CHALLENGE – A sounding rocket, also known as a research rocket, is used to perform scientific experiments during its sub-orbital flight. Since most sounding rockets do not possess an active control system, they must be aerodynamically stable. To ensure this, solid fins are often used to shift the center of pressure towards the rocket’s center of gravity. Designing the fin is a multi-disciplinary problem involving three disciplines - aerodynamics, trajectory and structures - and multiple conflicting objectives such as maximizing peak altitude, maximizing factor of safety and minimizing fin deformations.
SOLUTION – The three multi-objective design optimization studies presented in the paper approach focused on: 1) maximizing peak altitude and minimizing tip torsion angle of the fin 2) maximizing peak altitude and the factor of safety and 3) maximizing peak altitude and aerodynamic static margin.
The NSGA-II algorithm in modeFRONTIER was used to run the optimization. After obtaining the Pareto Optimal Front, three solutions were presented to verify response surface fitness.
BENEFITS – modeFRONTIER’s multi-disciplinary multi-objective capabilities allowed the researchers to determine which constraints affect rocket performance the most. Results from the first optimization study found that tip torsion angle increases drastically if peak-altitude exceeds 50 km. The second study found that two objectives (maximizing peak altitude and safety) are conflicting. In the third study, results showed that the static margin significantly influences the optimal peak altitude and it is best to keep the static to the minimum required value.