Critical diameter is the minimum diameter of pseudoinfinite cylinder of
material that will propagate a supersonic detonation wave in that material.
Good questions were asked about what distance at that diameter a wave will run
before it fails, if a detonation wave can go through a "solid" component etc.
short answers: 'it depends' on distance, and most assuredly yes for going
through a solid buffer. Some materials less so (steel undergoes a phase
transition and tends to absorb shockwaves, but aluminum propagates them some
distance, as does brass).
The distance depends on confinement - the heavier the walls the longer the
distance, and that also affects critical diameter as heavier walls confine the
reaction more efficiently.
You have to look at reacting explosive and confinement specific test series to
see what the specifics are for your case. Don't use aluminum tube numbers and
assume they're safe with stainless, etc.
As a rule, once you have an actual detonation wave, from the rocketry
perspective you lost the game. You may need to contain the damage and now blow
the whole tank, and may or may not succeed at preventing that from happening.
But you're just looking at managing disassembly promptness...
George William Herbert
Sent from my iPhone
On Dec 4, 2015, at 9:44 AM, Paul Mueller <paul.mueller.iii@xxxxxxxxx> wrote:
Yeah, I'm not familiar with the "critical diameter" and what it means that it
is about 1/4" for liquid nitrous oxide.
Paul M
On Thu, Dec 3, 2015 at 9:41 AM, <snyder@xxxxxxxxxx> wrote:
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Date: Wed, 2 Dec 2015 10:13:19 -0700
From: Ben Brockert <wikkit@xxxxxxxxx>
Date: Wed, 2 Dec 2015 16:00:21 -0500
Subject: [AR] Re: ALASA canceled because... Mixed Mono
I downloaded their 22mb catalog, their hardware is all gas phase. For
rocketry you want to know the critical diameter of the liquid. For
pure nitrous it's somewhere around a quarter of an inch, for
nitrous/fuel it's somewhere under a sixteenth. For mixed LOX/Methane I
expect it would also be very very small.
Can someone explain the Detonation Diameter a little better ?
We played this game, I distinctly remember using a desktop CNC to
peck drill 10 thousandths holes in a brass plug to try and muffle the
back prop with mixed N20. (looked like trying ot poke a hair through a
piece of metal). Temperature, Pressure, Flow ? Something seemed to
let it blow through. Can the detonation slam on one side of a
component and just start up on the other side ?
At the time, with one that worked once, the thought was that the
powder in the injector was absorbing and dissipating the energy, and
stopping the detonation, right there.
We ran out of time before we could do to much like ramping up the
engines in a slow and controlled manner hard-ish starts were
assumed.
I guess another question with Detonation Diameter is; How long does the
limited diameter section need to be to snuff it out ? D, 2*D, 10*D ?
-Gar.