Rocket Propulsion

Propellant:
a rocket carries both the fuel and the oxygen to burn it. This is how a rocket, unlike any other engine, can operate in the vacuum of space. It is also why rocketry is the technology of space travel.
Oxidizer:
this is the oxygen or an oxygen equivalent that is used to burn the fuel. In reality, most rocket motors use some other substance to serve the function of oxygen in burning. One example - the black powder motors in model rockets use saltpeter (potassium nitrate) as the oxidizer to burn charcoal. Both of these are found in the black powder propellant, so you could fly your model rocket in space, if you really wanted to. The fuel will burn in a vacuum.
Thrust:
is the force, or "push" the rocket develops, measured in newtons or pounds (or tons for very big rockets).
Nozzle:
increases the thrust of the rocket by increasing the speed of the exhaust.
Impulse:
the thrust multiplied by the burn time. This figure tells the "total push" the motor gives the rocket. For motors using the same propellant (e.g. black powder), a motor with twice the impulse will usually have twice the propellant, so it can burn twice as long for twice the total push.
 
Solid Fuel Rocket:
use a solid mixture of fuel and oxidizer for a propellant. Since it has no moving parts, it is very reliable. However, once a solid rocket is ignited it cannot be shut down until all the propellant has been burned.

Propulsion

Liquid Fuel Rocket:
use separate liquid fuel and oxidizer, which are combined only at the moment of combustion. Pumps are required to get the fuel & oxidizer to the motor quickly enough to develop desired thrust. This makes liquid fuel rockets more complicated, however liquid fuel is up to twice as powerful as solid. Also, liquid fuel rockets can be turned off and then turned on again. On the space shuttle, they can be throttled for more or less thrust. So liquid fuel rockets are not only more powerful, they are more controllable.
Hybrid Rocket:
use separate liquid oxidizer and solid fuel, which are combined only at the moment of combustion. The oxidizer will be presurised by gas to push it into to the motor quickly enough to develop desired thrust. This makes hybrid fuel rockets more complicated than solids but simpler than liquid fueled rockets. Hybrids are covered more in depth here...

 

This new page is a re-write of the old hpr.org.uk pages with usefull scientific formulas and explanations that are usefull to understand Rockets from the basics of Newtons Laws to more complicated equations used to design motors and predict their performance. The old HPR.ORG.UK web site contained a lot of out of date information that has now been archived, if you are looking for any of the old information and cant find it please contact us.

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