小川 博之

This paper summarizes the cut-rent status of the BepiColombo Mercury magnetospheric orbiter (MMO) spacecraft design. The MMO is a spinning spacecraft of 223 kg mass whose spin axis is nearly perpendicular to the Mercury orbital plane. The current status of the overall MMO system and subsystems such as thermal control, communication, power, etc., are described. The critical technologies are also outlined. Furthermore, the outline of the international cooperation between Japan Aerospace Exploration Agency and European Space Agency is also presented. (C) 2008 Elsevier Ltd. All rights reserved.

A new composition of the hydroxyl ammonium nitrate (HAN)-based solution containing ammonium nitrate, methanol, and water had been developed for monopropellant in a reaction control system (RCS) as an alternative to conventional hydrazine. Comparing this solution with hydrazine, Isp is 20% higher, density is 1.4 times, the freezing point is much lower, and the toxicity is low, which makes this solution promising as a RCS propellant. The linear burning rate of the solution is moderate at the operating pressures of an RCS thruster. However, it was found that the linear burning rate had some characteristics whose mechanisms had not been understood. The combustion mechanism of this solution was investigated, the burning behavior was observed using a medium speed camera, and a temperature profile for the combustion wave was measured with a fine 2.5 mu m-diameter thermocouple. From these results, the instability of the liquid interface may trigger a sudden increase in the burning rate to a violently high region, and methanol was found to be effective in reducing the bubble growth rate in the solution. For RCS thruster use, reactivity with several catalysts was evaluated in an open-cup test. Consequently, the S405 catalyst for hydrazine showed the best performance among Pt-based, Pd-based, Ru-based, Ir-based, and S405 catalysts. Thruster tests were conducted successfully using S405 in both the pulsing and continuous modes. As a result, it was found that S405 has little effect in activation of the reaction of methanol contained in the propellant. High-concentration Pd catalyst was found to improve the decomposition characteristic of the solution.

Hydrazine (N2H4) and NTO (dinitrogen tetroxide: N2O4) mixtures are used in spacecraft bipropellant systems, having the advantage, for sampling missions, of having no carbon composition. However, no reasonable hydrazine and NTO combustion model has been developed. To construct a hydrazine and NTO combustion model that is useful for bipropellant thruster CFD simulation, we extracted efficient elementary reactions from detailed kinetic reaction model proposed by Ohminami and Ogawa in 2007. The reduced hydrazine and NTO combustion model was composed of 61 extracted reactions with 23 chemical species and was coincident with the original detailed kinetic reaction model in terms of combustion gas temperatures and ignition delay times over O/F(oxidizer and fuel mass ration) =0.82-1.84. Also the simulated combustion gas temperatures were good agreed with the adiabatic flame temperatures, and the simulated ignition delay time at O/F=1.2 was consistent with the literature value. Chemical reaction paths before and after ignition were showed, and could explain hydrazine and NTO combustion network mechanism change.

近年、惑星探査や月面着陸などミッションの高度化に伴い、より高性能で複雑な熱制御技術が必要とされている。特に、熱環境が複雑に変動するミッションにおいて、衛星の熱設計を高温側および低温側で同時に満足できるような熱制御技術が重要である。そこで、アメリカをはじめ海外では次世代のスタンダードな熱制御技術として毛細管駆動型二相流体ループ（ループヒートパイプ：LHP）が開発されてきた。本研究では日本の将来の宇宙ミッションを見据え、100W級の小型LHPに着目し、その起動特性ならびに熱輸送特性の評価を行った。

This paper describes thermal performance of a small loop heat pipe device in an atmospheric condition. A comprehensive test program including start-up, power step up, power cycle and low power tests was performed. The effects of gravity on start-up and heat transport capability were also evaluated. An analytical model for the loop was developed to predict and evaluate the steady state operating performance. The test results demonstrated the robustness of the LHP. The analytical results showed good agreement with the test results except at the low power region. The feasibility of loop temperature control through compensation chamber temperature control was also experimentally demonstrated.

A vertical take-off and vertical landing rocket is one of the future space transportation vehicle expected as fully reusable system. In the landing phase of vertical lander, the vehicle is decelerated by the main engine thrust and lands softly to the ground site. Then its aerodynamic characteristics are affected by the interaction between the engine plume and the subsonic free-stream against the vehicle. In order to investigate the influence of such interaction, wind tunnel tests were conducted. The aerodynamic forces and surface pressure were measured by using scale model of the Reusable Vehicle Testing (RVT) which is a small vehicle built for flight tests in ISAS/JAXA. Flowfield around the vehicle model was visualized by using Particle Image Velocimetry (PIV) method. As a result, the drag force and pitching moment acting the vehicle were affected by the change of pressure distribution due to the jet/free-stream interaction.

Magnetic Sail is a propulsion system making use of the solar wind for deep space exploration missions. The interaction between the solar wind and the magnetic field of Magnetic Sail was simulated based on magnetohydrodynamics for various attack angles, and propulsive characteristics of Magnetic Sail were analyzed. When the attack angle is 90 degrees, the thrust is maximum: the drag coefficient (non-dimensional thrust value) is about 5, and when the attack angle is 30 degrees, the maximum steering angle (12 degrees) is obtained. The thrust direction of Magnetic Sail is stable only when the attack angle is 0 degree, whereas Magnetic Sail experiences a torque for other attack angles.

宇宙機における二液式推進系は多くの研究がなされ，また多くの実績を持つ．その燃料としては，ヒドラジンは自然性・燃焼温度が高く熱制御が難しいことから，通常安定なMMH（モノメチルヒドラジン）が適用されてきた．しかしながら，近年，サンプルリターンをミッションとする宇宙機が多くになるにつれ，ターゲット天体へのスラスタによる汚染防止及び高比推力化を鑑み，ヒドラジン(N2H4)とNTO（四酸化二窒素；N2O4）の燃料／酸化剤の組合せの適用が求められるようになった．ヒドラジン－NTOに含まれるN/H/O系の燃焼反応は多くの研究がなされてきたものの，実際にヒドラジン－NTO燃焼モデルは確立されていない．そこで本報告では，ヒドラジン－NTOを用いた二液式スラスタ設計のための反応モデルを構築することを研究目的とし，その一環として，これまで発表された１６論文を網羅的に調査し，そこから，ヒドラジン－NTO燃焼に関与するN/H/O系の２４５の素反応を抽出した．反応機構は各２４５素反応に対し、素反応及びArrhenius式で表される反応速度定数により表現した．集めた式は今後感度解析を実施することでヒドラジン－NTO系において有効な反応を抽出し，スラスタの燃焼解析に反映させる方針である．

The magneto-plasma sail (mini-magnetospheric plasma propulsion) produces the propulsive force due to the interaction between the artificial magnetic field around the spacecraft inflated by the plasma and the solar wind erupted from the Sun with a speed of 300-800 km/s. The principle of the magneto-plasma sail is based on the magnetic sail whose original concept requires a huge mechanical coil structure, which produces a large magnetic field to capture the energy of the solar wind. Meanwhile in the case of the magneto-plasma sail, the magnetic field will be expanded by the inertia of plasma flow to a few tens of kilometer in diameter, resulting in a thrust of a few Newton R. Winglee's group of the University of Washington originally proposed the idea of magnetic field inflation by the plasma. This paper investigates the characteristics of the magneto-plasma sail by comparing it with the other low-thrust propulsion systems (i.e., electric propulsion and solar sail), and the potential of its application to near future outer planet missions is studied.Furthermore, an engineering validation satellite concept is proposed in order to confirm the propulsion system specification and operation methodology. The main features are summarized as: (1) The satellite mass is around 180kg assuming the H-IIA piggyback launch. (2) Since the magnetopause of the Earth magnetosphere is about 10 Re at Sun side and the bow shock is located at about 13 Re from the Earth, the satellite is injected into an orbit with 250 km perigee altitude and 20 Re apogee distance where apogee is located at the Sun side. (3) The magneto-plasma sail is turned on only in the vicinity of apogee outside the Earth's magnetosphere. (4) The thrust is estimated by the orbit determination result, and the plasma wind monitor is installed on the satellite to establish the relationship between the solar wind and the thrust. (c) 2005 Elsevier Ltd. All rights reserved.

A magnetic sail (Magsail) is a unique deep-space propulsion system that captures the momentum of the solar wind by a large artificial magnetic field produced around a spacecraft. To clarify the momentum transfer process from the solar wind to the spacecraft, we simulated the interaction between the solar wind and the artificial magnetic field of the Magsail using the magnetohydrodynamic model. The result showed the same plasma flow and magnetic field as those of the magnetic field of the Earth; when the solar wind passes a bow shock, the solar wind is decelerated and deflected because the solar wind cannot penetrate into the magnetic field, which is called the magnetosphere around the spacecraft. The change of the solar-wind momentum resulted in a pressure distribution along the magnetopause, which is the boundary between the solar-wind plasma and the magnetosphere. The pressure on the, magnetopause is then transferred to the spacecraft via the Lorentz force between the induced current along the magnetopause and the current along the coil of the spacecraft. The simulation successfully demonstrated that the change of the momentum of the solar wind is transferred to the spacecraft via the Lorentz force, and the drag coefficient of the Magsail was estimated to be 0.9 +/- 0.1 when the magnetic dipole is parallel to the solar wind.

BepiColombo is an interdisciplinary mission to Mercury, conducted as a joint project by ESA and JAXA: a cornerstone mission in the ESA Cosmic Vision Program and one of the major missions in the JAXA Space Science Program. The mission consists of two spacecraft: the Mercury planetary orbiter (MPO), a three-axis stabilized satellite dedicated to the remote sensing of Mercury, and the Mercury magnetospheric orbiter (MMO), a spin-stabilized satellite devoted to the study of the Hermean magnetosphere and its interaction with the solar wind. JAXA is responsible for development of the MMO and its operation. This paper gives an overview of the scientific payload of the MMO, which was formally selected in the fall of 2004 by JAXA. (c) 2005 COSPAR. Published by Elsevier Ltd. All rights reserved.

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.

BepiColombo is an interdisciplinary mission to Mercury, conducted as a joint project by ESA and JAXA: a cornerstone mission in the ESA Cosmic Vision Program and one of the major missions in the JAXA Space Science Program. The mission consists of two spacecraft: the Mercury planetary orbiter (MPO), a three-axis stabilized satellite dedicated to the remote sensing of Mercury, and the Mercury magnetospheric orbiter (MMO), a spin-stabilized satellite devoted to the study of the Hermean magnetosphere and its interaction with the solar wind. JAXA is responsible for development of the MMO and its operation. This paper gives an overview of the scientific payload of the MMO, which was formally selected in the fall of 2004 by JAXA. (c) 2005 COSPAR. Published by Elsevier Ltd. All rights reserved.

A fully reusable rocket vehicle is proposed to demonstrate good operability characteristics both on the ground and in flight. The proposed vehicle is to be used as a sounding rocket and has the capabilities of ballistic flight, returning to the launch site, and landing vertically making use of clustered liquid hydrogen rocket engines. Before initiating the development of this type of reusable rocket, a small test vehicle with a liquid hydrogen rocket engine was built and flight-tested. A demonstration of vertical landing and exercise of turnaround operation for repeated flights are the major objectives of the test vehicle. Three series of flight tests were performed in 1999, 2001 and 2003, and the flight test operation provided repeated flight environment and many valuable lessons were learned for designing the fully reusable rocket vehicle. © 2005 Published by Lister Science.

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.

For achieving a fully reusable rocket vertical as a future space transportation system, the conceptual designs of vehicle systems and flight tests by a small test vehicle are presently being conducted in ISAS/JAXA. In this system design, aerodynamic design considerations are made on a vertical take-off and vertical landing vehicle. One of the considerable issues of a vertical lander is the effect of the interaction between a supersonic nozzle jet and a free-stream when the vehicle is decelerated by the main engine thrust in the landing phase. In order to investigate the influence of such counter-flow interaction in detail, wind tunnel tests were conducted in low speed wind tunnel in ISAS and ISTA/JAXA. The aerodynamic forces and pressure on the base surface were measured by using a scale model of the vehicle. The flowfield around the model was visualized by using smoke and tuft. The velocity distribution was measured by a particle image velocimetry (PIV) technique. The aerodynamic characteristics in the vertical landing phase are affected by not only the reduction of the base pressure but also the non-separated flow around the model side.

The magneto-plasma sail (mini-magnetospheric plasma propulsion) produces the propulsive force due to the interaction between the artificial magnetic field around the spacecraft inflated by the plasma and the solar wind erupted from the Sun with a speed of 300-800 km/s. The principle of the magneto-plasma sail is based on the magnetic sail whose original concept requires a huge mechanical coil structure, which produces a large magnetic field to capture the energy of the solar wind. Meanwhile in the case of the magneto-plasma sail, the magnetic field will be expanded by the inertia of plasma flow to a few tens of km in diameter, resulting in a thrust of a few N. R.Winglee's group of the University of Washington originally proposed the idea of magnetic field inflation by the plasma. This paper investigates the characteristics of the magneto-plasma sail by comparing it with the other low-thrust propulsion systems (i.e., electric propulsion and solar sail), and the potential of its application to near future outer planet missions is studied. Furthermore, an engineering validation satellite concept is proposed in order to confirm the propulsion system specification and operation methodology. The main features are summarized as: The satellite mass is around 180kg assuming the H-IIA piggyback launch. 2) Since the magnetopause of the Earth magnetosphere is about 10Re at Sun side and the bow shock is located at about 13Re from the Earth, the satellite is injected into an orbit with 250km perigee altitude and 20 Re apogee distance where apogee is located at the Sun side. 3) The magneto-plasma sail is turned on only in the vicinity of apogee outside the Earth's magnetosphere. 4) The thrust is estimated by the orbit determination result, and the plasma wind monitor is installed on the satellite to establish the relationship between the solar wind and the thrust.

We developed a cryogenic system, which houses 3 cartridge-type superconductor-insulator-superconductor receivers for millimeter and submillimeter wavelengths. Since it was designed as a prototype receiver of the Atacama Large Millimeter/submillimeter Array (ALMA), high stability, accurate alignment, and easy handling were required. To meet these requirements, the cryogenic system included the following technologies: 1) a thermal link without screws for receiver cartridges; 2) a central support structure to reduce vacuum and gravitational deformation; 3) bellows structures to reduce mechanical vibration of the cryocooler; and 4) a 3-stage Gifford McMahon (GM) cryocooler with an He pot (temperature stabilizer) to reduce the thermal ripple. The cryostat and receiver cartridges are composed of three stages. The temperatures on the 4 K, 12 K, and 100 K stages of the cartridge are 3.5 K, 13.4 K, and 78.3 K, respectively. The thermal conductances of the thermal links showed high performances of 1.7 W K-1 at the 4 K stage, 5.6 W K-1 at the 12 K stage, and 3.3 W K-1 at the 100 K stage. The mechanical vibration on the 4 K stage of the cartridge was reduced to one-tenth, as small as approximate to 2 mum peak-to-peak, compared to that on the 4 K coldhead of the cryocooler, approximate to 20 mum peak-to-peak. The temperature ripple on the cartridge was reduced to as small as 2 mK peak-to-peak, which corresponds to one-seventh of the ripple on the 4 K coldhead with an He pot.

This paper shows the latest results of the feasibility study of the BepiColombo MMO (Mercury Magnetospheric Orbiter) Spacecraft, which was conducted by the ISAS (Institute of Space and Astronautical Science) Mercury Exploration Working Group. (C) 2002 International Astronautical Federation. Published by Elsevier Science Ltd. All rights reserved.

This paper describes outline of the piggy-back satellite "INDEX" for demonstration of advanced satellite technologies as well as for observation of fine structure of aurora. Aurora observation will be carried out by three cameras(MAC) with a monochromatic UV filter. Electron and ion spectrum analyzer (ESA/ISA) will measure the particle phenomena together with the aurora hanging. INDEX satellite will be launched in 2002 by Japanese H2-A. The satellite is mainly controlled by the high-speed, fault-tolerant on-board RICS processor (three-voting system of SH-3). The attitude control is a compact system of three-axis stabilization. Although the size of INDEX is small (50Kg class), several newly-developed technologies are applied to the satellite system, including silicon-on-insulator devices, variable emittance radiator, solar-concentrated paddles, lithium-ion battery, and GPS receiver with all-sky antenna-coverage. © 2001 International Astronautical Federation. Published by Elsevier Science Lt d.

A shock-shock hot interaction problem is studied numerically. A high-order Godunov-type scheme coupled with solution-adaptive unstructured grids has been employed to compute a hypersonic thermochemically nonequilibrium viscous flow; the impinging shock generated by a wedge interacts with the bow shock around a 2-D circular cylinder. The dynamic grid adaptation to solution and the high-resolution methods contribute to a considerable improvement in both accuracy and efficiency. High-temperature real gas effects have been evaluated by a thermal and chemical non-equilibrium model. Type IV interaction of Edney near the transition between Type III and Type IV is obtained. The shock interaction structure is clearly captured with high resolution.

The paper deals with the confluence of three shock waves at a point, in a magnetohydrodynamic (MHD) fluid. Based on the three-shock theory, the equations governing the flow field in the vicinity of the intersection point are obtained. The three shock confluences in field-aligned cases are studied here using shock polars, revealing that only seven combinations of three shock types are possible. The relations among (a) the combinations of incident and reflected shock types, (b) the angle between incident and reflected shacks, and (c) the streamline deflection angle across the reflected shock are shown. As an example of application, the flow field induced by a supersonic MHD flow over a concave double wedge is studied both analytically and numerically. (C) 1996 American Institute of Physics.

This paper deals with the reflection of a planar magneto-hydrodynamic shock wave propagating at a gasdynamic Mach number of 2 (twice the gasdynamic sound speed) in an applied magnetic field, colliding with a perfectly-conducting two-dimensional metallic wedge of 30 degrees. Numerically calculated results show that the reflected wave configuration in the magnetic field becomes far more complicated than the one without magnetic field; i.e. an initially plane shock wave decomposes into the fast and slow shocks which interact again with the reflected shock wave. Four types of wave interaction configurations are observed, depending upon the intensity of initial magnetic field; these can be, in general, categorized into regular and irregular reflections.

The ''total pressure-deflection angle'' shock polars are obtained to apply to magnetohydrodynamic (MHD) shock reflection problems. They are categorized into four kinds, based on the type of shocks; the conditions for their appearance are given as well. Among several possible reflections, the regular reflection phenomena are studied here using shock polars, revealing that only four incident-reflection combinations are possible for regular reflection. The range of upstream conditions giving a specified-combination regular reflection is shown graphically. Simultaneously, the relations among three types of incident shock and four kinds of reflected shock polars are also exhibited graphically. (C) 1995 American Institute of Physics.