User:Milton Beychok/Sandbox: Difference between revisions
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Thrust is the [[force]] ('''''F''''') which moves a rocket through the air. Thrust is generated by the rocket engine through the reaction of [[acceleration|accelerating]] a mass of gas. The gas is accelerated to the the rear and the rocket is accelerated in the opposite direction. Force may be mathematically expressed as:<ref>[http://exploration.grc.nasa.gov/education/rocket/rktthsum.html Rocket Thrust Summary] from a website page of the [[National Aeronautics and Space Administration]] (NASA)</ref><ref>[http://exploration.grc.nasa.gov/education/rocket/specimp.html Specific Impulse] from a website page of the National Aeronautics and Space Administration (NASA)</ref> | Thrust is the [[force]] ('''''F''''') which moves a rocket through the air. Thrust is generated by the rocket engine through the reaction of [[acceleration|accelerating]] a mass of gas. The gas is accelerated to the the rear and the rocket is accelerated in the opposite direction. Force may be mathematically expressed as:<ref>[http://exploration.grc.nasa.gov/education/rocket/rktthsum.html Rocket Thrust Summary] from a website page of the [[National Aeronautics and Space Administration]] (NASA)</ref><ref>[http://exploration.grc.nasa.gov/education/rocket/specimp.html Specific Impulse] from a website page of the National Aeronautics and Space Administration (NASA)</ref> | ||
:<math>F = \dot {m} V_e + (p_e - P_o) | :<math>F = \dot {m} V_e + (p_e - P_o)A_e</math> | ||
and also this form, by defining a new term '''''v<sub>eq</sub>''''' : | and also this form, by defining a new term '''''v<sub>eq</sub>''''' : | ||
:<math>F = \dot {m} V_{eq} = \dot {m} \left [V_e + \frac {(p_e - P_o) | :<math>F = \dot {m} V_{eq} = \dot {m} \left [V_e + \frac {(p_e - P_o)A_e}{\dot {m}} \right ]</math> | ||
The total impulse of a rocket ( '''''I''''' ) is defined as the average thrust multiplied by the total time ( '''''t''''' ) of propellant burning: | The total impulse of a rocket ( '''''I''''' ) is defined as the average thrust multiplied by the total time ( '''''t''''' ) of propellant burning: | ||
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:where: | :where: | ||
:'''''F''''' = | :'''''F''''' = force in newtons, N | ||
:'''''ṁ'''''  = mass flow rate of exhaust gas, kg/s | |||
:'''''V<sub>e</sub>''''' = exhaust velocity at nozzle exit, m/s | |||
:'''''p<sub>e</sub>''''' = absolute pressure of exhaust gas at nozzle exit, Pa | |||
:'''''p<sub>o</sub>''''' = external ambient pressure, Pa | |||
:'''''A<sub>e</sub>''''' = cross-sectional area of nozzle exhaust exit, m² | |||
{{reflist}} | {{reflist}} |
Revision as of 19:40, 24 March 2010
Rocket thrust and specific impulse
Thrust is the force (F) which moves a rocket through the air. Thrust is generated by the rocket engine through the reaction of accelerating a mass of gas. The gas is accelerated to the the rear and the rocket is accelerated in the opposite direction. Force may be mathematically expressed as:[1][2]
and also this form, by defining a new term veq :
The total impulse of a rocket ( I ) is defined as the average thrust multiplied by the total time ( t ) of propellant burning:
The specific impulse ( Isp ) is the total impulse divided by the weight of the exhaust gas:
- where:
- F = force in newtons, N
- ṁ = mass flow rate of exhaust gas, kg/s
- Ve = exhaust velocity at nozzle exit, m/s
- pe = absolute pressure of exhaust gas at nozzle exit, Pa
- po = external ambient pressure, Pa
- Ae = cross-sectional area of nozzle exhaust exit, m²
- ↑ Rocket Thrust Summary from a website page of the National Aeronautics and Space Administration (NASA)
- ↑ Specific Impulse from a website page of the National Aeronautics and Space Administration (NASA)