A solid rocket or a solid-fuel rocket is a

rocket with a motor that uses solid propellants

(fuel/oxidizer)

Simple solid rocket consists of

1. Motor

2. Casing

3. Nozzle

4. Grain (propellant charge)

5. Igniter

Solid Rocket Motor

MOTOR

Conceptually, solid rocket motors are simple

devices with very few moving parts

An electrical signal is sent to the igniter

which creates hot gases which ignite the

main propellant grain

CASING

Casing may be constructed from a range of materials

Cardboard is used for small black powder model motors

Aluminum is used for larger composite-fuel hobby motors.

Steel is used for the space shuttle boosters

Filament wound graphite epoxy casings are used for high-performance motors.

Casing must be designed to withstand the pressure and resulting stresses of the rocket motor

Casing serves as a highly loaded pressure vessel

TYPICAL LARGE SOLID ROCKET MOTOR MADE OF WELDED ALLOY STEEL

NOZZLE

The supersonic nozzle provides

for the expansion and

acceleration of the hot gases and

has to withstand the severe

environment of high heat transfer

and erosion

Nozzles range in size from 0.05

in throat diameter to about 54 in

with operating durations of a

fraction of a second to several

minutes

Nozzles for solid propellant rocket motors can be

classified into five categories

1. Fixed Nozzle

2. Movable Nozzle

3. Submerged Nozzles

4. Extendible Nozzle

5. Blast-Tube-Mounted Nozzle

SIMPLIFIED DIAGRAMS OF FIVE COMMON NOZZLE CONFIGURATIONS

IGNITER

The ignition process of a

solid rocket motor occurs in a

very short time interval of

about 200 milliseconds

Although the process is very

fast it is still complicated and

is composed of two phases.

The first phase is the ignition

of the motor igniter, which is

essentially a small rocket

motor positioned inside the

bigger rocket motor

In the second phase of the ignition the

propellant surface starts burning and the flow

field is dominated by the mass flow injected

from the propellant

In this phase the motor chamber is filled with

burning gases and the motor pressure rises

sharply from ambient pressure to the motor

working pressure.

GRAIN

Solid fuel grains are usually molded from a thermoset elastomer, fuel,

oxidizer and catalyst .

Ammonium perchlorate is the most common oxidizer

This fuel mixture is known as Ammonium perchlorate composite

propellant (APCP)

The grain is cast in different forms for different purposes.

Slow, long burning rockets have a cylinder shaped grain, burning from

one end to the other.

Most grains, however, are cast with a hollow core, burning from the

inside out as well as from the ends.

The thrust profile over time can be

controlled by grain geometry

Example, a star shaped core will have

greater initial thrust because of the

additional surface area. As the star

points are burned up, the surface area

and thrust are reduced

Some solid rocket motors, such as the

ones used in the AGM-114 Hellfire

missile, utilize a "rod and tube" grain

design

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