Anthony:
That certainly seems reasonable.
I have for years wondered why the 9” dart booster didn’t burn through: it
had eight grains an thus lots of opportunity.
In static test the motor case never got even hand warm which leaves me
thinking that any heating at the Bates grain joints must have been either
minimal or rapidly quenched by the aluminum mass.
Bill
On Thu, Feb 1, 2018 at 12:27 PM Anthony Cesaroni <acesaroni@xxxxxxxxxxx>
wrote:
That totally depends on the design. In a standard HPR type, cartridge
loaded Bates grain configuration, the grains are not sealed against each
other. That means there is a gas equalization path at the joint. At
ignition, you have hot gas flow at that location and the larger the motor,
the more of it there is. You will also get gas flow due to pressure
oscillation and a lot of it if it’s lousy propellant. Just because it
burns, doesn’t necessarily mean it’s propellant. Blast that directly
against the case and you risk a burn through.
Anthony J. Cesaroni
President/CEO
Cesaroni Technology/Cesaroni Aerospace
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 *William Claybaugh
*Sent:* Thursday, February 1, 2018 1:21 PM
*To:* arocket@xxxxxxxxxxxxx
*Subject:* [AR] Re: Phenolic regression rate
Anthony:
That makes sense but why then use liners to backup Bates grains? Just
belt and suspenders or is the ability of the motor wall to soak up heat
partly playing here? Does a thinner wall—or non aluminum—risk over
heating, thus requiring a liner that isn’t needed when the wall is
relatively thick aluminum and the burn time short?
Bill
On Thu, Feb 1, 2018 at 10:43 AM Anthony Cesaroni <acesaroni@xxxxxxxxxxx>
wrote:
Assuming a stable chamber pressure and minimum gas equalization path
between the grain inhibitors and insulation/case, the Bates grain joints
are generally considered a stagnation area. Heat soak notwithstanding.
Anthony J. Cesaroni
President/CEO
Cesaroni Technology/Cesaroni Aerospace
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 *William Claybaugh
*Sent:* Wednesday, January 31, 2018 6:51 PM
*To:* arocket@xxxxxxxxxxxxx
*Subject:* [AR] Re: Phenolic regression rate
Troy:
In theory, the joint of two adjacent BATES grains exposes the underlying
liner to the full duration of the burn; on that basis we might use the
liner thickness and burn time to deduce longevity.
However, Garboden didn’t use a liner on the 9” ballistic dart vehicle and
had no problem in five flights and three static tests (albeit w/ a 4.5
second burn) which leaves me thinking there may not be—in practice—any
significant heat leak at the joint between BATES grains.
So I dunno too.
Bill
On Wed, Jan 31, 2018 at 4:41 PM Troy Prideaux <troy@xxxxxxxxxxxxxxxxxxxxx>
wrote:
Bill, dunno. I’d be surprised if you needed that much wall. I’ve used
2-2.5mm wall for long(ish) burn (~7sec) larger motors and they held up fine
although they were BATES grains so… dunno
Troy
*From:* arocket-bounce@xxxxxxxxxxxxx [mailto:arocket-bounce@xxxxxxxxxxxxx]
*On Behalf Of *William Claybaugh
*Sent:* Thursday, 1 February 2018 10:16 AM
*To:* arocket@xxxxxxxxxxxxx
*Subject:* [AR] Re: Phenolic regression rate
Troy:
Let me add that given 0.8 mm and a (conservative) 1.2 second burn, it
follows that this liner was good for about 0.66 mm per second, implying a
need for 6.66 mm for a 10 second burn.
With enough similar data it will be possible to estimate a number, with
variance, that at the low end allows for a (probably) safe flight.
Bill
On Wed, Jan 31, 2018 at 4:05 PM William Claybaugh <wclaybaugh2@xxxxxxxxx>
wrote:
Troy:
Thanks, that’s very useful.
Bill
On Wed, Jan 31, 2018 at 3:54 PM Troy Prideaux <troy@xxxxxxxxxxxxxxxxxxxxx>
wrote:
Okay, I wasn’t sure if it was for a liner or nozzle or whatever, but
rereading, it’s obvious it’s for a liner. Okay, many moons ago I developed
a 29mm reloadable solid that was specially designed for maximum performance
(230s Isp @ ground level). Propellant was 75% AP, 7.2% metals, 17.8%
organics and chamber pressure was generally run between 750-1000 Psi. I
utilised a paper phenolic liner for the casing that measured ~25.4mm OD x
~0.8mm wall. Propellant grain was a C-Slot (ie. one side of the liner
exposed to the total burn duration). Burn time was generally between 1.2 –
1.6 secs.
I was also trying to make the system with motor recovery which turned
out to be problematic due to the combination of the pressures involved and
the paper-phenolic tube I was using for the tracking smoke column. This
resulted in a lot of testing (about 200 static tests) to get the whole
thing nailed down.
Anyway, the liner was marginal – generally didn’t burn through, but was
right on the edge.
Troy
Troy
*From:* arocket-bounce@xxxxxxxxxxxxx [mailto:arocket-bounce@xxxxxxxxxxxxx]
*On Behalf Of *William Claybaugh
*Sent:* Thursday, 1 February 2018 9:28 AM
*To:* arocket@xxxxxxxxxxxxx
*Subject:* [AR] Re: Phenolic regression rate
Ignacio:
Hazel and Huang reference (page 382 of the 1992 AIAA edition) an emperical
equation for silica-phenolic exposed to NTO and hydrazine-like combustion
products.
I’m looking to develop a similar understanding for paper-phenolic and
solid propellant. I can do that if I get enough user experience as to what
did not burn through.
Bill
On Wed, Jan 31, 2018 at 3:13 PM ignacio belieres <
ignacio_belieres@xxxxxxxxxxx> wrote:
Bill,
I believe you can find something similar to what you are looking for in
huzel and huang. I implemented a version of the ablative model described
there and it seemed to give fairly reasonable results.
Cheers,
IB
-------- Original message --------
From: William Claybaugh <wclaybaugh2@xxxxxxxxx>
Date: 1/31/18 7:03 PM (GMT-03:00)
To: arocket@xxxxxxxxxxxxx
Subject: [AR] Re: Phenolic regression rate
Anthony:
I do understand the many variables; I’m just looking for user experience.
If I can get enough data on what doesn’t burn through I can estimate how
thick XX needs to be for the 10 seconds at which I’m looking.
Bill
On Wed, Jan 31, 2018 at 1:34 PM Anthony Cesaroni <acesaroni@xxxxxxxxxxx>
wrote:
Depends where in the motor, the grain geometry, the gas velocity and
conditions as well as the type of phenolic, the reinforcement used as and
any fire retardants added.
Anthony J. Cesaroni
President/CEO
Cesaroni Technology/Cesaroni Aerospace
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 *William Claybaugh
*Sent:* Wednesday, January 31, 2018 3:08 PM
*To:* arocket@xxxxxxxxxxxxx
*Subject:* [AR] Phenolic regression rate
Does anyone have any data on how long I can expect XX phenolic to survive
the conditions in a solid rocket motor?
Anecdotal data helps: if some part of the phenolic wall was fully exposed
to hot gas and was xx.xx inches or millimeters thick and did not fail;
that’s data. If it did fail, that is data too.
I’m adept at squeezing trends out of limited data but 20 or so usable data
points are sort of a minimum; I’m very happy to share any conclusions I may
reach.
Bill