[AR] Re: P&W GTF
- From: Henry Spencer <hspencer@xxxxxxxxxxxxx>
- To: Arocket List <arocket@xxxxxxxxxxxxx>
- Date: Sat, 4 Apr 2020 01:20:53 -0400 (EDT)
On Fri, 3 Apr 2020, ken mason wrote:
I would love to see a scaling analysis of modern electric driven pumps
and where their advantage is lost to GG cycle,kind of like the expander
cycle is ~ 20KLbF,i.e. the RL-10...
Not everybody thinks the expander cycle poops out at 20klbf -- P&W's bid
for the J-2 (200klbf) was an expander, as was a much later proposal for a
600klbf engine. It's not a well-explored part of the design space.
As for the electrics, note that Rocketlab found it important to jettison
spent batteries from the second stage. The need for that added complexity
suggests that straightforward electric isn't currently performing as well
as GG even at Electron size. The advantage is simpler hardware and easier
development. (Which is to say, an analysis showing that advantage would
be economic more than technical, and would have to make a bunch of
debatable assumptions.)
That said, even a purely technical scaling analysis of electric pumps
definitely *would* be interesting reading.
Henry
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