For more than one hundred years the combat helmet has been an essential part of the personal equipment of the soldier. In that time, helmet designs have evolved dramatically, as have the materials used to construct helmets.
There is also far more medical information available which allows helmet designs to be fully optimised to provide the highest levels of protection. Despite all of these advances, the evolution of the combat helmet continues as new data becomes available and understanding of changing mission requirements leads to new helmet solutions.
Another factor that has influenced helmet design is that there is a vast amount of recent combat experience to take into account, Operation Enduring Freedom in Afghanistan began in late 2001. This was subsequently followed by operations in Iraq and since then operational activity has spread across the Middle East, into Africa and beyond. All of this combat experience inevitably generated a lot of lessons, and this saw changes across the whole spectrum of equipment, from boots, to uniforms to Personal Load Carrying Equipment (PLCE) to body armour and other protective equipment. Responding to the requirements generated by almost two decades of combat has been aided by the fact that there have been significant advances in materials technology over that time period.
It is also important to take into account the medical aspects of developing effective soldier systems and, crucially, to increase the ability of the soldier to avoid or survive serious wounds or trauma. Experience is vital here. Over the years of the ‘Troubles’ in Northern Ireland, the Royal Victoria Hospital in Belfast developed enviable expertise in treating victims with gunshot wounds, becoming a global centre of excellence in the field. Lessons drawn from Belfast would be applied internationally, and would also contribute to the development of medical systems and devices that would increase survival rates in the wake of gunshot wounds.
Combat in Afghanistan, Iraq and elsewhere has provided important information on the treatment and prevention of wounds, and even non-combat injuries. In parallel with this, there has been consistent funding of research covering medical factors and materiel factors seeking solutions to issues raised during combat operations. Combat operations still continue, and, as we shall see, lessons are still being learned and critical research is still ongoing.
The trench warfare of the First World War led to an urgent requirement to provide protection against the overhead threat of shrapnel and fragments. The solution was the helmet and the first to field a helmet were the French Army in 1915, in the form of the M15 ADRIAN helmet (an evolved version was introduced in 1926). The M15 ADRIAN had limitations, the steel used was very light in comparison to what other helmets would use. On the other hand, the crest on top of the helmet would help to deflect fragments and the liner was designed as an element of shock protection. As we shall see, the design of the ADRIAN helmet has suddenly become very interesting to those working on next generation helmets.
The next year saw the arrival of two significant helmet designs, the German
STAHLHELM and the British BRODIE design. The STAHLHELM was inspired by the medieval Sallet helmet and offered good neck and side of the head protection, the final evolution of this helmet design was the M-56 steel helmet as used by the DDR Nationale Volksarmee (NVA). The British BRODIE helmet was also inspired by a medieval helmet used by archers; the helmet provided no protection to the side of the head though.
The BRODIE design remained in first-line service with Britain until replaced by the MkIII helmet in 1944. In turn this was replaced by the MkIV helmet in 1959, this was the last British steel helmet. The Mk6 helmet, made of ballistic nylon, entered service in the early 1980s. Then came the Mk6A in 2005, followed by the evolved Mk7 design in 2009. This was superseded by a part of the British Army Project VIRTUS personal protection system, where the Revision BATLSKIN COBRA helmet came into service from 2015. The same helmet was also selected by Denmark. Key characteristics of British helmets in the post-steel era were weight reduction, increased ballistic protection and ergonomic design.
The first helmet used by US was the British BRODIE design and this remained in service until the end of 1941 when it started to be replaced by the iconic M1 steel helmet. The M1 would remain as the standard helmet through to 1985. The M1 helmet design would be widely adopted by NATO and throughout the world, until it started to be replaced from the mid-1980s. For the US military, the successor to the M1 was developed under the Personal System for Ground Troops (PASGT) programme, with the PASGT helmet becoming the de facto standard from 1985 onwards.
The next stage beyond the PASGT helmet was to be the Modular Integrated Communication Helmet (MICH), although non-US helmet solutions had also been evaluated as potential PASGT successors. The MICH helmet entered service in 2001. It was followed by an evolution of the MICH design in the form of the Advanced Combat Helmet (ACH) from 2002 onwards, with the design evolving further into the Enhanced Combat Helmet (ECH) which started entering service from 2013 onwards. The successor to the ACH/ECH will be the Integrated Head Protection System (IHPS), which started entering service in 2019.
The transition from the PASGT through to the current ECH and beyond to the IHPS, has seen weight reduction, increased ballistic protection and changes in helmet structure and shape to better integrate with the other aspects of soldier equipment. The key point with the IHPS is that it offers the same level of ballistic protection as the ECH, more importantly the new helmet is said to offer double the level of protection provided by the ECH in terms of blunt impact injury or trauma to the head of the soldier. The challenge of ballistic protection has been resolved. Now the emphasis is on dealing with an issue that is increasingly become critical – that of Traumatic Brain Injury (TBI).
In January 2020, an Iranian missile attack on US forces at Ain al-Assad air base in Iraq saw eight missiles hit the base. The US forces were dispersed and in bunkers having had an attack warning. No US troops were killed or seriously injured in the attack. However, it later became clear that injuries had occurred, with 110 of the US troops on the base being diagnosed with TBI at various levels of seriousness. The cause of the TBI was the blast shockwave caused by the impact and detonation of the incoming missiles.
According to the Defense and Veterans Brain Injury Center (DVBIC) in the US,” a Traumatic Brain Injury (TBI) can be classified as mild, moderate, severe or penetrating. The severity is determined at the time of injury. A TBI is a blow or jolt to the head that disrupts the normal function of the brain. It may knock you out briefly or for an extended period of time, or make you feel confused or “see stars” (alteration of consciousness). Not all blows or jolts to the head result in a TBI. The most common form of TBI in the military is mild. Concussion is another word for a mild TBI.”
The primary causes of TBI in the military are blasts, bullets, fragments, falls, motor vehicle crashes and rollovers, sports and assaults according to the DVBIC. On deployment the primary cause of TBI is blast. Physical symptoms of TBI include headaches, sleep disturbance, dizziness, balance problems, nausea and vomiting, fatigue, visual disturbance, sensitivity to light and ringing in the ears. Cognitive TBI symptoms are concentration problems, temporary memory loss, attention problems, slow thinking and difficulty in finding words. Emotional issues caused by TBI include irritability, anxiety, and mood swings. The DVBIC notes that TBI can cause prolonged or even permanent neurological damage, even early onset dementia.
How prevalent is TBI? According to the DVBIC, between 2000 and the third-quarter of 2019 the number of US service members diagnosed with TBI totalled 413,858. From a high point of 32,834 TBI cases in 2011, numbers had been reduced to between 17,000 and 18,000 cases per annum from 2016 to 2018. The figures for nine months of 2019 were 15,262 TBI cases, suggesting the final numbers for 2019 were liable to be at the higher end of the spectrum. It is important to note that multiple concussions, even at the relatively low end of the TBI spectrum can lead to neurological damage.
The modern helmet has certainly met the test as far as protecting against ballistic threats, but clearly there is now a shift in emphasis to find enhanced protection levels to defeat the threat posed by TBI. The TBI injuries sustained at Ain al-Assad put the spotlight firmly on the TBI issue. Then, in February 2020, a university research study into helmets came out with the claim that the French ADRIAN helmet of 1915 provided better blast wave protection than the ACH currently deployed by the US military.
The Past Guides the Present
A team of PhD students at the Department of Biomedical Engineering, Pratt School of Engineering at Duke University, Durham, North Carolina had conducted a peer reviewed study entitled “Primary blast wave protection in combat helmet design: A historical comparison between present day and World War I.” This had made the claim about the greater blast wave protection of the ADRIAN helmet over the current ACH, based on an extensive testing regime that saw researchers evaluate the performance of the ACH, in comparison with World War 1 helmets such the BRODIE (as used by the British and the US), the STAHLHELM used by Germans and the ADRIAN.
The Duke study notes that, “Since World War I, helmets have been used to protect the head in warfare, designed primarily for protection against artillery shrapnel. More recently, helmet requirements have included ballistic and blunt trauma protection, but neurotrauma from primary blast has never been a key concern in helmet design.” The authors of the study went on to state that “only in recent years has the threat of direct blast wave impingement on the head – separate from penetrating trauma – been appreciated.” To provide more data on blast wave protection, the objective was to “compare(s) the blast protective effect of historical (World War I) and current combat helmets, against each other and ‘no helmet’ or bare head, for realistic shock wave impingement on the helmet crown.”
The testing process in the Duke study was described as follows: “Helmets were mounted on a dummy head and neck and aligned along the crown of the head with a cylindrical shock tube to simulate an overhead blast. Primary blast waves of different magnitudes were generated based on estimated blast conditions from historical shells. Peak reflected overpressure at the open end of the blast tube was compared to peak overpressure measured at several head locations. All helmets provided significant pressure attenuation compared to the no helmet case. The modern variant did not provide more pressure attenuation than the historical helmets, and some historical helmets performed better at certain measurement locations. The study demonstrates that both historical and current helmets have some primary blast protective capabilities and that simple design features may improve these capabilities for future helmet systems.”
The World War 1 helmets were all manufactured using similar materials, although it was noted that the French steel was thinner, and all of the helmets provided protection against blast. Where the ADRIAN helmet differed from the others was that it had a crest on top of the helmet crown and it was believed that this crest might have an effect in terms of deflecting shock waves. During testing, the peak reflected pressure on the helmet crown of the ADRIAN was the lowest of all of the helmets tested in terms of brain injury risk, substantially better than the other World War 1 helmets. More surprisingly, while the ADRIAN was rated as having a one percent moderate bleeding risk in terms of brain injury, the ACH was rated as having a close to five percent moderate bleeding risk.
The crest on the ADRIAN certainly seemed to play a role in improved blast protection, but the study also noted that the helmet brim was also important, as was the level of coverage of the head offered by the helmet. The different structural layers in a modern helmet can provide increased protection as “a shock wave is reflected every time it encounters a new material with a different acoustic impedance.” The Duke study demonstrates that blast protection can be increased through structural layering, and enhanced helmet designs that have optimum design crest and brim. All of which indicates that the search for the perfect helmet continues.