THE RESEARCH OF AEROBRAKE TECHNOLOGY USING ELECTRODYNAMIC TETHER

1. Master Thesis Presentation THE RESEARCH OF AEROBRAKE TECHNOLOGY USING ELECTRODYNAMIC TETHER Kazuhiko Yotsumoto Space Systems Dynamics Laboratory Department of Aeronautics and Astronautics

2. Contents • Introduction • Objective • Background • EDT (Electro-Dynamic Tether) • Simulation • Simulation Models • Initial and Final Conditions in Simulation • Comparison Differences • Simulation Results • Conclusions

3. Objective To verify the • Use of EDT • Aerobraking due to the Earth’s Atmosphere from GTO to LEO around the Earth. GTO (Geostationary Transfer Orbit) LEO (Low Earth Orbit)

4. Background Tether and Aerobraking are Attractive Orbit Transfer Means A 50-kg class Tether Satellite named “QTEX” is developed in SSDL Demonstrating this Concept around the Earth QTEX (Kyushu University Tether Satellite Experiments), H-IIA Rocket

5. Principle of EDT Earth @Equatorial Plane Induced EMF ： Decelerating Force ： EMF (Electro-Motive Force)

6. Tether Dynamics • Tether Conditions • Tether is rigid and straight • Tether has Mass • Assumptions • Point mass • Derivative of Moment of Inertia is assumed Constant • Inclination is Constant f : True Anomaly

7. Simulation Models 1 • Target Satellite • QTEX ： Summary of Configuration • Emitter Field Emitter Array Cathode • Collector Bare (Conductive) Tether

8. Simulation Models 2 • Orbital Perturbation • Only Atmospheric Drag is considered • Atmospheric Density used Exponential Model • Plasma Model • Original Model based on Test Case of International Reference Ionosphere 2001

9. Original Plasma Model Test Case Results

10. Simulation Models 3 • Magnetic Field Model • International Geomagnetic Reference Field 2005 • Numerical Integration Method • Adams-Bashforth-Moulton Method Procedure to obtain Solutions “Prediction→Evaluation→Correction→Evaluation”

11. Tether e e Simulation Models 4 • Current Estimation Method • OML (Orbital-Motion Limited) Theory can be adopted if Debye Length (2.3mm) ＞ Tether Radius d/2 (1mm) Debye Length OML Current per unit Length

12. Initial and Final Conditions • Initial Conditions At Perigee, is 0 [deg] and is 0 [deg/s] Starting Date and Time is January 1, 2000, at 0:00 a.m. Initial Attitude at Perigee is shown below m : Mother Satellite d : Daughter Satellite : Loading Emitter -90 < ψ [deg] < 90 • Final Condition • QTEX Altitude reaches 80 [km]

13. Comparison Differences Comparisons: [A] Between EDT and NOT EDT Satellite [B] Among various Tether Lengths [C] Among various Tether Diameters [D] Between “one-way current” Mode and “two-way current” Mode

14. Constraints of H-IIA Rocket ≦ 50kg Assumed QTEX Weight 40kg Comparison Differences Assumed Tether Parameters Available Tether Weight 10kg

15. Simulation Results 1 [A] Between EDT and NOT EDT Satellite EDT Satellite NOT EDT Satellite 35920 [km] / 53.8 [hours] 750 [km] / 1 [year] Due to only Atmospheric Drag Around Apogee “one-way” 750 [km]

16. Case 1 Results

17. Simulation Results 2 “one-way” [B] Among different Tether Lengths Case 1 Case 2 • Longer Length is more effective • Induced Electromotive Force Case 3 • Decelerating Force

18. Simulation Results 3 “one-way” [C] Among different Tether Diameters Case 1 Case 4 • Wider Diameter is more effective • OML Current Case 7

19. Simulation Results 4 [D] Between “one-way current” Mode and “two-way current” Mode “one-way” “two-way” Fs : Drag

20. Simulation Results 5 [D] Between “one-way current” Mode and “two-way current” Mode “one-way” “two-way” Fs : Drag

21. Conclusions • Orbit Transfer using the • Electrodynamic Tether • Aerobraking due to the Earth’s Atmosphere from GTO to LEO around the Earth is very effective. • Efficiency of EDT depends mainly on Angle GTO (Geostationary Transfer Orbit) LEO (Low Earth Orbit)

22. Thank you for your attention