CHAPTER 2 - AIRCRAFT ROCKETS AND ROCKET LAUNCHERS

The history of rockets covers a span of eight centuries, but their use in aircraft armament began during World War II. Rockets answered the need for a large missile that could be fired without recoil from an aircraft.

Since the airborne rocket is usually launched at close range and measured in yards or meters, its accuracy as a propelled projectile is higher than a free-falling bomb dropped from high altitude.

AIRCRAFT ROCKETS

LEARNING OBJECTIVE: State the principles of rocket propulsion. Identify rocket components to include motors, warheads, and fuzes. Identify the purpose and use of service rocket assemblies to include the 2.75-inch folding-fin aircraft rocket (FFAR), the low-spin folding-fin aircraft rocket (LSFFAR), and the 5.00-inch FFAR.

There are two rockets currently used by the Navy. The first is the 2.75-inch, folding-fin aircraft rocket (FFAR) known as the Mighty Mouse. The second, a 5.0-inch, folding-fin rocket known as the Zuni. The Mighty Mouse and the Zuni are discussed in detail later in this chapter.

ROCKET AND ROCKET FUZE TERMINOLOGY

Some of the more common terms peculiar to rockets and rocket components used in this chapter are defined as follows:

Acceleration/deceleration. These terms apply to fuzes that use a gear timing device in conjunction with the setback principle. Prolonged acceleration completes arming the fuze, and deceleration or proximity initiates detonation.

Igniter. The initiating device that ignites the propellant grain. It is usually an assembly consisting of an electric squib, match composition, black powder, and magnesium powder.

Hangfire. A misfire that later fires from delayed ignition.

Misfire. A rocket does not fire when the firing circuit is energized.

Motor. The propulsive component of a rocket. It consists of the propellant, the igniter, and the nozzle(s).

Propellant grain. The solid fuel used in a rocket motor, which, upon burning, generates a volume of hot gases that stream from the nozzle and propel the rocket (also known as the propellant or propellant powder grain).

Rocket. A missile propelled by the sustained reaction of a discharging jet of gas against the container of gas.

Setback. This term is applied when internal parts react to the acceleration of the rocket. Setback is a safety feature designed into those fuzes that use a gear timing device.

Thrust. The force exerted by the gases produced by the burning of the rocket motor propellant.

PRINCIPLES OF ROCKET PROPULSION

Rockets are propelled by the rearward expulsion of expanding gases from the nozzle of the motor. The necessary gas forces are produced by burning a mass of propellant at high pressure inside the motor tube. Rockets function even in a vacuum. The propellant contains its own oxidizers to provide the necessary oxygen during burning.

As you read this section, refer to figure 2-1. To understand how a rocket operates, visualize a closed container that contains a gas under pressure. The pressure of the gas against all the interior surfaces is equal (view A). If the right end of the container is removed (view B), the pressure against the left end will cause the container to move to the left.

In the rocket motor, gases produced by the burning propellant are confined to permit a buildup of pressure to sustain a driving force. The size of the opening is restricted by a Venturi-type nozzle (view C). The Venturi-type nozzle decreases the turbulence of escaping gases and increases the thrust. In this design, gas pressure inside the container provides about 70 percent of the force, and the escaping gases provide about 30 percent of the force necessary to move the container forward.

ROCKET COMPONENTS

A complete round of service rocket ammunition consists of three major components-the motor, the

Figure 2-1.-Principles of rocket propulsion.

warhead, and a fuze. A general description of these components is given in the following paragraphs.