During this project, lead-free double base (DB) formulations will be examined and compared to the fielded, lead containing DB formulation used in 2.75” outer diameter (OD) rockets via strand burning rates and sensitivity, mechanical, and physical property tests. The objective of this project is to achieve at least equivalent performance (i.e., variation from that of the fielded formulation may pose benefits, an exact match may not be the only path for program success) and pose less risk to the environment. Formulations will include lead-free, commercially off the shelf (COTS) items sold within the 48 contiguous United States (CONUS) and the District of Columbia. Of particular interest as propellant additives are cerium compounds. Additional to investigating novel energetics formulations, propellant will be processed via an engineering approach designed at U.S. Army Development Command (DEVCOM) Aviation and Missile Center (AvMC). If successful, formulations may have application as a replacement to lead containing fielded DB propellants currently manufactured at high volumes. There is possible application in future higher energy formulations which are free of lead, ammonium perchlorate, cyclotrimethylene trinitramine, and isocyanates. These efforts support the Army Modernization Priorities by providing increased performance and long term sustained availability of propellants for the Long Range Precision Fire Cross-Functional Teams.

To generate lead-free DB propellant formulations and compare properties to that of the fielded lead containing DB formulation used in 2.75” OD rockets, the DEVCOM AvMC research team will utilize a well-established approach (i.e., proposed tests are standard operating procedures) of small scale (~100 gram) solventless DB slurry-mixing and propellant consolidation and testing. Materials (e.g., conventional {i.e., nitrocellulose, nitroglycerin} and novel {i.e., cerium compounds} propellant ingredients) are sold within CONUS as COTS items. Material compatibility will be assessed by Differential Scanning Calorimetry (DSC). Materials or material combinations exhibiting a DSC decomposition onset no less than 150°C will be allowed to proceed to formulation work. Lab scale propellant sheets will be generated by a method developed at DEVCOM AvMC and tested for strand burning rates (in/s) at ambient temperature interval pressure steps (100 to 5000 psi). Lead-free formulations that exhibit desired catalyzed burning rates will be further tested (i.e., alongside that of leaded fielded formulation for 2.75” OD rockets) for high and low temperature burning rates (-45°F to 145°F), sensitivity (e.g., impact, friction, and electrostatic discharge), mechanical properties (e.g., stress, strain, and modulus), physical properties (e.g., coefficient of linear thermal expansion), and aging (i.e., Allied Ordnance Publication, AOP-48). The research team will leverage knowledge gained from other Department of Defense (DoD) funded programs to conduct research that parallels the current proposal.

This project seeks to eliminate lead based burn rate modifier (BRM) catalysts currently used in minimum signature propellants. In addition to the advancement of scientific understanding of lead-free BRM alternatives, if successful, this effort can initiate the exclusion of lead based materials and the associated environmental, safety, and occupational health risks, from solid rocket motor propellant formulations for DoD tactical missile platforms, without introducing significant new environmental, safety, or occupational health concerns, and without sacrificing propellant safety or performance.

Unclassified/ Distribution A: Approved for public release: distribution unlimited.