Wedge:
The erosive burning characterizations in the article were for some composite
solid propellants, and for the Deville D8 AP-HTPB propellant. For the Deville
D8 propellant, it is a "typical" AP-HTPB propellant, and thus a typical
hardness.
If your propellant was particularly hard or soft, the erosive burning results
would be different.
Note on Figure 3 from the technical article (velocity based erosive burning)
and Figure 5 (mass flux based erosive burning), that for the different
composite solid propellants, while there is variation in the velocity based and
mass flux based erosive burning, there are some good design rules that can be
ascertained from the data, which the Deville D8 propellant also matched. Which
was the intent of the technical article, Erosive Burning Design Criteria.
If you have a non-representative really hard or really soft propellant, you'll
need specific erosive burning characterization tests.
Charles E. (Chuck) Rogers
CRogers168@xxxxxxx
-----Original Message-----
From: Wedge Oldham <wedgeoldham@xxxxxxxxx>
To: arocket <arocket@xxxxxxxxxxxxx>
Sent: Sat, Apr 15, 2017 4:39 pm
Subject: [AR] Re: Erosive burning rule of thumb?
How does grain hardness effect erosiveness? To minimize would we lean towards
harder or more pliable?
Sent from my iPhone
On Apr 12, 2017, at 3:46 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
