10-12-2012, 02:00 PM
Rocket Engines
Rocket Engines.ppt (Size: 209 KB / Downloads: 59)
Rocket Thrust
Thrust is produced by the expanding propellants.
There is thrust from the difference between the ambient pressure and that of the exhaust gases at the nozzle exit (Pressure Thrust) and from the momentum of the propellants (Momentum Thrust).
Specific Impulse
A measure of the energy in the propellants and of the efficiency of the rocket engine design
Specific Impulse is the ratio of the Thrust (Force) produced divided by the weight rate flow of propellants
Rocket Propellants
Rocket propellant is material that is stored in some form of propellant tank, prior to being used as the propulsive mass that is ejected from a rocket engine in the form of a fluid jet to produce thrust. A fuel propellant is often burned with an oxidizer propellant to produce large volumes of very hot gas which in turn expand and push on a nozzle, which accelerates them until they rush out of the back of the rocket at extremely high speed, making thrust. Chemical propellantsThere are solid, liquid, and hybrid:1)Solid propellants:Solid propellants consist of an oxidizer and a fuel.the standard high-energy solid rocket fuel, Ammonium Perchlorate Composite Propellant (APCP) which is primarily ammonium perchlorate powder as oxidizer, combined with fine aluminium powder as fuel. The mixture is formed as a liquid cast into solid.2)Liquid propellants:-LOX and kerosene: is widely regarded as the most practical for civilian orbital launchers.-LOX and liquid hydrogen, used in the Space Shuttle-Nitrogen tetroxide (N2O4) and hydrazine (N2H4), MMH, or UDMH-Monopropellants such as hydrogen peroxide, hydrazine and nitrous oxide3)Hybrid propellantsA hybrid rocket usually has a solid fuel and a liquid or gas oxidizer. The fluid oxidizer can make it possible to throttle and restart the motor just like a liquid fuelled rocket. Because just one propellant is a fluid, hybrids are simpler than liquid rockets.