the 2.75-inch diameter of the rocket. The fins are
notched at the tips to allow attachment of a fin retainer.
The fin-actuating mechanism is a steel cylinder and
a piston with a crosshead attached to its aft end. When
the rocket is fired, gas pressure from the motor operates
the piston, cylinder, and crosshead. The crosshead is
pushed against the heels of the fins, causing the fins to
rotate on the fin pivot pins to the open position after the
rocket leaves the launcher. After the fins have opened to
the final flight position, the crosshead prevents the fins
There are four nozzle inserts and the detent groove
in the aft end of the nozzle plate. They hold the rocket in
position after it is loaded in the launcher.
The Mk 71 Mods motor has a modified igniter and
a modified nozzle and fin assembly. The nozzle and fin
assembly (fig. 2-4) contains four, spring-loaded,
wraparound fins inside the motor diameter. The steel
nozzle expansion cone has flutes that cause the rocket
to spin during free flight. This permits the rocket to be
launched from high-speed aircraft, helicopters, and
The Mk 71 Mods spring-loaded fins (fig. 2-5)
deploy after emerging from the rocket launcher tube.
They lock in place (open) by sliding into a locking slot
in the flange at the aft end of the fin nozzle assembly.
When not actually installed in the launcher, the fins are
held in the closed position by a fin retainer band, which
must be removed when the rocket is installed into the
interchangeable with the shielding band.
REVIEW NUMBER 1
List the two rockets currently used by the
If a rocket does not fire when the firing circuit
is energized, it is known as a _____________.
What is meant by the rockets thrust?
In rocket propulsion, the Venturi nozzle
decreases turbulence of escaping gases and
increases thrust. Gas pressure inside the
container provides about _______, and the
escaping gases provide about __________ to
move the container forward.
List the three components of a rocket.
List the components of rocket motors.
What is the purpose of the inhibitor?
What rocket component is salt coated to
prevent unstable burning of the rocket
When should you remove the fin retainer band
on a Mk 71 rocket motor?
Different tactical requirements demand different
types of rocket warheads be used with airborne rockets.
Figure 2-5.Mk 71 Mods motor, nozzle, and fin assembly.