عباس خلقانی

The flight dynamics of nine configurations of supersonic continuous deflectable nose guided missiles have been investigated. The studied configurations consist of a spherical nose tip, a tangent ogive, a set of stabilizing tail fins and a cylindrical body that its mid-section is flexible to form an arc of a circle. So the cylindrical body consists of a fix part in vicinity of nose, middle flexible part and main body with stabilizers. The effects of fix length and flexible length parameters on the flight dynamics of surface to surface, antiaircraft and antimissile missiles have been studied. A code has been developed to solve full Navier-Stokes equations using finite volume and modified Baldwin-Lomax turbulence model. Further, a 3 degree of freedom code has been developed to compare planar flight dynamics of missiles. This code consists of a guidance subroutine based on pure persuit law. The results show that even increase of fixed and flexible lengths enhance the maneuverability of the missile, but in some scenarios this can lead to increased flight time and more errors in the target engagement. Deflected nose relocates mass center away from the axis and a thrust vector torque is created. Study of surface to surface scenario shows that this torque improves accuracy of targeting and the ability of target dislocation. In air defense missiles, increase of Fix and Flex variables, will extend the limits of allowable firing angle. However, a heavy nose increases the role of thrust torque and subsequently decreases the role of nose geometry.

The aerodynamic characteristics of nine configurations of supersonic continuous deflectable nose guided missiles have been investigated. Then the optimized geometry is achieved based on the maneuverability from aerodynamic and flight dynamic point of view. The studied configurations consists of a spherical nose tip, a tangent ogive, one set of stabilizing tail fins and a cylindrical body that its mid-section is flexible to form an arc of a circle. So the cylindrical body consists of a fix part in vicinity of nose, middle flexible part and main body with stabilizers. The effects of fix length and flexible length parameters on the aerodynamic and flight dynamics of guided missile have been studied. A code has been developed to solve full Navier-Stokes equations using finite volume and modified Baldwin-Lomax turbulence model. Multi-block technique is also used to solve main body and fin parts flow field. Further, a 3 degree of freedom code has been developed to compare planar flight dynamic of missiles. It is found that missiles with bigger lengths for fix and flexible parts show more aerodynamic maneuverability, but drag force grows concurrently. Flight dynamic analysis shows that drag effect is negligible and aerodynamic maneuverability analysis is compatible with flight maneuverability.

Three-dimensional viscous flow has been studied around a supersonic missile with three methods of guidance and control surfaces. The nose can provide aerodynamic control by angular rotation in the pitch plane by a pivot or through continues deflection. If a canard control and a deflectable nose missile have the same trim angle at Mach number 3, the canard control produce bigger drag and smaller lift at zero degree of attack angle, but smaller drag and bigger lift at trim condition. Trim angles of pivoted nose and deflectable nose designs are approximately identical. At zero angle of attack, steering command of deflectable nose design is quite stronger than canard design and this priority maintains to be effective up to trim condition. Drag (Lift) coefficient of pivoted nose is always bigger (smaller) than deflected nose design, from zero up to trim angle. Also steering command of deflectable nose design is slightly stronger than pivoted nose. With increasing Mach number, trim angles of all designs increase. Pitch moment of bent nose increases strongly at Mach number 5, but pitch moment of canard control missile increases less than the other two. The trim angles of deflectable and pivoted nose missiles at Mach number 5 are also identical. At higher Mach numbers, drag and moment coefficients of pivoted nose design approach the moment and drag coefficients of deflectable nose, but lift coefficient of deflectable nose grows faster than pivoted nose design.

The aim of this work is to find an efficient aerodynamic-based design algorithm for projectile fins and configuration shape optimization. Three-dimensional supersonic flow over a projectile with fins at Much number 5 and one degree angle of attack was studied. The Runge-Kutta method and multi-block technique was used to solve the governing equations. A basic configuration was assumed for the fins. The front and rear straight edges of the fins were replaced with polynomial curved edges and the aerodynamic effects were considered. Using this method, the optimized shape of these edges were achieved. At this step, the geometrical parameters of fins and projectile were changed and their effects on drag and stability moment were investigated. The CFD code was ran for several different geometries and the effect of each parameter was investigated. At the end, the design algorithm of fins was derived and configuration shape optimization of projectile’s body and fins for one example was presented.

In this study, the idea of “Soft recovery using un-stablizing” technique applied to a supersonic rocket. The tail of rocket is separated and the tumbling ogive-cylinder body decelerates very soon and then recovers with a two stage parachute mechanism. Aerodynamics of tumbling ogive-cylinder was solved numerically by a finite volume method using a pressure based implicit upwind scheme. Further, second order upstream interpolation and Spalart-Almaras turbulence model were employed. Governing flight dynamics equations of tumbling body were solved numerically using fourth order Runge-Kutta integration method. Numerical results were verified using available velocity-time curve of tumbling fore-body, which recorded experimentally by Doppler radar. Finally, comparing with commercial soft-recovery methods the un-stablizing technique was proposed.