DINO MAGIC Tether 982021 MAGIC Tether Trade Study

DINO: MAGIC Tether 9/8/2021 MAGIC Tether Trade Study Anthony Lowrey Ryan Olds Andrew Mohler November 10, 2003

DINO: MAGIC Tether 9/8/2021 Background • Purpose of trade study – To assess the feasibility of the MAGIC Tether system • Concern about design was raised at the PDR • Thought of as high risk for DINO – To investigate possible alternatives to the tether • Requirements from DINO – Spacecraft must be nadir pointing • Affects Science, Power, Comm, ADCS Colorado Space Grant Consortium 2

DINO: MAGIC Tether 9/8/2021 Introduction to Tethers in Space • Gravity Gradient Stabilization – Lower mass has more gravitational than centrifugal force – Upper mass has more centrifugal than gravitational force – Lower mass slower – Upper mass faster Colorado Space Grant Consortium 3

DINO: MAGIC Tether 9/8/2021 Introduction to Tethers in Space • Important issues – Tether length and tension • The longer the tether length, the more tension – Tether material properties • Thermal expansion • Shape memory • Debris/micrometeorite resistance – Tether deployment • Recoil • Tip-off rate Colorado Space Grant Consortium 4

DINO: MAGIC Tether 9/8/2021 Past Tether Missions Org Satellite/ Tip Mass TSS-1 NASA Shuttle/550 kg 20 km Failure SEDS NASA Delta 2 nd Stage/25 kg 20 km Success SEDS II NASA Delta 2 nd Stage/25 kg 20 km Success (cut tether) TSS-R 1 NASA Shuttle/550 kg 20 km Ti. PS NRL ATEx NRL STEX/50 kg Tether Length Success/ Failure 4 km Success 6 km Failure Colorado Space Grant Consortium 5

DINO: MAGIC Tether 9/8/2021 Post-Deployment Tether Dynamics

DINO: MAGIC Tether 9/8/2021 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 Colorado Space Grant Consortium 7

DINO: MAGIC Tether 9/8/2021 Current Issues • Tension and Libration • Pendulum Motion Requires Accurate Deployment • Tether Tape Material Properties Colorado Space Grant Consortium 8

DINO: MAGIC Tether 9/8/2021 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. Colorado Space Grant Consortium 9

DINO: MAGIC Tether 9/8/2021 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. Colorado Space Grant Consortium 10

DINO: MAGIC Tether 9/8/2021 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. Colorado Space Grant Consortium 11

DINO: MAGIC Tether 9/8/2021 Tether Deployment

DINO: MAGIC Tether 9/8/2021 Design at PDR • Open-Loop Deployment – Lightband will provide kickoff velocity of 2 ft/s Brake • Deployment will take approximately 40 sec Tether – Tether will be “left-behind” by tip mass – Braking system will slow tip-mass near end of travel – Simple compared to a complex motor system Tip Mass Wheel (turning) Tether Guides Velocity Lightband Brake shoe (fixed) Braking System Tether Z-fold Colorado Space Grant Consortium 13

DINO: MAGIC Tether 9/8/2021 Deployment Suggested Changes • • • Longer tether Have extra tether on board Put tether on spool Add a feedback control system for braking Keep fast deployment Keep “leave-behind” method Colorado Space Grant Consortium 14

DINO: MAGIC Tether 9/8/2021 Booms

DINO: MAGIC Tether 9/8/2021 Introduction to Booms • Provides gravity gradient stabilization on small spacecraft – Accurate to within 5 deg of nadir • Used for “short” deployments (< 6 m) • High stiffness compared to tethers • Bigger and heavier than a tether Colorado Space Grant Consortium 16

DINO: MAGIC Tether 9/8/2021 Boom Types • There are 6 main boom types to consider: – STEM Boom – Elastic Memory Composite (EMC) Boom – STACER Boom (SSTL) – Coilable Booms – Inflatable Boom – Student-designed Colorado Space Grant Consortium 17

DINO: MAGIC Tether 9/8/2021 Student-Designed Boom (Cont. ) • Starsys – Designs many booms for customers – Jeff Harvey and Carlton Devillier offered to help • Both worked on booms at AEC Able for years • Suggested using 1 inch Stanley tape – Poor torsional stiffness, but more than tether – Deployment and damping mechanism still needed – Once deployed, it is sure to work • Said we should design ourselves – They will review our designs • Can provide flight qualified tape • Lightband could still be used Colorado Space Grant Consortium 18

DINO: MAGIC Tether 9/8/2021 Conclusions and Recommendations

DINO: MAGIC Tether 9/8/2021 Tether • Pros – Low mass – Already procured – Design started • Cons – – Hard to predict dynamics Very low tension at current length Difficult to deploy Tether material is not ideal Colorado Space Grant Consortium 20

DINO: MAGIC Tether 9/8/2021 Ways Tether Could Work • Lengthen tether – Longer tether would mean more tension • Tether Spool – More predictable control of tether • Controlled braking – Prevents recoil • Treat as an “experiment” and provide backup • Focus more attention on subsystem Colorado Space Grant Consortium 21

DINO: MAGIC Tether 9/8/2021 Boom • Pros – – Structurally rigid Easier to deploy More predictable dynamics A lot of flight experience • Cons – Greater mass and volume than tether – 6 meter (20 ft) maximum length – New design Colorado Space Grant Consortium 22

DINO: MAGIC Tether 9/8/2021 Trade Study Conclusion • Tether could work • Boom is better decision for DINO – Less risk than tether • Easier to win flight competition – Direct help from industry – Still a lot of student involvment Colorado Space Grant Consortium 23

DINO: MAGIC Tether 9/8/2021 Appendix A Colorado Space Grant Consortium 24

DINO: MAGIC Tether 9/8/2021 Advanced Tether Experiment (ATEx) • Purpose – Demonstrate tether stability and control – Fly a long term, survivable tether – 6 km tether experiment was to last 61 days • Deployment – Deployed at steady 2 cm/s using a stepper motor – Deployment was to take 3. 5 days • Sensors – Local angle sensor – 16 LED/detector pairs in a plane – Turns counter to measure length of deployed tether Colorado Space Grant Consortium 25

DINO: MAGIC Tether 9/8/2021 ATEx Deployment Colorado Space Grant Consortium 26

DINO: MAGIC Tether 9/8/2021 ATEx Failure • Launched atop STEX on 8/3/98 • Experiment began in 1/99 • Deployed 22 meters before being jettisoned by STEX – Tether blocked out-of-bounds LAS due to “excessive slack tether” • Determined reason for failure – Tethermal expansion • From eclipse to sun, tether expanded 6 inches Colorado Space Grant Consortium 27

DINO: MAGIC Tether 9/8/2021 ATEx Lessons Learned • Tethers can’t be fully tested on Earth – Good math models required in design – Provide large margins for error in design • Deployability of tether needed more consideration – Shape memory and CTE proved downfall • Experiment should be focus of mission Colorado Space Grant Consortium 28

DINO: MAGIC Tether 9/8/2021 STEM Boom • STEM: Storable Tubular Extendable Member – – – One of the oldest and most successful deployable booms Current stems use either Beryllium Copper or Stainless Steal Limited in size due to stored energy strains and high density Reel-stored Extendable Boom Analysis shows: • Significant reduction of mass • Improved specific stiffness • Reduced stored strain energy Colorado Space Grant Consortium 29

DINO: MAGIC Tether 9/8/2021 Elastic Memory Composite (EMC) Boom • CTD’s STEM boom – – A coilable Longeron Deployable Boom Deployment force provided by stain energy Made of unidirectional S-glass/epoxy Prototype EMC longerons exhibited • • • Highly predictable Repeatable structural response Packaging performance Significant reduction in system mass Reduced stored strain energy Colorado Space Grant Consortium 30

DINO: MAGIC Tether 9/8/2021 STACER Boom • SSTL-Weitzmann 6 m Deployable boom is – A rigid structure – Contains a prefabricated 1 -13 kg tip mass and deploying mechanism – Deploys at a rate of 0. 3 m/s – Has a mass of 2. 2 kg (without tip mass) – Requires 5 A for >10 msec. – A history of 25 years, with over 600 Units used Cons: *Has a storage size of 102 x 115 x 264 mm *Deploys using Pyro-Cutter actuation Colorado Space Grant Consortium 31

DINO: MAGIC Tether 9/8/2021 Coilable Booms • ABLE Coilable Booms – 100% Successful Flight Heritage – Two types • Lanyard Deployed – – – Most common Compact mass stowage (2% of deployed length) Extremely light weight capability (<50 g/m) Stowed strain energy gives positive deployment force Least expensive • Canister Deployed – Motor driven – Retractable/deployable – Larger stowage volume Colorado Space Grant Consortium 32

DINO: MAGIC Tether 9/8/2021 Inflatable Boom • Inflatable boom from ILC Dover – – Thermoset composites Thermally cured Power requirement of 0. 01 W/in^2 Heater performance(survivability) validated – Outgassing negligible outside of MLI – Deployment Component if desired (as shown above) BUT: -Expanded in a inflation gas reaction (gas tank required) -Less stiff of a structure than other boom types Colorado Space Grant Consortium 33

DINO: MAGIC Tether 9/8/2021 Student-Designed Boom • Citizen Explorer – 4 m boom, 2 kg tip mass – Uses three roles of stanley tape measure – Deployed using Starsys’ HOP Colorado Space Grant Consortium 34