The goal of this project was to develop and evaluate a family of “green” gun propellants that could be manufactured without emission of volatile organic compounds or hazardous air pollutants. The unique approach to this otherwise traditional formulation effort was to develop and use a model-based methodology for formulation development. This approach will minimize the pollution generated during a propellant development program and, at the same time, include environmental impact as a parameter in the development process for new formulations.
The goals of the project were the following: (1) development of benign energetic materials and manufacturing and disposal methods which provide for safer, more cost-effective insensitive munitions and which meet increasingly stringent environmental regulations and (2) bring together a number of modeling and simulation modules to design a gun propellant which meets all the operational requirements for military guns.
The project’s technical approach was to use ammonium dinitramide (ADN) as an ingredient in military explosives and propellants. ADN is an attractive ingredient because its combustion products are more environmentally benign than hydrocarbon molecules and ammonium perchlorate. ADN decomposes to water and laughing gas.
Various risks were involved in the technical approach. They included the following: (1) whether propellants and explosives using ADN would meet all military operational and safety requirements for ordnance, (2) whether the manufacture of ADN would be environmentally preferable to the materials it replaces, and (3) whether during demilitarization an ADN-based formulation would have less environmental impact than the materials it displaces. To mitigate these risks, models were developed to help guide the formulation of green gun propellants based on a simulation of the ability of the formulation to meet the operational requirements. In addition, batch mixers and continuous twin-screw extruders were utilized to demonstrate the affordable manufacture of propellant and explosive formulations.
The modules that make up the green gun propellant model and a flow chart showing how data flows from one module to the next have been defined. The user enters various performance requirements including muzzle velocity, projectile shape, gun design, and vulnerability requirements along with known environmental concerns, such as the local environmental regulations governing the locality where manufacturing might be done. The model then accepts proposed gun propellant formulations from a gun propellant formulator and calculates performance properties, the burn rate of the formulation, mechanical properties of gun propellant, erosion and wear of the gun barrel caused by the formulation, toxicity of the ingredients, manufacturing characteristics and wastes for each proposed formulation, emissions from formulations burns and storage, and likely wastes produced through demilitarization by processes other than burning and detonation. This project was completed in FY 1999.
The new "green" energetic materials and manufacturing processes will reduce the adverse life-cycle impact of ordnance on the environment. The green materials simultaneously will provide higher performance energetics and reduce life-cycle weapons costs during development, procurement, and demilitarization. Modeling of propellants will enable the propellant designer to make decisions based on inexpensive models rather than expensive trial and error testing of numerous experimental propellant formulations.