ao-ejection(1) Compute rocket ejection charges


ao-ejection diameter(mm) length(mm) force(N)


ao-ejection computes the amount of black powder necessary to generate the desired force to separate sections of a rocket airframe. It assumes a cylindrical airspace covered by a circular cap. With that and the force to be exerted on the cap, ao-ejection can compute the necessary pressure rise within the chamber, the volume of gas necessary and finally the mass of BP to generate the gas.


        $ ao-ejection 54 300 500
        Input parameters:
            Diameter: 54.0 (mm) 2.126 (in)
            Length: 300.0 (mm) 11.811 (in)
            Force: 500.0 (N) 112.404 (lb)
        Chamber values:
            Area: 2290 (mm²) 3.550 (in²)
            Volume: 687066 (mm³) 41.927 (in³)
            Pressure: 31.66 (lb/in²) 0.21832 (N/mm²)
            FFFF powder: 0.685 (g)

This demonstrates that a 54mm airframe with a 300mm chamber requires .685g of FFFF BP to generate 112lb of force on the end of the chamber. This is usually sufficient to sever two 2x56 nylon screws.


Keith Packard