William W. Erikson

Development of scalable cook-off models using real-time in situ measurements.

Scalable thermal runaway models for cook‐off of energetic materials (EMs) require realistic temperature‐ and pressure‐dependent chemical reaction rates. The Sandia Instrumented Thermal Ignition apparatus was developed to provide in situ small‐scale test data that address this model requirement. Spatially and temporally resolved internal temperature measurements have provided new insight into the energetic reactions occurring in PBX 9501, LX‐10‐2, and PBXN‐109. The data have shown previously postulated reaction steps to be incorrect and suggest previously unknown reaction steps. Model adjustments based on these data have resulted in better predictions at a range of scales.

Radiant heating cookoff experiments and predictive simulations for fast cookoff.

Thermal initiation (cookoff) of energetic material-laden devices (rocket motors and munitions) during accidental fires is an important safety concern. An article within a pool fire is an example of potential fast cookoff scenerio that has significant potential for a catastrophic result. Beginning in 2007, a collaborative experimental and model development research program under the Joint Munitions Program (JMP) was initiated at SNL/NM to address energetic material response to fast cookoff. The efforts expanded our ongoing research program studying slow cookoff phenomena and sought to answer the key question of ”Can our kinetics models derived under slow cookoff conditions be applied to accurately represent energetic material behavior at fast cookoff conditions?” The simplest categorization of slow cookoff is material centered within the energetic material whereas a fast cookoff event is material ignition that occurs at a heated boundary. The external heating rate related to the heat conduction within the energetic material determines the ignition location and thus, the cookoff charaterization of slow or fast. We have developed a benchtop experiment that confines an energetic material sample and exposes it to constant incident heat fluxes common in fire in a controlled and reproducible fashion. Temperatures within the sample near the heated surface are measured using thermocouples and the time-to-event is determined

Effect of pressure vents on the fast cookoff of energetic materials.

The effect of vents on the fast cookoff of energetic materials is studied through experimental modifications to the confinement vessel of the Radiant Heat Fast Cookoff Apparatus. Two venting schemes were investigated: 1) machined grooves at the EM-cover plate interface; 2) radial distribution of holes in PEEK confiner. EM materials of PBXN-109 and PBX 9502 were tested. Challenges with the experimental apparatus and EM materials were identified such that studying the effect of vents as an independent parameter was not realized. The experimental methods, data and post-test observations are presented and discussed.

Consequences of Surface Deposition of Molten Aluminum in High-Temperature Oxidizing Environments

In a potential accident scenario with a solid-propellant fire, aluminum present in the propellant and in surrounding structures is exposed to high-temperature environments. The enthalpy present in the aluminum particles is a substantial component of the heat release, both in terms of the particle sensible energy and its chemical energy. This paper examines the consequences of the deposition of aluminum particles present in the propellant in terms of heat transfer to surfaces. Also examined is the possibility that deposited aluminum will ignite in the high-temperature oxidizing environment. The examination is made using a computational fluid dynamics approach with some new models to describe the aluminum oxidation. In addition, these models provide a means to predict the aluminum ignition criteria that will be discussed.Copyright