[SS2S-Main] Sugar Shot Weekly Activity Report -- Jan.6-12, 2014

  • From: Richard Nakka <richard.rocketry@xxxxxxxxx>
  • To: sugarshot@xxxxxxxxxxxxx
  • Date: Tue, 14 Jan 2014 21:32:07 -0600

Highlights of recent developments on the DoubleSShot project
-Rick Maschek has provided photos and video of the recent test firing
of the K-motor with 4 DD slot grains:
    New bulkhead assembly made by Rick:
   Bulkhead installed in motor (note steel wool inlet filter):
    Motor under thrust:
   Burn-through beginning at 400 psi:
   Rick and Kevin Jalalipour (student at UC Irvine) examining motor
after firing:
    View of motor in test stand, post-firing:
    View of nozzle exit, post-firing:
    View of bulkhead and igniter fitting, post-firing:
    View of bulkhead removed:
(photos and video courtesy Rick Maschek)

-The recorded chamber pressure for the K-motor with 4 DD slot grains,
compared to the design curve, has been plotted:
As can be seen, the actual curve deviates significantly from the
design curve. The reason was discovered to be an error in the type of
inhibitor that was used to restrict grain burning. The inhibitor was
intended to consist of two layers of fiberglass fabric soaked in a
mixture of polyester resin and glass microballoons. Due to an
interpretive error, the fiberglass fabric was omitted from the actual
inhibitor. The lesson learned from this is the importance of properly
documenting key procedures, such as grain preparation and motor
assembly. Historically, this is something that SS2S has done
effectively for most motor test projects. Such documentation has not
used for the “ad-hoc” K-motor tests of the DD-grain configuration.

-Randy Dormans has kindly agreed to fabricate a replacement motor
casing for the one that suffered a burn-through during the test firing
of the K-motor with 4 DD slot grains. Randy will also fabricate a
second casing to hold six propellant grains.

- Vicente Alvero has performed further testing of the prototype Pyro
Separation Device (PSD). Modifications were made to reduce friction of
the six arms, and the quantity of pyro charge was increased. The
result was positive, with the PSD performing as designed with all six
arms retracting as expected. The next test will be to activate the PSD
fully assembled with simulated coupler and body tube.

- Vicente Alvero has cast the two propellant grains for the first test
firing of theVIC-2 rocket motor. This motor will be utilized for
conducting testing of new ablative materials and a graphite nozzle
exhaust cone. The grains each have a mass of approximately 2.3 kg (5
lbs), have diameter of 100mm (3.9 in.) and a length of 180mm (7 in.).
A small amount of red iron oxide (0.1%) was added to the propellant.
The first test firing is tentatively scheduled for mid-February.
(photos courtesy Vicente Alvero)

-Richard has completed the experimental graphite composite exhaust
cone for the VIC-2 test motor. This “first article” suffered some
wrinkling while in the autoclave. The cure was at a temperature of
300F (150C) and a pressure of 45 psi (3 bar), combined with full
vacuum. Due to the conical shape of the mandrel, there was some
sliding of the prepreg plies. For the second try, the mandrel will be
slightly modified to allow “tie-back” of the plies, which should
eliminate this shifting. The part came off the mandrel easily (Frekote
release agent was used), revealing a couple of long narrow “voids” on
the inside. The part will nevertheless be used for the first test
firing of the VIC-2 motor, with the voids being filled with a mixture
of epoxy and milled glass.
   Cone (still on mandrel) in lathe with wrinkles visible. Surface
being machined smooth:
   Surface machined smooth and two parting cuts made:
   Finished cone:
   View of interior, revealing voids caused by wrinkles:
(photos courtesy Richard Nakka)

- Oscar Pazos Comesaña, who’d expertly machined many of the components
of the prototype PSD, has come up with an alternative PSD design.
Oscar is currently fabricating this PSD and has provided CAD

-To obtain a qualitative assessment of an Estes A3-4 model rocket
motor for use as a potential pyrogen unit for the TM-4 motor, Richard
performed a static firing. The video indicates that a pair of A motors
should work admirably for the purpose.

-Richard has performed additional testing of the prototype de-spin
system. The objective of the latest series of test runs was to
estimate the mechanical efficiency of the electric motor that drives
the de-spin flywheel. This data is needed to compare actual
performance to theoretical predictions, in order to come up with a
de-spin system design methodology.

Coming soon…!
(graphic courtesy Knut Gangåssæter)

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  • » [SS2S-Main] Sugar Shot Weekly Activity Report -- Jan.6-12, 2014 - Richard Nakka