[AR] Re: electric pumps (was Re: piston pumps and...)
- From: Henry Spencer <hspencer@xxxxxxxxxxxxx>
- To: Arocket List <arocket@xxxxxxxxxxxxx>
- Date: Sun, 9 Apr 2023 00:47:03 -0400 (EDT)
On Sat, 8 Apr 2023, Matthew JL wrote:
I think there’s an evolutionary pathway you’ve missed though - using an
expander cycle to drive a dynamo that, in turn, directly powers electric
turbopumps. On paper, this would help decouple the powerhead from the
rest of the engine in the same way battery-driven turbos would...
Well, no, not quite -- there's still a feedback loop there, although it's
probably easier to control with part of the loop closed electrically.
There's still potential for irregularities in the pump to feed back into
the turbine and thence back to the pump, causing runaway or oscillations.
*Not* powering the pump with the fuel it pumps is what breaks that loop.
(If you don't exercise that option for control, this is basically just a
fancy way of putting a gearbox between turbine and pump, and you'd have to
trade it against a real gearbox to decide whether it was worth the
trouble. Rocket-pump gearboxes have been out of fashion, at least in the
West, for a long time, but there are still plenty of them in legacy
systems, e.g. the RL10.)
Henry
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