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authornatronics <natronics@web>2011-08-04 04:43:11 (GMT)
committer wiki <iki-wiki@psas.svcs.cs.pdx.edu>2011-08-04 04:43:11 (GMT)
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some frames and commentary from the tower cam.
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@@ -73,4 +73,28 @@ Unfortunately the rocket motor failed on ignition, ejecting the fuel (unburnt) f
- Spin Can got dirt in bearings
- Upper aeroshell is damaged?
+## CATO Analysis
+
+We know that the motor stopped almost immediately after ignition. The rocket continued into the air for a short period of time unpowered and came to a rest just behind the tower. When the recovery team reached the rocket we discovered that the aft enclosure and nozzle were missing and most of the fuel had ejected from the motor casing.
+
+Examining the motor casing we found the forward enclosure was also dislodged, though not entirely. Most interestingly the threads on both sides were undamaged. When cleaned and screwed back into the casing the aft enclosure still fit. This suggests that the motor casing expanded under motor pressure enough to disengage the threads of the two enclosures. What remains to be seen is why the pressure was high enough to allow this to happen.
+
+### Images
+
+The tower cam had a wide angle lens that captured the event at 30 frames per second. Here we see four consecutive frames around the event:
+
+[[!img liftoff_frames_short.png size="650x164"]]
+
+The motor comes up to pressure in the first and second frame, then the enclosure appears to fail in the third. By the last frame there is little flame left, the motor has already failed and rapid depressurization extinguished the fuel (dP/dt failure).
+
+A fuel grain is seen leaving the end of the motor two frames (0.667 seconds) after the event:
+
+[[!img ejected_grain.png size="650x366"]]
+
+We can see the leftover debris from inside the motor scattered on the ground after the smoke cleared.
+
+[[!img end_state_labled.png size="650x366"]]
+
+There were three fuel grains missing from the motor when we recovered it. The other three were stuck inside the casing with some kind of spacer wedged sideways blocking their escape. Only one grain was seen leaving the motor in the video so the other two must have been ejected in the initial event both so fast -- also suggested because they were found heavily damaged -- and still masked by flame and smoke.
+
[[!tag announcement]]