Mode Selector Switch

The mode selector switch (figs. 2-29, 2-30, and 2-31) is used on all launchers. The switch is located in the aft bulkhead of the launcher. The switch permits preflight selection of either ripple or single firing of the rockets by controlling the functioning of the pod intervalometer.

Intervalometer

The intervalometer for the LAU-10 (series) pods is located in the forward bulkhead of the center section (fig. 2-29) and in the aft bulkhead for the LAU-61 and LAU-68 (series) (figs. 2-30 and 2.-31). Intervalometers, whether installed in 5.0-inch or 2.75-inch launchers, perform the same function.

If the mode selector switch is in the SINGLE fire position, the intervalometer fires one rocket on each

Figure 2-31.-Mode selector switch and intervalometer (LAU-61A/A, LAU-61B/A, and LAU-61C/A).

firing pulse. If the mode selector switch in the 19-shot pod is in the SINGLE fire position, the intervalometer fires the rockets in pairs. If the mode selector switch is in the RIPPLE fire position, the intervalometer converts the firing pulse into a ripple pulse and successively fires all rockets at 95-millisecond intervals. Ripple firing functions the same on all pods.

The intervalometer used with the 2.75-inch pod has a shaft that extends through the aft bulkhead of the launcher and a knurled knob with a reference (index) mark mounted on the shaft. Intervalometer switch positions are marked on the aft bulkhead of the center section. The intervalometer should NOT be manually rotated through the numbered positions except when checking an empty pod.

Intervalometers used in the LAU-10 (series) pods cannot be manually rotated When the intervalometer has made a complete four-round firing cycle, it automatically homes in on the original starting point (zero) and does not recycle without first de-energizing the circuit, and then re-energizing it.

5.0-INCH (SERIES) LAUNCHERS

The LAU-10 (series) launchers are reusable launchers intended for shipping (without warheads), stowing, and firing four 5.0-inch rockets. When loaded with four completely assembled rounds, the total weight varies with rocket configuration from 500 to 550 pounds.

The rockets are retained in the launcher tubes during shipping, handling, and flight by engagement of a spring-loaded detent pawl in the rocket detent groove (fig. 2-32). When the rocket is loaded and unloaded, a detent lift tool is used to raise and lower the detent pawl by rotating the detent lift handle, which is located at the forward end of the launcher. The detent also supports the firing pin. Each firing pin (fig. 2-32) is part of the detent assembly and is raised and lowered concurrent with the pawl. The firing pin extends into the tube and

Figure 2-32.-LAU-10 (series) detent pin and firing pin assembly.

contacts the rocket tiring contact band, which is located aft of the rocket detent groove.

When the switch in the aircraft firing circuit is closed, electrical current flows from the aircraft firing circuit through the electrical receptacle, safety switch, mode selector switch, intervalometer, and the firing pin in the launcher to the contact band in the forward end of the motor, and through the lead wire to the squib in the igniter. The current entering the rocket squib heats the squib primer mixture, which, in turn, ignites the igniter charge.

Pressure within the igniter unseats a blowout plug, permitting the burning charge to ignite the propellant grain. The whole process of ignition requires about 0.005 second. Pressure of the hot propellant gases from the burning grain bursts the nozzle seal and provides the thrust to propel the rocket. Thrust overrides the detent spring, releasing the pawl from the rocket detent groove. The thrust then pushes the rocket out the forward end of the tube. The impact from the first rocket out shatters the forward fairing and the blast removes the tail fairing.