Saturday, December 11, 2010
Head Blast Protection
One of the more poignant tales out of the Second World War reports on a bitter cold winter’s night in which a Finnish unit was bracing for a heavy soviet assault coming from over a rise to the front. Their artillery sent over a barrage of high explosive that exploded in the air into the face of the Soviets. After which nothing happened.
After some time, patrols were sent out to see what was happening. An entire Soviet regiment was laid out in position to jump off out in the open. They had all been killed form shock wave proximity. In this case if my memory serves me we are talking several thousand in place for a mass assault.
Obviously a visor is needed to ablate the shock, but it also needs to be out of the way a lot of the time or soldiers will soon toss them. This will be a difficult design problem. A god plan may be to design the function into the gas masks. The periods of vulnerability and need tend to overlap and soldiers will put more value on the mask as shock protection in the face of incoming artillery and unlikely gas.
Helmet Visor Could Protect Troops From Shock Waves
November 22, 2010 |
Adding a face shield to the standard-issue helmet worn by
U.S. troops could help protect soldiers from
traumatic brain injury, the signature wound of the recent wars in Iraq and . A new study that
models how shock waves pass through the head finds that adding a face guard
deflects a substantial portion of the blast that otherwise would steamroll its
way through the brain. Afghanistan
The study, to appear in the Proceedings of the
of Sciences, is part of a spate of new work tackling traumatic brain injury. An
estimated 1.5 million Americans sustain mild traumatic brain injury each year,
and nearly 200,000 service members have been diagnosed with it since 2000,
according to the National Academy Armed Forces Health
in . Silver Spring, Maryland
While direct impact, such as banging the head, clearly can injure the brain, the forces endured when explosives send shock waves crashing through the head are much more difficult to characterize.
In the new study, researchers led by Raúl Radovitzky of MIT’s Institute for Soldier Nanotechnologies created an elaborate computer model of a human head that included layers of fat and skin, the skull, and different kinds of brain tissue. The team modeled the shock wave from an explosion detonated right in front of the face under three conditions: with the head bare, protected by the currently used combat helmet and covered with the helmet plus a polycarbonate face shield.
The results showed that today’s helmet doesn’t exacerbate the damage, as some previous research had suggested. But at least in terms of blast protection, the current helmet doesn’t help much either. Addition of a face shield would improve matters, the team reports.
“The face shield contributes a lot to deflecting energy from the blast wave and not letting it directly touch the soft tissue,” says Radovitzky. “We’re not saying this is the best design for a face shield, but we’re saying we need to cover the face.”
To validate the model, researchers at MIT and elsewhere will have to conduct experiments in the real world. But the work points to an intrinsic flaw in the current helmets.
“These helmets weren’t designed to stop a pressure wave; they were designed to stop bullets,” says Albert King, director of the
at Wayne State
University in . “Just like a football helmet wasn’t
designed to stop a concussion, but to stop skull fracture.” Detroit
Designing a blast-resistant helmet requires a better knowledge of what happens in the brain when an explosion washes over it. Soldiers experiencing explosions often describe a wind or wave that makes them see stars. “I really got my bell rung,” is a common report.
The resulting “mild” traumatic brain injury doesn’t lead to long-term loss of consciousness, and brain scans yield normal results. But labeling these injuries as mild is a misnomer, says Douglas Smith, director of the Center for Brain Injury and Repair at the University of Pennsylvania in Philadelphia.
“It is not mild; that term has led people astray,” says Smith. “It is something very serious that can lead to severe dysfunction.”
Smith and his colleagues have been working on a sensor that could be placed in a helmet or vehicle and that, like the radiation badges worn by nuclear-plant workers, would indicate exposure to blast forces likely to cause brain injury. The sensor is described in a paper to be published in NeuroImage.
While a sensor would indicate exposure to blast forces, it still isn’t clear exactly how that energy translates into brain trauma. Under everyday conditions, the brain can easily withstand a little jostling. “Plop down in your chair and your brain blobs around like Jell-O,” Smith says. But at tremendously high speeds, instead of gently stretching, brain cells can snap and break (SN: 3/13/10, p. 11) like glass.
The long-term effects of these busted brain cells are largely unknown. In addition to chronic headaches, vertigo and difficulty remembering words, research suggests that when the brain shuts down for even a few minutes, depression is more likely down the road.
Scott Matthews, a psychiatrist at the University of California, San Diego, who studies mild traumatic brain injury in returning veterans, notes that causality can’t be established. But among soldiers who were exposed to combat, he sees depression twice as often in people with traumatic brain injury.
“There’s more and more evidence that loss of consciousness changes the brain,” Matthews says.
Unraveling cause and effect and designing useful experiments to illuminate traumatic brain injury and its aftermath remains extremely challenging. And translating those scientific findings into meaningful policy can be just as difficult. Even implementing something as simple as a helmet with a face shield poses problems, says Smith.
“How do you deploy something like that?” he asks. “There are practical things like temperature issues. And then there’s wanting soldiers to be able to meet and greet in villages without looking like spacemen.”
Image: Computer model of the head./Michelle Nyein.