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authornatronics <natronics@web>2010-07-06 05:45:22 (GMT)
committer Portland State Aerospace Society <psas@psas.pdx.edu>2010-07-06 05:45:22 (GMT)
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Wrote up findings about fin flutter.
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@@ -142,3 +142,16 @@ Raw data from the [ARTS2 flight computer](http://www.ozarkaerospace.com/)
- [[arts20100627.odf]]
#### Roll (CAN logger)
+
+## Data Analysis/Conclusions
+
+### Fin Flutter
+
+Careful viewing of the on board camera footage shows the fins fluttering for about one second around frame 31535. Liftoff was on frame 31423. At 30 frames per second this suggests the flutter happening about 3.7 seconds into the flight. This would correspond to the transonic region of flight right as the rocket enters Mach 1 according to both simulations and the flight computers.
+
+[[!img fins.png size="600x600"]]
+
+The above image shows two nearby frames from the on board camera with the right fin highlighted. In frame 31535 the fin is painted red and in 31537, blue. On the right the two images have been stacked and the fin highlights compared. The fin appears to undergo a flutter with an amplitude of about 4&deg;s.
+
+#### Conclusion
+In general fin flutter is not a good thing. Oscillations can exceed material shear strength and break off fins resulting in catastrophically unstable flight. For flights any faster than Mach 1 we should reconsider our fin material and attachment.