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Highlights of recent developments on the MiniSShot Project
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- The test firing of the MiniSShot motor which was planned for Oct.25th
was canceled. The cancellation was due to technical concerns, and a
"no-go" decision was made by the members of the Propulsion Team late
Thursday at the conclusion of a readiness review telecon. The
cancellation came as a disappointment to the team members, as an
outstanding effort had been put forth over the past several weeks by all
members to (successfully) have everything ready in time. The concerns
focused on two issues. One was the condition of several of the
propellant grains which had suffered damage during (difficult) coring
rod removal. Photos of two such grains:
http://www.sugarshot.org/downloads/damaged_grain1.jpg
http://www.sugarshot.org/downloads/damaged_grain2.jpg
A second concern came to light followed a second static firing of the
MiniSShot "Short Stack motor" on October 21st. The purpose of this
static firing was to assess the performance of the titanium casting
tubes. Although the titanium tubing survived the firing intact, there
was significant deformation of the thin wall (0.020" or 0.5mm) caused by
thermal softening combined with a yet-to-be-determined mechanism that
caused inward bulging, seen here:
http://www.sugarshot.org/downloads/titanium_tubes_postfiring.jpg
http://www.sugarshot.org/downloads/titanium_tube_postfiring.jpg
In the first photo, the 3 tubes can be seen with the steel foil joint
wrappers and Coupler Rings. The second photo shows the inward
deformation just aft of the section of tube that was supported by the
Coupler Ring.
One possible cause for the inward bulging is due to the pressure
differential between the outside of the grain assembly of the inside,
where pressure is lower due to the high velocity gas flow.
The problem of coring rod removal seems to have already been resolved,
with special thanks to Rick Maschek. Here is a photo of a recently cast
grain:
http://www.sugarshot.org/downloads/grain_titanium.jpg
And the new setup for casting grains in titanium tubes:
http://www.sugarshot.org/downloads/new_setup.jpg
The MiniSShot motor test firing has been rescheduled for Nov.22nd.
-Hans reports that he has received the gyro breakout board parts for the
Flight Computer.
- Contributions to the MiniSShot project are needed more than ever. The
extraordinary efforts put forth by team members to have the MiniSShot
motor ready for firing have strained our coffers. Donations are highly
welcome and can be made at any time at our Sponsor webpage:
http://www.sugarshot.org/sponsors.html#Donors
Your support is highly appreciated !
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