ASEN 3200 Orbital Mechanics and Attitude Dynamics Spring 2006
Assigned:
Report Due:
7 April 2006
18 April 2006
This experiment explores various characteristics of spinning spacecraft by observing animations created from numerical simulations and by interacting with a hardware mockup of a satellite. The concepts to be explored are
1) the effects of external torque, 2) the effects of energy dissipation on spin stability, and 3) oblate vs. prolate spin.
1) What conditions are required for the angular momentum vector of a spacecraft to move as seen from an inertial frame?
2) How does the angular velocity vector move in the body frame when the body is rigid (no internal dissipation)?
How does dissipation change this motion?
3) What distinguishes axisymmetric vs. asymmetric spacecraft? How can these cases be discriminated by observing spacecraft motion?
4) What do the terms oblate and prolate spin mean? How can these be distinguished by observing spacecraft motion?
5) If a spacecraft is spinning, describe how thrust must be applied to move the angular momentum vector in a desired direction.
6) What distinguishes nutation, precession, and simple spin?
A.
Begin by logging into your account on one of the ITLL computers. The files you will need are located in
H:\Spring 2005\asen3200\Public . This directory contains several AVI files, which can be opened and viewed by clicking on the corresponding icon. Each file contains an animation of a spinning spacecraft. The animation can be replayed, paused, etc., using the AVI player controls. View each AVI file, one at a time, to determine the properties of the spacecraft for part B below.
Classify the behavior of the spacecraft in each case according to the following criteria:
A1.) Torque-free motion or not? If torque is present, is the torque vector fixed in the inertial frame?
A2.) Internal energy dissipation or not? If dissipation is present, determine which principal axis (major, minor, or intermediate) is most closely aligned with the initial angular velocity.
A3.) Symmetric or asymmetric mass properties? (For spin about minor or major axis only.)
A4.) Is the spin oblate or prolate? (Use final spin when dissipation is present.)
B.
Sketch the physical hardware spacecraft mockup (i.e. the bicycle wheel with thrusters). Draw a diagram of the s/c showing the principle axes, the thruster direction, the angular velocity vector, and the angular momentum vector. Draw a block diagram of the components of the equipment and how they interact. Label all boxes and lines in your diagram. Determine when to fire the thruster on the spinning spacecraft mockup in order to precess the spin axis toward you. Try your idea on the actual hardware. Note the observed behavior carefully, distinguishing between nutation, precession, and simple spin.
A.
Present your analysis of the simulated s/c motions. Discuss your strategy for classifying the simulated behaviors. Justify your judgments with specific reasoning based on descriptions of observed motion, including diagrams as appropriate, together with the corresponding theory applying to that behavior.
B.
Describe your strategy for part B using diagrams, equations, and text. Discuss any difficulties encountered with the experimental hardware. Did you observe any nutation after thruster pulses were applied? How quickly did this dissipate into simple spin?
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ASEN 3200 Orbital Mechanics and Attitude Dynamics Spring 2006
Title Page (1 pt) – Lab, Course Number, Group Members, Date
Abstract (5pts)– short summary of objectives, experiment, results, and analysis
A. Spacecraft Animations (40 pts)
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Preliminary questions 1-4

Description of simulations

Analysis of spacecraft motion
B. Hardware Mockup Experiment (40 pts)

Preliminary question 5 and 6
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Experiment – 3 diagrams, procedures, observations

Analysis of results
Conclusions and Recommendations (5 pts)

What did you learn from this experiment?

What would you recommend to improve the experiment or to extend it beyond the given objectives?
Acknowledgements (1 pt) Who did what in the group and what outside assistance you received
References
[Style & Clarity 8 pts]
Organization (2) – clear flow, follows required outline, numbered pages
Figures (2) – clear figures, appropriate axes, informative titles
Tables (2) – clear tables, significant figures, headings, informative titles
Spelling & Grammar (2)
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