The main objective of this project is to develop an enhanced, melt-pour explosive formulation and warhead system capable of replacing environmentally-objectionable Composition B (a melt-castable mixture of 1,3,5-Trinitro-1,3,5-triazacyclohexane (RDX) and 2,4,6-trinitrotoluene (TNT)) from common small military items such as the M67 hand grenade. The new design will not only avoid the use of toxic ingredients/casing materials, but is intended to meet or exceed the lethality and insensitive munition (IM) compliance of the existing Comp B/M67 system.
The approach will focus on the combination of a three-dimensional (3D) printed metal casing design and a non-traditional explosive compound, MTNI (1-methyl-2,4,5-trinitroimidazole), chosen for its stable melt-phase behavior and highly favorable explosive properties; explosive performance data collected to date indicate that MTNI already exceeds Comp B explosive performance prior to formulation, suggesting that significant quantities of desensitizing agents can still be added to enhance processability and IM compliance. The metal casing printing method will be based on Selective Laser Sintering (SLS), whereby a laser is applied to a bed of powdered steel in additive fashion to form metal structures of tailorable strength. The overall project will consist of three phases:
- Synthesis and optimization of MTNI: The existing literature synthesis for MTNI will be optimized/altered to develop a kilogram scale process. Up to 10 kg of MTNI will be produced for characterization, environmental testing, and use in Phases 2 and 3.
- Explosive formulation of MTNI: Theoretical thermochemical calculations will be the starting point for selecting formulation ingredients and proportions. Melt-castability studies as well as explosive performance and sensitivity testing (detonation velocity/pressure, gap testing, cylinder expansion, etc.) will be used to down-select a formulation with the optimal balance of performance, insensitivity, and environmental compliance.
- Fabrication, loading, and functioning of a printed M67 grenade with the MTNI formulation: Computer-generated models will be used to design tailorable-fragmenting grenade bodies, which will be printed and tested with baseline Comp B to assess performance and optimize the printed design. The finalized printed design will be loaded with the MTNI formulation(s) and tested to assess fragment patterns and velocities in comparison to standard M67 grenades.
Benefits to the Department of Defense (DoD) are expected to include the development of a simple, environmentally-acceptable, IM-compliant melt-castable option for small munitions which, up to now, has not been forthcoming with available alternatives (e.g. IMX-104). Additionally, this project would demonstrate the utility of SLS-based additive manufacturing methods for warheads, opening the door for applications in numerous other DoD munitions of all sizes.