Transcript Slide 1

E80: The Next
Generation
Rocket Analysis
Student
Student
Student
Student
1
2
3
4
May 5, 2008
Introduction

Investigation of rocket dynamics




Lab calibration
Motor tests
Flight modeling
Field Test

Rocket launches in Lucerne Valley
Outline of Post-flight Analysis

Medium IMU (Inertial Measurement Unit)
rocket


Small IMU rocket




Rocket motion
Rocket motion/frequencies
Casualty analysis
Medium Pressure/Temperature rocket
Medium Vibration rocket
Rocket Motion Analysis
(Med. IMU w/G79W)



Useful for determining overall motion of the rocket

Orientation of rocket relative to ground/initial
position

Position/velocity during flight
Measuring acceleration and angular velocity
 3 accelerometers (one for each axis) and 3
gyroscopes (one for each axis of rotation)
Raw data stored on rocket/transmitted by telemetry
(radio signal)
Rocket Motion Analysis
(Med. IMU w/G79W)
Medium IMU rocket Video
Rocket Motion Analysis
(Med. IMU w/G79W)


Analyze raw data
 Raw data → Local accelerations (using given calibrations)
 Rotation matrix (local → global acceleration)
Z-acceleration compares to static motor test
Global Accelerations of Medium IMU Rocket with Motor G79W
Rocket Motion Analysis
(Med. IMU w/G79W)

Velocity data
 Integration by Reimann sums of accelerations
 Propagation of error
 Baseline drift
 Z-velocity compares to Pitot tube
Global Velocities of Medium IMU Rocket with Motor G79W
Rocket Motion Analysis
(Med. IMU w/G79W)

Position data
 Integration by sums of velocity
 Effect of velocity drift on position
 Z-position compares to altitude from pressure sensor
Positions of Medium IMU Rocket with Motor G79W
Frequency/Motion Analysis
(Sml. IMU w/G104T)

First launch
 Pressure trigger failure
 Fatal crash/data recovered
Frequency/Motion Analysis
(Sml. IMU w/G104T)

Analyze IMU signal
 50 Hz periodic function
 Camera power draw
Frequency domain of the Z-direction acceleration
Frequency/Motion Analysis
(Sml. IMU w/G104T)



Refine data
 Remove 50 Hz signal
 Zoom in on remaining data
Conclusion: Camera/IMU on same circuit problematic
No further tests possible
Local Z direction acceleration from small IMU rocket after 50 Hz signal is removed.
Pressure and Temperature
(Med. P/T Rocket w/G61W)



Important for determining rocket’s environment
 Altitude
 Heat effects
Also useful for troubleshooting an unsuccessful
launch
For our Pressure/Temperature Analysis:
 R-DAS (Rocket Data Acquisition System) data
(no IMU measurements)
Pressure and Temperature
(Med. P/T Rocket w/G61W)

Pressure is measured using two pressure transducers




We use R-DAS transducer, not IMU
Pressure → Voltage → Raw data (1024 bits)
Raw data stored on rocket/transmitted with telemetry
Received/downloaded raw data used to find pressure


Calibration values from lab
Altitude equation
Pressure Analysis
Temperature Analysis

Temperature measured using 4 thermistors
 Change resistance depending on temperature
Resistance → Voltage → Raw data (1024 bit)
Analysis similar to how we handled the pressure raw data:
 Calibration from lab to find resistance
 Temperature equation with lab calibration values


Temperature Analysis
Vibration Analysis
(Med. Vibration Rocket w/G61W)


Equipment: Dynamic Strain Gauges
Task: Find natural frequencies of rocket’s axial
displacement
Vibration Analysis
(Med. Vibration Rocket w/G61W)
Vibration Analysis
(Med. Vibration Rocket w/G61W)
Vibration Analysis
(Med. Vibration Rocket w/G61W)
Conclusions

Rocket Motion



Frequency/Motion



Originally appeared accurate, but evidence suggests otherwise
Possible verification of data impossible due to fatal crash
Pressure/Temperature




Found plausible values for global acceleration, velocity, and position
Recommend higher sampling rate or Kalman filter to decrease error
Found reasonable pressure/altitude results
Better raw data to pressure resolution would improve results
Consistent calibration of thermistors, check beforehand to verify status
Vibration



Found probable natural frequency at around 42 Hz
Our methods of analysis demand a system without changing inputs
A valid tap test of the rocket would allow for filtering and better analysis
References/Acknowledgements









5, Student. Consultation with on May 3, 2008.
4, Student; 3, Student; 2, Student and 1, Student. “E80: The Next Generation
Lab Notebooks.” Spring 2008.
Cardenas, Mary. Rocket Dynamics Lecture. February 25, 2008.
DiMaggio, Sam. Consultation with on April 29, 2008.
Miraghaie, Reza. Consultations with during the week of April 28 – May 2, 2008.
Spjut, Erik. Consultations with during the week of April 28 – May 2, 2008.
Wang, Ruye. Inertial Measurements Lecture. February 26, 2008.
Yan, Bruce.
E80 proctors and professors
Questions?
Frequency Response (2.0-6.5 s)
Tap Testing the Rocket
Thermistor Locations
Rocket Motion Analysis
(Med. IMU w/G79W)

Pitot tube
 Velocity along rocket length only
 Local z velocity vs. global z
 Measures using pressure
 Only accurate up to apogee
Comparison of Pitot Tube Velocity and Integrated Velocity
Altitude for Medium IMU Rocket
Comparison of Thrust Curves
Motion Analysis Numerical Results
Values found from
accelerometers and
gyroscopes
Values from other sensors
Max. thrust of rocket = 67 N
-taking drag and weight into account = 82 N
Max thrust of static motor test = 80 N
Max. calculated velocity = 56.8 m/s
Max. Velocity from pitot tube = 48.7 m/s
Max. calculated altitude = 198.4 m
Max. altitude from pressure sensor =189.6 m
Rocksim Numbers
(Med. IMU w/ G79W)
Value
Prediction
Mass
1kg
Apogee
297 m
Max. Velocity
74 m/s
Time to Apogee
8.2 s