DINO PDR 1212020 Gravity Gradient Tether Deployment Requirements
- Slides: 7
DINO PDR 12/1/2020 Gravity Gradient Tether Deployment • Requirements – 11 lb (5 kg) tip-mass must be deployed 65 ft (20 m) – Tip-mass must stay within 60º from zenith to retain gravity gradient stability – Tip off rate should be less than 3 °/s • Assumptions – ADCS will de-tumble satellite and make tip-mass zenith pointing • Pitch: ± 15º from zenith, ω < 0. 1 °/s • Roll: ± 5° from zenith, ω < 0. 25 °/s • Yaw: no pointing requirement, ω <. 5°/s Colorado Space Grant Consortium 1
DINO PDR 12/1/2020 Deployment Method • Open-Loop Deployment – Lightband will provide kickoff velocity of 2 ft/s • Deployment will take about 40 sec – Tether will be “left-behind” by tip mass – Coulomb Damper will provide braking for end of travel Main Satellite Tip Mass Tether Guides Velocity Lightband Braking System Tether Z-fold Colorado Space Grant Consortium 2
DINO PDR 12/1/2020 Tether • Low-density polyethylene tape – Along length are three strands of 0. 003 inch thick Spectra® 1000 • Used for rip-stop protection, not loadbearing • 0. 005 inch by 1 inch cross-section • Linear Density = 0. 002173 kg/m • Young’s Modulus = 3. 069 x 1010 N/m 2 • Flown on Advanced Tether Experiment (ATEx) mission Colorado Space Grant Consortium Tether Material 3
DINO PDR 12/1/2020 Lightband • 15 inch motorized separation system • Delta V = 2 ft/s • m ≈ 6. 5 lbm • Tip-off rate < 1º/s • Flight proven – Deployed Starshine-3 satellite from Athena launch vehicle in 2001 Colorado Space Grant Consortium 4
DINO PDR 12/1/2020 Braking System • Uses friction to dissipate deployment energy • Brakes tip-mass in last 3 ft. of deployment • Materials – Wheel – Anodized Al – Brake Shoe – Delrin AF • Ediss = 8. 22 in-lb – Ff =. 2284 lb Wheel Tether Brake shoe Colorado Space Grant Consortium 5
DINO PDR 12/1/2020 Failure Contingencies • Tether catching/snaging – Tether expected to twist after deployment – DOF of tether z-fold limited – Room provided between guides • Imperfect energy dissipation • Tip-off/stiction • Recoil Colorado Space Grant Consortium 6
DINO PDR 12/1/2020 Appendix A – Drag-along vs. Leave Behind Colorado Space Grant Consortium 7
