November 30 th, 2010

Introduction On April 17 th, 2010, the Madison West SLI2010 Senior Team exceeded SLI target altitude of 5,280ft by 34% (barometric altimeter recorded flight apogee of 7,070ft). Purpose of this investigation: Re‐evaluate data and procedures that led to the overshoot Determine the failure point in data analysis Devise safety measures that will prevent a repeat of such or similar incident

Vehicle

Investigation FOCUS - possible absence of red flags in apogee prediction Rocket reassembled All parts weighted and compared to records in PDR, CDR, and FRR No significant discrepancies were found Existing RockSIM model verified for accuracy All calculations and data analysis of flight data verified

Scale Model Flight Barometric altitude data compared with simulated altitude and velocity. Model fitting provided C d of The motor used was AT H250G. C d = 0.49 C d = ft1350ft

Full Scale Low Flight - AT J800T The Simulated vs. Actual flight data. C d of 0.65 was calculated by model fitting using flight data and RockSIM. C d = 0.65 C d = ft1110ft Weather concerns (low visibility) forced the team to limit the flight to 1,200ft AGL.

Motor Selection Deadline At this point, motor selection for SLI launch had to finalized. Based on the measured C d = 0.65, team selected AMW L1080BB motor, with apogee prediction being 5543ft. Because of AMW L1080BB and AT L850W shortage, the team ended up choosing AT 1390G motor. AMW L1088BB, predicted apogee 5,543ft AT L1390G, predicted apogee 5,843ft

Full Scale High Flight - AT L850W Barometric altitude data from flight. Model fitting provided C d of 0.48 (this value should have been carried over to further simulations) C d = 0.48 C d = ,100ft6,100ft

Comparison: Cd = 0.48 vs At this moment, the inaccurate C d = 0.65 prediction should have been replaced with the new value C d = Data and simulation indicate that the switch never occurred and the team continued using the incorrect C d = 0.65 which resulted in 34% overshoot. At this moment, the inaccurate C d = 0.65 prediction should have been replaced with the new value C d = Data and simulation indicate that the switch never occurred and the team continued using the incorrect C d = 0.65 which resulted in 34% overshoot. C d = 0.48 C d = 0.65 Motor: AT L1390G

Full Scale SLI Flight – AT 1390G Barometric altitude data from final flight at Braggs Farm, AL. Model fitting in RockSIM provided C d of 0.46 C d = 0.46 C d = ft7070ft

Flight Tests

Conclusions The multiphase apogee prediction procedure is reliable however: SLI2010 senior team missed the indication of severe overshoot because they switched two data analysis results. C d from low (AT-J800T) full-scale test flight C d = 0.65 C d from high (AT-L850W) full scale test flight C d = 0.48 Had the correct C d been carried to further rounds of simulations, the indication of overshoot would have been clear (simulation predicts 6,900ft  )

Incident Repeat Prevention Better management of project files, data and documentation More detailed labor division among team members Closer initial estimates of flight apogee Using the same motor for final test flight and SLI launch flight

Questions?