1. 1 Miniature Parachute-Probe Dynamics Test-Bed Jessica Dooley* Ralph Lorenz** *Aerospace and Mechanical Engineering Department, University of Arizona **Lunar and Planetary Laboratory, University of Arizona

2. 2 Introduction Importance of detailed kinematics of descent Importance of detailed kinematics of descent  Motions affect scientific measurements  Wind shear response allows shears to be measured Critical review Critical review  Complex degree-of freedom models  Large cost for full-scale, instrumented vehicles

3. 3 Objective: Create a miniature test-bed… Create a miniature test-bed…  Low cost -Off-the-shelf components  Easy to use -Small-scale parachute-sensor packages -Hand-dropped from within a building  Gain familiarity with sensor data and corresponding motions of system

4. 4 Instrumentation Instrumentation on the probes Instrumentation on the probes  BASIC Stamp 2 and Basic-X24 micro controllers  Orthogonal triad of FGM-1 fluxgate magnetometers  ADXL202 2-axis accelerometers  MPi resonant piezo-electric rotation sensors  Nutex wireless video camera  Daventech SRF-04 sonar module Parachutes Parachutes  Apogee Rockets BasicX24 board, accel., gyro, SRF-04 Inside of multi-sensor probe

5. 5 Testing and Set-up Testing Phases Testing Phases  Preliminary pendulum  Preliminary drops  Compact probe drops  Probe drops with on-board camera  Multi-sensor drops Camcorder footage of descent with yellow chute Three versions of the parachute-probe Dynamics test-bed

6. 6 Data Analysis (1 of 4) General visualization with camcorder data General visualization with camcorder data  Vector between parachute apex and probe center  Cannot capture swings and motion towards and away from the camera Possible solution- use length of vector to indicate motion in other plane

7. 7 Data Analysis (2 of 4) Horizontal and vertical velocity with camcorder Horizontal and vertical velocity with camcorder  Reveal general patterns associated with simple pendulum motion - sinusoidal pattern -horizontal velocity has double the period of vertical velocity

8. 8 Data Analysis (3 of 4) On-Board sensor data On-Board sensor data  Z-axis acceleration record is asymmetric, not sinusoidal -Broad troughs and narrow peaks  Spikes often superimposed “hand-guided” pendulum test with 180 degree rotation at end-points “hand-guided” pendulum test with 180 degree rotation at mid-points Compact probe drop utilizing purple parachute.

9. 9 Data Analysis (4 of 4) On-board camera data On-board camera data  Plot constructed from frame by frame camcorder analysis shown below  Results inspired the use of gyros 3.063.133.263.333.46 3.533.633.733.863.93

10. 10 Simple Pendulum Model  Assumes probe-parachute system is a rigid pendulum  Parameters include length l, initial angular displacement theta0, phase, bias, and drag Model rarely matched data for more than one oscillation using measured values for model parameters Accelerometer data for 6 th drop on June 10th (on-board camera data on previous slide). No drag, relatively same effective l. Drag=0.40, l model=2.8m (where l measured = 2.11m)

11. 11 Summary Salient results: Salient results:  Correlation of spin with bottom of swing  Need for an effective pendulum l longer than measured l Miniature test-bed helped explore… Miniature test-bed helped explore…  Descent kinematics of planetary probe through an atmosphere  Interactions of parachute system with in-situ measurements Experiments… Experiments…  Relatively inexpensive and easy to assemble  May be useful in an educational setting

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