Rehology is very important in solid propellant processing. Propellant
chemists spend a lot of time developing processable formulations. While fine
particulate size materials can reduce mix viscosity, too much can have the
opposite effect. Also too fine of a size can produce unprocessable propellants
as evidenced by the use of nano-aluminum powders. As particle size decreases
surface area increases making for thick, viscous mixes.Barry
I learned this from Ray Goodson when he used to use a helical vacuum mixer. Whe
dropping the bowl after the course AP was mixed the propellant was like peanut
butter stuck to the mixer blades. Seemingly counterintuitively he then added
the fines and after a brief mixing he dropped the bowl again and the propellant
just ran off of the mixing helix. I forever learned an important lesson in
particle distribution physics.
Vacuum mixing is important too for the best physical properties with the
highest solids loading.
Ken
On Sat, Apr 29, 2023 at 7:02 AM Terry McCreary <prfesser@xxxxxxxxxxx> wrote:
It did. In one batch I used 200 um AP that had caked and needed to be rubbed
through a screen. The resulting mixture should have been fairly stiff, for
packing. The fines created by rubbing made the mix more like peanut butter;
sticky and hard to pack. Got it packed but the fines also increased the burn
rate significantly, with a rather high peak in the test runs.
From: arocket-bounce@xxxxxxxxxxxxx <arocket-bounce@xxxxxxxxxxxxx> on behalf of
roxanna pprMason <rocketmaster.ken@xxxxxxxxx>
Sent: Friday, April 28, 2023 9:39 produce
To: arocket@xxxxxxxxxxxxx <arocket@xxxxxxxxxxxxx>
Subject: [AR] Re: APCP properties, was Re: Re: starship abort?d size A little
fines really makes a difference in viscosity, as I discovered to my dismay.
Tests did not go well.than than aborate?The right size and amount of fines
should have lowered the viscosity like puttingt BB's in a jar full of golf
balls and marbles. It will displace the binder out of the voids into the rest
of the mix matrix.
Ken
On Fri, Apr 28, 2023 at 4:57 PM Terry McCreary <prfesser@xxxxxxxxxxx> wrote:
The sizes that seem to be available to amateurs are 400, 200, and 90 um. A
little fines really makes a difference in viscosity, as I discovered to my
dismay. Tests did not go well.
From:arocket-bounce@xxxxxxxxxxxxx <arocket-bounce@xxxxxxxxxxxxx> on behalf of
roxanna Mason <rocketmaster.ken@xxxxxxxxx>
Sent: Friday, April 28, 2023 1:40 PM
To: arocket@xxxxxxxxxxxxx <arocket@xxxxxxxxxxxxx>
Subject: [AR] Re: APCP properties, was Re: Re: starship abort? They don't say
what the AP size was, just "coarse" and "fine", but the professionals usually
consider fines to be on the order of 10 micron or less,
Isn't 20-25u considered an explosive ass far as DOT? The finest sold on FireFox
is or at least was 90u.At Edwards we used a trimodal mix containing 200/90/25u.
Ken
On Fri, Apr 28, 2023 at 8:51 AM Terry McCreary <prfesser@xxxxxxxxxxx> wrote:
Thank you, Hagen. That kind of work is something I'd avoid with extreme
prejudice. They don't say what the AP size was, just "coarse" and "fine", but
the professionals usually consider fines to be on the order of 10 micron or
less, often purchased as a suspension in HTPB to avoid the researchers having
to handle such fine material. Coarse might be 200 micron or it could be finer
than that. And they do mention the fracture of AP as being a possible reason
for some of the behavior.
Reproducibility was a concern of the authors. Three runs with an 8.8mm nozzle
throat gave peak pressures from about 270 to 325 kg/cm^2. Not good.
An exponent of 0.845, and dramatic changes in burn rate with 0.1mm (0.004" for
us 'muricans) changes in the nozzle throat diameter...and one of the references
mentions studies that showed an exponent of 1.05.....oh no, no thank you. I
already know a number of ways to dismember this body, I don't need any more. 🙂
Terry
From:arocket-bounce@xxxxxxxxxxxxx <arocket-bounce@xxxxxxxxxxxxx> on behalf of
Hagen Hübner <hagen.huebner@xxxxxx>
Sent: Friday, April 28, 2023 10:07 AM
To: arocket@xxxxxxxxxxxxx <arocket@xxxxxxxxxxxxx>
Subject: [AR] Re: APCP properties, was Re: Re: starship abort?
Terry, speaking of the library... work was done up to 15000 psi - with
interesting results:
https://www.eucass.eu/component/docindexer/?task=download&id=4434 (notice:
1kg/cm^2 = 0,981 bar = 14,2 psi)
Hagen
------ Originalnachricht ------Von "Terry McCreary" <prfesser@xxxxxxxxxxx>An
"arocket@xxxxxxxxxxxxx" <arocket@xxxxxxxxxxxxx>Datum 28.04.2023 14:32:41Betreff
[AR] Re: APCP properties, was Re: Re: starship abort?
Kevin, I apologize for my earlier post. It was snide and uncalled for.
Now, to address your question: Aerotech has/had, somewhere on the web,
properties of their propellants. Some of them were extremely high performance,
highly aluminized mixes intended for commercial/military use. You might check
the propellant "sticks" they sell on rocketmotorparts.com, see if properties
are described there. However...
From earlier posts it sounds as though you want to work at extremely high
pressures, ten to thirty times those normally used in APCP motors. The
coefficient, exponent, etc. around 1000 psi is surely going to be very
different from those values at 30,000 psi. There may be some plateau burning or
some regions where the exponent decreases (ok) or jumps dramatically (very
bad), I don't know.
Moreover, there is a well-known problem with propellants containing a large
amount of 400 micron AP. Apparently at pressures around (I think) 1000psi or a
bit higher, the 400 micron can crack, exposing more surface area and leading to
a rapid unscheduled disassembly. I hypothesize that the same thing would occur
to 200 micron (which makes up most of the usual APCP) and even 90 micron, which
is as fine as the amateur can obtain without grinding, at the kind of pressures
you're considering. There's also the issue of the binder; that which works well
at 1000 psi is unlikely to be satisfactory at 10-30 times that pressure.
There's an old tongue-in-cheek saying that my own research students have heard:
Six months in the laboratory will save you six hours in the library. I don't
know whether the professionals have done work with APCP at very high
pressures...but before attempting such work it would be wise to find out what
has already been done, and with what kind of success. Unfortunately such work
may be behind a paywall; that's how most professional journals do it these days.
Before expending a single dollar or hour on propellant/motor making it would be
wise to find out if the kind of work you're considering is even possible. There
is some reason to think that it may not be.
From: arocket-bounce@xxxxxxxxxxxxx <arocket-bounce@xxxxxxxxxxxxx> on behalf of
kevin ward <kevinward46@xxxxxxxxx>
Sent: Thursday, April 27, 2023 11:17 PM
To: arocket@xxxxxxxxxxxxx <arocket@xxxxxxxxxxxxx>
Subject: [AR] Re: APCP properties, was Re: Re: starship abort? Ap\htpb\+al
(294isp, 70\13\12 ?)
I'm asking for any and all stats re open rocket
Ty kindly