bobkrech
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I've conducted hundreds of analysis to discover what anomalies occurred during a rocket flight. The process involves the compilation of as much hard data (flight recorder data, videos, photos, etc. and as many first hand observer reports as possible, and developing a self-consistent event line of the flight and one or more possible explanations for the flight anomaly.Except for one thing. The rocket weather cocked away from us and drifted back to us. When it reached approx 200', it was less than 25 yds away from us. So distance 75", elevation 200". Well within distance to hear a report.
Hard data provides a permanent record of what happened while the first person accounts provide supplementary or confirming information to assist in the development of possible scenarios. A problem with first person accounts is that they may not be complete and the resulting time-line or analysis may be inaccurate because information was left out. In this case, the original description of the flight was incomplete. The reported wind at launch was 12-15 mph and it was reported the rocket exhibited slight weather cocking on ascent. From the altimeter the descent rate of the rocket from a 1344' apogee to 200' is know to be ~14 fps. Using the maximum estimated 15 mph wind speed (22 fps) and the altimeter's 80 second difference between time markers, a calculated maximum 1760' downwind drift of the rocket could have occurred. If the rocket exhibited only slight weather cocking, the downwind drift would have caused the rocket to be far away from the observers, most likely well over 1000' downwind. This was a key element in the previous analysis.
Now after is added the rocket was less than 100' from the observers at ~200' altitude, the conclusions obtained in the original analysis must be reassessed.
- Was the wind velocity actually 12-15 mph, or was it lower?
- If yes, then the description of slight weather-cocking is incorrect based on the new information.
- If no, it was lower, then the observation of slight weather-cocking would be consist with the new observation of a recovery relatively close to the observers.
- Neither result would effect what happened, but will effect the analysis of what most likely caused the anomaly.
- If the rocket was indeed close to the observers when the 200' main deployment charge was commanded to fire as confirmed by the altimeter, then it should have been heard.
- This puts more credence to the initial observer initial statement that the apogee charge seemed louder than usual that could indicate both charges fired at apogee.
- This leads to the possibility of there was problem with the connections of the e-matches to the altimeter and both the apogee and main deployment charges fired at apogee by the apogee pyrocircuit.
- Or the bulkhead flanges of the altimeter compartment are not gas tight and the apogee ejection charge pressurized the altimeter compartment and fooled the altimeter to into believing that the rocket had descended to 200' agl which caused the main to fire.
- Or the charges were wired backward and the apogee charge was wired to the main, fired and the apogee charge wired at the same time.
- This puts more credence to the initial observer initial statement that the apogee charge seemed louder than usual that could indicate both charges fired at apogee.
- Of these possibilities, the only one consistent with the StratoLogger data is:
- The apogee pyrocircuit fired both the apogee and main e-matches at apogee.
- Both charges had a common connection to the switched side of the apogee pyrocircuit.
- All preflight beeps would have appeared normal.
- Since the main pyrocircuit triggered at 200' as recorded by the altimeter, the other 2 possible explanations can be eliminated.
- The apogee pyrocircuit fired both the apogee and main e-matches at apogee.
So the new observation alters the original conclusion. The probable cause of the flight anomaly is:- Either a wire end or heavy soot deposit formed a bridge to enable the cross-connection.
The corrective actions to avoid the same event from occurring in the future is:
- Conducting a visual inspection of the altimeter pyrocircuit connections and any other wiring connections prior to each flight.
- Developing and using a written check list prior to each flight to insure that proper procedures and sufficient inspections occur before each flight to avoid these issues.
Bob