Bill, fair enough. It sounds like a pretty tenuous chain of assumptions, but it
does shed light on the difference. I’m curious on how you arrived at the
assumption that the denser propellant would deliver a noticeable increase in
specific impulse? I can understand how that can occur in small motors where you
might expect noticeable deviations in pressure from varying surface area
exposure, but for a large motor?
Troy
From: arocket-bounce@xxxxxxxxxxxxx [mailto:arocket-bounce@xxxxxxxxxxxxx] On ;
Behalf Of William Claybaugh
Sent: Friday, 12 July 2019 10:14 AM
To: arocket@xxxxxxxxxxxxx
Subject: [AR] Re: Vacuum processing of solid propellant
Troy, David:
Let me be the first to agree that sims are just sims and reality awaits.
I too was surprised by the seemingly large change and have spent some time
trying to understand it:
First this is a two stage rocket and the effect of higher propellant fraction
is accordingly magnified in a way we don’t see in a single stage.
Second, the propellant is not just denser, it is also slightly higher
performance, a trajectory average of about four seconds for the first stage and
around seven seconds for the upper stage (which lights at around 40k feet and
burns out above 75k feet); this appears to be a significant second order effect.
Lastly, the propellant is slightly slower burning (because of fewer voids).
When optimized w/ my 2-DOF sim the longer burn in the first stage (10 seconds
instead of eight) produces a much lower MaxQ which—in the sim—produces a
notably higher burnout velocity and altitude.
When the coast between burns is adjusted (was 21 seconds, now 12) because of
the higher and faster booster burnout the upper stage gains almost a Mach
number in burnout velocity (was Mach 5.2, now 6.1).
Then it gets tricky: the upper stage violates the two-caliber rule above Mach
5.25. It looks like seven pounds of ballast behind the nose tip take care of
that but it does not look like the aluminum fins survive the ride. I’m
currently looking at titanium leading edges for the upper stage fins.
I don’t know if the sims are reliable (but the program has a long history of
accuracy); I’ll probably be flying one of the upper stages early next year and
then we’ll get a better idea of what to expect.
Let me also address a favorite topic, the cost benefit: this has cost about
$350 in out of pocket infrastructure investment (a vacuum tight lid for the
mixing bowl w/ view port). Everything else—including the vacuum pump, gauges,
and lines—was already in hand.
Bill
On Thu, Jul 11, 2019 at 5:35 PM David Summers <dvidsum@xxxxxxxxx
<mailto:dvidsum@xxxxxxxxx> > wrote:
That is fascinating! Is your propellant mass fraction unusually high? I can't
think of another reason for that result, and I'd like to understand it better.
Thanks!
-David Summers
On Thu, Jul 11, 2019 at 1:15 PM William Claybaugh <wclaybaugh2@xxxxxxxxx
<mailto:wclaybaugh2@xxxxxxxxx> > wrote:
David:
In flight simulations of my two-stage, stuffing 3% more propellant into the
same volume raises the peak altitude from a tad over 150km to 210km in the most
recent runs.
Bill
On Thu, Jul 11, 2019 at 4:47 PM David Summers <dvidsum@xxxxxxxxx
<mailto: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
<mailto: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>
[mailto:arocket-bounce@xxxxxxxxxxxxx ;<mailto:arocket-bounce@xxxxxxxxxxxxx> ] On
Behalf Of Anthony Cesaroni
Sent: Friday, 12 July 2019 6:31 AM
To: arocket@xxxxxxxxxxxxx <mailto: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/> http://www.cesaronitech.com/
(941) 360-3100 x101 Sarasota
(905) 887-2370 x222 Toronto
From: <mailto:arocket-bounce@xxxxxxxxxxxxx> arocket-bounce@xxxxxxxxxxxxx <
<mailto:arocket-bounce@xxxxxxxxxxxxx> arocket-bounce@xxxxxxxxxxxxx> On Behalf
Of Edward Wranosky
Sent: Thursday, July 11, 2019 3:43 PM
To: <mailto:arocket@xxxxxxxxxxxxx> 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 <
<mailto:wclaybaugh2@xxxxxxxxx> 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 < <mailto:uwe@xxxxxxxxxxxxxxxxxxx>
uwe@xxxxxxxxxxxxxxxxxxx> wrote:
Am 07.07.2019 um 19:59 schrieb William Claybaugh:
Uwe:
For safety we can’t mix the Al & AP together;
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 < <mailto:uwe@xxxxxxxxxxxxxxxxxxx>
uwe@xxxxxxxxxxxxxxxxxxx
<mailto: ;<mailto:uwe@xxxxxxxxxxxxxxxxxxx> 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
