Pressure over time: These images show the pressure contours at various times following detonation of 1.5 kilograms of C4 explosives three meters from a mannequin. Different colors represent the different pressure measurements. Dark blue indicates pressure below 0.5 atmospheres; black is 1.0 atmosphere; green, yellow, and red are higher pressures, up to 3.5 atmospheres. The helmet protects unexposed regions of the head from the initial pressures generated by the blast pressure wave, but waves enter the gap between helmet and head as the wave passes. These transmitted waves are focused at some point beneath the helmet, generally on the side farthest away from the source of the blast.
One of the next steps for the researchers is to couple the pressure-wave information with structural-analysis algorithms that model the head to see how these applied pressures would be transmitted into the soft matter of the brain. Computational models that allow scientists to see how the wave hits the brain will help them better understand what is happening neurologically, says Radovitzky.
Mott says that the eventual goal is to create a system to be used in triage so that medical personnel can download an injured soldier’s blast-exposure history and treat him accordingly.
The researchers’ findings could ultimately improve helmet designs and better protect soldiers in the field. They are collaborating with another team of NRL scientists who are designing small sensors that can be embedded in a soldier’s helmet to record key information about exposure to a blast. Other teams are doing similar work: last year, the U.S. Army awarded a million-dollar contract to Simbex, of Lebanon, NH, to build sensor-studded helmets; more recently, the U.S Defense Advanced Research Project Agency (DARPA) awarded a three-year contract worth $5 million to the Palo Alto Research Center (PARC) to develop a simple plastic strip that can be “taped” onto a soldier’s helmet to measure the intensity of an explosion.