Yeah, PVC fails in a brittle manner, without much warning as I understand
it (no leak before burst--it just lets go and sharp pieces fly everywhere).
Obviously it can be used for pressure systems (e.g. sprinkler systems,
etc.) but with large safety factors. That makes it less than ideal for
flight hardware by itself. But if you fiber-overwrap it, it could work.
I've made some KNSU and hybrid motor grains with thin-walled PVC wrapped
with strapping tape (the kind with fibers) and they work great.
And without any credible evidence that nitrogen dissolves rapidly in
nitrous, I still recommend it. Also, compressing the liquid nitrous with
nitrogen also helps suppress cavitation/bubble formation in the plumbing
per Monroe's concerns
On Tue, Jan 9, 2018 at 8:49 AM, <snyder@xxxxxxxxxx> wrote:
I think this is a really bad idea,
"Back-in-the-day" of several projects with N2O monopropellants
we once used a 'Clear PVC" tank to observe mixing.
Now, I don't believe "clear pvc" is PVC, but schedule 80 was
close enough in pressure rating to hold room temp N2O.
For a while.
It would spontaneously burst after about 90 min.... about!
It wasn't really dangerous, since it was well contained in a
concrete test cell, and the event was expected. The rebuild
time was trivially short, so testing was performed daily.
As it turned out, the test firings generally were much more
catastrophic, and sooner, than the tank bursts, so the
program was not effected. The system rarely lasted the full
90 minutes.
I was still against it on principle.
There were some interesting results, but 'The Great One' would never
allow any intelligent concepts in his lab.
-Gar.
From: "xtatrax1" <xtatrax1@xxxxxxxxx>
Subject: [AR] AW: Re: Lightweight LN2O tank
Date: Mon, 8 Jan 2018 08:58:19 +0100
Just found out that DARE is using PVC for their N2O hybrid
(http://dare.tudelft.nl/2016/06/stratos-iii-composite-tank-prototype/) .
Haven’t seen any tests of it though…
I’m actually surprised that a well-funded student group is using
“fuel” inside an oxidizer tank…
Michael
