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Imagine I have a combustion chamber with a nozzle. There is a high pressure oxygen bottle and a high pressure gaseous fuel bottle connected to the chamber. Would the fuel efficiency be lower if I performed combustion in a series of many very short burns than if I emptied the tanks in one go? Since at the end of any burn there's a period where pressure decreases, I imagine that the total impulse of the engine will be lower for the intermittent combustion since it will go through many of these periods instead of just one, leading to increased fuel consumption.

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    $\begingroup$ In many systems, including electrical, intermittent power delivery yealds better performance. You really should test your theory, taking care of thrusting after the air decompression period. But at the same time we ask: why NASA doesn't do that ? $\endgroup$ – Lucas BS Dec 4 '19 at 16:24
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    $\begingroup$ If your choice is between intermittent pulses and running the engine at reduced fuel/oxidizer feed, the pulses will be better because the lower pressure will be only at ignition / flameout, not during the stable combustion period. Tere's a reason why RCS works with pulses, and Falcon 9 runs on 3 out of its 9 engines during the hover-slam. Pulsing reduces efficiency less than deep throttling. $\endgroup$ – SF. May 3 '20 at 9:34
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The built-up to momentum in the mass of gas flowing out of the nuzzle and building the design exit Mach and stability of the combustion is better left alone from the disruption of on-off cycles.

Avoiding flame blow out in the combustion chamber and continuity in vector thrust navigation lend better to long bursts.

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