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E80 Final Report

E80 Final Report. Section 4 Team 2 Student 1 Student 2 Student 3 Student 4 May 5, 2008. Introduction. Goals: Simulate rocket flights Analyze rocket flight data Compare simulation to analysis and explain discrepancies Three analyses Large Inertial Measurement Unit (IMU)

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E80 Final Report

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  1. E80 Final Report Section 4 Team 2 Student 1 Student 2 Student 3 Student 4 May 5, 2008

  2. Introduction • Goals: • Simulate rocket flights • Analyze rocket flight data • Compare simulation to analysis and explain discrepancies • Three analyses • Large Inertial Measurement Unit (IMU) • Large Vibration • Small IMU Rocket—fatal flat spin

  3. Background • IMU • Placed the IMU board on a turntable • Measured distance from center to IMU • Spun at several different frequencies • Plotted ADC values as a function of known angular velocity and linear acceleration

  4. Background • Vibration • Placed strain gauges on a hollow cylinder • Performed a tap test with an impulse hammer • Created Bode plots of output compared to force • Flight Modeling • Created 2-dimensional model of flight path using thrust curves and coefficient of drag • Predicted time to apogee and height at apogee

  5. Flight Preparation • Set the configuration on the R-DAS unit • Check transmission channel and settings • Checked R-DAS and video telemetry • Two flights did not have working video • Loaded parachute and wadding • Proctor loaded motor • Proctor loaded ejection charge • Loaded rocket on launch pad • Turned on R-DAS unit to transmit • Launch

  6. IMU Analysis Procedure • MATLAB code used calibration curves to convert ADC values to acceleration and angular velocity • Numerically integrate angular velocities to find angles at each time step • Create rotation matrix to convert local acceleration to global • Numerically integrate in 3-dimensions to find velocity and position

  7. Large IMU Analysis

  8. Large IMU Simulation • Analyzed and launched with G339N Motor • Rocksim predicted • Time to apogee: 6.627 s • Height at apogee: 701.7 ft • Burnout: 0.360 s • Distance from launch pad: 254.44 ft

  9. Large IMU Data—Flight 1 • Only able to analyze to apogee • Too much error accumulated past apogee to analyze the data • Time to apogee: 6.220 s • Height at apogee: 522.22 ft • Burnout: 0.35 s

  10. Large IMU Data—Flight 2 • Only able to analyze to apogee • Too much error accumulated past apogee to analyze the data • Time to apogee: 5.2150 s • Height at apogee: 454.35 ft • Burnout: 0.34 s

  11. Large IMU Analysis • Sensitivity to calibration curves • Bias changes due to temperature • Propagation of error

  12. 15 10 7 6 1 12 1.5” 13” 17” 33.25” Large Vibration Flight Data • Collected data for 6 sensors • Used the sensor closest to the motor as the input • Graphed plots of the output of each sensor vs. the designated input

  13. Large Vibration Analysis • Sampling at 200 Hz gave frequencies between 0 and 100 Hz • Based on Fourier transform and hollow cylinder results expected frequencies ~10 Hz and ~50 Hz within window • Observed frequencies matched expected frequencies at both liftoff and apogee • Mode shapes were arbitrary because of limited sensor resolution

  14. 3D Analysis

  15. Small IMU Simulation • Analyzed and flown with G104T motor • Analysis performed without parachute • Rocksim predicted: • Time to apogee: 7.864 s • Height at apogee: 938.31 ft • Burnout: 0.901 s • Distance from launch pad: 126.91 ft • Time to impact: 15.68 s

  16. Small IMU Flight Data • Data was corrupted throughout flight • No distinct impulse and landing curves as in other plots • Signal present only noise • MATLAB analysis gave useless data • From visual and video analysis: • Height at apogee: ~850 ft • Time at apogee: ~7.8 s

  17. Small IMU Analysis • Cause of data corruption may be low voltage to R-DAS and IMU • Could have also led to failure of parachute to open at apogee • From video, rocket experienced greater weather cocking than predicted by Rocksim • Traveled nearly twice the predicted distance from launch pad • Also likely due to higher wind gusts than predicted • Noise in acceleration signal prevents accurate numerical analysis of flight path

  18. Conclusions • RockSim Simulations were relatively accurate when compared to flight data • Variable winds and launch conditions contribute to discrepancies • High amount of error after apogee for all IMU flights • Resonant peaks for vibration rocket were observed during liftoff as expected • Mode shapes could not be resolved

  19. Acknowledgments • Professors Spjut, Wang, Cardenas, Miraghie, and Yang • Proctor A, Proctor B, Proctor C, and Proctor D

  20. Questions?

  21. Extra Figures

  22. Modal Shape Magnitude vs. Position, with theoretical mode on top Sensor 10 as input, 7, 6, 1 as outputs 80 Hz

  23. Large IMU Day 1 : Without Rotation

  24. VI Front Panel

  25. First Modal Shape Magnitude of Vibration (dB) Position along Rocket (in)

  26. Second Modal Shape Magnitude of Vibration (dB) Position along Rocket (in)

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