arming (S&A) device, a target-detecting device (TDD),
or a combination of these devices.
There are two general types of fuzes used in guided
missiles—proximity fuzes and contact fuzes. Both fuzes
are armed by acceleration forces upon missile launching.
Arming is usually delayed until the fuze is subjected to
a given level of accelerating force for a specified amount
of time. In the contact fuze, the force of impact closes
a firing switch within the fuze to complete the firing
circuit, detonating the warhead. Where proximity
fuzing is used, the firing action is very similar to the
action of proximity fuzes used with bombs and rockets.
SAFETY AND ARMING (S&A) DEVICES.—
S&A devices are electromechanical, explosive control
devices. They maintain the explosive train of a fuzing
system in a safe (unaligned) condition until certain re-
quirements of acceleration are met after the missile is fired.
TARGET-DETECTING DEVICES (TDD).—
TDDs are electronic detecting devices similar to the
detecting systems in VT fuzes. They detect the presence
of a target and determine the moment of firing. When
subjected to the proper target influence, both as to
magnitude and change rate, the device sends an
electrical impulse to trigger the firing systems. The
firing systems then act to fire an associated S&A device
to initiate detonation of the warhead.
Air-to-air guided missiles are normally fuzed for a
proximity burst by using a TDD with an S&A device.
In some cases, a contact fuze maybe used as a backup.
Air-to-surface guided missile fuzing consists of
influence (proximity) and/or contact fuzes. Multifuzing
is common in these missiles.
Propulsion Section
Guided missiles use some form of jet power for
propulsion. There are two basic types of jet propulsion
power plants used in missile propulsion systems-the
atmospheric (air-breathing) jet and the thermal jet
propulsion systems. The basic difference between the
two systems is that the atmospheric jet engine depends
on the atmosphere to supply the oxygen necessary to
start and sustain burning of the fuel. The thermal jet
engine operates independently of the atmosphere by
starting and sustaining combustion with its own supply
of oxygen contained within the missile.
ATMOSPHERIC JET PROPULSION
SYSTEM.— There are three types of atmospheric jet
propulsion systems-the turbojet, pulsejet, and ramjet
engines. Of these three systems, only the turbojet
engine is currently being used in Navy air-launched
missiles.
A typical turbojet engine includes an air
intake, a mechanical compressor driven by a turbine, a
combustion chamber, and an exhaust nozzle. The
engine does not require boosting and can begin
operation at zero acceleration.
THERMAL JET PROPULSION SYSTEM.—
Thermal jets include solid propellant, liquid propellant,
and combined propellant systems. As an AO, you come
in contact with all three systems, The solid propellant
and combined propellant systems are currently being
used in some air-launched guided missiles.
The majority of air-launched guided missiles used
by the Navy use the solid propellant rocket motor. They
include the double-base and multibase smokeless
powder propellants as well as the composite mixtures.
Grain configurations vary with the different missiles.
Power characteristics and temperature limitations of the
individual rocket motors also vary.
In some guided missiles, different thrust
requirements exist during the boost phase as compared
to those of the sustaining phase. The dual thrust rocket
motor (DTRM) is a combined system that contains both
of these elements in one motor. The DTRM contains a
single propellant grain made of two types of solid
propellant—boost and sustaining. The grain is
configured so the propellant meeting the requirements
for the boost phase burns at a faster rate than the
propellant for the sustaining phase. After the boost
phase propellant burns itself out, the sustaining
propellant sustains the motor in flight over the designed
burning time (range of the missile).
REVIEW NUMBER 2
Q1.
Q2.
Q3.
Q4,
Q5,
Q6.
Q7.
Q8.
List the major sections of guided missiles.
What section is considered the brains of the
missile ?
List the three types of homing systems.
If a missile gets its target illumination from the
launching aircraft, what type of homing system
does it have?
List the components of the armament section.
Describe the function of safety and arming
(S&A) devices.
What are the two types of propulsion used with
guided missiles ?
Describe the basic difference between the two
types of propulsion.
3-7
