Difference Between Turbojets And Rockets
Perhaps the best-known jet-type engine is the turbojet, or turbine-jet. In this form of propulsion, air is drawn from the atmosphere through intakes, usually located in either the nose or the wing roots of the plane. The air is compressed, led into a combustion chamber, mixed with injected fuel, and ignited. The resulting gases are forced rearward at high velocity. They drive a turbine connected to the main engine shaft on which the compressor is mounted. Then they escape through the nozzle. The reaction from the spurt of gases provides thrust. The escaping gases propel the plane and also serve to compress the air drawn in through the intakes.
Some turbojet engines are equipped with a device called an afterburner, or reheat tube. This is simply a tail pipe attached to the rear of the engine proper. Fuel is injected and burned in the afterburner. This causes further expansion of the gases escaping from the engine, adding to the basic thrust and increasing the velocity. Another way of increasing thrust is to place a large cold-air fan in front of or behind the turbine. The fan forces masses of air into the exhaust stream, in addition to the air from the turbine itself. This kind of engine is known as a turbofan, and it is widely used on commercial airliners.
A rocket engine is really only a combustion chamber in which fuel, either solid or liquid, is burned. The resulting gases expand enormously under intense heat and are forced out from the rear of the rocket tube at high velocity, creating thrust. Unlike other types of jet engines, the rocket does not draw air from the atmosphere. It carries its own oxygen with it, in the form of liquid oxygen or a compound such as hydrogen peroxide.
The great disadvantage of rocket power is the extremely high rate of fuel consumption. The chief advantage of the rocket lies in its ability to generate very high thrust in a comparatively small package. Because rocket engines do not require an outside source of oxygen, they are well-suited for use in spacecraft.