Same reason SpaceX subcools their RP and LOX, and why designing a
sugar rocket that starts in the erosive burning regime is worthwhile:
at some point the casing/tank size exists and is fixed. If you want to
maximize performance you cram all the propellant you can in there.
Eliminating voids in solids is its own reward since every bubble that
opens is a sudden change in surface area/ Kn.
On Thu, Jul 11, 2019 at 3:47 PM David Summers <dvidsum@xxxxxxxxx> wrote:
Hoping to take this on a learning tangent:
Why take all the effort to get a few percent higher density? I'd imagine that
it translates to less than 3% higher performance, so wouldn't a simpler
process with a few percent larger chamber be more optimal?
What am I missing? Or is it just a why not go for perfect kind of thing?
Thanks!
-David Summers
On Thu, Jul 11, 2019 at 12:41 PM Troy Prideaux <troy@xxxxxxxxxxxxxxxxxxxxx>
wrote:
If I vaguely recall (I could be mistaken) it was Mark Spiegl (?) who 1st
mentioned this process here about maybe 15 odd years ago. If I recall he was
utilising this process as an amateur and achieving some pretty good results.
Troy
From: arocket-bounce@xxxxxxxxxxxxx [mailto:arocket-bounce@xxxxxxxxxxxxx] On ;
Behalf Of Anthony Cesaroni
Sent: Friday, 12 July 2019 6:31 AM
To: arocket@xxxxxxxxxxxxx
Subject: [AR] Re: Vacuum processing of solid propellant
Not with traditional solid constituents and configurations and I’ll leave it
at that.
One technique that does have some merit is centrifugal casting. In this
example you have more energy at your disposal to consolidate the solid
loading in the absence of proper vacuum processing equipment. The propellant
mix is prepared and post degassed using vacuum, turnover and vibration as
usual. The prepared propellant is then transferred into the motor case or
casting tube with a cap on one end. The case is then closed with a cap on
the remaining open end and the whole affair is spun, longitudinally in a
spin fixture or a lathe equipped with explosion proof electrics (I’m sure).
The case is spun at moderate speed until the propellant cures.
After the propellant has cured, a section through the propellant will show
very high solid consolidation with a resin rich condition on the ID surface.
The next step is to use your explosion proof lathe to bore out the excess
resin on the ID and you will have an extraordinarily high solids loaded
propellant grain remaining. Some experimentation is required to optimize the
particle morphology and the speed should be optimized to produce the most
consolidation while minimizing the migration of the smaller diameter
particles.
To optimize the process further, one end of the case should be supported by
a roller steady and the dam on that end should have an opening to allow the
slow and well placed transfer of the propellant into the case while it’s
spinning instead of putting the whole mess in there at the beginning. This
actually works and you can achieve some impressive densities using this
method.
Anthony J. Cesaroni
President/CEO
Cesaroni Technology/Cesaroni Aerospace
http://www.cesaronitech.com/
(941) 360-3100 x101 Sarasota
(905) 887-2370 x222 Toronto
From: arocket-bounce@xxxxxxxxxxxxx <arocket-bounce@xxxxxxxxxxxxx> On Behalf
Of Edward Wranosky
Sent: Thursday, July 11, 2019 3:43 PM
To: arocket@xxxxxxxxxxxxx
Subject: [AR] Re: Vacuum processing of solid propellant
Is there any sort of VARTM like process for manufacturing propellant?
Edward
On Mon, Jul 8, 2019 at 8:39 AM William Claybaugh <wclaybaugh2@xxxxxxxxx>
wrote:
Uwe:
Yeah, as Anthony observed it is air trapped on the solids that produces the
problem.
The AP is tri-modal (200, 400, 600 micron) and mixed via a sieve on-site,
lots of opportunity for air to entrain in that process.
The Al is 5 micron and picks up air rather like a sponge. Wetting it and
degassing might help some but the subsequent final mixing w: the AP is going
to introduce air.
I’m thinking the strategy is going to be to post processing degas a set of
samples (5 minutes, 10, 15) and compare density gain per step. That should
offer a guess as to what can be achieved before the mix sets up.
Bill
On Mon, Jul 8, 2019 at 12:18 AM Uwe Klein <uwe@xxxxxxxxxxxxxxxxxxx> wrote:
Am 07.07.2019 um 19:59 schrieb William Claybaugh:
Uwe:
For safety we can’t mix the Al & AP together;
reminds me of the special 3 outlet can used for
chemically silvering mirrors back when. :-)
Hmm.
create separate airless pastes with each component as a first step?
Delayed wetting of solids always introduces air.
processing usually
proceeds by mixing the liquids (including catalyst), adding the aluminum
to the liquid mix w/ careful hand stirring), then folding into the AP
followed by final mixing.
Bill
On Sun, Jul 7, 2019 at 11:37 AM Uwe Klein <uwe@xxxxxxxxxxxxxxxxxxx
<mailto:uwe@xxxxxxxxxxxxxxxxxxx>> wrote:
Am 07.07.2019 um 18:39 schrieb William Claybaugh:
> Does degassing the liquid components before mixing help or does the
> subsequent mixing just reintroduce air?
Use mixing machinery where the mixing implements don't break the
surface. i.e. avoid "whipped cream" effects.
Any fine grained solids will need degassing after they
have been immersed in but not fully wetted by fluid components.
IMU no way around it.
Mix solids superficially, evacuate, add liquids on top.
return pressure to normal.
Then start mixing ( top mentioned prerequisites apply :-)
Uwe
