[AR] Re: APCP properties, was Re: Re: starship abort?

  • From: Hagen Hübner <hagen.huebner@xxxxxx>
  • To: arocket@xxxxxxxxxxxxx
  • Date: Fri, 28 Apr 2023 15:07:08 +0000



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

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