[AR] Re: Orions and PDEs (was Re: More MAX delays.)
- From: Jim Davis <jimdavis2@xxxxxxxxxxxxx>
- To: arocket@xxxxxxxxxxxxx
- Date: Thu, 30 Jan 2020 16:00:08 -0600 (GMT-06:00)
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.
Again, constant volume heat addition is extremely challenging which is why we
don't see rocket engines exploiting it. But the thermodynamic advantage is
still there if the difficulties can ever be overcome.
Jim Davis
Other related posts:
