If what you say is true then you are stating that the jet exhaust propels you forward and not the pressure differential between the forward wall of the combustor can and the lower pressure due to mass acceleration. If you had a means of generating gas pressure separate from the nozzle and introduced that pressure the gas would be expelled from the nozzle and the reaction would move the nozzle forward. That is how a pneumatic tip jet helicopter works. The gas pressure inside the engine drives a compressor and the compressed air drives the blade forward. I think there was some Greek or Roman by the name of Hero that demonstrated this theory. Werner Von Braun and later on a company called Rocketdyne adapted this principle and sent men to the moon (assuming you believe that). I think Mr. Newton said that for every action there is an equal and opposite reaction. In this case, the expelling of the gas from the combustor creates this differential and it is the force imbalance between the forward wall of the containing vessel and the exit nozzle. The faster you can expel the gas the greater the pressure drop at the nozzle which increases the differential. Since the containing vessel is attached to the conveyance it propels, the conveyence is moved.
I saw on another posting on this thread and it had as picture of a jet engine
with the pressure levels at different points in the engine. If I remember correctly, the internal pressure peak in the combuster was 250 PSIA. As I said previously the internal pressure in an Atlas rocket engine was 600 PSIA and that created 150,000 pounds of thrust. Efficiency in a rocket engine is measured by dividing the thrust by the amount of fuel and oxidizer that is pumped into the engine. It is refered to as ISP or Specific Impulse. If you are right, then Von Braun, Rocketdyne and all of the other rocket scientists are wrong.
Here is a point I should have brought out earlier in this posting. Are you familiar with a pulse jet. If you are old enough you would remember that they did a lot of damage in the UK and parts of Europe. These jets are started up on the ground. Just before start up, you could look through the engine from front to back with minimal restriction. However once the combustion pressure builds louvers at the front of the engine are closed due to the increase of pressure. Under full combustion the pressure builds and the gas is ejected rearward and the the V 1 is shot off a ramp at a very high cyclical rate the internal pressure drops and the louvers open letting in ram air at a fairly high pressure. Ignition takes place and the louvers close allowing the pressure level to raise again propelling the rocket forward. If the louvers did not create a forward wall to allow pressure build up the rocket would have fallen into the water or, not even started. It is that forward wall that takes the reactive force and transfers it to the airframe structure. A more simple system is the ram jet which has no moving parts. However it is the ram effect that creates the forward wall just like the pulse jet louvers. Only in this case the propulsive force is much greater as is the speed of the rocket.
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The Cat
[This message has been edited by Lu Zuckerman (edited 28 October 2000).]
[This message has been edited by Lu Zuckerman (edited 28 October 2000).]