Chuck:
I am using the port area / throat area greater than 1.36 criteria as well
as mass flow below 1.75 lbm/sec-sq. in. rule.
The issue is that I am working with a relatively complex core burning grain
that consists of a cylinder, a cone, and a finacyl where I could really use
a top-level rule of thumb to assist initial diameter and length assignment
for each section.
I have a design that meets the two criteria in each section and overall but
have little short of brut force to test whether it is the highest loading
that can be achieved w/o erosion. Will brut force the modeling if
necessary, but would love a rule of thumb that quickly eliminated designs
that are likely to erode.
Currently at 82% volumetric loading, btw.
Bill
On Wed, Apr 12, 2017 at 4:47 PM Redacted sender crogers168 for DMARC <
dmarc-noreply@xxxxxxxxxxxxx> wrote:
There's a technical article I authored on Erosive Burning Design Criteria
for Solid Rocket Motors which was published in High Power Rocketry Magazine
which can be downloaded from the RASAero web site from the Solid Rocket
Motor Technical Report Downloads page at:
http://www.rasaero.com/dl_solid_motor.htm
Scroll down to the bottom for the Erosive Burning Design Criteria for High
Power and Experimental/Amateur Solid Rocket Motors technical article.
There's a short technical summary available of the article, and the full
article for download.
The combined Core Mach Number/Core Mass Flux design criteria is what was
used to design the core of the 2004 CSXT GoFast rocket. The technical
article includes data for burn rate as a function of chamber pressure and
core mass flux for the Derek Deville D8 propellant which was used for the
2004 CSXT GoFast S motor. The core mass flux for the onset of erosive
burning can be seen in the D8 propellant burn rate experimental data.
Chuck Rogers
CRogers168@xxxxxxx
-----Original Message-----
From: William Claybaugh <wclaybaugh2@xxxxxxxxx>
To: arocket <arocket@xxxxxxxxxxxxx>
Sent: Wed, Apr 12, 2017 1:54 pm
Subject: [AR] Erosive burning rule of thumb?
Is there any experience-based rule for erosive burning in
cylinderical-type grains (Bates, Finocyl, etc.)? I am particularly looking
for experience as to how small the core diameter can be as a percentage of
grain diameter: 50% appears to assure no erosion at L/D of 10:1 or less,
what about 33%?
When does overall length begin to play? I know that around 15:1 will lead
to erosion with a 50% core diameter, for example. What is the "critical"
length at 33%? What about other core diameters?
Bill
