1. University of Tokyo Dept. Aeronautics and Astronautics 43rd AIAA Aerospace Sciences Meeting, Reno, NV Inductively Coupled Plasmas Supported by Laser Plasmas for High Enthalpy Flow University of Tokyo O Takayoshi Inoue O Takayoshi Inoue Susumu Uehara Kimiya Komurasaki Yoshihiro Arakawa

2. University of Tokyo Dept. Aeronautics and Astronautics University of Tokyo Dept. Aeronautics and Astronautics 43rd AIAA Aerospace Sciences Meeting, Reno, NV Next decade of the space exploration Report produced by “ SSEDS ” “ New Frontiers in the Solar System ： An Integrated Exploration Strategy ” THE NATIONAL ACADEMIES PRESS, Washington DC, 2003. “ Venus In Situ Explorer ” is one of the prioritized missions http://www.nap.edu/

3. University of Tokyo Dept. Aeronautics and Astronautics University of Tokyo Dept. Aeronautics and Astronautics 43rd AIAA Aerospace Sciences Meeting, Reno, NV Venus probe Pioneer Venus ( 1978 ) Sever environment around the probe Heat flux~10 4 W/cm 2 Specific enthalpy ~44 MJ/kg Stagnation pressure~0.7 MPa T hermal P rotection S ystem (TPS) is a single-point-failiure subsystem TPS performance evaluation Development of new TPS material [B.Laub, and E.Venkatapathy; Proceedings of International Workshop on Planetary Probe Atmospheric Entry and Descent Trajectory Analysis and Science, Lisbon, 2003]

4. University of Tokyo Dept. Aeronautics and Astronautics University of Tokyo Dept. Aeronautics and Astronautics 43rd AIAA Aerospace Sciences Meeting, Reno, NV Need in Ground Facility State of development of ICP wind tunnels Power leveloperation pressure NAL/ JAXA (Japan)100-kW IPG1 ~ 50 kPa IRS ( Stuttgart Univ.)350-kW IPG3 ~ 2 kPa von Karman Inst.1-MW IPG3.5 ~ 10 kPa 100-kW IPG4 1 ~ 100 kPa Inductively Coupled Plasma (ICP) wind tunnel Atmospheric constituent of Venus 96 % CO 2 (H 2 O, SO 2 ….) Mars (Current target)Venus (Next target) Higher pressure of 0.7 MPa ・ electrodeless ・ less contamination

5. University of Tokyo Dept. Aeronautics and Astronautics University of Tokyo Dept. Aeronautics and Astronautics 43rd AIAA Aerospace Sciences Meeting, Reno, NV Objectives 1.To clarify the characteristics of Inductively Coupled Plasma with pressure of more than 1 atm »Development of an ICP generator »Operational condition »Stability 2.A proposal to stabilize the ICP by using a Laser plasma

6. University of Tokyo Dept. Aeronautics and Astronautics University of Tokyo Dept. Aeronautics and Astronautics 43rd AIAA Aerospace Sciences Meeting, Reno, NV ICP generator Tangential flow injection ring RF power supply 1.2 kW [13.56 MHz] Impedance Matching Network ICP discharge chamber Load coil 5 turns – 30 mm in diam. Work gas Argon

7. University of Tokyo Dept. Aeronautics and Astronautics University of Tokyo Dept. Aeronautics and Astronautics 43rd AIAA Aerospace Sciences Meeting, Reno, NV Atmospheric ICP generation ISet the mass flow rate to 0 g/s and the RF power output to 500 W resulting capacitively coupled plasma generation. IIGradually increased the mass flow rate and pressure coming to about 1 atm the mode transition occurred. III Once the ICP were produced, the flow rate, the pressure and RF power could be adjusted without inductive-capacitive mode transition. IIIIII

8. University of Tokyo Dept. Aeronautics and Astronautics University of Tokyo Dept. Aeronautics and Astronautics 43rd AIAA Aerospace Sciences Meeting, Reno, NV ICP instability Video images RF power 750 W, Argon

9. University of Tokyo Dept. Aeronautics and Astronautics University of Tokyo Dept. Aeronautics and Astronautics 43rd AIAA Aerospace Sciences Meeting, Reno, NV Operational condition Tangential flow effect Tangential flow injection bores 2 bores 1 mm in diam.  /2 to the axis Min. mass flow rate Pressure regulation gas : 0 g/s No contribution of Axial flow to the stable ICP generation

10. University of Tokyo Dept. Aeronautics and Astronautics University of Tokyo Dept. Aeronautics and Astronautics 43rd AIAA Aerospace Sciences Meeting, Reno, NV Operational condition Minimum mass flow rate Independent of the RF power Increase with the pressure Maximum mass flow rate Dependent on the RF power Decrease with the pressure Instabilities in a high power operation in a low mass flow rate operation have been reported. Instabilities in a high power operation in a low mass flow rate operation have been reported.

11. University of Tokyo Dept. Aeronautics and Astronautics University of Tokyo Dept. Aeronautics and Astronautics 43rd AIAA Aerospace Sciences Meeting, Reno, NV Tangential flow stabilization Analogy with the planer geometry Buoyancy force Gravity Stable Unstable Buoyancy force Centrifugal force Buoyancy force Stable

12. University of Tokyo Dept. Aeronautics and Astronautics University of Tokyo Dept. Aeronautics and Astronautics 43rd AIAA Aerospace Sciences Meeting, Reno, NV Injection rings Diameter of the bores  Type I 2 mm Type II 1 mm Type III 0.7 mm

13. University of Tokyo Dept. Aeronautics and Astronautics University of Tokyo Dept. Aeronautics and Astronautics 43rd AIAA Aerospace Sciences Meeting, Reno, NV Effect of the coil location Min. mass flow rate Tangential flow injection bores 2 bores 1 mm in diam.  /2 to the axis The decay of tangential flow lead to the increase in the mass flow rate.

14. University of Tokyo Dept. Aeronautics and Astronautics University of Tokyo Dept. Aeronautics and Astronautics 43rd AIAA Aerospace Sciences Meeting, Reno, NV Injection rings Injection angle Type IV has the angle of  /4 to the axis

15. University of Tokyo Dept. Aeronautics and Astronautics University of Tokyo Dept. Aeronautics and Astronautics 43rd AIAA Aerospace Sciences Meeting, Reno, NV Oscillation 15 Hz 17 Hz 34 Hz 51 Hz 68 Hz 32 Hz CCD images Light emission Reflected power

16. University of Tokyo Dept. Aeronautics and Astronautics University of Tokyo Dept. Aeronautics and Astronautics 43rd AIAA Aerospace Sciences Meeting, Reno, NV Oscillation frequency Frequency v.s. Mass flow rate Strong relation between the frequency and the mass flow rate

17. University of Tokyo Dept. Aeronautics and Astronautics University of Tokyo Dept. Aeronautics and Astronautics 43rd AIAA Aerospace Sciences Meeting, Reno, NV Interim summary Experimental investigation on Inductively Coupled Plasmas stability were conducted, and can be summarized as follows; ICP was stably generated with 0.1 ~ 0.4 MPa atmospheres by using 1.25 kW RF power source. Stably operational condition became limited with the increase in the pressure. Tangential flow injection has the essential role in the stable ICP generation though the design of the injection ring affects the operational conditions of ICPs.

18. University of Tokyo Dept. Aeronautics and Astronautics University of Tokyo Dept. Aeronautics and Astronautics 43rd AIAA Aerospace Sciences Meeting, Reno, NV Stable ICP generation w/o tangential flow

19. University of Tokyo Dept. Aeronautics and Astronautics University of Tokyo Dept. Aeronautics and Astronautics 43rd AIAA Aerospace Sciences Meeting, Reno, NV Stabilization using LASER PLASMA Requirement for the stabilization There should be some mechanisms which keep the ICP geometry axisymmetric

20. University of Tokyo Dept. Aeronautics and Astronautics University of Tokyo Dept. Aeronautics and Astronautics 43rd AIAA Aerospace Sciences Meeting, Reno, NV Experimental setup CO 2 TEM 00 Laser Wage length 10.6  m Max. power 2 kW Specifications Condensing lens MaterialZnSe Focal length210 mm F-number6.3

21. University of Tokyo Dept. Aeronautics and Astronautics University of Tokyo Dept. Aeronautics and Astronautics 43rd AIAA Aerospace Sciences Meeting, Reno, NV Fundamental experiment Laser 700 W + RF 0W Laser 700 W + RF 700W LSP Ignition rod Focal point Lens Laser Coil

22. University of Tokyo Dept. Aeronautics and Astronautics University of Tokyo Dept. Aeronautics and Astronautics 43rd AIAA Aerospace Sciences Meeting, Reno, NV Fundamental experiment LSP Ignition rod Focal point Coil Lens Laser

23. University of Tokyo Dept. Aeronautics and Astronautics University of Tokyo Dept. Aeronautics and Astronautics 43rd AIAA Aerospace Sciences Meeting, Reno, NV Fundamental experiment Laser 700 W + RF 0W Laser 700 W + RF 700W Stabilization w/o tangential flow was successfully demonstrated Zoom of the discharge torch CCD images Absorbed laser power 300 W LSP Ignition rod Focal point Coil Lens Laser Gas

24. University of Tokyo Dept. Aeronautics and Astronautics University of Tokyo Dept. Aeronautics and Astronautics 43rd AIAA Aerospace Sciences Meeting, Reno, NV Double tube configuration

25. University of Tokyo Dept. Aeronautics and Astronautics University of Tokyo Dept. Aeronautics and Astronautics 43rd AIAA Aerospace Sciences Meeting, Reno, NV LSP in the double tube configuration LSP was sustained in the inner tube stably Operational condition was improved LSP generation limit

26. University of Tokyo Dept. Aeronautics and Astronautics University of Tokyo Dept. Aeronautics and Astronautics 43rd AIAA Aerospace Sciences Meeting, Reno, NV ICP generation in the double tube configuration Z~45mm Z~30mm Z ~ 40 mm Also in the double tube configuration, ICP was generated stably w/o tangential flow injection

27. University of Tokyo Dept. Aeronautics and Astronautics University of Tokyo Dept. Aeronautics and Astronautics 43rd AIAA Aerospace Sciences Meeting, Reno, NV Summary Tangential flow injection has the essential role in the stable atmospheric ICP generation though the design of the injection ring affects the operational conditions of ICPs. By using Laser plasma, atmospheric ICP can be generated stably. Double tube configuration enable to control the flow parameters of the LSP and ICP independently.

28. University of Tokyo Dept. Aeronautics and Astronautics University of Tokyo Dept. Aeronautics and Astronautics 43rd AIAA Aerospace Sciences Meeting, Reno, NV Next issues In this study ….  Modeling of the stabilization is not enough  No production of the free jet.  No discussion in terms of the enthalpy and the efficiency. Efforts should be directed to … Establishment of an analytical model of the stability. Acceleration of the flow by a Laval nozzle. Evaluation of the performance of the Atmospheric ICPG and its relation with the stability

29. University of Tokyo Dept. Aeronautics and Astronautics University of Tokyo Dept. Aeronautics and Astronautics 43rd AIAA Aerospace Sciences Meeting, Reno, NV Other researches Herdrich, G., et.al., @ IRS J.Thermophyscs Heat Trans., Vol16, 448, 2002