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Student 1, Student 2, Student 3, Student 4 Section 3 Team 2. Experimental Engineering: Rocket Flight and Analysis. Intro/Background. E80: Experimental Engineering Rocket launches on 4/19 and 4/26 Lucerne Valley dry lake bed Rockets had various sizes, sensors, and motors - PowerPoint PPT Presentation
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Student 1, Student 2, Student 3, Student 4Section 3 Team 2
E80: Experimental Engineering Rocket launches on 4/19 and 4/26 Lucerne Valley dry lake bed Rockets had various sizes, sensors, and
motors Take data, analyze it, and compare it to
theoretical models we developed
Photo courtesy of Professor Cardenas
Configure and verify RDASConfigure and verify video telemetryConnect jumpers for vibration sensorsPhysical launch preparationsLaunchRecover data
Inertial Measurement Unit mounted on a large and small rocket Accelerations Angular velocities
IMU calibrated with a turntable apparatusEuler method and rotation used to find
global variables
Experimental and Theoretical Results IMU DataIMU Data
Flight ModelFlight Model
RockSimRockSim
Vertical Position Horizontal Position
Both RDAS and IMU have pressure sensors
Mounted on a medium rocketPressure sensors calibrated with a
pressure chamberAltitude can be calculated from pressure
RDAS pressure
IMUpressure
RDAS altitude
IMU altitude
Flight Model
RockSim
RDAS
IMU
RockSim Flight Model RDAS Data Analysis
IMU Data Analysis
Apogee (m) 262.76 290.75 191.23 208.20
Time (s) 7.89 8.2052 7.045 7.8
Sources RockSim and Flight Model
RockSim and RDAS
RockSim and IMU
Flight Model and RDAS
Flight Model and IMU
RDAS and IMU
% difference in apogee
10.11 31.51 23.17 41.30 33.09 8.50
Apogees from data consistently lower than predicted apogees from the flight model and RockSim
Calibration errorLaunch angleDynamic wind vs. static wind
Theoretical resonant frequencies, obtained by modeling the rocket as a hollow tube with free-free boundary conditions.
f1 = 165 Hz, f2 = 456 Hz, f3 = 893 Hz.
Expected peaks after folding = 35 Hz, 56 Hz and 93 Hz.
€
fn =ωn2π
=(β nL)2
2π
EIzρAL4
E = Young’s modulus, Iz = second moment of the beam, A = cross sectional area of the beam ρ = densityßn= a property dependent on boundary conditions
Resonant peaks also determined by taking data with the DAQ, to get rid of folding.
DAQ data can only be obtained for half of the rocket. Resonant peak obtained for half-rocket and extended onto
the full rocket. Assumed only parameter changing is length.
First resonant frequency at 178 Hz, which should appear at 22 Hz after folding.
€
f full =Lhalf
2
L full2 fhalf
Large vibration Strain gages along the body of the large
vibration rocket Strain gages measure changes in length
The magnitudes of the length changes can be used to determine characteristic vibration
Large vibration Strain gages along the body of the large
vibration rocket Strain gages measure changes in length
The magnitudes of the length changes can be used to determine characteristic vibration
Obtain raw data from the RDAS. Split up raw data according to events.
Takeoff, ejection charge and deployment, landing.
Perform FFT on each output channel. Assume the sensor closest to the motor is the
input for take off. Obtain FRF by taking the ratio of the output and
the input for the first event of the rocket. Determine resonance frequencies.
77 Hz
51 Hz46 Hz
f=77 Hz
0
100
200
300
400
500
600
0 20 40 60 80 100 120
Position (cm)
Relative Amplitude
f = 46 Hz
0
10
20
30
40
50
60
0 20 40 60 80 100 120
Position (cm)
Relative Amplitude
f = 51 Hz
0
50
100
150
200
250
0 20 40 60 80 100 120
Position (cm)
Relative Amplitude
Theoretical Predictions:
• Hollow beam model - 165 Hz
• DAQ experimental prediction - 178 Hz
Experimental Value - 154 Hz
Difference - 7%
Theoretical Predictions:
• Hollow beam model - 456 Hz
Experimental Value - 451 Hz
Difference - 1%
Theoretical Predictions:
• Hollow beam model - 893 Hz
Experimental Value - 877 Hz
Difference - 2%
Experimental vibration data matched theoretical model fairly closely
Data from large IMU rocket fit with flight model and RockSim shapes, but differed in altitude
RDAS and IMU data from temperature and pressure rocket agreed with each other, but fit neither of the theoretical models
Change sampling rate of RDAS (200 Hz is too low)
Use low-pass filters to block out unwanted noise
Have more than 6 channels collecting data
Have Global Positioning System onboard rocket for confirmation
Experimental ResultsA: x-positionB: y-positionC: z-position
Theoretical PredictionsA: z-position
(Rocksim)
Recovery charge did not ignite
Fatal flat spinDamage to the
RDAS
The natural frequency of a hollow tube is given by:
€
fn =ωn2π
=(β nL)2
2π
EIzρAL4
E = Young’s modulus, Iz = second moment of the beam, A = cross sectional area of the beam ρ = densityßnL= a property dependent on boundary conditions independent of length.
€
fhalf =(β nL)2
2π
EIzρA
1
Lhalf2
⎛
⎝ ⎜ ⎜
⎞
⎠ ⎟ ⎟
€
f full =(β nL)2
2π
EIzρA
1
L full2
⎛
⎝ ⎜ ⎜
⎞
⎠ ⎟ ⎟
k k
€
fhalff full
=L full
2
Lhalf2
€
f full =Lhalf
2
L full2 fhalf
€
⇒