A rocket is a machine that develops

thrust by the rapid expulsion of

matter. The major components of a

chemical rocket assembly are a

rocket motor or engine,

propellant consisting of fuel and an

oxidizer, a frame to hold the

components, control systems and a

cargo such as a satellite

THRUSTIs the force generated, measured in pounds or

kilograms. Thrust generated by the first stage

must be greater than the weight of the

complete launch vehicle while standing on the

launch pad in order to get it moving. Once

moving upward, thrust must continue to be

generated to accelerate the launch vehicle

against the force of the Earth's gravity. To

place a satellite into orbit around the Earth,

thrust must continue until the minimum

altitude and orbital velocity have been

attained or the launch vehicle will fall back to

the Earth. Minimum altitude is rarely

desirable, therefore thrust must continue to

be generated to gain additional orbital

altitude.

The IMPULSEsometimes called total

impulse, is the product of

thrust and the effective firing

duration. A shoulder fired

rocket such as the LAW has

an average thrust of 600 lbs

and a firing duration of 0.2

seconds for an impulse of

120 lb­sec. The Saturn V

rocket, used during the

Apollo program, not only

generated much more thrust

but also for a much longer

time. It had an impulse of

1.15 billion lb­sec.

A rocket in its simplest form is a chamber

enclosing a gas under pressure. A small

opening at one end of the chamber allows

the gas to escape, and in doing so

provides a thrust that propels the rocket

in the opposite direction. A good example

of this is a balloon. Air inside a balloon

is compressed by the balloon's rubber

walls. The air pushes back so that the

forces on each side are balanced. When

the nozzle is released, air escapes through

it and the balloon is propelled in the

opposite direction.

With space rockets, the gas is produced by

burning propellants that can be solid or

liquid in form or a combination of the

two.

There are several Different Types

of rocket. The following articles

contain lists of rockets by type:

List of missiles

List of orbital launch systems

List of sounding rockets

List of unguided rockets

List of upper stages