Technical note | Validation of a Pressed Pentolite Donor for the Large Scale Gap Test (LGST) at DSTO

Abstract

 The requirement of validating a new donor for the LSGT used at DSTO has arisen due to changes in ingredient availability for local donor manufacture, and also the availability to import commercial donors from overseas. A donor (manufacture by Accurate Energetic Systems) has been selected for evaluation for use in the LSGT at DSTO by performance and LSGT characterisation. The donor specifications are identical to the donors used in the NOL LSGT and a calibration for the LSGT at DSTO has also been reviewed. The changes recommended in this report have been adopted by DSTO and the test will now be referred to as the DSTO LSGT (previously, the MRL LSGT).

Executive Summary

The MRL Large Scale Gap Test (LSGT) was commissioned at Materials Research Laboratory (MRL, now the Defence Science and Technology Organisation (DSTO)) in 1993 for the purpose of measuring shock sensitivity of explosive formulations and is still the most common Gap test used by DSTO today. The shock sensitivity of an explosive provides insight into its suitability for military use and involves establishing the amount of pressure required which will permit detonation of the test charge in 50% of fired shots (critical gap).

The requirement of validating a new donor for the Australian LSGT arose due to changes in ingredient availability for local donor manufacture and also the availability to import commercial donors from overseas. A donor (manufactured by Accurate Energetic Systems, AES) was selected for evaluation for use in the LSGT by performance and LSGT characterisation. The donor specifications matched that as used by Naval Surface Warfare Center (NSWC), and thus calibration of the LSGT at DSTO was also reviewed.

The performance evaluation demonstrated that the AES donor provided a consistent velocity of detonation and detonation pressure, which is critical for LSGT. The LSGT trials also produced acceptable results with the new donor. The calibration review determined the Australian LSGT can now become a calibrated system using the AES donor based upon calibration data produced by NSWC for a donor of matching specifications. The previous donors manufactured by DSTO while dimensionally the same as AES, could only be produced with a different (but consistent) density due to the nature of melt cast manufacture. Therefore until now the MRL LSGT had only been capable of producing approximated critical gap pressure results. In light of these changes it was decided an appropriate opportunity to update the name of the test from the MRL LSGT to the DSTO LSGT.