[AR] Re: Pogo Accumulator Assembly
- From: "John Dom" <johndom@xxxxxxxxx>
- To: <arocket@xxxxxxxxxxxxx>
- Date: Fri, 15 Dec 2017 18:09:12 +0100
Well put Noman. Thanks.
John
-----Original Message-----
From: arocket-bounce@xxxxxxxxxxxxx [mailto:arocket-bounce@xxxxxxxxxxxxx] On ;
Behalf Of Norman Yarvin
Sent: vrijdag 15 december 2017 17:42
To: arocket@xxxxxxxxxxxxx
Subject: [AR] Re: Pogo Accumulator Assembly
On Fri, Dec 15, 2017 at 11:11:35AM +0100, Uwe Klein wrote:
Am 14.12.2017 um 23:30 schrieb William Claybaugh:
Brian:
Pogo is a system level interaction between thrust variation and the
vehicle structure; to the extent that your systems has thrust
pulsation--from whatever source--pogo is a possibility.
so the solution is to somehow reduce thrust on short term increase of
acceleration? "fluid High pass filter" ??
I think the idea is that pogo arises from rocket acceleration producing
increased pressure at the pump inlet. In big rockets, one has a long column of
fluid, which yields a proportionately large pressure increase from
acceleration. This pressure increase translates to increased pressure at the
pump outlet, which translates to more thrust. By itself, this would just be a
mechanism for runaway, but the control system senses it and reduces thrust;
thus it becomes an oscillation.
Of course this explanation makes it sound like instead of adding an extra
device to stop pogo one could put more cleverness into the design of the
control system.
This particular anti-pogo device is described as an "accumulator", which I
think is something like the anti-water-hammer devices one puts on home water
pipes: it has a gas-pressurized volume into which the fluid can move when its
pressure increases. It's more of a low-pass filter than a high-pass one.
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