I use a bit of steel brake line press fit into the sampling port in the forward
closure to move the pressure sampling point an inch or so into the chamber to
avoid slag plugs. Works great.
Bdale
On December 6, 2020 2:24:43 PM MST, Rick Maschek <dmarc-noreply@xxxxxxxxxxxxx>
wrote:
The motor started out ~6 feet tall and after each test got shorter as
we had to cut off destroyed ends. The propellant in this fourth test
was a tapered cylindrical core with inhibited ends to be progressive
until it either blew off the ends or the case failed elsewhere...it
didn't. We had pressure transducers in the bulkhead and I didn't want
any dirt backfilled in because that traps in the heat. We compromised
with filling in half way to somewhat stabilize the motor. We got data
but the sensors were in the bulkhead and were destroyed from heat soak.
That data shows an extremely regressive burn.
I don't like testing sugar motors of this size nozzle up because of the
buildup of slag (liquid KCO3) on the bulkhead insulation instead of
being blown out the nozzle during the burn. I think that insulation and
or slag somewhat plugged the pressure port resulting in a correct
initial reading but thereafter not.
Because the audio file for all of our videos looks to be a really nice
level output, we think the end inhibiters, an 1/8" acrylic disk with a
two inch hole in the center was placed over the nozzle convergent
followed by a layer of cardstock from a frozen 'pizza box' (PB) placed
on top of the acrylic above the nozzle at the beginning of the pour and
then another 'PB' layer on top of the just poured hot propellant failed
and became a large BATES style neutral burning grain. The top 'PB' then
had RTV smeared on with a second layer of PB applied on it and then the
1/4" steel bulkhead with the pressure port. I think parts of that may
have caused the 'ejection events' Ray mentioned as seen during the burn
in the video.
The third test was also to have been a progressive burn to failure
except we had a burn through at the bulkhead that blew all the dirt out
of the filled hole before the motor took flight utilizing its new
larger second 'nozzle'. In anticipation of something happening during
both tests, we put a large chain around the 8" steel nozzle that
limited the motor's flight to about 10 feet on the third test.
We are planning on a fifth and final test of that motor on Dec 19 using
a steel nozzle throat reducer to build more pressure and better end
grain inhibiting (anyone have good ideas for the inhibiter). The usual
that I've used in the past for small grains burning for just a couple
seconds of so just haven't been holding up.
Yesterday was cold, when I left home it was 28F and we estimate the
motor in the hole at around 45F. Much different than our two summer
tests with ambient air temperatures around the vertical test stand of
110F. In studies with commercial APCP, burn rate increase was shown tobe as high as ~25% depending on the temperature. We now believe that
temperature has a strong influence on 'sugar' propellant burn rate (we
are still doing qualitative testing on that).
David, attached is the audio file (all of them look the same from the
other video cams (I think we had 5 going from different places). I
still have data coming in from the team members tasked with those
operations but not sure if that data was compromised by a plugged
bulkhead pressure port. Our August 1st CATO (nozzle down) damaged some
of the FAR test stand shearing 1/2" bolts and cutting 1/4" steel plate
like butter on the flame bucket and so did the last two tests in the
ground.
If our next test proves successful, we may launch a large Q or small R
in January. If that is successful, a follow up 2-stage is planned for
the spring.
Rick
On Sunday, December 6, 2020, 12:14:54 PM PST, David Snyder
<dvdsnyd@xxxxxxxxx> wrote:
Great job Rick!Look forward to seeing the next test, assuming it will
be on a stand for data collection?
On Sun, Dec 6, 2020 at 1:35 PM Redacted sender tadserralt for DMARC
<dmarc-noreply@xxxxxxxxxxxxx> wrote:
How long was that motor, Rick? 8 x what.
Tad
-----Original Message-----
From: Rick Maschek <dmarc-noreply@xxxxxxxxxxxxx>
To: SugPro <sugpro@xxxxxxxxxxxxx>
Sent: Sun, Dec 6, 2020 9:07 am
Subject: [sugpro] Sugar Shot to Space 8 inch (200 mm) static test
Video from our fourth test of this fiberglass case using 65/35 KNSB
propellant.1st test on July 4, 2020 resulted in a motor CATO.2nd test
on August 1st also resulted in a CATO.3rd test November 21 suffered a
burn through at the bulkhead.
Dec 5 2020 Sugar Shot to Space 8 inch (200mm) static test
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Dec 5 2020 Sugar Shot to Space 8 inch (200mm) static test
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This was to be the last test of this fiberglass case motor using case
bonding instead of segmented 'BATES' grains.Motor will be tested once
more in two weeks, Dec 19.
Rick
