MAGIC Tether Post Deployment Analysis Deployed Tether Geometry

MAGIC Tether Post Deployment Analysis

Deployed Tether Geometry Tip Mass (5 kg) Velocity 20 m Libration Angle Nadir Main Structure (25 kg) Zenith Oscillating Frequencies: • Roll Oscillating Frequency = 0. 000368 Hz • Pitch Oscillating Frequency = 0. 000316 Hz • Yaw Oscillating Frequency = 0. 000177 Hz

Current Issues • Tension and Libration • Pendulum Motion Requires Accurate Deployment • Tether Tape Material Properties

Tension Analysis • For a 20 m tether, Tension will be approximately 0. 3 m. N. – Tension this low could fail to provide adequate control in the pitch and roll axes of DINO. – At low tension, tip mass and main structure would rotate freely until tension builds up.

Pendulum Motion • Pendulum motion of DINO in the pitch and roll axes might not damp out over time. • Accuracy of the deployment would define the pointing accuracy of DINO. – ± 10º off of nadir would be possible.

Material Properties • Thermal Expansion (20 x 106 mm/mm/K) 13. 7 cm expansion in sun • Thermal Snap-Contraction (100 x 10 -6/mm/mm/K) 68. 6 cm contraction in shade • Stress vs. Strain of Tether – Effective Modulus could differ from specs.

Conclusion • Issues/Risks – Lack of Tension – Pendulum Motion will not damp out – Tether expands and contracts in and out of sunlight • Recommendation – A boom would be more rigid and could provide more predictable control. – Build a emergency release mechanism for the tether if it is used and provide a backup such as a reaction wheel.

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