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> 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>
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> 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 1
st 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 usuallyaluminum
proceeds by mixing the liquids (including catalyst), adding the
to the liquid mix w/ careful hand stirring), then folding into the APdoes the
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
> 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
