Rocket engine are built to work either with liquid of solid propellants or even a mixture of the two, hybrid propulsion systems like the one used in SpaceShips. Liquid rocket engines are subdivided into mono-propellant and bi-propellant. The first works either as a system of cold gas or catalyst for propellant’s exothermal decomposition. Typical bi-propellant engines are used as storable propellants on earth. Therefore, a rocket engine is a jet engine using only a stock f propellant mass in formation a jet of a supersonic speed. Unlike other engines, they are reactions engines obtaining thrust by following Newton’s third law.
Since there is no requirement of any external material in formation of jet, rockets engines are mostly used for propulsion of spacecraft and missiles. Most of them are internal combustion engines. In other words, rocket engines are conversion systems having heat release in the combustion chamber exceeding the values recorded in a nuclear power plant and that is 3.4 GW.
Even, though they have the capacity of reaching up to 30GW, the most powerful liquid engine has their peak at 20GW whereas most of rocket engine operates by less than 10GW. Rocket engines are classified depending on the method of power for example; physical power, chemical power, electrical power, nuclear and thermal power. The third set of engine after solid and liquid is hybrid engine which is a different class of jet propulsion in which two propellants are normally reacted in an open volume Rocket Propellant This is a mass stored in the propellant tank before being removed from the rocket engine taking the form of fluid jet producing thrust. The commonly used ones are chemical rocket propellants. These normally go through an exothermic chemical reaction process producing hot gases which rockets use for propulsion. Instead of this, heating of a chemically inert reaction mass can be done by the use of a high power source through a heat exchanger.
Solid rockets are madefrom a mixture of oxidizing components and fuel known as “grain” and the casing of propellant storage. Hybrid rocket engines combine both liquid and solid or gaseous propellants. Both hybrid and liquid rocket engines require injectors for introducing the propellant into the combustion chamber. Combustion chamber Chemical rocket engines have combustion chamber taking a form of a cylinder with specific dimensions set to increase combustion rate in the propellant. Different type of propellers need different sizes of chambers for combustion to take place as required. Rocket NozzlesCone shaped expandable nozzles and large bells give the rocket engine its exact shape.
The hot gases emanating from the combustion chamber is allowed to escape through an opening lying within a high expansion-ratio 'de Laval' nozzle. The nozzle chokes under sufficient pressures and a high speed jet is formed, accelerating the gas by converting most of the heat energy to kinetic energy. The speeds of the exhaust vary in accordance with the expansion ration designed in the nozzle. Hybrid rocket engines These engines are different because their propellant is fitted with a rocket motor that works either in solid state or liquid and even gas. They are associated with advantages over solid and liquid rockets in terms of their cost, simplicity and safety. Nevertheless, they tend to fail more at the beginning since it is hard to form a mixture of oxidizer and fuel intimately.
Similar to liquid rockets and not solid rockets, hybrid engines can be shut down easily by simple throttle. This is because the engines have higher performance in term of specific impulse as compared to solid and liquid rockets. Hybrid engines are more complex in structure as compared to both solid and liquid engines. The engines are made of think walled and light weigghted tanks for oxidized flights.
This is meant to save weight. Unlike other two, it allows the passage of oxidizer over the fuel with the aid of a control valve that allows throttling of the motor or even shut down when needed to. Compared to: In conclusion, development of hybrid technology has made it easy through handling, casting, simplicity, throttling, cost, restart and total performance. This is due to their ability to inherently combine the safety features of a liquid propulsion system (throttle, shut-down, restart) while at the same time deriving the cost and operational benefits of a solid propulsion system.
