J. Morote

Prediction of Nonlinear Rolling and Magnus Coefficients of Cruciform Finned Missiles

†A new method combining strip and slender body theories has been developed to predict the aerodynamic roll and wing-induced Magnus coefficients of cruciform tailed missiles at high angles of attack. The method, based on the wing alone lifting capability, is applicable over the Mach number range and for large angles of attack at arbitrary bank angles, providing analytical expressions of the nonlinear rolling moments: roll damping, roll driving, induced roll moments and additional coupling terms. The analytical expressions fit the form of the Maple-Synge expansion and the degree of nonlinearity shown by experimental results.

Analytic Model of Catastrophic Yaw

A quantitative model of the non-linear motion leading to catastrophic yaw of finned missiles is presented. The coupled roll-yaw dynamics of the missile, acted on by the trim angle of attack due to slight configurational asymmetries, is represented by pitch-yaw and roll equations of motion that include cubic aerodynamic coefficients and roll orientation-dependent induced moments. The steady-state equilibrium points of the system are found and their stability is determined by linearization. The solutions are evaluated by comparison with numerical integration of the equations of motion, proving the capability of the model to predict catastrophic yaw. Nomenclature CD = drag force coefficient CLα = angle of attack coefficient of the lift force CNα = angle of attack coefficient of the normal force CMα = angle of attack coefficient of the pitch moment Cli = induced roll moment coefficient Clp = roll damping moment coefficient Clδ = roll effectiveness moment coefficient CMpα = angle of attack coefficient of the Magnus moment

Roll-Rate Stability Limits of Unguided Rockets with Wraparound Fins

The linearized theory of lateral motion of unguided rockets with wraparound fins shows that, unlike planar configurations, they have different roll-rate stability boundaries depending on the roll direction. An analysis of the asymmetry-governing parameters is presented. An operational criterion is developed expressing the roll-rate limits as a function of a factor accounting for the relative effect of the asymmetry terms.

Nonlinear Rolling Motion of Triform Finned Missiles

A theoretical investigation of the rolling motion of triform configurations at high angles of attack is presented. A nonlinear aerodynamic flow model, derived from strip and slender body theories, ...

Multiple Roll Angle Fitting of Static Aerodynamic Coefficients of Cruciform Missiles

The aerodynamic characterization of unguided missiles at high angles of attack has been of primary interest for researchers, since nonlinear effects may lead to unexpected steady-state solutions. The usual approach is to add cubic terms to the linear aerodynamic coefficients. However, experiments show the strong roll-orientation dependence of the static normal force and pitch moment, which cannot be addressed with the mere inclusion of cubic terms. This paper presents a fitting procedure based on the Maple-Synge expansion to analytically represent high order roll orientation-dependent aerodynamics of cruciform finned missiles. The study shows that, even at moderate angles of attack of about 15o, expansions to the seventh power may be insufficient to accurately describe the high degree of nonlinearity in the static coefficients.