>I suspect the best helmet for blunt impacts is probably a one/few-time use deal with crumple zones to absorb the energy of the impact and increase the time of

>I suspect the best helmet for blunt impacts is probably a one/few-time use deal with crumple zones to absorb the energy of the impact and increase the time of the impact. After it's crumpled you would have to swap it out for a new helmet. Bicycle and motorbike helmets already work like this. The energy-dissipative layer is made from expanded polystyrene foam, which permanently deforms and fractures on impact. The downside is that they're a one-shot item - once a helmet has taken an impact, it loses integrity and should be disposed of. Helmets for football and hockey use a polypropylene foam, which doesn't absorb as much energy but will withstand multiple impacts. Polystyrene foam would be impractical at best for these helmets. There is often no visible evidence that a polystyrene helmet liner has been structurally compromised, so a player or coach has no way of checking that the helmet is still providing useful protection. If the helmet isn't replaced after every impact, then it might be offering less protection in practice than a polyurethane helmet. The real villain here isn't the blunt force of a linear impact, but the rotation of the brain within the skull. This causes deep structural damage in the lower parts of the brain. Dealing with these forces is far more challenging, but I suspect that there are significant gains to be made with respect to the shape and structure of the wire face shield. The smooth plastic of the helmet's shell tends to produce glancing impacts with minimal rotation, but the face shield can snag and create horrendous rotational forces. https://www.popsci.com/what-happens-to-football-players-brain-during-concussion https://www.popsci.com/what-happens-to-football-players-brai... https://www.frontiersin.org/articles/10.3389/fbioe.2013.00015/full https://www.frontiersin.org/articles/10.3389/fbioe.2013.0001...