I was looking for! Roughly 14" of composite armor is DR 1680. Reducing to DR 100 per inch for starships due to the armor having several more important considerations than kinetic energy impact, such as radiation protection. Assuming 1.5" thick times armor value, that gives a well protected armor-8 cruiser 12" of armor worth DR 1200, should a situation where that matters ever come up. My current cruiser, fast and heavily armed but with only armor-7, would have 10.5" of armor worth DR 1050, while Admiral Oldenburg's flagship with armor-12 has 18" worth DR 1800. Thanks.

I'll likely adjust it so armor-1 is thicker then 1.5," "grading on a curve," so to speak, so the relationship between armor value and it's thickness isn't quite as simple. At least it has the benefit of only having to work for whole numbers, so I can just make a table. Kind of like how I wound up simply throwing out the radiation numbers and replacing them with the results I wanted, which was easy since after I came up with a few values I discovered it was pretty much armor value squared for number of missile hits per gray.

[Fred Brackin]

Originally Posted by BraselC5048

And Here we have what I was looking for! Roughly 14" of composite armor is DR 1680. .

Maybe for the specific type of composite known as "Chobham". Composite is more than a general class of armor it's close to being a meta-class.

[The_Ryujin]

Ok, just to give you some values...

Modern Titanium armors have a DR of around 55 and 60 per inch and weighs between 0.43 and 0.39lbs per ft^2 per point of DR.

RHA steel armor has DR 70 and weighs 0.58lbs per ft^2 per point of DR, the highest grade of modern, high hardness, steel has DR90 and weighs 0.45lbs per ft^2 per point of DR.

Earlier non-DU "chobham" used on the first generation of M1's has only DR 55 and weighs 0.4lbs per ft^2 per point of DR and is counted as laminate, DU insert "chobham" has a much higher DR/inch at 92 and weighs 0.3lbs per ft^2 per point of DR but should only be treated as spaced armor against shape-charges. The most modern generation used on the M1A1 SEP has DR 110 and weighs 0.25lbs per ft^2 per point of DR but should also only counted as spaced armor.

Sloping also effects armors DR, increasing it's effective thickness by (armors thickness/COS(angle of slope)) as well as increasing the likelihood that a round will just bounce off of it. For simplicity GURPS combines the increased thickness and chance of bouncing a round and assumes that an slope of 30° will increase effective DR by 1.5× and a 60° slope will increase it by 2×