Rocket Flight Dynamics

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Rocket Flight Dynamics. Section 1, Team 4 Student 1, Student 2, Student 3 May 5, 2008. Rockets Analyzed. Large IMU rocket Large vibration rocket Small vibration rocket All launches at Lucerne Valley dry lake bed Altitude: 2848 feet. How the RDAS functions. 6 channels of data

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Rocket Flight Dynamics

Section 1, Team 4

Student 1, Student 2, Student 3

May 5, 2008

Rockets Analyzed
• Large IMU rocket
• Large vibration rocket
• Small vibration rocket
• All launches at Lucerne Valley dry lake bed
• Altitude: 2848 feet
How the RDAS functions
• 6 channels of data
• Onboard accelerometer
• Onboard pressure sensor
• Samples at 200 Hz
• Runs on 9V battery supply
IMU and Vibration Sensors
• IMU
• 3 MEMS Accelerometers
• 3 MEMS Gyroscopes
• Vibration
• Piezoelectric strain gauges

X axis Y axis

Z axis

Mode 1:

Mode 2:

Mode 3:

.

Modal Shapes
• Model rocket as a uniform beam
• At natural frequencies, distinct modal shapes
• Values of natural frequencies depend on beam dimensions and material properties
Large IMU Rocket
• Launched April 26, 2008 with G339N motor
• RockSim used to model launch
• Estimated Apogee of 482.66 ft
Large IMU Rocket
• Approximations
• Any point before time=0 needs to be set to zero
• Account for calibration drift
• Over thrust curve, all other sensors should be zero
• Noisy x and z gyroscopes have negligible effect
• Integration error doesn’t affect apogee
Large IMU Rocket
• Apogee at 5.45 seconds
• Made several approximations to eliminate noise
• Model only works until apogee
Large Vibration Rocket
• Launched April 19, 2008 with G69N motor
• Severe weathercock
• RockSim trajectory portrays weathercock
3 5 6 7 8 10

72.39cm 60.64cm 46.67cm 31.75cm 15.875 cm 0 cm

Large Vibration Rocket
• Six vibration sensors connected to RDAS
• Sensor 10 assumed as input
Large Vibration Rocket
• Applied Fourier transform
• Treating sensor 10 as input, plotted FRF
Large Vibration Rocket
• Identified three resonant peaks
• Mode 1 assumed to be at 23.85 Hz
Large Vibration Rocket
• Mode 2 assumed to be at 0.9569 Hz
Large Vibration Rocket
• Higher Mode at 19.65 Hz
Small Vibration Rocket
• Launched April 19, 2008 with G104T motor
• Camera drew power from battery
• Parachute did not deploy
1 5 6 8 10

37 in 28 in 22 in 8 in 1 in

Small Vibration Rocket
• Five vibration sensors connected to RDAS
• Sensor 10 chosen as input
Small Vibration Rocket
• Applied Fourier transform and 50 Hz filter
• Treating sensor 10 as input, plotted FRF
Small Vibration Rocket
• Identified two resonant frequency peaks
• Mode 1 assumed to be at 7.997 Hz
Small Vibration Rocket
• Mode 2 assumed to be at 0.5831 Hz
Summary
• Large IMU
• Apogee at 5.45 seconds
• Modeled altitude at apogee of 3382 feet
• Large Vibration
• Three natural frequencies: 23.85 Hz, 0.956 Hz, 19.65 Hz
• Small Vibration
• Two natural frequencies: 7.997 Hz, 0.5831 Hz
Acknowledgements
• E80 lab professors
• Mary Cardenas, Reza Miraghaie, Erik Spjut, Ruye Wang, and Qimin Yang
• Lab proctors and Rocket Development Team
• Reference 1
• Reference 2
• Reference 3
References
• Miraghaie, Reza, Modal Vibration, http://www.eng.hmc.edu/NewE80/PDFs/ModalVibrationLecture.pdf
• Remote Data Acquisition System, http://www.aedelectronics.nl/rdas/index.htm
• Spjut, Erik, http://www.eng.hmc.edu/NewE80/