Gas Transport in the Insensitive High Explosive PBX 9502

Small‐scale laboratory experiments were performed to analyze gas transport mechanics in PBX 9502, an insensitive high explosive (IHE) composition. Two independent investigations are reported here. First, gas permeametry and dynamic pycnometry techniques were used to measure the molecular flow (Knuds...

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Bibliographic Details
Published in:Propellants, explosives, pyrotechnics explosives, pyrotechnics, 2020-06, Vol.45 (6), p.942-949
Main Authors: Englert‐Erickson, Michael A., Holmes, Matthew D., Parker, Gary R., Schmidt, Chad C., Meyer, Brad A.
Format: Article
Language:English
Subjects:
Composition
Cookoff
Cracking (fracturing)
Damage
Deflagration
Diffusivity
Gas transport
Ignition
Molecular flow
PBX (explosives)
PBX 9502
Permeability
Pressure dependence
Pressure vessels
Pycnometry
TATB
Void fraction
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Summary:Small‐scale laboratory experiments were performed to analyze gas transport mechanics in PBX 9502, an insensitive high explosive (IHE) composition. Two independent investigations are reported here. First, gas permeametry and dynamic pycnometry techniques were used to measure the molecular flow (Knudsen) coefficient and the internally interconnected void fraction of pristine and thermally damaged samples in two uniaxial pressing orientations. The permeability of PBX 9502 was found to be unmeasurably low (of the same order of magnitude as PTFE) with gas transport being diffusion‐dominated. Secondly, a pressure vessel experiment was developed to measure quasi‐static and dynamic gas generation as the explosive was heated to self‐ignition (cookoff). The gas generation results and the permeability/diffusivity findings provide evidence that PBX 9502 remains impermeable until seconds prior to self‐ignition. At ignition, internal void‐pressure drives macro‐scale cracking and the sample becomes uniformly incorporated in the following deconsolidating deflagration. These results are discussed within the context of previous observations of pressure‐dependent cookoff behavior of PBX 9502 and provide a more complete description of thermal damage evolution in this explosive composition.
ISSN:0721-3115
1521-4087
DOI:10.1002/prep.201900337