Computational modeling of blast exposure associated with recoilless weapons combat training

Military personnel are exposed to blast as part of routine combat training with shoulder-fired recoilless rifles. These weapons fire large-caliber ammunitions capable of disabling structures and uparmored vehicles (e.g., tanks). Scientific, medical, and military leaders are beginning to recognize the blast overpressure from these shoulder-fired weapons may result in acute and even long-term physiological effects to military personnel. However, the back blast generated from the Carl Gustav and Shoulder-launched Multipurpose Assault Weapon (SMAW) shoulder-fired weapons on the weapon operator has not been quantified. By quantifying and modeling the full-body blast exposure from these weapons, better injury correlations can be constructed. Blast exposure data from the Carl Gustav and SMAW were used to calibrate a propellant burn source term for computational simulations of blast exposure on operators of these shoulder-mounted weapon systems. A propellant burn model provided the source term for each weapon to capture blast effects. Blast data from personnel-mounted gauges during weapon firing were used to create initial, high-fidelity 3D computational fluid dynamic simulations using SHAMRC (Second-order Hydrodynamic Automatic Mesh Refinement Code). These models were then improved upon using data collected from static blast sensors positioned around the military personnel while weapons were utilized in actual combat training. The final simulation models for both the Carl Gustav and SMAW were in good agreement with the data collected from the personnel-mounted and static pressure gauges. Using the final simulation results, contour maps were created for peak overpressure and peak overpressure impulse experienced by military personnel firing the weapon as well as those assisting with firing of those weapons. Reconstruction of the full-body blast loading enables a more accurate assessment of the cause of potential mechanisms of injury due to air blast even for subjects not wearing blast gauges themselves. By accurately understanding the blast exposure and its variations across an individual, more meaningful correlations with physiologic response including potential TBI spectrum physiology associated with sub-concussive blast exposure can be established. As blast injury thresholds become better defined, results from these reconstructions can provide important insights into approaches for reducing possible risk of injury to personnel operating shoulder-launched weapons.