Propagation of Firebrands From Burning Ammunition Stacks

An informal review of ammunition accident history reveals that the most common mechanism of propagation of reaction between ammunition stacks involves ignition of fires by fragments, debris, or firebrands from the source explosion and subsequent violent reaction of munitions in those fires. The nature of burning debris ejected from an ammunition fire and the way in which it is distributed is not well understood, and the response of ammunition stacks to burning debris had not been determined. In support of the Armys Munitions Survivability Technology program, a series of tests was conducted at the Naval Air Warfare Center, China Lake, CA, in an attempt to characterize the material ejected from burning ammunition stacks that represent a hazard to other stacks nearby. Specifically, measurements of the direction, velocity, range, and incendivity of the firebrands were desired. Six representative ammunition items were chosen to act as cook-off firebrand donors. They were chosen from ordnance that has the greatest potential for producing firebrands and that is present in large quantities in the Army inventory. Six items were tested 1 25-mm M791 armor-piercing, discarding sabot with tracer APDS-T projectiles 2 Hellfire missiles 3 155-mm M549 rocketassisted projectiles RAP 4 M1 high-explosive HE projectiles 5 155-mm M864 improved conventional munition ICM projectiles and 6 105-mm M416 white phosphorus-tracer WP-T. For the tests, each item was arranged in a scaled-down shipping or storage configuration and mounted on a sturdy steel burn stand over a large propane burner assembly. After the burner was ignited, observations of the distribution of firebrands were made by means of video coverage and witness panels containing wood and gun propellant. The test observations indicate that material from the stacks was thrown as far as 1,400 ft, secondary explosions occurred out to 300 ft, and live bomblets were found out to 917 ft.