Arocket (from Italian: rocchetto, lit. 'bobbin/spool') is a vehicle that uses jet propulsiontoaccelerate without using any surrounding air. A rocket engine produces thrust by reaction to exhaust expelled at high speed. Rocket engines work entirely from propellant carried within the vehicle; therefore a rocket can fly in the vacuum of space. Rockets work more efficiently in a vacuum and incur a loss of thrust due to the opposing pressure of the atmosphere.
Chemical rockets are the most common type of high power rocket, typically creating a high speed exhaust by the combustionoffuel with an oxidizer. The stored propellant can be a simple pressurized gas or a single liquid fuel that disassociates in the presence of a catalyst (monopropellant), two liquids that spontaneously react on contact (hypergolic propellants), two liquids that must be ignited to react (like kerosene (RP1) and liquid oxygen, used in most liquid-propellant rockets), a solid combination of fuel with oxidizer (solid fuel), or solid fuel with liquid or gaseous oxidizer (hybrid propellant system). Chemical rockets store a large amount of energy in an easily released form, and can be very dangerous. However, careful design, testing, construction and use minimizes risks. (Full article...)
Arocket-powered aircraftorrocket plane is an aircraft that uses a rocket engine for propulsion, sometimes in addition to airbreathing jet engines. Rocket planes can achieve much higher speeds than similarly sized jet aircraft, but typically for at most a few minutes of powered operation, followed by a gliding flight. Unhindered by the need for oxygen from the atmosphere, they are suitable for very high-altitude flight. They are also capable of delivering much higher acceleration and shorter takeoffs. Many rocket aircraft may be drop launched from transport planes, as take-off from ground may leave them with insufficient time to reach high altitudes.
Rockets have been used simply to assist the main propulsion in the form of jet assisted take off (JATO) also known as rocket-assisted takeoff (RATOorRATOG). Not all rocket planes are of the conventional takeoff like "normal" aircraft. Some types have been air-launched from another plane, while other types have taken off vertically – nose in the air and tail to the ground ("tail-sitters"). (Full article...)
Image 3Rocket vehicle mechanical efficiency as a function of vehicle instantaneous speed divided by effective exhaust speed. These percentages need to be multiplied by internal engine efficiency to get overall efficiency. (from Rocket engine)
Image 17Robert Goddard and the first liquid-fueled rocket. (from History of rockets)
Image 18The four expansion regimes of a de Laval nozzle:• under-expanded• perfectly expanded• over-expanded• grossly over-expanded (from Rocket engine)
Image 19A "long serpent enemy breaking" fire arrow launcher as depicted in the Wubei Zhi (17th century). It carries 32 medium small poisoned rockets and comes with a sling to carry on the back. (from History of rockets)
Image 21An illustration of fire arrow launchers as depicted in the Wubei Zhi (17th century). The launcher is constructed using basketry. (from History of rockets)
Image 24Rocket thrust is caused by pressures acting in the combustion chamber and nozzle. From Newton's third law, equal and opposite pressures act on the exhaust, and this accelerates it to high speeds. (from Rocket engine)
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