There’s also a U.S. patent that describes subjecting AP with a higher than
normal moisture content to vacuum and heat using at higher than normal drying
parameters. This results in extensive micro-fracturing of the particles. The
burn rate increases but other ballistic characteristics can as well. The
repeatability of the practice is suspect.
A few years ago, there was a Delta failure shortly after launch. The burning
propellant chunks from the GEM solid boosters left much larger impact craters
than were expected when they hit the ground. This led the investigators to
suspect localized DDT upon impact. Shortly thereafter, the DoD began seeking
wide area gap testing on all solid rocket motors over 6” in diameter as I
recall. The DOT declined claiming the DoD did not have jurisdiction.
On a side note, I once examined a particle of AP in a scanning electron
microscope without any sputter coating and at a fairly high acceleration
voltage. When I zoomed in, the electron beam bored an almost perfectly square
hole through the particle!
Best.
Anthony J. Cesaroni
President/CEO
Cesaroni Technology/Cesaroni Aerospace
<http://www.cesaronitech.com/> http://www.cesaronitech.com/
(941) 360-3100 x101 Sarasota
(905) 887-2370 x222 Toronto
From: arocket-bounce@xxxxxxxxxxxxx [mailto:arocket-bounce@xxxxxxxxxxxxx] On
Behalf Of James Padfield
Sent: Thursday, July 23, 2015 8:59 AM
To: arocket@xxxxxxxxxxxxx
Subject: [AR] Re: PEPCON AP explosion report
Peter, that sounds like it could be an interesting student project...
Investigate the shock sensitivity and critical diameter of "pristine" AP
crystals, and then heat treat them to produce the strange porous crystals we
are talking about. What do you think? I still have a good relationship with
my previous employer, perhaps we could come up with a plan, I can contact them
and we could do some research into the matter.
On 23 July 2015 at 13:55, Peter Fairbrother <zenadsl6186@xxxxxxxxx
<mailto:zenadsl6186@xxxxxxxxx> > wrote:
On 23/07/15 11:39, James Padfield wrote:
Peter: I helped with a student project a couple of years ago at the
university I was working at. She was examining baking AP (I don't
recall the initial particle size) at fairly high temperatures (200,
maybe 220 degC) to alter the particle porosity. As you say, some mass
is lost, 30% sounds about right, and the resulting particles are no
longer regular crystals, but porous. She took some nice Scanning
Electron Microscope photos of the particles. She then formulated them
(IIRC) with PVC/DOA binder system (easier than mucking about with a
curable HTPB/IPDI system). Don't recall how far she progressed with the
project, I don't believe it got as far as measuring burnrates...
James: What I'd really like to know is how the detonatability changes. The
product has submicron particles, which would be easy to detonate if they were
normal crystals - but they aren't, and I don't know what happens.
IMO this could be very significant, for AP in fires ..
John: Thinking again about AP flowing. while it does not melt in bulk, it may
flow as a bulk powder in some circumstances. If it is for instance on top of
and reacting with tarmac or polythene, the reaction will produce lots of gas,
at a prodigious rate.
This effusion of gas may be fast enough to fluidise any overlying AP powder,
which would then flow almost like a liquid.
-- Peter Fairbrother
