On Thu, Jan 30, 2020 at 04:00:08PM -0600, Jim Davis wrote:
But rockets don't spend nearly as much energy on compression as jet
engines do: they're pumping liquid, not gas, and that's much lower
volume. They also don't have the fan; if you were to extract
mechanical horsepower from a rocket engine, there'd be nothing to
spend it on that could boost thrust -- or at least nothing comparable
to leaving the energy in the combustion chamber and letting it boost
thrust that way.
You're completely missing the point. For a given amount of heat
addition the constant volume process has a higher pressure rise, a
higher temperature rise, and (most importantly) a lower entropy
increase. This means that more of the energy is available to
accelerate the fluid and less has to be rejected as heat.
