scope:

Description of Driving Event:

The accident investigation into the fire and destruction of a Pershing II stage I missile motor in Germany revealed that it was accepted that the propellant (QBJ-29) was insensitive to ESD. The cause of the accident was attributed to ESD. Older ESD sensitivity tests based upon the determination of spark energy, such as the layer test, the dust test, and the human spark test, were found to be inaccurate when U.S. hazard technologists began determining the ESD sensitivity of QBJ-29. It was found that the spark gap tests did not accurately reflect the actual energy delivered to a propellant sample. U.S. technologists, in addition, did not consider how changes in humidity or temperature affected the electrical properties of the propellant samples. Therefore, U.S. investigators borrowed the test techniques, which SNPE has been developing since 1976. The SNPE employed a three-part test methodology based on the RC discharge test, volume resistivity measurements as a function of temperature, and percolation coefficient calculations. While the SNPE test is more discriminating than the older tests, it is itself unreliable.