[SS2S-Main] Sugar Shot Weekly Activity Report - Dec.22-Jan.5 2014

  • From: Richard Nakka <richard.rocketry@xxxxxxxxx>
  • To: sugarshot@xxxxxxxxxxxxx
  • Date: Tue, 7 Jan 2014 22:10:29 -0600

Highlights of recent developments on the DoubleSShot project

- On January 4th, Rick Maschek test fired the 89mm (3.5”) K-rocket
motor with DD-slot grains once again, this time fitted with 4 grains
(it had previously been fired with 2 grains). The test firing was
conducted at the FAR site, with the motor mounted on the horizontal
test stand. Ignition of the motor occurred promptly, and burned well
for the expected duration. Near the end of the burn, the motor casing
suffered a burn-through near the nozzle, where maximum heating was
expected. Upon disassembly, the 1/8” (3mm) cardboard thermal liner was
found to have been fully burned away. Good pressure readings were
recorded over the full duration of the burn. The maximum chamber
pressure was about 1260 psi (8.7 Mpa), which was significantly higher
than expected. Two hypotheses are being looked into. Partial blockage
of the “sliver catcher” by liner debris may be responsible for the
higher pressure. Another possibility is “rotation” of one or more of
the four DD grains, at some point during the burn,  that may have
partially restricted the flow. For expediency, it had been decided
that he four grains would not be bonded together as a single grain. A
misalignment of 90 degrees could potentially cause a restriction of
the flow channel. To eliminate this possibility in the future, all
grains will be aligned and bonded together.
   Illustration of two grains misaligned:
   Sliver catcher:
   Sliver catcher with grain support:
   Newly made bulkhead with removable ignition plug:
   Panoramic view of the motor under full thrust:
   Video of the test firing will be posted soon.
(photos courtesy Rick Maschek)

- The pressure data from the Dec.21st test firing of the K-motor with
2 DD-slot grains has been compiled and plotted, and compared to the
design curve. The resulting comparison shows good correlation and
marks a promising step forward in validating this particular grain
   Pressure curves:

-A regular Avionics telecon was held this past Sunday. Participants
were Chris King, Hans Olaf Toft, Richard Nakka and Mattias Lampe. This
was a relatively short session, as limited progress had been made over
the past few weeks due to the holidays. However, Hans did have some
positive progress to report. Hans stated that he finally had success
with figuring out the Telemetrum software code. As such, it should be
feasible to modify the code to suit our needs with respect to
trajectory calculations and in particular, estimating point of apogee.
The next telecon will be held on January 19th.

-Vicente Alvero has made good progress on preparing the prototype Pyro
Separation Device (PSD) for testing. The original igniter design
proved problematic, so this was replaced with a miniature R/C airplane
“glow plug” which worked out very well. There were some fit-up
problems that are in the process of being overcome. The fit-up issues
were a result of manufacturing as well as design deficiencies, which
are in the process of being rectified. The first test of PSD operation
with a live charge resulted in only one of the six arms being
withdrawn due to excessive friction. A fix is being implemented and a
repeat test will be done in the near future
   Glow plug for the PSD igniter:
   Test of glow plug with crimson powder charge:
   Video of first live test of PSD:
    Vicente describing fit-up issue with the piston arms:
    Fit-up improved  when joint screws removed:
(videos courtesy Vicente Alvero)

-The “DoubleSShot Pyrotechnic Separation Device (PSD) Prototype
Operating Manual” has been uploaded to our documentation page:

-Ben Brockert has posted some further information on numerical
approaches and material
selections relating to SS2S nosecones:

-Richard Nakka, with help from brother Blair Nakka, conducted further
testing of the prototype de-spin system. Earlier, test runs had been
performed with an aluminum flywheel. A steel flywheel with twice the
angular moment of inertia was recently fabricated in order to get
comparison data. The more massive steel flywheel (1 kg) proved
challenging to secure to the motor shaft. The high torque resulted in
slippage of the delrin flywheel mandrel. This was overcome by using a
set screw tightened against a flat milled in the motor shaft. Several
runs were made this past weekend with both flywheels. Data was
gathered using a digital wattmeter to measure power input to the
electric motor (which drives the flywheel). The initial spin of the
simulated rocket body was 330 RPM (achieved by using a power drill).
A higher spin was also attempted (550 RPM) but the flywheel was unable
to bring the body to a full stop.
   Digital wattmeter reading:
   Steel and aluminum flywheels:
   Power curve for one of the runs:
   Energy curves for all of the runs:

- Chris North, has become our newest Bronze Donor, kindly making a
donation of $25.

Coming soon…!
(graphic courtesy Knut Gangåssæter)

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  • » [SS2S-Main] Sugar Shot Weekly Activity Report - Dec.22-Jan.5 2014 - Richard Nakka