Now for the rocket engine. I'm having a tough time with this and I must admit that I intuitively think that for vehicles propelled by ejected mass, rather than a driven member that is coupled to a stationary medium like the ground or air, or water, that the speed that is valid for the calculation of Force to the frame of reference of the passenger, is the speed difference between the gases and the nozzle. Which might simply indicate that the term constant Power doesn't apply to such engines which will have fairly constant force at the nozzle. I'm having a hard time finding anything to contradict this. I was hoping to find some model rocketry pages with measured thrust data to compare to the well documented bench testing of the various engines which could show if speed comes into play.
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ThrustCurve Hobby Rocket Motor Data
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The efficiency of a rocket engine changes, starting at near 0% on lift off because the only thing moving is the ejected matter. And increases to the best efficiency when the speed of the exhaust gas referenced to the nozzle is equal and opposite to the speed of the rocket referenced to the Inertial Frame of Reference. The rocket is flying away from the ejected mass at mach 10 or whatever and leaving the mass which is exiting the nozzle at mach 10, essentially motionless in space behind it. And a rocket engine can continue to supply force to a vehicle that is traveling faster than the exhaust speed at the nozzle. But with decreasing efficiency as now the exhaust will have speed and momentum of it's own left over and in the same direction as the vehicle.
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Rocket engine - Wikipedia, the free encyclopedia
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Rocket - Wikipedia, the free encyclopedia