Effectiveness Analysis of Spin Motion in Reducing Dispersion of Sounding Rocket Flight due to Thrust Misalignment

Abstract

This paper explores the effectiveness of spin motion in mitigating the flight dispersion of a two-stage solid-propellant rocket model due to thrust misalignment. The aerodynamic coefficients of the rocket model are obtained by the use of a panel method and semi-empirical equations. A simulation program is developed to solve the equations of motion while considering the variations of the inertial parameters. Monte Carlo simulation techniques are applied to provide statistical data that are used to analyze the relationship between the spin motion and flight dispersion. The spin motion is generated by canting the fins to generate the axial aerodynamic moment. The results show that thrust misalignment at the first stage of the rocket has a great impact on the dispersion of rocket flight. By canting the first-stage fins at a relatively large angle to create the spin motion right after launch, the dispersion area of the payload-release location can be minimized considerably. However, thrust misalignment as well as the fin cant angle at the second stage appear to have insignificant effects on the rocket flight trajectory. On the other hand, canting the fins of the second stage at a large angle may lead to an increase in the spin rate, which may be harmful to the rocket operation. The paper also shows the variation of the dispersion characteristics of rocket flight when the fin size is modified.