Structural optimization of elliptical-tip star propellant grain using sub-problem approximation

A method is presented here for structural optimization of elliptical-tip star grain. The grain structural integrity was improved by minimizing the most critical area of inner bore hoop strain during cool down. Optimization was done by sub-problem approximation method in conjunction with finite element analysis. Both radii of the ellipse were varied during optimization to find the optimal ellipse. The optimization resulted in grain geometry having minimum level of Inner bore hoop strain without violating the preset limits of burning perimeter. The von mises strain at grain inner bore was also reduced in resultant grain.