I would not want someone who wrote this sort of review to use my
software.
https://www.reddit.com/r/rocketry/comments/12xbxct/burnsim_is_unreliable/
On Sat, Apr 29, 2023 at 8:16 AM kevin ward <kevinward46@xxxxxxxxx> wrote:
Which motor sim should i use, as this is serious stuff ???
On Fri, Apr 28, 2023, 11:51 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 14:32:41
Betreff [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