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CHAPTER 2 AIRCRAFT ROCKETS AND ROCKET LAUNCHERS - 14023_63
IGNITER - 14023_65

Aviation Ordinanceman 2 & 3 - Aviation theories and other practices
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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. Motors The rocket motor consists of components that propel and stabilize the rocket in flight. Not all rocket motors are identical, but they do have certain common components. These components are the motor tube, propellant, inhibitors, stabilizing rod, igniter, and nozzle and fin assembly. The rocket motors discussed in the following paragraphs are for the 2.75-inch Mk 4 Mods, Mk 40 Mods, the 5.0-inch Mk 16 Mods, and Mk 71 Mods. MOTOR TUBE.— The motor tube (fig. 2-2) supports the other components of the rocket. Presently, all motor tubes are aluminum, threaded internally at the front end for warhead installation, and grooved or threaded internally at the aft end for nozzle and fin assembly installation. The Mk 4 Mods 1 through 6 and the Mk 40 Mod 0 have a nonintegral (two-piece) bulkhead at the forward end of the tube. This bulkhead has a disc that blows out in case of accidental propellant ignition before installation of the warhead. This action neutralizes rocket thrust by allowing gas produced by the burning propellant to escape from both the forward and aft ends of the motor tube, making it nonpropulsive. It is still a fire hazard. All other Mark and Mod motors discussed in this chapter have tubes with integral bulkheads that do not rupture. In case of accidental propellant ignition, these motors are propulsive, becoming a missile hazard as well as a fire hazard. PROPELLANTS.— The propellant grain (fig. 2-2) contained in the Navy’s 2.75-inch and the 5.0-inch rocket motors is an internal burning, star perforation, double-base solid propellant. The star perforation is designed to produce a nearly constant thrust level. The Mk 66 rocket motor has the star points machined off (conned) to reduce erosive burning. In addition this propellant grain is 5 inches longer than the Mk 4/40 propellant grain. INHIBITORS.— Inhibitors restrict or control burning on the propellant surface. In the 2.75-inch and the 5.0-inch motors, the propellant grains are inhibited at the forward and aft ends, as well as the entire outer diametral surface. The forward and aft end inhibitors are molded plastic (ethyl cellulose) components bonded 2-2







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