Solid Propellant Rockets
These rockets were first used by the Chinese in the 1200s.

These rockets, as the name implies, use a solid fuel,
that is usually made up of individual grains
that contain both the oxidizer and fuel.

These must be ignited by introducing a spark,
or another chemical (usually liquid chlorine)
that begins the burning of the grain.

Panzerfaust and other anti-tank weapons us them.

 They are also used in model rockets, anti-
aircraft, ICBMs and satellite launch vehicles.

The simplest forms are used in 2 in. long
'bottle' and other rockets for celebrations.

The most devious use is in the 2.75 in. flechette rocket
launched from U.S. helicopters to kill Vietnamese
in the Second Indo-China War.

Military, solid propellant rockets usually burn
between 3,000 and 6,000 degrees F.

The chamber holding the grains is made from,
steel, titanium, fiberglass or plastic.

Solid propellants burn fast, but w/ less energy than liquid- propellants.

The 1st practical military application was in the British Congreve rocket.

They are easier to store for long periods than liquid-propellant rockets.

They do not need equipment for the fill-up of a tank,
like liquid-propellants rockets.

Once started, however, they are almost impossible to stop.

They are often used as disposable 'booster' rockets
for jet aircraft and liquid-propellant rockets.

The most famous of these rockets are the Atlas launch vehicle.

As the picture below shows these rockets are cylindrical in shape
w/ a shaft drilled from 1 end almost thru the other.
This shaft vents the expanding exhaust gases
in the opposite direction the rocket is aimed .

I got the info below from Howstuffworks.com.

Solid-Fuel Rockets: Channel Configuration
When you read about advanced solid-fuel rockets like the
Shuttle's solid rocket boosters, you often read things like:

    The propellant mixture in each SRB motor consists of an ammonium perchlorate (oxidizer, 69.6 percent by weight), aluminum (fuel, 16 percent), iron oxide (a catalyst, 0.4 percent), a polymer (a binder that holds the mixture together, 12.04 percent), and an epoxy curing agent (1.96 percent). The propellant is an 11-point star-shaped perforation in the forward motor segment and a double- truncated- cone perforation in each of the aft segments and aft closure. This configuration provides high thrust at ignition and then reduces the thrust by approximately a third 50 seconds after lift-off to prevent overstressing the vehicle during maximum dynamic pressure.

This paragraph discusses not only the fuel mixture but also the configuration of the channel
drilled in the center of the fuel. An "11-point star-shaped perforation" might look like this:

The idea is to increase the surface area of the channel,
thereby increasing the burn area and therefore the thrust.
As the fuel burns the shape evens out into a circle. In the case of the SRBs,
it gives the engine high initial thrust and lower thrust in the middle of the flight.

Solid-fuel rocket engines have three important advantages:

  • Simplicity

  • Low cost

  • Safety

They also have two disadvantages:

  • Thrust cannot be controlled.

  • Once ignited, the engine cannot be stopped or restarted.

The disadvantages mean that solid-fuel rockets are useful for short-lifetime
tasks (like missiles), or for booster systems. When you need to be
able to control the engine, you must use a liquid propellant system.

Rockets

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