A U.S. military-created enhanced helmet meant to protect service members from traumatic brain injuries suffered in explosive blasts may cause more harm than good, researchers said.
Scientists at the Naval Research Laboratory tested the Conformal Integrated Protective Headgear System -- developed by Army engineers -- and determined that the percussive shockwaves caused by exploding ordinance may actually get trapped in the geometric design and cause additional injuries. (Image source: NRL)
The Army Times reported that Naval Research Laboratory scientists tested various configurations of an innovative helmet, but haven't yet cracked the code on a prototype that protects the jaw and face from explosions without creating intense atmospheric pressure around the skull from blast waves.
Simply put, just because the helmet covers more of the face doesn't mean it's actually protecting the soldier's head from some of the most harmful blast effects. The Conformal Integrated Protective Headgear System — a helmet developed by the Army engineers can include a visor and jaw protector — will need further work because of the shockwave hitch.
[sharequote align="center"]"Specific injury mechanisms, and prediction of injury severity ... remains elusive." [/sharequote]
"In some cases waves trapped by the geometry produced increased pressure when reduced pressure was expected," the report said.
The researchers are pushing the issue because helmets need to do much more than just protect against flying bullets or potential vehicle crashes. According to Defense Department statistics, more than 73 percent of all U.S. military casualties in Operation Enduring Freedom and Operation Iraqi Freedom were caused by explosive weaponry, and as of January 2008, the Defense Department reported over 5,500 soldiers suffered traumatic brain injuries.
Via the Army Times, the current version of the helmet fails in several ways:
• In a front-facing blast, pressures on the forehead were higher with the jaw protector, or mandible, in place and with the mandible-visor combination than they were with the helmet alone.
• Wearing just the jaw protection for a front-facing blast doubled the strength of the secondary shockwave pressure on the forehead from 2 atmospheres (one atmosphere is a little less than 15 pounds per square inch) to 4 atmospheres.
• In a rear-facing blast, pressures on the forehead were more than twice as high for the mandible-visor combination than for the helmet alone.
"The military actually has specific criteria that helmets have to meet to be certified for use in ballistic and blunt force,” said Daniel Mott, an NRL aerospace engineer. “No such criteria exists for pressure because the medical community is still working on what the injury mechanisms are, and we don’t know where to set those desirable levels anyway, at this point."
The researchers said helmet systems that reduce the blast loading on the head are considered advantageous in reducing the likelihood of injury -- even though the specific injury mechanisms and thresholds are not well understood.
"Significant research efforts characterizing the effect of blast loading on helmet-head geometries have been pursued in order to understand, predict and ultimately mitigate Traumatic Brain Injury," the researchers said. "At present, identification of specific injury mechanisms, and prediction of injury severity from a specific loading scenario (or a particular history of incidents) remains elusive."
For the helmet tests, the research team used "surrogate body technologies" -- also known as gel dummies -- to test the shock waves, and found the current version of the helmet lacking. From a safe distance, the researchers set off explosive charges; the charge can be with or without fragments, and is made to imitate an IED a Marine might have encountered in Iraq or Afghanistan.
The time and pressure data from each sensor tells the researchers how pressure from the blast dissipates or is passed through the helmet and skull.
"Ultimately," said Dr. Amit Bagchi, a scientist in Matic's division, "the goal is to minimize the energy and the pressure that goes into the brain."
The gel dummies, here testing a different model, can be seen in this Naval Research Laboratory photo; the dummies are blasted with explosive charges that simulate what soldiers and Marines may face in the field, and the researchers gather pressure data from sensors embedded in the gel skulls. (Image source: NRL)
The most important part of the test is over in a fraction of a second.
"The most harmful part," Bagchi said, "is in approximately the first 25th of a second, or about 40 milliseconds."
NRL also uses sensors to evaluate blunt impacts. Rather than simply whacking GelMan with a hammer, however, the lab has a 23-foot tall drop tower. As Matic described: "You mount the helmet on a metal head form, which rides the rail down and hits an anvil. The helmet then bounces off the anvil, and you can measure the acceleration during that event." A smaller bounce means the helmet is better absorbing the impact and protecting the brain.
Their research paper pointed out that increased pressures in one area generally come with decreased pressures in another. As an example, in the front-blast test, the visor-mandible combo dropped the peak of the highest-pressure wave on the back of the head in half when compared with the helmet-only setup.
It’s one of a series of tradeoffs designers must make, Mott said — determining which areas to channel blasts away from, and balancing the need for blast-wave protection against other concerns; a soldier may want to wear the mandible or visor, even with elevated blast-wave pressures in some areas, to prevent a bomb fragment from bouncing off his face.
At some point, it's the soldier's decision what to protect, but the Army wants to give each military member the best equipment possible, according to the team.
"DoD is providing the best possible equipment to the soldiers and warfighters, but then we keep constantly looking for a better solution," Dr. Bagchi said.
(H/T: USA Today)
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