SMS GUIDED MISSILES, AERODYNAMICS, AND FLIGHT PRINCIPLES

Weapon systems consist of four major equipment areas-the Detect, Direct, Deliver, and Destroy units. For the last two chapters, we have concentrated on the Delivery units -the GMLSs. We will now discuss the units that Destroy -the guided missiles.

The purpose of this chapter is to familiarize you with the basic principles associated with guided missiles. We will study the major systems of a missile and learn why and how the missile flies. You should then be able to apply these basic principles to the missiles used in the surface missile system (SMS) in the fleet. Pay attention to the terminology of these new equipments.

STRUCTURE

LEARNING OBJECTIVE: Recall the basic structure of a missile to include its three primary sections.

Missiles, for the most part, are made up of several sections or shells (fig. 9-1). They are machined from metal tubing and contain the essential units or components of the missile. Sectionalized construction of a structure has the advantage of strength with simplicity. It also provides for easier replacement and repair of the components, since some sections are removable as separate units. The sections are joined by various types of connections which are also designed for simple operation. Covers and access doors are often installed on the outside of the structure to provide easy access to key interior components.

The missile exists to carry the warhead to the target. Therefore, the structure is designed around the size and weight of the warhead. The structure of the missile

Figure 9-1.-Sectionalization of a missile.

must be as light and compact as possible, yet strong enough to carry all the necessary components. The structure must also be able to withstand the forces to which it will be subjected. These "forces" will be encountered during preflight shipping, handling, and stowage periods. Other forces, such as gravity, heat, pressure, and stresses of acceleration, will also be experienced in flight.

In most missiles, the main body is a slender, cylindrical structure capped on either end by nose and tail sections. Several types of nose sections can be used (fig. 9-2). If the missile is intended to fly at supersonic speeds (greater than the speed of sound), the forward (nose) section usually is designed with a pointed-arch profile. The sides taper in lines called "ogive" curves. With missiles intended for subsonic speeds, the nose is often not as sharp or even blunt. The forward section of most SMS missiles is covered by a "radome." This type of nose protects a small radar antenna inside the missile.

Typical structures (airframes) contain a main body that terminates in a flat base or tail cone. When the contour of the tail cone is slightly streamlined at the rear, it is said to be "boattailed." Attached to the body (also known as the skin or outer surface) are one or more sets of airfoils. These airfoils (wings, fins, or control surfaces) contribute to in-flight stability, provide lift, and control the flight path of the missile.

Figure 9-2.-Missile noses.

The design configuration of a particular missile depends on various factors. Consideration must be given to the speed, the operating range, and the turning rate of the missile. 'The purpose of the missile and the medium(s) through which the round will travel (such as water, air, or a combination of the two) are other important factors. The location of the primary control and/or lifting surfaces also determines the configuration of the missile. Two popular designs are wing-control and tail-control missiles (fig. 9-3). Wing-control airfoils are mounted at or near the center of gravity of the structure. Tail-control airfoils are located at the rear of the missile.

Most SMS missiles have dorsal fins and tail-control surfaces (fig. 9-4). The dorsal fins are attached to the main body of the missile. These stationary surfaces are used to provide stability and (some) lift during missile flight. The tail-control surfaces normally are folded during stowage. These surfaces are erected (unfolded) just before launch. The tail-control surfaces are turned or pivoted to control (steer) the missile along its flight path.