[AR] electric pumps (was Re: piston pumps and...)
- From: Henry Spencer <hspencer@xxxxxxxxxxxxx>
- To: Arocket List <arocket@xxxxxxxxxxxxx>
- Date: Sun, 9 Apr 2023 00:35:23 -0400 (EDT)
On Sat, 8 Apr 2023, Ben Brockert wrote:
It will take some time because deep space programs are extremely
conservative, but eventually electric pumps will gain a lot of
traction there.
Jordin Kare tried to sell the Pluto Fast Flyby (as it was then) folks on
the LLNL piston pumps, unsuccessfully. Of course, that mission didn't
need much spacecraft delta-V, so the incentive was limited.
As I think I noted before, Capstone is in lunar NRHO with a gear-pump
hydrazine-monoprop system from <
https://www.stellar-exploration.com/>;
that may help break the ice for the idea. (By the sounds of it, part of
the motivation there was the belief that people would be more comfortable
with hazardous propellants in a system built by a small semi-startup if
the tank(s) *weren't* at high pressure for launch.) There were some
difficulties, including in propulsion, along the way but they made it.
<
https://spaceref.com/space-commerce/flight-works-pump-powers-the-nasa-capstone-propulsion-module-towards-the-moon/>
<
https://www.flightworksinc.com/>
Capstone was originally *meant* to have a peroxide propulsion system (not
clear whether that was monoprop or biprop), but it didn't end up fitting
in the mass constraints -- turned out the technology wasn't as mature as
its (unnamed) supplier had claimed.
In missions like moon landers where you have a few large burns that are
separated in time, electric pumped main propulsion that is recharged by
solar is much higher performance than big pressure-fed tanks.
Provided that the battery is big enough and the recharge time long enough,
which can be problematic for some missions. E.g., for a lunar lander,
once perilune altitude goes negative, there just isn't anywhere you can
hit "pause" :-) until touchdown.
(I ran into something like this myself not long ago -- different mission,
and the limit on burn length was for a different reason, but it took some
head-scratching to decide whether that propulsion system could actually be
made to work for that mission. An awkward constraint. I will say that
this propulsion supplier was basically honest about it: if you read the
datasheet carefully, you'd hit a number which said there was a limitation
of some sort there, although I had to talk to the supplier to find out how
bad it was.)
Henry
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