High tech armor vs Ultra-tech armor

[Kallatari]

Originally Posted by Varyon

As for layering, this strikes me as a "sum of squares" situation.

I am curious. Would the physics behind this root-sum-squares approach for layering two equipment armor with respect to determining how protective it is against an attack also apply for wearing armor over natural DR? Does that not count as "two layers" in that regard?

Second question. Does distance play a factor? If I was shooting through multiple walls of a building to hit someone on the other side, does the fact that the walls are several metres apart mean they get to use full DR, or are they also root-sum-squared?

[Varyon]

Originally Posted by Kallatari

I am curious. Would the physics behind this root-sum-squares approach for layering two equipment armor with respect to determining how protective it is against an attack also apply for wearing armor over natural DR? Does that not count as "two layers" in that regard?

Yeah, it should. Note this rather devalues the Cannot Wear Armor Limitation on natural DR - but then I've never really thought that made sense mechanically (you get more points back the less use you'd get from wearing armor) and should just be a flat Disadvantage (probably worth a bit more than a Vow to not wear armor).

Originally Posted by Kallatari

Second question. Does distance play a factor? If I was shooting through multiple walls of a building to hit someone on the other side, does the fact that the walls are several metres apart mean they get to use full DR, or are they also root-sum-squared?

It should play a factor, but the interaction would be complicated and highly dependent on the projectile. When a projectile strikes a barrier, it may deform and will typically be partially deflected; many projectiles will also tumble or "keyhole." You can see this in a lot of GunTuber videos, particularly when they line up water jugs and shoot them. Having to shoot through a barrier (wall, armored door, pane of glass, another person, etc) that is a yard or more from your target should probably call for something like the "Hitting the Wrong Target" rules, although depending on how much the projectile is deflected the skill cap may be something other than 9. But how much deflection occurs depends on a lot of factors - the materials (and constructions) involved, the angle of impact, etc. Some projectiles may also have a damage cap beyond which the projectile is considered deformed when striking later layers, which results in a poor armor divisor but possibly a boosted wounding modifier (projectiles that are particularly susceptible to tumbling probably have a lower cap that results in keyholing instead, with a similar effect). And honestly, calling for a full yard of separation is probably inappropriate - LT (or maybe LTC2) has several examples of things like feather shields or capes designed to stream behind the wearer on horseback that it assigns DR 1 vs arrows to, but realistically they take advantage of this deflection phenomenon to make the arrows less likely to hit (or maybe tumble and hit at a poor angle). But that would all be extraordinarily complicated.

[Anthony]

Originally Posted by Kallatari

Second question. Does distance play a factor? If I was shooting through multiple walls of a building to hit someone on the other side, does the fact that the walls are several metres apart mean they get to use full DR, or are they also root-sum-squared?

Realistically... neither one. The projectile loses energy (based on the energy required to penetrate the barrier) but also might lose stability or break apart. The first doesn't much matter when the layers are close together but will significantly reduce penetration against spaced barriers, the second can be important even against close layers and has the interesting effect that the order of your armor layers matters -- you want the hard armor on the outside, the soft armor on the inside.

[RyanW]

Originally Posted by Anthony

Realistically... neither one. The projectile loses energy (based on the energy required to penetrate the barrier) but also might lose stability or break apart. The first doesn't much matter when the layers are close together but will significantly reduce penetration against spaced barriers, the second can be important even against close layers and has the interesting effect that the order of your armor layers matters -- you want the hard armor on the outside, the soft armor on the inside.

One house rule I've seen proposed (possibly by Doug Cole) is to have armors like ballistic fiber reduce the damage from a bullet by a fraction of its DR if it fails to completely stop the bullet. Kevlar and it's kin tend to either stop a bullet or barely slow it.

As to the question of spaced armor, one effect is the probable reduction of armor penetration modifier for AP type ammunition. The hardened cap/core is destabilized and not hitting the rear layer the way it was designed to.

[Anthony]

The realistic answer to armor layering is "armor functions best if used in the way it was designed to be used". Typically the way rigid armor works is that you have a high hardness outer layer that will damage or destroy the penetrator and spread the impact, and then a softer inner layer that's there to absorb the energy and limit damage to the outer layer (something very hard, without the softer layer, will often shatter, which will probably do the job for the first impact but isn't much good against the second). In the case of steel plate, the hard/soft is achieved by hardening the outer surface of the plate and leaving the inner surface softer. You do get hard armor inserts that are only rated to provide protection if used in combination with a vest; in that case the vest is acting as the soft layer (and because it doesn't hold the plate together very well, tends to result in fairly ablative armor). In the case of personal armor you may also have a soft outer layer that's designed to capture shrapnel and ricochets.

An insufficient hard layer may let the penetrator through without a lot of damage, in which case it might go through multiple layers.

[Rupert]

Originally Posted by RyanW

As to the question of spaced armor, one effect is the probable reduction of armor penetration modifier for AP type ammunition. The hardened cap/core is destabilized and not hitting the rear layer the way it was designed to.

The problem with stating this is that while it'll work better than a single plate against threats up to its limit, the outer layer will get shot up by minor threats, which might be important if its the outer skin of a ship or aeroplane, and threats that are too great for the system will penetrate more readily than they would against a single plate. Also, non-capped projectiles will be quite happy with a 'thin plus thick' scheme compared to the same weight in a single plate.