

Bullet-proof Human Skin - mschonfeld
http://io9.com/5830664/this-is-bullet+proof-spider-silk-skin-+-made-from-goats-milk-yes-really

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thestranger
Pretty cool, but wouldn't it still severely damage your internal organs? It's
not like the force of the bullet just disappears once it hits your skin.

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briggsbio
This is interesting, and might be possible. The worry is that even if you have
bullet-proof skin, your bones would break and internal organs be turned to
mush. but would it?

The name of the project is 2.6g 329m/s, after the mass and velocity of the
bullet.

Using 1/2MV^2 to calculate the force, in Newtons (1):
=(1.2)(0.0026kg)(329m/s)^2 = 140.7 kg _m/s^2 = 140.7 N

Convert to foot_pounds (lbf): (2) 1 N = 0.22481 lbf 140.7N (0.22481) = 31.6
lbf

So you body would have to dissipate 31.6 foot-pounds of force. Yes, it would
loose some from friction mid-air, and your skin would dissipate some, but for
the sake of argument, let's assume this is in a vacuum or some magical
container, ceteris paribus. There's always the "it only takes 8 pounds of
force to break a bone" but that's why you have soft tissue surrounding your
bones. If it hit you in the head, you'd probably be screwed no matter what. I
think this is more to be a replacement for body kevlar, not to wear as a
batman cowl.

I once heard that a pro boxer can his with over 900 PSI, which would be about
30 lbf, but that's dissipated across a whole fist. Here's an article
discussing that, it ranges widely (3). We need a better correlary.

So I continued to look and found a paper on bite force (4). It shows that a
human can have a bite force of an average of 162 lbf. And specifically the
incisors had a range of 22.5-33.7 lbf. That is roughly equivalent to the 31.6
lbf of a bullet. But what does this mean? A strong bite can ravage tissue, and
a hollowpoint bullet would be a pretty sharp point and would likely slice
right through the underlying tissue if it broke the skin (as it was designed
to do).

I think it's important to look at other properties of the "pseudoskin" layer.
They used a small little patch on ballistics gel, and at the end of the video
the patch was pushed into the gel and folded in on itself. So if you'd been
wearing the patch and got shot it would be embedded 2 inches into your
epidermis and underlying tissue (but at least it would be easy to pull the
slug out!).

I would think we'd need to see more info on the shear-thickening properties of
the gel, see what more than just a "patch" would do; say, ballistics gel with
a complete outer layer of the pseudo-skin, and other properties. The little
patch has no way to grab onto the surrounding skin and provide tension to
dissipate the force across the surface of the tissue (think like springs on a
trampoline). And significant shear thickening would cause the pseudoskin to
instantaneously harden with the force of the bullet, protecting the underlying
real skin and tissue.

Need more info, but this could actually be promising.

(Note: Can someone check my calculations? I did them REALLY quickly. I can't
confirm their reliability.)

Sources: 1: <http://en.wikipedia.org/wiki/Physics_of_firearms#Force> 2:
<http://en.wikipedia.org/wiki/Newton_(unit)> 3:
<http://www.connectsavannah.com/news/article/102548/> 4:
<http://www.glapbta.com/BFBP.pdf>

