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> [...] absorbed the kinetic energy caused by an impact almost 30 times better than liners currently used in US military helmets. That's not quite the same thi
by p-e-w 3y ago
> [...] absorbed the kinetic energy caused by an impact almost 30 times better than liners currently used in US military helmets.
That's not quite the same thing as claimed in the headline. Of course there's a correlation between the two, but I see no reason to assume (and the article certainly doesn't provide any evidence) that an x-fold decrease in kinetic energy delivered to the head translates to an x-fold decrease in the likelihood of concussions. Most complex systems respond to external inputs in a highly nonlinear fashion.
- kube-system 3y agoYeah. How good are US military helmets good at absorbing impacts? I’d like to know how this compares to helmets that meet Snell SA2020, B-95, ECE 22.06, or other more widely used standards that people use widely.
- livueta 3y agoUnsure about impacts, but a surprising result I remember reading about a while ago is that certain military helmets can actually increase blast wave overpressure vs. a bare head: https://www.researchgate.net/publication/344332027_Factors_Contributing_to_Increased_Blast_Overpressure_Inside_Modern_Ballistic_Helmets https://www.researchgate.net/publication/344332027_Factors_C...
- bookofjoe 3y agoRelated: >U.S. Troops Still Train on Weapons With Known Risk of Brain Injury https://www.nytimes.com/2023/11/26/us/military-brain-injury-rocket-launcher.html https://www.nytimes.com/2023/11/26/us/military-brain-injury-... https://archive.ph/WDlpR https://archive.ph/WDlpR >The Army Said Tank Blasts Don’t Harm Troops. His Case Raises Doubts. https://www.nytimes.com/2023/12/21/us/army-blast-safety-brain-injuries.html https://www.nytimes.com/2023/12/21/us/army-blast-safety-brai... https://archive.ph/WZRJQ https://archive.ph/WZRJQ
- colechristensen 3y agoConcussions don’t have a particularly objective diagnosis or a very clean phase transition between “concussion” and “not concussion”, they are more so continuous with a soft floor, and they do get progressively worse with vague intensity of injury. It’s not really until your brain starts bleeding and such that there are clear diagnostic signs and there are definite but more vague long term effects from lesser concussions. Reducing kinetic energy is exactly the kind of metric you can take in absence of any others.
- jeremyjh 3y agoKinetic energy is definitely the better design and test metric. But you still can't claim a linear relationship without large - yet controlled studies. And if it is as good as they, a large/long trial could be unethical versus just widely deploying it and collecting the data you can. It is just as likely it is only twice as good at preventing concussions. The headline is almost click-bait.
- yummypaint 3y agoRight, a concussion is caused by sudden acceleration of the skull relative to the brain. The acceleration is the result of momemtum transfer, not energy transfer, and momentum is always conserved. Therefore, to first order, the key factors should be the mass of the projectile, the speed of the projectile, and the combined mass of the skull+helmet. Spreading the impulse over a slightly longer time with energy absorbers should help a little, but im skeptical of the size of the effect without making the helmet significantly larger. Given the comparison with military helmets, It sounds like this design might be more about bleeding energy from projectiles to prevent penetration, so the sports claims seem confusing.
- kazinator 3y agoEnergy absorption (if full) means that the skull won't bounce back from the cushioning. That would send it toward the brain, making the brain-skull impact worse.
- yummypaint 3y agoThats a good point. The theoretical best case is an inelastic collision.
- kazinator 3y agoAlso, in general, any energy removed from the collision and dissipated is energy that is not available for doing damage.
- digdugdirk 3y agoHas anyone checked to make sure they're not just using the worst possible liners for US military helmets?
- m463 3y agoI remember buying a motorcycle helmet, and there are a couple different standards to protect your head, yet they are almost incompatible with each other. Maybe it is better now. EDIT: https://agvsport.com/blog/which-helmet-standard-is-the-best-snell-dot-ece-sharp-or-fim.html https://agvsport.com/blog/which-helmet-standard-is-the-best-...