Helmets From WWI Just As Protective Against Overhead Blasts As Modern Helmets

Helmets From WWI Just As Protective Against Overhead Blasts As Modern Helmets
A modern helmet (left) and a French helmet (right) exposed to blasts meant to simulate an exploding artillery shell. (Image: J. O. Eynde et al., 2020/PLOS One)

New research suggests helmets used in World War I protected soldiers against overhead artillery blasts just as well as modern helmets—and one, the French Adrian helmet, actually performed better.

When the First World War started, soldiers didn’t wear helmets. Military planners hadn’t fully anticipated the horrific extent of modern warfare until it stared them back in their stubborn faces. As the war raged on, and with no end in sight, it became increasingly clear that heads needed to be protected, compelling the warring nations to equip their soldiers with steel helmets.

Now, there’s a common misconception that most deaths in WWI were caused by machine gun fire, but the majority of deaths actually came from artillery, according to G. J. Meyer’s excellent book, A World Undone: The Story of the Great War. Death was often delivered by artillery shrapnel, but close proximity to an exploding shell and exposure to its powerful shock wave resulted in serious head trauma, often causing permanent brain damage and death.

The French were first to introduce a steel helmet, with their M15 Adrian, followed by the iconic bowl-like Brodie helmet used by British troops, both of which were deployed in 1915. The Germans eventually followed suit, replacing their leather pickelhaube caps with the steel Stahlhelm in 1916.

Blasts from explosions remain a threat to the modern soldier, so naturally helmets continue to be a critically important component of military gear. An interesting new research paper published in PLOS One considered the effectiveness of modern helmets as compared to those used in WWI. The new research, co-authored by PhD student Joost Op ‘t Eynde from the Department of Biomedical Engineering at Duke University, found that at least one helmet used in WWI—the French M15 Adrian helmet—performed better in tests, specifically in terms of its ability to protect against overhead shock waves, compared to other WW1 helmets and modern designs.

This is a surprising result for a number of reasons, including the fact that WWI helmets were primarily designed to defend against shrapnel and bullets and that these helmets were mass produced during times of economic and material stress. This finding suggests the French had stumbled upon a particularly effective design and that modern helmets could be improved further. As the authors wrote in the new paper, this was “an investigation into whether improvements have been made in combat helmet primary blast protection or if there is a lesson to be learned from these 100-year-old designs.”

To that end, the researchers tested four different helmets, the Adrian, Brodie, Stahlhelm, and the Advanced Combat Helmet, which is currently in use by the U.S. military. These helmets were placed atop an artificial head equipped with pressure sensors, and then exposed to blasts of varying intensity.

Schematic showing the shock tube setup. (Image: J. O. Eynde et al., 2020/PLOS One)

To simulate the blast from a WWI-era artillery shell, the researchers used a shock tube filled with helium that, when pressurised, burst through a membrane, causing a powerful shock wave.

The helmets were tested with blasts of different strengths and at distances ranging from 1 to 5 metres. All shock waves came from directly above the head, as this “orientation and blast exposure simulate an overhead blast scenario, as would have been common in trench warfare due to artillery shells exploding above trenches,” according to the paper. At the same time, however, “it would not be as applicable to other cases such as improvised explosive devices (IEDs) used as roadside bombs, a significant cause of injury and death in conflicts in Iraq and Afghanistan,” wrote the authors.

High-speed video showing the test on a French helmet. (Image: J. O. Eynde et al., 2010/PLOS One)

Pressure from the blasts were recorded at the top (crown), forehead, right ear, left eye, and back of the head. The simulated blasts resulted in “mild to severe brain injuries,” explained Op ‘t Eynde in an email to Gizmodo, but the helmets reduced this risk significantly. The “estimates for brain injuries were based on bleeding in the brain caused by blasts in earlier studies performed in our lab,” he added.

Needless to say, all four helmets tested were far better than wearing no protection at all, reducing the risk of brain injury by up to 10-fold.

“While we found that all helmets provided a substantial amount of protection against blasts, we were surprised to find that the 100-year-old helmets generally performed just as well as modern ones, suggesting that helmet design that performs better for ballistic protection is not necessarily better for protection against shock waves,” said Op ‘t Eynde.

But not all helmets performed equally. The German, British, and modern American helmets performed roughly the same, but the French Adrian was better than the rest, resulting in very low probability of bleeding risk.

French infantry M15 Adrian helmet, featuring the crest on the crown. (Image: Casque de Marcel Hébrard)

“A likely reason for the performance of the French helmet at the crown of the head is the shape of the deflector crest on top of the helmet, directing the blast wave around the head and providing an extra layer of material at the crown of the head for the blast to reflect off,” Op ‘t Eynde told Gizmodo. That said, the “French helmet did not result in lower pressures at any of the other measurement locations.”

Indeed, it’s this detail—the crest—that may have made the difference, as other parts of the Adrian helmet didn’t appear to offer the same level of protection. Interestingly, the protection of other areas, such as the ears, was determined by the shape of the helmet itself and whether or not the helmet covered these exposed parts.

Importantly, the researchers aren’t saying the modern helmet isn’t a good design. In fact, they say the new helmet is actually quite good, featuring a layered structure that works to absorb incoming shock waves.

“In terms of protection against handgun and rifle bullets and against blunt impacts such as falls, the modern Advanced Combat Helmet performs vastly better than any of the historical helmets,” said Op ‘t Eynde, adding that the new study “specifically looked at overhead blast.”

What the new research does suggest, however, is that modern designs can still be improved—and possibly with technology developed during the First World War. Looking ahead, the researchers are planning to use historical data of blast injuries during WWI to analyse similar injuries in modern combat situations.