Ikkoh Funaki | Japan Aerospace Exploration Agency (original) (raw)
Papers by Ikkoh Funaki
Journal of Spacecraft and Rockets, 2006
= vibrational-electronic-electron enthalpy of species s I s = first ionization energy of species ... more = vibrational-electronic-electron enthalpy of species s I s = first ionization energy of species s J = vector of electric current density J r , J θ , J z = components of electric current density in the r , θ , and z directions
Astrophysics and Space Science, 2007
To propel a spacecraft in the direction leaving the Sun, a magnetic sail (MagSail) blocks the hyp... more To propel a spacecraft in the direction leaving the Sun, a magnetic sail (MagSail) blocks the hypersonic solar wind plasma flow by an artificial magnetic field. In order to simulate the interaction between the solar wind and the artificially deployed magnetic field produced around a magnetic sail spacecraft, a laboratory simulator was designed and constructed inside a space chamber. As a solar wind simulator, a high-power magnetoplasmadynamic arcjet is operated in a quasisteady mode of 0.8 ms duration. It can generate a simulated solar wind that is a high-speed (above 20 km/s), high-density (1018 m−3) hydrogen plasma plume of ∼0.7 m in diameter. A small coil (2 cm in diameter), which is to simulate a magnetic sail spacecraft and can obtain 1.9-T magnetic field strength at its center, was immersed inside the simulated solar wind. Using these devices, the formation of a magnetic cavity (∼8 cm in radius) was observed around the coil, which indicates successful simulation of the plasma flow of a MagSail in the laboratory.
Transactions of The Japan Society for Aeronautical and Space Sciences, 2006
In the MUCES-C mission conducted by JAXA (Japan Aero Exploration Agency), a microwave neutralizer... more In the MUCES-C mission conducted by JAXA (Japan Aero Exploration Agency), a microwave neutralizer is mounted with a microwave ion engine on the HAYABUSA space probe. The neutralizer consists of an L-shaped antenna to inject microwaves and samarium cobalt magnets to provide ECR (electron cyclotron resonance). Plasma production of a higher density than the cutoff density is expected in the discharge chamber, but the neutralizer is so small that high-precision measurements using a probe are difficult. To clarify the plasma production mechanism in the microwave neutralizer, numerical analysis was conducted using a code coupling PIC (particle-in-cell) method, and a FDTD (finite-difference-time-domain) method. This paper describes effects caused by varying magnetic field configuration and antenna position in the neutralizer. The calculation results show that bringing the antenna closer to the ECR region is effective for plasma production.
Journal of Spacecraft and Rockets, 2006
The problem of plasma flow relative to a modulated magnetic field has been the subject of several... more The problem of plasma flow relative to a modulated magnetic field has been the subject of several studies. One motivation for studying this problem is the possibility of using a deliberately imposed surface of magnetic islands as a means of velocity profile control. This subject is also of importance for the study of stability against ideal and resistive magnetohydrodynamic (MHD) modes and the topic of locked modes. A two-dimensional (2-D) MHD simulation code is used to examine the behavior of a plasma flowing, in steady state, past a modulated magnetic field in "slab geometry." It is shown that at "low" velocities the stress is dominated by the Maxwell and the viscosity terms and that forces are exchanged between the plasma and the magnetic field in a narrow boundary surrounding the island. It is found that the island is suppressed when the viscous force at the separatrix exceeds the maximum force that can be supported by an island. For "high" velocities (velocities beyond the critical velocity for island suppression), the stress is dominated by the Maxwell and the Reynolds terms, and the exchange of forces is taking place in a narrow region around the point where the plasma flow velocity matches the Alfvin speed. 0 199.5 American Institute of Physics.
Journal of The Japan Society for Aeronautical and Space Sciences, 2006
ABSTRACT In order to simulate the interaction between the solar wind and the artificially deploye... more ABSTRACT In order to simulate the interaction between the solar wind and the artificially deployed magnetic field produced around a magnetic sail spacecraft, a laboratory simulator was designed and constructed inside the space chamber (2m in diameter) at ISAS. As a solar wind simulator, a high-power magnetoplasmadynamic arcjet is operated in a quasisteady mode of ˜0.8ms duration. It can generate a simulated solar wind flow that is a high-speed (above 20km/s), high-density (above 1017m-3) hydrogen plasma plume of ˜70cm in diameter. A small coil (18mm in diameter), which is to simulate a magnetic sail spacecraft and can obtain 1.9-T magnetic field strength at its center, was immersed inside the simulated solar wind. Using these devices, the formation of a magnetic cavity (˜8cm in radius) was observed around the coil, which indicates successful simulation of the plasma flow around the coil (simulated magnetic sail spacecraft) in the laboratory.
Japanese Journal of Applied Physics, 1998
ABSTRACT Operation of an ion engine in space requires an electron source to maintain the spacecra... more ABSTRACT Operation of an ion engine in space requires an electron source to maintain the spacecraft's electrical neutrality. To neutralize exhausted ions, a low-power, compact microwave electron source was developed. An 18-mm-diameter noncavity-type discharge chamber consisting of an L-shaped antenna and a magnetic circuit was developed, and electron emission current of 100 mA was obtained at the power level of 10 W, maintaining the mass flow rate of xenon at 0.5 sccm.
Journal of Propulsion and Power, 2009
A spacecraft propulsion system utilizing the energy of the solar wind was reviewed. The first pla... more A spacecraft propulsion system utilizing the energy of the solar wind was reviewed. The first plasma sail concept was proposed by Prof. Winglee in 2000, and that was called M2P2 (mini-magnetospheric plasma-propulsion). However, the first M2P2 design adopting a small (20-cm-diamter) coil and a small helicon plasma source design was criticized by Dr. Khazanov in 2003. He insisted that: 1) MHD is not an appropriate approximation to describe the M2P2 design by Winglee, and with ion kinetic simulation, it was shown that the M2P2 design could provide only negligible thrust; 2) considerably larger sails (than that Winglee proposed) would be required to tap the energy of the solar wind. We started our plasma sail study in 2003, and it was shown that moderately sized magnetic sails in the ion inertial scale (~70 km) can produce sub-Newton-class thrust. Currently, we are continuing our efforts to make a feasibly sized plasma sail (Magnetoplasma sail) by optimizing its physical processes and spacecraft design.
Journal of Propulsion and Power, 2007
ABSTRACT A miniaturized microwave ion source with a 1.6-cm beam diameter grid system was designed... more ABSTRACT A miniaturized microwave ion source with a 1.6-cm beam diameter grid system was designed and then evaluated experimentally. based on the HAYABUSA mu 10 neutralizer, we fabricated a small 18-mm-diam discharge chamber, into which 4.2 GHz microwaves were launched through an L-shaped antenna that was located in a magnetic field created by permanent magnets and iron yokes. Ion beams were emitted from the small discharge chamber when operated with a grid system whose respective hole diameters of the screen grid and acceleration grid were 0.72 and 0.43 mm, and the total number of grid holes was 211. For a beam voltage of 1500 V and a microwave input power of 10 W, the typical thruster performance was thrust of 0.34 mN, a thrust/power ratio of 16 mN/kW, propellant utilization efficiency of 68%, and a specific impulse of 3200 s. If we were able to further reduce the ion production cost (circa 3000 W/A in the current experiment), this thruster would be a candidate for main propulsion of a small satellite or precise attitude control of various sizes of satellites.
Journal of Propulsion and Power, 1998
ABSTRACT Thrust performance and internal plasma flowfield of a 1-MW class self-field magnetoplasm... more ABSTRACT Thrust performance and internal plasma flowfield of a 1-MW class self-field magnetoplasmadynamic (MPD) arcjet were measured to evaluate their dependence on the cross-sectional geometry of the electrodes. A multichannel two-dimensional MPD arcjet in quasisteady operation was used to visualize the two-dimensional flowfield and reveal the correlation between the internal flowfield and the thrust performance. The experimental results for six different electrode configurations show that the thrust performance strongly depends on the thruster chamber cross-sectional geometries for the I-sp range of interest, 1000-3000 s. The cathode length determined the engine performance, regardless of the anode geometry. In particular, the convergent-divergent anode with a short cathode showed the best performance. The superior acceleration mechanism of the short cathode was explained on the basis of typo-dimensional plasma distributions such as discharge current contours and plasma density obtained by Mach-Zehnder interferometry. A dense plasma region near the tip of the short cathode was observed and subsequent expansion guided by the diverging nozzle call enhance aerodynamic acceleration, which contributes to large thrust generation.
Electron Cyclotron Resonance (ECR) discharge ion engine system, which is operated at a total powe... more Electron Cyclotron Resonance (ECR) discharge ion engine system, which is operated at a total power level of 1 kW and a thrust level of 30mN. This paper presents experimental results on the development of a 20-cm-diam ECR discharge chamber. This plasma generator utilizes samarium-cobalt magnets and microwave power at a frequency of 4.25GHz. The microwave power is introduced from a microwave power source via a coaxial cable followed by a coaxial-to-waveguide transformer. The performance of the device at its most optimum configuration features 500mA of extracted ion current, and 260eV/ion of discharge loss at a net microwave power of 130W.
Journal of Propulsion and Power, 2004
ABSTRACT Plasma characterization was conducted for an electron-cyclotron-resonance (ECR) type ion... more ABSTRACT Plasma characterization was conducted for an electron-cyclotron-resonance (ECR) type ion thruster. For a 10-cm diameter microwave discharge ion source consisting of two samarium cobalt magnet rings surrounding a centered waveguide for launching microwaves, plasma profiles were found to have severely non-uniform distributions, with localized plasma found near the magnet rings. This localized plasma is mainly produced in the magnetic flux tubes between the two ring magnets, where electrons gain microwave energy as they pass the ECR line during the bouncing movement between magnetic mirrors. To obtain a low-cost microwave ion source, this type of ionization mechanism can be exploited. When introducing microwaves through a low magnetic field boundary, however, it is impossible to eliminate the accessibility difficulty related to the cutoff density, which results in a plasma below the cutoff density. Because of the accessibility difficulty, in this work, only a relatively small ion beam current density of 1.8 mA/cm(2) was achieved.
ABSTRACT Magneto Plasma Sail (MPS) is a propulsion system making use of the solar wind. This prop... more ABSTRACT Magneto Plasma Sail (MPS) is a propulsion system making use of the solar wind. This propulsion system creates a strong magnetic field using a super-conducting coil and plasma jets, and the magnetic field works as a "sail" catching the solar wind to generate thrust. However, the feasibility of MPS is now under discussion because the momentum transfer process from the solar wind to the spacecraft is a complicated electromagnetic process and so the process has not been clarified specifically. In this study, we studied the process based on the ideal magnetohydrodynamic approximation. We simulated MPS for various Alfven Mach numbers of the plasma jet at the nozzle exit, and the relation between the thrust of MPS and the Alfven Mach number of the plasma jet was analyzed in detail. As the result, when the plasma jet at the high Alfven Mach number is injected in all direction and the termination shock forms all around the spacecraft, MPS can not produce thrust. This means the magnetohydrodynamic waves play important roll to transfer the momentum of the solar wind to the spacecraft as thrust. However, the plasma jet at a low Alfven Mach number can not produce large thrust because the large magnetosphere can not be created. Based on that result, the improved method for MPS was proposed; using the high Alfven Mach number plasma jet in only one direction, MPS can generate not only the large thrust by capturing the solar wind but also the thrust by the plasma jet.
Astrophysics and Space Science, 2007
To propel a spacecraft in the direction leaving the Sun, a magnetic sail (MagSail) blocks the hyp... more To propel a spacecraft in the direction leaving the Sun, a magnetic sail (MagSail) blocks the hypersonic solar wind plasma flow by an artificial magnetic field. In order to simulate the interaction between the solar wind and the artificially deployed magnetic field produced around a magnetic sail spacecraft, a laboratory simulator was designed and constructed inside a space chamber. As a solar wind simulator, a high-power magnetoplasmadynamic arcjet is operated in a quasisteady mode of 0.8 ms duration. It can generate a simulated solar wind that is a high-speed (above 20 km/s), high-density (1018 m−3) hydrogen plasma plume of ∼0.7 m in diameter. A small coil (2 cm in diameter), which is to simulate a magnetic sail spacecraft and can obtain 1.9-T magnetic field strength at its center, was immersed inside the simulated solar wind. Using these devices, the formation of a magnetic cavity (∼8 cm in radius) was observed around the coil, which indicates successful simulation of the plasma flow of a MagSail in the laboratory.
ABSTRACT Both experimental velocimetry with plasma diagnostics and numerical analysis in the disc... more ABSTRACT Both experimental velocimetry with plasma diagnostics and numerical analysis in the discharge chamber of a two-dimensional magnetoplasmadynamic (2D-MPD) arcjet were conducted in order to investigate the acceleration mechanisms in the case of hydrogen propellant. In the experiment, we estimated the velocity and temperature of the neutral atoms from the laser absorption profile, ion velocity and Mach number from TOF and Mach probe method respectively and electron temperature and plasma density from the Langmuir probe method. Results using two types of anodes, one being a conventional flared type anode and the other being a converging- diverging (C-D) type anode, were compared. It was found that there is region where ion-neutral velocity slip takes place and the acceleration of the neutral particles is not high enough. This phenomenon is the factor that decreases thrust performance and is due to the fact that the number of ion-neutral momentum transfer collisions is not high enough, so that neutrals cannot accelerate sufficiently. Comparing two types of anodes, the performance of the configuration employing a C-D anode was found to be relatively high especially at low Isp operation. This was explained by considering that the ion-neutral couple region was wider in this case, or, in other words, the region where velocity slip takes place was relatively small. However, at high Isp operation, flared anode is superior because electromagnetic acceleration is dominant in this anode shape.
Journal of Propulsion and Power, 2002
Transactions of The Japan Society for Aeronautical and Space Sciences, 2006
In the MUCES-C mission conducted by JAXA (Japan Aero Exploration Agency), a microwave neutralizer... more In the MUCES-C mission conducted by JAXA (Japan Aero Exploration Agency), a microwave neutralizer is mounted with a microwave ion engine on the HAYABUSA space probe. The neutralizer consists of an L-shaped antenna to inject microwaves and samarium cobalt magnets to provide ECR (electron cyclotron resonance). Plasma production of a higher density than the cutoff density is expected in the discharge chamber, but the neutralizer is so small that high-precision measurements using a probe are difficult. To clarify the plasma production mechanism in the microwave neutralizer, numerical analysis was conducted using a code coupling PIC (particle-in-cell) method, and a FDTD (finite-difference-time-domain) method. This paper describes effects caused by varying magnetic field configuration and antenna position in the neutralizer. The calculation results show that bringing the antenna closer to the ECR region is effective for plasma production.
Journal of The Japan Society for Aeronautical and Space Sciences, 2004
ABSTRACT A magneto-plasma sail produces the propulsive force due to the interaction between the a... more ABSTRACT A magneto-plasma sail produces the propulsive force due to the interaction between the artificial magnetic field around a spacecraft inflated by the plasma and the solar wind erupted from the Sun. The inflation of the magnetic field by the plasma was proposed by a group of the University of Washington and the basic research has just started. This paper summarizes the characteristics of the magneto plasma sail by comparing with the other low-thrust propulsion systems, and investigates its potential application to near future planetary missions. Finally, an engineering satellite to demonstrate the magneto-plasma sail is proposed as a first step.
Journal of Spacecraft and Rockets, 2006
The problem of plasma flow relative to a modulated magnetic field has been the subject of several... more The problem of plasma flow relative to a modulated magnetic field has been the subject of several studies. One motivation for studying this problem is the possibility of using a deliberately imposed surface of magnetic islands as a means of velocity profile control. This subject is also of importance for the study of stability against ideal and resistive magnetohydrodynamic (MHD) modes and the topic of locked modes. A two-dimensional (2-D) MHD simulation code is used to examine the behavior of a plasma flowing, in steady state, past a modulated magnetic field in "slab geometry." It is shown that at "low" velocities the stress is dominated by the Maxwell and the viscosity terms and that forces are exchanged between the plasma and the magnetic field in a narrow boundary surrounding the island. It is found that the island is suppressed when the viscous force at the separatrix exceeds the maximum force that can be supported by an island. For "high" velocities (velocities beyond the critical velocity for island suppression), the stress is dominated by the Maxwell and the Reynolds terms, and the exchange of forces is taking place in a narrow region around the point where the plasma flow velocity matches the Alfvin speed. 0 199.5 American Institute of Physics.
Journal of The Japan Society for Aeronautical and Space Sciences, 2002
Noise and oscillatory behavior of a plasma column produced in front of the microwave discharge ne... more Noise and oscillatory behavior of a plasma column produced in front of the microwave discharge neutralizer developed for MUSES-C mission were experimentally investigated. Radiated electric field emissions were measured following to MIL-STD-461 E. The average noise level exceeded the narrowband specification by 30 dBμV/m at frequencies less than 5 MHz. Noise in electron emission current was also measured by using a current probe and a spectrum analyzer, and was compared with the noise of a hollow cathode. The microwave discharge neutralizer generates a broadband noise and oscillations which have a fundamental frequency of about 160 kHz and are accompanied by its harmonics up to the 5th. Considering the dependence on the diameter of the plasma column, they are probably the radial oscillation modes of ion acoustic waves. Although the hollow cathode shows nearly the same noise level at frequencies less than 1 MHz, intense oscillation exists in the 1-10 MHz range, which is generated by the keeper plasma.
Journal of Spacecraft and Rockets, 2006
= vibrational-electronic-electron enthalpy of species s I s = first ionization energy of species ... more = vibrational-electronic-electron enthalpy of species s I s = first ionization energy of species s J = vector of electric current density J r , J θ , J z = components of electric current density in the r , θ , and z directions
Astrophysics and Space Science, 2007
To propel a spacecraft in the direction leaving the Sun, a magnetic sail (MagSail) blocks the hyp... more To propel a spacecraft in the direction leaving the Sun, a magnetic sail (MagSail) blocks the hypersonic solar wind plasma flow by an artificial magnetic field. In order to simulate the interaction between the solar wind and the artificially deployed magnetic field produced around a magnetic sail spacecraft, a laboratory simulator was designed and constructed inside a space chamber. As a solar wind simulator, a high-power magnetoplasmadynamic arcjet is operated in a quasisteady mode of 0.8 ms duration. It can generate a simulated solar wind that is a high-speed (above 20 km/s), high-density (1018 m−3) hydrogen plasma plume of ∼0.7 m in diameter. A small coil (2 cm in diameter), which is to simulate a magnetic sail spacecraft and can obtain 1.9-T magnetic field strength at its center, was immersed inside the simulated solar wind. Using these devices, the formation of a magnetic cavity (∼8 cm in radius) was observed around the coil, which indicates successful simulation of the plasma flow of a MagSail in the laboratory.
Transactions of The Japan Society for Aeronautical and Space Sciences, 2006
In the MUCES-C mission conducted by JAXA (Japan Aero Exploration Agency), a microwave neutralizer... more In the MUCES-C mission conducted by JAXA (Japan Aero Exploration Agency), a microwave neutralizer is mounted with a microwave ion engine on the HAYABUSA space probe. The neutralizer consists of an L-shaped antenna to inject microwaves and samarium cobalt magnets to provide ECR (electron cyclotron resonance). Plasma production of a higher density than the cutoff density is expected in the discharge chamber, but the neutralizer is so small that high-precision measurements using a probe are difficult. To clarify the plasma production mechanism in the microwave neutralizer, numerical analysis was conducted using a code coupling PIC (particle-in-cell) method, and a FDTD (finite-difference-time-domain) method. This paper describes effects caused by varying magnetic field configuration and antenna position in the neutralizer. The calculation results show that bringing the antenna closer to the ECR region is effective for plasma production.
Journal of Spacecraft and Rockets, 2006
The problem of plasma flow relative to a modulated magnetic field has been the subject of several... more The problem of plasma flow relative to a modulated magnetic field has been the subject of several studies. One motivation for studying this problem is the possibility of using a deliberately imposed surface of magnetic islands as a means of velocity profile control. This subject is also of importance for the study of stability against ideal and resistive magnetohydrodynamic (MHD) modes and the topic of locked modes. A two-dimensional (2-D) MHD simulation code is used to examine the behavior of a plasma flowing, in steady state, past a modulated magnetic field in "slab geometry." It is shown that at "low" velocities the stress is dominated by the Maxwell and the viscosity terms and that forces are exchanged between the plasma and the magnetic field in a narrow boundary surrounding the island. It is found that the island is suppressed when the viscous force at the separatrix exceeds the maximum force that can be supported by an island. For "high" velocities (velocities beyond the critical velocity for island suppression), the stress is dominated by the Maxwell and the Reynolds terms, and the exchange of forces is taking place in a narrow region around the point where the plasma flow velocity matches the Alfvin speed. 0 199.5 American Institute of Physics.
Journal of The Japan Society for Aeronautical and Space Sciences, 2006
ABSTRACT In order to simulate the interaction between the solar wind and the artificially deploye... more ABSTRACT In order to simulate the interaction between the solar wind and the artificially deployed magnetic field produced around a magnetic sail spacecraft, a laboratory simulator was designed and constructed inside the space chamber (2m in diameter) at ISAS. As a solar wind simulator, a high-power magnetoplasmadynamic arcjet is operated in a quasisteady mode of ˜0.8ms duration. It can generate a simulated solar wind flow that is a high-speed (above 20km/s), high-density (above 1017m-3) hydrogen plasma plume of ˜70cm in diameter. A small coil (18mm in diameter), which is to simulate a magnetic sail spacecraft and can obtain 1.9-T magnetic field strength at its center, was immersed inside the simulated solar wind. Using these devices, the formation of a magnetic cavity (˜8cm in radius) was observed around the coil, which indicates successful simulation of the plasma flow around the coil (simulated magnetic sail spacecraft) in the laboratory.
Japanese Journal of Applied Physics, 1998
ABSTRACT Operation of an ion engine in space requires an electron source to maintain the spacecra... more ABSTRACT Operation of an ion engine in space requires an electron source to maintain the spacecraft's electrical neutrality. To neutralize exhausted ions, a low-power, compact microwave electron source was developed. An 18-mm-diameter noncavity-type discharge chamber consisting of an L-shaped antenna and a magnetic circuit was developed, and electron emission current of 100 mA was obtained at the power level of 10 W, maintaining the mass flow rate of xenon at 0.5 sccm.
Journal of Propulsion and Power, 2009
A spacecraft propulsion system utilizing the energy of the solar wind was reviewed. The first pla... more A spacecraft propulsion system utilizing the energy of the solar wind was reviewed. The first plasma sail concept was proposed by Prof. Winglee in 2000, and that was called M2P2 (mini-magnetospheric plasma-propulsion). However, the first M2P2 design adopting a small (20-cm-diamter) coil and a small helicon plasma source design was criticized by Dr. Khazanov in 2003. He insisted that: 1) MHD is not an appropriate approximation to describe the M2P2 design by Winglee, and with ion kinetic simulation, it was shown that the M2P2 design could provide only negligible thrust; 2) considerably larger sails (than that Winglee proposed) would be required to tap the energy of the solar wind. We started our plasma sail study in 2003, and it was shown that moderately sized magnetic sails in the ion inertial scale (~70 km) can produce sub-Newton-class thrust. Currently, we are continuing our efforts to make a feasibly sized plasma sail (Magnetoplasma sail) by optimizing its physical processes and spacecraft design.
Journal of Propulsion and Power, 2007
ABSTRACT A miniaturized microwave ion source with a 1.6-cm beam diameter grid system was designed... more ABSTRACT A miniaturized microwave ion source with a 1.6-cm beam diameter grid system was designed and then evaluated experimentally. based on the HAYABUSA mu 10 neutralizer, we fabricated a small 18-mm-diam discharge chamber, into which 4.2 GHz microwaves were launched through an L-shaped antenna that was located in a magnetic field created by permanent magnets and iron yokes. Ion beams were emitted from the small discharge chamber when operated with a grid system whose respective hole diameters of the screen grid and acceleration grid were 0.72 and 0.43 mm, and the total number of grid holes was 211. For a beam voltage of 1500 V and a microwave input power of 10 W, the typical thruster performance was thrust of 0.34 mN, a thrust/power ratio of 16 mN/kW, propellant utilization efficiency of 68%, and a specific impulse of 3200 s. If we were able to further reduce the ion production cost (circa 3000 W/A in the current experiment), this thruster would be a candidate for main propulsion of a small satellite or precise attitude control of various sizes of satellites.
Journal of Propulsion and Power, 1998
ABSTRACT Thrust performance and internal plasma flowfield of a 1-MW class self-field magnetoplasm... more ABSTRACT Thrust performance and internal plasma flowfield of a 1-MW class self-field magnetoplasmadynamic (MPD) arcjet were measured to evaluate their dependence on the cross-sectional geometry of the electrodes. A multichannel two-dimensional MPD arcjet in quasisteady operation was used to visualize the two-dimensional flowfield and reveal the correlation between the internal flowfield and the thrust performance. The experimental results for six different electrode configurations show that the thrust performance strongly depends on the thruster chamber cross-sectional geometries for the I-sp range of interest, 1000-3000 s. The cathode length determined the engine performance, regardless of the anode geometry. In particular, the convergent-divergent anode with a short cathode showed the best performance. The superior acceleration mechanism of the short cathode was explained on the basis of typo-dimensional plasma distributions such as discharge current contours and plasma density obtained by Mach-Zehnder interferometry. A dense plasma region near the tip of the short cathode was observed and subsequent expansion guided by the diverging nozzle call enhance aerodynamic acceleration, which contributes to large thrust generation.
Electron Cyclotron Resonance (ECR) discharge ion engine system, which is operated at a total powe... more Electron Cyclotron Resonance (ECR) discharge ion engine system, which is operated at a total power level of 1 kW and a thrust level of 30mN. This paper presents experimental results on the development of a 20-cm-diam ECR discharge chamber. This plasma generator utilizes samarium-cobalt magnets and microwave power at a frequency of 4.25GHz. The microwave power is introduced from a microwave power source via a coaxial cable followed by a coaxial-to-waveguide transformer. The performance of the device at its most optimum configuration features 500mA of extracted ion current, and 260eV/ion of discharge loss at a net microwave power of 130W.
Journal of Propulsion and Power, 2004
ABSTRACT Plasma characterization was conducted for an electron-cyclotron-resonance (ECR) type ion... more ABSTRACT Plasma characterization was conducted for an electron-cyclotron-resonance (ECR) type ion thruster. For a 10-cm diameter microwave discharge ion source consisting of two samarium cobalt magnet rings surrounding a centered waveguide for launching microwaves, plasma profiles were found to have severely non-uniform distributions, with localized plasma found near the magnet rings. This localized plasma is mainly produced in the magnetic flux tubes between the two ring magnets, where electrons gain microwave energy as they pass the ECR line during the bouncing movement between magnetic mirrors. To obtain a low-cost microwave ion source, this type of ionization mechanism can be exploited. When introducing microwaves through a low magnetic field boundary, however, it is impossible to eliminate the accessibility difficulty related to the cutoff density, which results in a plasma below the cutoff density. Because of the accessibility difficulty, in this work, only a relatively small ion beam current density of 1.8 mA/cm(2) was achieved.
ABSTRACT Magneto Plasma Sail (MPS) is a propulsion system making use of the solar wind. This prop... more ABSTRACT Magneto Plasma Sail (MPS) is a propulsion system making use of the solar wind. This propulsion system creates a strong magnetic field using a super-conducting coil and plasma jets, and the magnetic field works as a "sail" catching the solar wind to generate thrust. However, the feasibility of MPS is now under discussion because the momentum transfer process from the solar wind to the spacecraft is a complicated electromagnetic process and so the process has not been clarified specifically. In this study, we studied the process based on the ideal magnetohydrodynamic approximation. We simulated MPS for various Alfven Mach numbers of the plasma jet at the nozzle exit, and the relation between the thrust of MPS and the Alfven Mach number of the plasma jet was analyzed in detail. As the result, when the plasma jet at the high Alfven Mach number is injected in all direction and the termination shock forms all around the spacecraft, MPS can not produce thrust. This means the magnetohydrodynamic waves play important roll to transfer the momentum of the solar wind to the spacecraft as thrust. However, the plasma jet at a low Alfven Mach number can not produce large thrust because the large magnetosphere can not be created. Based on that result, the improved method for MPS was proposed; using the high Alfven Mach number plasma jet in only one direction, MPS can generate not only the large thrust by capturing the solar wind but also the thrust by the plasma jet.
Astrophysics and Space Science, 2007
To propel a spacecraft in the direction leaving the Sun, a magnetic sail (MagSail) blocks the hyp... more To propel a spacecraft in the direction leaving the Sun, a magnetic sail (MagSail) blocks the hypersonic solar wind plasma flow by an artificial magnetic field. In order to simulate the interaction between the solar wind and the artificially deployed magnetic field produced around a magnetic sail spacecraft, a laboratory simulator was designed and constructed inside a space chamber. As a solar wind simulator, a high-power magnetoplasmadynamic arcjet is operated in a quasisteady mode of 0.8 ms duration. It can generate a simulated solar wind that is a high-speed (above 20 km/s), high-density (1018 m−3) hydrogen plasma plume of ∼0.7 m in diameter. A small coil (2 cm in diameter), which is to simulate a magnetic sail spacecraft and can obtain 1.9-T magnetic field strength at its center, was immersed inside the simulated solar wind. Using these devices, the formation of a magnetic cavity (∼8 cm in radius) was observed around the coil, which indicates successful simulation of the plasma flow of a MagSail in the laboratory.
ABSTRACT Both experimental velocimetry with plasma diagnostics and numerical analysis in the disc... more ABSTRACT Both experimental velocimetry with plasma diagnostics and numerical analysis in the discharge chamber of a two-dimensional magnetoplasmadynamic (2D-MPD) arcjet were conducted in order to investigate the acceleration mechanisms in the case of hydrogen propellant. In the experiment, we estimated the velocity and temperature of the neutral atoms from the laser absorption profile, ion velocity and Mach number from TOF and Mach probe method respectively and electron temperature and plasma density from the Langmuir probe method. Results using two types of anodes, one being a conventional flared type anode and the other being a converging- diverging (C-D) type anode, were compared. It was found that there is region where ion-neutral velocity slip takes place and the acceleration of the neutral particles is not high enough. This phenomenon is the factor that decreases thrust performance and is due to the fact that the number of ion-neutral momentum transfer collisions is not high enough, so that neutrals cannot accelerate sufficiently. Comparing two types of anodes, the performance of the configuration employing a C-D anode was found to be relatively high especially at low Isp operation. This was explained by considering that the ion-neutral couple region was wider in this case, or, in other words, the region where velocity slip takes place was relatively small. However, at high Isp operation, flared anode is superior because electromagnetic acceleration is dominant in this anode shape.
Journal of Propulsion and Power, 2002
Transactions of The Japan Society for Aeronautical and Space Sciences, 2006
In the MUCES-C mission conducted by JAXA (Japan Aero Exploration Agency), a microwave neutralizer... more In the MUCES-C mission conducted by JAXA (Japan Aero Exploration Agency), a microwave neutralizer is mounted with a microwave ion engine on the HAYABUSA space probe. The neutralizer consists of an L-shaped antenna to inject microwaves and samarium cobalt magnets to provide ECR (electron cyclotron resonance). Plasma production of a higher density than the cutoff density is expected in the discharge chamber, but the neutralizer is so small that high-precision measurements using a probe are difficult. To clarify the plasma production mechanism in the microwave neutralizer, numerical analysis was conducted using a code coupling PIC (particle-in-cell) method, and a FDTD (finite-difference-time-domain) method. This paper describes effects caused by varying magnetic field configuration and antenna position in the neutralizer. The calculation results show that bringing the antenna closer to the ECR region is effective for plasma production.
Journal of The Japan Society for Aeronautical and Space Sciences, 2004
ABSTRACT A magneto-plasma sail produces the propulsive force due to the interaction between the a... more ABSTRACT A magneto-plasma sail produces the propulsive force due to the interaction between the artificial magnetic field around a spacecraft inflated by the plasma and the solar wind erupted from the Sun. The inflation of the magnetic field by the plasma was proposed by a group of the University of Washington and the basic research has just started. This paper summarizes the characteristics of the magneto plasma sail by comparing with the other low-thrust propulsion systems, and investigates its potential application to near future planetary missions. Finally, an engineering satellite to demonstrate the magneto-plasma sail is proposed as a first step.
Journal of Spacecraft and Rockets, 2006
The problem of plasma flow relative to a modulated magnetic field has been the subject of several... more The problem of plasma flow relative to a modulated magnetic field has been the subject of several studies. One motivation for studying this problem is the possibility of using a deliberately imposed surface of magnetic islands as a means of velocity profile control. This subject is also of importance for the study of stability against ideal and resistive magnetohydrodynamic (MHD) modes and the topic of locked modes. A two-dimensional (2-D) MHD simulation code is used to examine the behavior of a plasma flowing, in steady state, past a modulated magnetic field in "slab geometry." It is shown that at "low" velocities the stress is dominated by the Maxwell and the viscosity terms and that forces are exchanged between the plasma and the magnetic field in a narrow boundary surrounding the island. It is found that the island is suppressed when the viscous force at the separatrix exceeds the maximum force that can be supported by an island. For "high" velocities (velocities beyond the critical velocity for island suppression), the stress is dominated by the Maxwell and the Reynolds terms, and the exchange of forces is taking place in a narrow region around the point where the plasma flow velocity matches the Alfvin speed. 0 199.5 American Institute of Physics.
Journal of The Japan Society for Aeronautical and Space Sciences, 2002
Noise and oscillatory behavior of a plasma column produced in front of the microwave discharge ne... more Noise and oscillatory behavior of a plasma column produced in front of the microwave discharge neutralizer developed for MUSES-C mission were experimentally investigated. Radiated electric field emissions were measured following to MIL-STD-461 E. The average noise level exceeded the narrowband specification by 30 dBμV/m at frequencies less than 5 MHz. Noise in electron emission current was also measured by using a current probe and a spectrum analyzer, and was compared with the noise of a hollow cathode. The microwave discharge neutralizer generates a broadband noise and oscillations which have a fundamental frequency of about 160 kHz and are accompanied by its harmonics up to the 5th. Considering the dependence on the diameter of the plasma column, they are probably the radial oscillation modes of ion acoustic waves. Although the hollow cathode shows nearly the same noise level at frequencies less than 1 MHz, intense oscillation exists in the 1-10 MHz range, which is generated by the keeper plasma.