wrapped ethyl cellulose tape bonded to the propellant
surface.
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,
located in the perforation of the motor propellant grain,
is salt coated to prevent unstable burning of the
propellant. It also reduces flash and after burning 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 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 pellets 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
either one of the nozzles or the fin-actuating piston to
the contact disc on the fin retainer. In the Mk 66 Mod 2,
both lead wires are connected directly to the HERO
filter wires, which extend out of the forward end of the
stabilizing rod. When the rocket is placed in the
launcher, the contact disc is automatically in contact
with an electrical terminal that transmits the firing
impulse to the rocket.
The igniter in the 5.0-inch motor (fig. 2-2) has an
electrical lead wire post that protrudes through the
forward bulkhead closure. The electrical lead connects
the igniter to the contact band. When the rocket is
placed
in
the
launcher,
the
contact
band
is
automatically in contact with an electrical terminal,
which transmits the firing impulse to the rocket. Until
actually loaded into a launcher, a metal shielding band
2-3
Figure 2-2.—Typical center electrical lead wire connection (5.0-inch motor).
