IGNITER

to the propellant ends. The outer surface inhibitor is spirally wrapped ethyl cellulose tape bonded to the propellant surface. Figure 2-2.—Components of a typical rocket motor. Inhibitors cause the propellant grain to burn from the center outward and from forward to aft uniformly. If inhibitors weren’t used, the burning surface of the propellant grain would increase, and result in an increased burning rate. This could cause the motor tube to explode from excessive pressure. If a motor is accidentally dropped and the propellant grain is cracked, the crack in the grain increases the burning surface and an identical hazard exists. STABILIZING ROD.— The stabilizing rod (fig. 2-2), located in the perforation of the motor propellant grain, is salt coated to prevent unstable burning of the propellant. It also reduces flash and afterburning in the rocket motor, which could contribute to compressor stall and flameout of the aircraft jet engines. When the propellant ignites, the stabilizing rod ensures that the grain ignites simultaneously forward and aft. IGNITER.— The igniter (fig. 2-2) heats the propellant grain to ignition temperature. The igniter used in the 2.75-inch motor is a disc-shaped metal container that contains a black powder and magnesium charge, a squib, and electrical lead wires. It is located at the forward end of the motor. The igniter used in the 5.0-inch motor is a disc-shaped metal container that contains a powder or pellet charge, two squibs, and electrical lead wires. It is located at the forward end of the motor. A contact disc or a contact band transmits the firing impulses to the motor igniter. The 2.75-inch motor has electrical leads that extend from the squib through the wall of the igniter. They are routed through the propellant perforation to the nozzle fin assembly. One of the wires is connected to the nozzle plate (ground), and the other passes through 2-3