The work of the hybrid fuel engines is based on combining the solid fuel and the oxidizer, which makes them partly belong to both types. Hybrid rocket engines have a number of modifications, depending on the constructor, but all of them have common constitution. They consist of the oxidizer tank, link with the rest of the parts by the valve. Other parts of it are injector, igniter, fuel grain and the nozzle.
Nitrous Oxide is the most common oxidizer, used for the hybrid fuel engines. Its popularity is quite easy to be explained – it has natural origin, there is no problem purchasing it, and it is easy to be applied. Other types of oxidizer, used nowadays, are gaseous oxygen, hydrogen peroxide, liquid oxygen, nitric acid. All the oxidizers are used with the same aim – to strengthen the combustion in the engine and accelerate the regression rate, which represents the velocity of the exhaust gases, leaving the engine.
Since oxidizer only makes the reaction in the engine stronger, the fuel is needed to apply the oxidizer to. Commonly polyethylene (PE), poly-methyl methacrylate(PMMA), poly-vinyl chloride(PVC) are used as the engine fuel. Fuel is ignited in the fuel chamber, though it may differ depending on the specific type of engine. Smaller engines have only the main combustion chamber, while the bigger ones usually have the pre-combustion and post-combustion chambers, used to distribute the fuel and the injected oxidizer. Using a pre-combustion chamber allows to make a perfect oxidizer mix before injecting it in the combustion chamber. Post-combustion chamber guarantees all the fuel will be properly burned.
The most important process is the ignition. It differs depending on the size of the engine, but mostly igniters used in traditional engines or identical technologies are used. Ignition takes place mostly in the combustion chamber, and depending on the specific model of the engine, fuel and oxidizer can be ignited either together, separately or sequentially.