Objective

The sustainment of military training ranges is a major concern for the Department of Defense. Research conducted under several SERDP projects (ER-1155ER-1481, and ER-2219) found that the greatest and most readily-available sources of energetic compounds on training ranges are low-order (LO) detonations. Comprehensive characterization of residual energetic particles from LO detonations are needed to understand range environmental impacts and to refine fate and transport models that estimate sustainment risks. Until recently, there has been no reliable method of quantifying energetic residues from different detonation scenarios or of realistically simulating a LO detonation. Under SERDP project ER-2219, a method was developed for controlling detonation order using a command detonation system and recovering intact post-detonation explosive particles.

The primary objective of this project was to validate and demonstrate a method of command LO detonation, residue sampling, and laboratory analyses for mortar munitions filled with conventional and insensitive high explosives. The secondary objective was to transfer collected comprehensive data on LO detonation particle characteristics to fate and transport models.

Technology Description

The technology utilizes sampling and analysis techniques developed through multiple SERDP and ESTCP projects. The major techniques demonstrated during this project include: 1) LO detonation sampling and analysis with insensitive and conventional munitions and 2) laser diffraction particle size analysis of post-detonation energetic particles. The ability to conduct LO command detonation testing starts with the Cold Regions Research and Engineering Laboratory fuze simulator (CFS), which consists of a center-drilled aluminum plug with a booster well at the threaded base. The booster well can be loaded with Composition-C4 (C4) explosive to simulate the booster pellet in a normal fuze. The fuze simulator is threaded into the body of an artillery projectile and initiated using a standard military blasting cap. The field-adjustable C4 booster is what drives the versatility of this system and allows it to be used for both high-order command detonations as well as LO detonations demonstrated here. The particles released from LO detonations can then be recovered when tests are conducted on ice. Ice provides an ideal testing surface because it isolates the test area from previous activities and allows for both large (>1 cm) and small (1 cm – 10 nm) post-detonation particles to be clearly visible for cataloguing by distance from the point of detonation. The smooth surface of the ice allows for incremental distance areas to be swept clean, ensuring that the majority of material ejected is recovered for characterization. These particles can then be isolated from any incorporated snow and ice by freeze drying in the lab. Following laboratory isolation, the particles can then be characterized by Laser Diffraction Particle Size Analysis, morphology by Scanning Electron Microscope and Micro Computed Tomography, and particle compositional analyses by High Performance Liquid Chromatography.

Results

The performance of the LO command detonation testing and particle characterization was tested through four quantitative and one qualitative performance objective(s). Phase 1 validation of laser diffraction – particle size analysis for energetics analysis was fully successful with all performance criteria met. Both Phase 2 and Phase 3 command detonation tests of 60 mm and 81 mm IMX-104 and Comp B rounds were partially successful as not all rounds detonated with filler consumption between the predefined LO ranges. The secondary success criteria of particle size distribution generation for these phases were fully successful for all samples collected. The final quantitative performance objective of calculating the radius of influence for all sampled rounds was fully successful. Feedback regarding the LO detonation particle database was received from stakeholders satisfying the success criteria for this projects one qualitative performance objective.

The costs of implementing the technology in this demonstration would be ~$70k to test a suite of seven rounds of a novel munition using the CFS at a site with suitable ice conditions, a local explosive ordnance disposal who can perform the testing, and sample processing/analysis systems are located nearby avoiding travel/shipping costs. This analysis also assumes that laboratory equipment used for this work is already suitable for processing energetic materials to those for any munitions efficiency test on a military training range with the primary caveat that the range must either already have or be able to sustain an ice testing surface of sufficient size and thickness. This technology provides an efficient method that will enable reproducible results for a LO detonation and costs can be further reduced by testing multiple munitions during the same field tests.

Implementation Issues

The main issues when implementing LO command detonation testing and sampling are the ability to consistently achieve LO detonation functioning, as currently defined, and building/maintaining a suitable testing site. More precise bounds on variability of LO detonation particle characteristics within a given munition would require an increased number of replicate detonations and accompanying increased numbers of samples and analyses. Implementation of this technology would be considered successful if it were to be adopted into use when performing a Life Cycle Environmental Assessment (LCEA) of a new munition. Following this, subject matter experts in the fate and transport of energetic materials within the environment could utilize the data from the LCEA to better refine their models and therefore predictions of relative impact of LO detonations. (Project Completion - 2022)