How many layers for Kevlar to stop a slow-moving .22?
Fastlane, the comparison against a Kevlar shoot-pack is a false equivalence. We don't know how many layers it would take for Kevlar panels to stop a .22. One? Two? Three?
Spider silk gains its toughness by its ability to stretch. Kevlar doesn't stretch much. It will reach its breaking point without much stretch. Spider silk stretches a lot more.
Because of the stretch, spider silk probably has a deep backface signature. Randy Lewis is fond of saying that a spider silk bullet-resistant vest will stop a bullet on the wrong side of the body. The depth of the backface signature is relevant because the bullet can cause blunt-force trauma that will kill just as a penetrating bullet can.
How a spider-silk shoot pack will perform depends on the speed of sound in the material. To my knowledge, this has never been reported for KBLB or even natural spider silk strands. If the speed of sound is high, the impact will be spread over a large region and thus a shallow backface signature. If the speed of sound is low, the impact will be narrow and deep.
Until testing is done, it is very difficult to predict how well spider silk shoot packs or DS 2.0 shoot packs will perform. Will Randy Lewis be right? Will it perform comparably to Kevlar? Show me the tests and we can discuss the matter. No tests means we simply don't know how well the material will perform.
Shoot packs also have to perform in conditions of high humidity or even wet. Silk tends to stretch when wet. Even if spider silk was better than Kevlar in dry conditions, it may be unsuitable because it fails in Jungle conditions.
Part of the testing protocol for shoot packs involves testing under high humidity conditions. Again, without any actual published research on the matter, we simply do not know whether this will be useful to the DoD for shoot-pack purposes.
There are other applications that may be less critical. A shoot-pack built into a car door might perform extremely well. You don't have to worry so much about the backface signature then. I'm sure there are other potential applications.
Finally, one poster indicated that a contract with the DoD would indicate DS is a success. That's true. But more troubling is the fact that we don't have a contract and the Army doesn't seem to be very interested in pursuing one. That also speeks volumes.
None of this speaks to the suitability of DS 2.0 for other applications. It could be great in other applications. Also, a poster recently shared a link to a video where a shoot pack was made by pressing silkworm cocoons in a resin matrix. They did not report backface signature data, but the resin matrix may propagate the impact force over a big area.
The moral of the story here is: we need more information before we can conclude any given application will be adopted. Until then, it is unwise to invest in KBLB under the belief that shoot packs are 'a sure thing.'
