Combustion of Flake Aluminum with PTFE in Solid and Hybrid Rockets *

Aluminum is used in the rocket industry primarily because it increases the specific impulse of the rocket motor. However, the combustion of aluminum sometime leads to various disadvantages such as slag accumulation and two-phase losses in the rocket motor. This study attempts to mechanically activate the aluminum using PTFE (polytetrafluoroethylene) and improve its ballistic performance in solid and hybrid rockets. This investigation established through various tests (such as thermogravimetric analysis [ TGA ], differential calorimeter [ DSC ], particle size analysis, scanning electron microscope [SEM] analysis, viscosity measurements, and other tests) that this mechanically activated aluminum is suitable for replacing regular aluminum in composite solid propellants. A significant improvement in the burn rate of solid propellant and reduction in the agglomeration of aluminum was observed when mechanically activated aluminum was incorporated in the composition. The solid propellant composition prepared with this mechanical activation of aluminum was also incorporated in a study where the characteristic of high burn rates of this composition can be used in an end burning grain configuration to increase the payload capacity of the Pegasus launch vehicle. This study also found that with the addition of this mechanically activated aluminum in hybrid rocket fuel grain, the ballistic performance (specific impulse, density specific impulse, combustion efficiency, regression rates, etc.) improved significantly in the hybrid rocket motor. The addition of mechanically activated aluminum in solid and hybrid rockets makes the system more compact by increasing the density-specific impulse of the rocket motor.