DESIGN AND ANALYSIS OF MISSILE CONTROL FINS

SUBMITED BY:VINAYAGAM.P (951011424017)

M.E.,AERONAUTICAL ENGG.

GUIDED BY:Mr.A.SYED IBRAHIM SHAHIDASST.PROF/AERONAUTICAL

ABSTRACT

This paper presents the result of a study demonstrating an approach for using aerodynamic coefficients for a missile with grid fins.

A grid fin is an unconventional lifting and control surface that consists of an outer frame supporting an inner grid of intersecting planar surfaces of small chord.

The calculations were made at Mach number 0.2 and angle of attack 00 for a missile with grid fins.

The modeling of unconventional grid fin is done by CAD software called CatiaV5.

INTRODUCTION

A missile is a self-propelled projectile used as a weapon. Missiles are typically propelled by rockets or jet engines. Missiles generally have one or more explosive warheads, although other weapon types may also be used.

 

The heart of a missile is the body, equivalent to the fuselage of an aircraft. The missile body contains the guidance and control system, warhead, and propulsion system. Some missiles may consist of only the body alone, but most have additional surfaces to generate lift and provide maneuverability.

Most missiles turns in flight do not have conventional rudders, ailerons, or elevators like those used on typical airplanes.

CLASSIFICATION OF MISSILES

Air to Air Missile.

Air to Surface Missile.

Surface to Air Missile.

Surface to Surface Missile.

MISSILE CONTROL SYSTEM

Tail control.

Canard control.

Wing control.

Unconventional control.

TYPES OF FINS

1.PLANAR FIN

The control fins project outwardly from the sides of the missile during self-controlled flight.

The control fins typically have a symmetric airfoil shape that is oriented edge-on or slightly upwardly inclined to the air flow when the missile is flying in a straight line.

To change the flight path, the control fins are slightly reoriented, singly or in groups, by the aircraft's control system

2.GRID FIN

Grid fin, also called lattice fin, are a relatively recent development in guided missile technology. Most guided weapons use planar control fins that are mounted parallel to the body axis.

These fins rotate back and forth to generate forces in the horizontal and/or vertical planes that cause the vehicle to yaw right and left, pitch up and down, or roll as the missile maneuvers towards a target.

These moving control fins are located forward of the weapon's center of gravity (CG) in a canard control layout, at the CG in a wing control format, or aft of the CG in a tail control design.  

ADVANTAGES Grid fins offers favorable lift characteristics at high angle of

attack as well as almost zero hinge moments allowing the use of small and light actuators.

Grid fins as a stabilization and control device on projectiles and missiles offers an interesting alternative to the classical fin design.

Good storability for potential tube-launched and internal carriage dispenser-launched applications

The high aerodynamic effectiveness at low weight and volume. Enhanced yaw stability at high incidence angles and improved

roll stability. Small hinge moments with minimal shift of the centre of

pressure.

DISADVANTAGES

The biggest disadvantages of these wings are their relatively high drag levels at given lift characteristics as well as the weak stability at transonic speeds. Grid fins are much effective only at supersonic speeds.

The chocking of the cell flow in the transonic regime, which happens because of the typical rectangular form of each grid fin cell.

LITERATURE SURVEY

EXPERIMENTAL INVESTIGATIONS OF GRID FIN AERODYNAMICS

AUTHOR: Wm. David Washington

In this paper Wm. David Washington tells he carried out a wind tunnel testing on grid fin and planar fin at various angle of attacks at various Mach numbers.

Then he listed the advantages of grid fins,

◦ Excellent supersonic control characteristics,

◦ Small center of pressure variations over wide Mach number ranges,

◦ Ability to tailor drag using frame shaping,

◦ Ability to alter lift and drag using fin sweep,

◦ High strength-to-weight ratios.

MISSILE FIN PLANFORM OPTIMIZATION FOR IMPROVED PERFORMANCE

AUTHORS: Daniel J. Lesieutre,

Marnix F. E. Dillenius,

Teresa 0. Lesieutre

The design process was done by using optimization based design tool and analyzed with cfd calculations, wind tunnel testing. He concluded Significant improvements to center-of-pressure travel, and hence hinge moments, can be obtained through plan form optimization.

LATTICE CONTROLS: A COMPARISON WITH CONVENTIONAL, PLANAR FINSAUTHORS: G. M. Simpson, A. J. Sadler

In this paper G. M. Simpson, A. J. Sadler they carried out the research on lateral and longitudinal controls of the grid and planar fins. Then they tells the advantages and disadvantages of these fins.

Advantages◦ Improved yaw stability at incidences up to 24⁰◦ Small hinge moments with minimal variation of Centre of pressure

with Mach number and incidence,

Disadvantages◦ Large axial force, which can be as high as 3 or 4 times that of a

conventional fin,

 

EXPERIMENTAL INVESTIGATION AND COMPUTATIONAL FLUID DYNAMICS ANALYSIS OF MISSILE WITH GRID FIN IN SUBSONIC FLOW AUTHOR: K.Mohamed Bak He carried out a work with the investigation of

aerodynamic force coefficients and flow field structure in subsonic flow on missile configuration with grid fin using Wind tunnel and CFD. The experimental work has been performed using the low speed wind tunnel.

After his test he finds the body with grid fin configuration

produces the greater normal coefficients at high angles of attack and the trend seems to be continuously increasing for high Mach numbers. The axial force on the grid fin missile configuration was about 0.8 times greater than planar.

DESCRIPTION OF THE GEOMETRYMissile has been designed by using Catiav5

and the implementation of grid fins with the missile carried out carefully

i) Baseline lattice grid fin, ii) Coarse lattice grid fin, iii) AFIT lattice grid fin.

It is believed that the AFIT design would be better than the other lattice grid fins because this layout doubles the area of the cells in the main body of the fin while retaining a similar shape

DESIGN

3D view of the missile

Enlarged view of fins on missile

3D view of missile with domain in ICEM CFD

Triangle mesh on missile surface

Surface mesh on domain

Missile geometry in CFX

DESCRIPTION OF MESHING

• The tetrahedral mesh for missile geometry is created using ICEM CFD.

• The tetrahedral elements are used for easy meshing as it is unstructured and requires less time to complete.

• Total elements: 1711046 and Total nodes: 287557.

• Thus both constitutes nearly 2 million cells.

DESCRIPTION OF SOLVER CFX is a general purpose Computational Fluid Dynamics

code, combining an advanced solver with powerful pre and

post‐processing capabilities

CFX includes the following features:i. An advanced coupled solver which is both reliable and robust.

ii. Full integration of problem definition, analysis and results presentation.

iii. An intuitive and interactive setup process, using menus and advanced graphics.

iv. Detailed online help

Boundary conditions

The following boundary conditions are used in this analysis.

For inlet, Velocity = 75 m/s.

Static temperature =300K.

For outlet, Static pressure = 0 Pa.

Velocity contour on Missile

Mach number contour on Missile

Static Pressure Contour On Missile

Velocity vector on Missile

Velocity vector behind fins

VELOCITY VECTORS TABLE

S.NO Velocity Vector on

Missiles

Velocity Vector behind

Missiles

1 7.478e-004 3.860e+001

2 2.032e+001 4.991e+001

3 4.065e+001 6.123e+001

4 6.097e+001 7.255e+001

5 8.129e+001 8.387e+001

6 Back side Blue Color Front side Yellow Color

VARIOUS CONTOURS ON MISSILES.NO Velocity contour on

MissileMach number

contour on MissileStatic Pressure

Contour On Missile

1 4.182e-004 1.200e-006 -4.535e+003

2 1.061e+001 3.064e-002 -3.476e+003

3 2.122e+001 6.127e-002 -2.378e+003

4 3.183e+001 9.191e-002 -1.280e+003

5 4.244e+001 1.225e-001 -1.821e+002

6 5.305e+001 1.532e-001 9.160e+002

7 6.366e+001 1.838e-001 2.014e+003

8 7.427e+001 2.145e-001 3.112 e+003

9 8.488e+001 2.451e-001 4.210 e+003

10 9.549e+001 2.757e-001 5.309 e+003

CONCLUSION The velocity contour shows color which differs from

region to region. The maximum velocity acceleration due to the

presence of fins and the body dimensions were indicated in leading edge (front side‐yellow color)

The ones which has maximum velocity decelerations were indicated in trailing edge(backside‐ blue color)as shown.

Stream plot is drawn over the missile with grid fin to view the flow visualization for zero angle of attack. The average Mach number over the missile is 0.21 i.e., subsonic as per as assumption.

Thus, the flow over missile is found to be satisfactory

Thank You