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Rocket Engines

Rocket Engines. Performance Energy Safety Simplicity Expanding Gases Thrust Termination Restart. Liquid Propellant Mono propellant Catalysts Bi-propellant Solid Propellant Grain Patterns Hybrid Nuclear Electric. Rocket Propulsion. Liquid Rocket Engine. Propellants. Oxidizer.

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Rocket Engines

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  1. Rocket Engines Performance Energy Safety Simplicity Expanding Gases Thrust Termination Restart • Liquid Propellant • Mono propellant • Catalysts • Bi-propellant • Solid Propellant • Grain Patterns • Hybrid • Nuclear • Electric

  2. Rocket Propulsion Liquid Rocket Engine Propellants Oxidizer Fuel Combustion Chamber Throat Nozzle

  3. Newton’s Laws F F • m = a = a m The force required to accelerate a body is proportional to the product of the mass of the body and the acceleration desired. F = ma

  4. Rocket Thrust Total Thrust = Momentum Thrust + Pressure Thrust Propellant Mass Flow times Velocity Nozzle Area times pressure differential . W Ve F = + Ae ( Pe - Pa) g • 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).

  5. Exhaust Plumes and Nozzles Pexhaust < Pambient Pexhaust = Pambient Pexhaust > Pambient Ideal Expansion Under Expanded Over Expanded

  6. Expansion Ratio Ae x = At • Ratio of the nozzle exit area divided by the area at the nozzle throat. Throat Exit

  7. Specific Impulse F . W • 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 Isp =

  8. Mass Ratio of a Vehicle mi mf MR = Mass Ratio is the ratio between the booster mass before the rocket engine burn divided by the booster mass after rocket engine burn. The Mass Ratio for a multistage rocket is the product of the Mass Ratios of all the stages, i.e. MROver All = MR1 x MR2 x MR3 x …x MRn

  9. Thrust-to-Weight Ratio F W Thrust Vehicle Weight = Y = • Measure of booster or stage design and manufacturing technology. • The higher the thrust-to-weight ratio the faster the vehicle will accelerate • The initial acceleration of a vehicle in “g’s” equals a = ( Y - 1 )

  10. Ideal Rocket Equation • The ideal velocity change ( DV ) for each stage of a rocket is a function of the mass ratio ( MR) of the stage and the specific impulse ( Isp ) of the rocket • Ideal means you do not consider gravity changes, drag, or rotating Earth DVi = Ispx g x ln MR

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