Journal of Applied Mechanical Engineering

Rocket Engine: An Overview

Stephan Wilson^* Private University in Los Angeles, California, USA
^*Correspondence: Stephan Wilson, Private University in Los Angeles, California, USA, Email:

Received: 07-Sep-2021 Published: 17-Sep-2021, DOI: 10.35248/2168-9873.21.10.386

Editorial

A rocket engine forms a high-speed propulsive jet of fluid, usually high-temperature gas, using stored rocket propellants as the reaction mass. Rocket engines are reaction engines that produce thrust by ejecting mass backwards, as Newton's third law dictates. Although most rocket engines rely on the combustion of reactive chemicals to provide energy, non-combusting alternatives such as cold gas thrusters and nuclear thermal rockets are also available. Rockets are vehicles that are propelled by rocket engines. Unlike most combustion engines, rocket engines have their own oxidizer, allowing them to be utilised in a vacuum to propel spacecraft and ballistic missiles. Rocket engines are the lightest and have the maximum thrust when compared to other types of jet engines, but they are the least propellant-efficient (they have the lowest specific impulse).

Although hydrogen is the lightest of all elements, chemical rockets produce a mixture of heavier species, lowering the velocity of the exhaust. The Oberth effect makes rocket engines more efficient at high speeds. Expulsion of an exhaust fluid that has been accelerated to a high speed through a propelling nozzle produces thrust in rocket engines. The fluid is often a gas produced by the high-pressure (150-to-4,350 pound-per-square-inch (10 to 300 bar)) combustion of solid or liquid propellants, which include fuel and oxidizer components, within a combustion chamber. The gases are pushed to a very high (supersonic) speed when they expand through the nozzle, and the reaction pushes the engine in the opposite direction. Combustion is the most common method of propulsion for practical rockets since high temperatures and pressures are required for optimal performance.

The water rocket, which uses water pressurized by compressed air, carbon dioxide, nitrogen, or any other readily available, inert gas, is a model rocketry alternative to combustion. Prior to being blasted from a rocket engine in the form of a fluid jet to provide thrust, rocket propellant is mass that is held, usually in some type of propellant tank or within the combustion chamber itself. The most often utilised rocket propellants are chemical rocket propellants. These go through exothermic chemical processes, resulting in hot gas that the rocket uses for propulsion. Alternatively, a chemically inert reaction mass can be heated via a heat exchanger utilising a high-energy power source, eliminating the need for a combustion chamber.

Solid rocket propellants are made up of a blend of fuel and oxidizers known as 'grain,' and the propellant storage shell serves as the combustion chamber. Separate fuel and oxidizer components are forced into the combustion chamber of liquid-fueled rockets, where they combine and burn. Solid, liquid, or gaseous propellants are used in hybrid rocket engines. Injectors are used in both liquid and hybrid rockets to introduce fuel into the chamber. Simple jets — holes through which the propellant escapes under pressure – are commonly used, although more complicated spray nozzles may also be used. When two or more propellants are injected, the jets usually intentionally make them to collide so that the flow is broken up into tiny droplets that burn more easily. Flame holders, which are employed to contain a portion of the combustion in a slower-flowing area of the combustion chamber, are not needed in chemical rockets because the combustion chamber is normally cylindrical. The cylinder's dimensions are such that the propellant can completely burn; different rocket propellants necessitate different combustion chamber diameters for this to happen.