德留 真一郎

Highlights • Strategy formulated under Inter-University Research Institute System unique to Japan. • To develop a competitive space transportation system by using advanced technologies. • To “start small” for fulfilling our target to achieve innovations in human society. • “Fusion of transportation with exploration” in deep space exploration missions. • “Small flying test bed system” to conduct flying technology demonstrations. Abstract The Space Transportation System Committee of the Institute of Space and Astronautical Science (ISAS) of the Japan Aerospace Exploration Agency (JAXA) has been continuously formulating medium-to long-term strategies in the field of space transportation systems under the Inter-University Research Institute System of ISAS since FY2018. This committee is considering the role of ISAS in cooperation with the organization-wide activities of JAXA to formulate strategies in the field of space transportation systems. Among its previous achievements, the committee assembled a strategic target and scenario for the space transportation system research field at the end of FY2018 and has been continuously revising it. Based on the formulated mission scenario, the committee identified three priority areas related to system technologies that must be tackled. These are a “reusable orbit transportation system” aimed for highly frequent mass transportation from Earth to low Earth orbits, “deep space interorbital transportation system” aimed for a marked improvement in space science and exploration missions in terms of frequency and flexibility, and “small flying test bed system” for flight demonstrations, which is indispensable in the research and development of space transportation systems. In this paper, the authors summarize the medium-to long-term strategies and their concrete implementation measures over the next two decades. Keywords Strategic R&D, Space transportation system, Deep space exploration, Small flying test bed, Start small

In order to use laser ignition systems for solid rocket motors operating in deep space environments, it is necessary to elucidate the laser ignition characteristics of the ignition charge in low-temperature environments. This study aims to design an experimental system that can confirm the ignition threshold, ignition delay, and ignition temperature by irradiating an ignition charge with a diode laser in a low-temperature environment. Ignition experiments at room temperature were conducted. The data were evaluated statistically to obtain an ignition threshold with the maximum likelihood method. The relationship between the laser irradiation duration and the laser power with respect to the ignition threshold was obtained. The target value of the low-temperature environment temperature was determined as -50 °C. We examined the requirements of the experimental system and conceptually designed the system to simulate the low-temperature environment. It was confirmed that the constructed experimental system cooled the ignition charge to -50 °C. In the ignition experiment, the ignition charge was successfully ignited at room temperature and at low temperature. The ignition delay, the ignition temperature, and the high-speed image were obtained. Eventually, the validity of the experimental system was confirmed through the function tests.

DESTINY+ requires a high-performance kick stage with a high mass ratio and high launch system safety. The kick stage requires a reliable laser ignition system, which is the subject of this study. Our development efforts included componentizing and dual redundancy elements, such as capacitors and laser diodes in the laser firing unit, which is designated LUUS. LUUS has two types of laser-initiated devices for motor ignition and separation device operation. An optical fiber path also enables a continuity check by an optical frequency domain reflectometry device. Further, we conducted continuity checks and laser ignition tests to validate the design in procedures simulating assembly- and launch-site operations. These tests successfully executed inspections and ignitions as planned. These results confirm the validity of our design, bringing us closer to realizing a reliable laser ignition system for launch operations applicable to DESTINY+. This contribution paves the way for future advances in high-performance, safe launch systems for solid rockets in space exploration.

Laser-initiated ignition systems (LIISs) have been developed with the aim of providing essential immunity to electrical disturbances. In the basic configurations of such systems, the electric circuits for generating the laser and detonator signals are electrically separated by a non-conductive optical fiber, increasing the resistance to ignition stimuli other than laser light on the detonator side. In this study, the various environmental resistance tests required for the detonators currently used in rockets were conducted for a new laser-initiated detonator (LID). As all of the tests show results satisfying the requirements, it is considered that the LID has reached the stage of practical use.

The S-520-RD1 was developed as a test-bed small launcher using the guidance and control system based on SS-520-5 for a cube-sat launcher and successfully launched a supersonic Combustion Tester on July 24, 2022. One of the key points of this launch success is the Rhumb-line control system to achieve the guidance target and the payload test conditions. This paper shows the outline of the guidance and control system and their development, and the flight results.

宇宙科学研究所（ISAS）の宇宙輸送系専門委員会において策定されている宇宙科学・探査分野における宇宙輸送系の中長期ミッションシナリオでは，2040年頃の達成を目指すミッションを「多様な宇宙科学の世界をカバーする軌道間輸送ネットワークを構築する」ことと設定している． ミッション達成に向けて，地上から地球周回軌道へ高頻度に大量の物資や人員を輸送する宇宙往還機を実現するためには，往還飛行において「極超音速飛行」を避けることはできない．本稿では，主に宇宙往還機の実現と競争力向上に資する極超音速エンジンの技術実証を中心に，極超音速飛行に係る技術課題に実証的に取り組むための飛行実験機の目的と検討例について紹介する．

To reduce the cost of space transportation, JAXA continues studying fully reusable space transporters with hypersonic airbreathing engines. To fulfill the requirement of acceleration capability from zero to hypersonic speed, the rocket-based combined cycle (RBCC) engine is one of the promising candidates and has been studied in JAXA Kakuda Space Center. In the researches of the engine, the specialized wind tunnel for the airbreathing engines (Ramjet Engine Test Facility, RJTF) has been always a practical tool to investigate the performance and detailed flow phenomena inside the engine. However, to simulate the hypersonic, high enthalpy flow, the wind tunnel uses gas hydrogen and oxygen to heat the flow, resulting the air contamination by water which affects to the combustion phenomenon. To clarify the effect of the contamination, series of the cooperative researches have been conducted in JAXA and universities. The final goal of the researches are to create the adjustment tools for contamination effects, which ensure more accurate estimation for the performances of engine in the real flight. For validating the tools, the real flight data are quite essential. In the researches, a flight experiment had been also planned to get combustion data during hypersonic flight to compare the results in the wind tunnel and estimated values by the tools. In this report, the flight experiment with “S-520-RD1” is described. In early phase of the development, several rocket systems, flight trajectories and flight test bed configurations were explored. For the experiment, the attitude control of the flight test bed was required and it was achieved by the rhumb line device. The flight conditions inwhich actual combustion experiment was conducted were determined by the air data system specifically designed and integrated into the test bed. The duration time for the combustion test reached as long as 5.8 sec, with highest Mach No. of 5.8. The summery of the results of combustion test is also presented.

The ammonium dinitramide-based ionic liquid propellant (ADN-based ILP), which is a mixture of ADN, monomethylamine nitrate (MMAN), and urea, is a low toxic monopropellant with a higher performance than that of hydrazine. To clarify the combustion wave structure of ADN-based ILP, which has low volatility, we focused on the relationship between the phase state and temperature in ADN-based ILP combustion and on clarifying the gas-liquid phase reaction. The combustion still image and temperature distribution of ADN-based ILP were obtained by strand burning tests with a high-speed camera. As a result, two stages of the stable temperature region were found in the gas-liquid phase. The pressure dependences of temperature in the stable temperature region were compared with the vapor pressure curves of some chemical substances and with the decomposition temperatures of ADN, MMAN, and urea. Then, it was inferred that the thermal decompositions of ADN, MMAN, and urea, as well as the evaporation of urea had occurred at the first stage of the stable temperature region. Also, it was found that the liquid ammonium nitrate had been dissociated at the second stage of the stable temperature region. For a report on the existence of dissociation products of MMAN and urea vapor on the burning surface at 1.2 MPa, the dissociation of MMAN and evaporation of urea would occur at the first stage of the stable temperature region at 1.2 MPa. As stated above, the combustion wave structure of ADN-based ILP was developed at 1.2 MPa.

The Space Transportation System Committee of the Institute of Space and Astronautical Science of JAXA (ISAS/JAXA) continuously draws up the Medium- to long-term strategy for the research field of space transportation system in ISAS/JAXA since FY2018. The committee is also considering about an ISAS’ role in JAXA in cooperation with a JAXAs organization-wide activity to formulate strategy for the space transportation system field in JAXA. The strategy planning in ISAS/JAXA was begun with the three documents as the point of departure; ”Long-term Vision for Space Transportation System” established by the space policy committee of the Cabinet Office, ”ISAS’ Missions”, and ”Strategic Scenario over the Next Medium- to Long-term Programs for the research field of Space and Astronautical Science” drawn up by the ISAS. As current achievements, the committee have drawn up a strategic target and scenario for the space transportation system research field at the end of last fiscal year and is continuously revising it. Based on the scenario formulated, the committee identified three major research field to be tackled. They are ”reusable orbit transportation system” becoming the key to the activation of space development and utilization, ”inter-orbit and interplanetary transportation systems” effectively supporting deep space explorations, and ”small flying test bed system” promoting the advancement of space transportation system technology. The authors introduce the summary of the medium- to long-term strategy and some medium-term research activities toward the realization of it.

This paper describes the development status of a laser ignition system for a solid rocket motor. This system is being developed as a simple, lightweight, and small design with a high resistance to electrical disturbances and a high level of safety. The most notable advantage of this system is that its high level of safety can decrease the cost of launching rockets into space. A laser initiator and a laser safe-and-arm device (laser S/A), which are essential components of the proposed system, were developed. In particular, prototypes of the laser initiator and laser S/A for the ignition of an upper stage rocket motor were manufactured, and some environmental tests, which are required for space rocket devices, were conducted. In addition, the lowest laser energy that is needed to ignite the laser initiator was determined by changing the laser power and operating time of the laser S/A. Furthermore, a small rocket motor vacuum fire test was successfully conducted.

The Japan Aerospace Exploration Agency, in partnership with academia and industry, are developing the Air Turbo Rocket for Innovative Unmanned Mission (ATRIUM) engine: an air turboramjet + rocket combine cycle propulsion system intended to replace conventional liquid rocket engines in Vertical Takeoff Vertical Landing applications, such as reusable sounding rockets. A subscale Flight Test Bed (FTB) vehicle is also being developed to demonstrate the ATRIUM engine in a flight environment. In this paper, the ATRIUM engine and FTB vehicle are introduced, and current progress in their development is summarized. Future test plans and practical applications are also discussed.

Since its debut in 2013, the Epsilon, alongside the H2A/B launch vehicles, has been playing a central role as a Japanese flagship space transport system. The fundamental purpose of the Epsilon is "to increase players in space development by the small launch vehicle with excellent operability." To this end, the Epsilon successfully launched four times since 2013. These launches contributed to an increase in newcomers to space. One of our future concepts is the system with a reusable orbiter that can perform operations in space and return to the earth. Such a system will allow more people to participate in space development. We are now studying several versions of this system which differ depending on which part of the present Epsilon is to be replaced. Also described here are several elemental technologies to realize these versions.

Many small launch vehicles are being developed and operated to meet the explosively increasing demand for small satellites. Taking this opportunity, we are studying a multipurpose reusable orbiter to be launched by a small launch vehicle. Such orbiters will add further value to small missions and promote space utilization. In this paper, we report the results of the system investigation on a 1-ton class reusable orbiter to be launched by the Epsilon Launch Vehicle and then return to the sea after performing its missions in orbit. Generally, mass design for a reusable orbiter is difficult because it needs a propulsion system for deceleration to re-entry speed and a TPS required for re-entry. Additionally, a conventional reusable TPS has a downside in operational performance as demonstrated by the Space Shuttle. In order to solve these problems, we conducted a trade-off study of propellant and evaluated the application of our innovative aeroshell system based on its sub-size flight test. These results are also included in this paper.

<p>A new space transportation system with an expendable solid-fuel booster and a reusable liquid-fuel orbiter is under consideration as part of activities in JAXA to construct a fully reusable space transportation system in the future. This paper shows this new system's conceptual study results, the system specifications, the new technology to be applied, the requirements to the subsystems, and the prospects.</p>

<p>The development of enhanced propulsion system for the next Epsilon rocket was progressed. The development of Enhanced Epsilon is mainly the renewal of the second stage, and also includes each subsystem's improvement. The second stage motor M-35 was newly designed and manufactured. In order to verify the design, the static firing test of the second motor M-35 under the condition of vacuum ambient was conducted in 2015. The JAXA successfully launched the first Enhanced Epsilon launch vehicle. All solid propulsion systems for the Enhanced Epsilon launch vehicle showed a very good behavior during the flight</p>

The third Epsilon launch vehicle, which was the Enhanced Epsilon launch vehicle optional configuration, was successfully launched with the payload of ASNARO-2 in January 2018. The post flight analysis was conducted. The chamber pressure and thrust include residual thrust of three main motors and chamber pressure of SMSJ and SPM were analysed to confirm the effectiveness of design and production methodologies. All solid propulsion systems for the third Epsilon launch vehicle showed a very good behaviour during the flight.

The development of Enhanced Epsilon is mainly the renewal of the second stage, and also includes each subsystem's improvement. The second-stage motor M-35 was newly designed and manufactured. In order to verify the design, the static firing test of the M-35 under the condition of vacuum ambient was conducted in 2015. The Epsilon's second flight, which was the first Enhanced Epsilon launch vehicle, was successfully conducted with the payload of Exploration of energization and Radiation in Geo-space (ERG) in Dec., 2016. After the flight, chamber pressure and thrust include residual thrust were analysed to confirm the effectiveness of design and production methodologies. All solid propulsion systems for the Enhanced Epsilon launch vehicle showed a very good behaviour during the flight.

The Epsilon Launch Vehicle, the newest version of Japan's solid propulsion rocket, has been further developed under the name of "Enhanced Epsilon" since its first flight in 2013. The second Epsilon (Epsilon-2), the first application of Enhanced Epsilon, succeeded in launching the satellite ARASE, the Exploration of energization and Radiation in Aerospace (ERG), into orbit as planned in December 2016. The aims of Enhanced Epsilon's development include the increase of the launch capacity and payload usable volume by enlarging the second stage motor, redesigning the total structure and lightening avionics components. The second flight achieved these aims and confirmed the new design's validity. As for the next plans, the third launch will demonstrate a new PBS (Post Boost Stage) with liquid propulsion system developed for Enhanced Epsilon. The fourth launch is planned to carry multiple payloads on a new PAF (Payload Attach Fitting), which development has just started. Meanwhile, aiming at synergy effect, we have been developing parts and components to be shared with the H3 Launch Vehicle, Japanese large-size next-generation launch vehicle. Looking further ahead, we are planning to start the concept study for the future Epsilon. This paper describes Epsilon-2 launch results, Epsilon's development status, and its plan.

The Epsilon launch vehicle, the newest version of Japan's solid propulsion rocket, made its maiden ight in September of 2013. The purpose of the Epsilon rocket is to provide small satellites with responsive launching with low-cost, user-friendly and efficient launch system. Now that the rst ight was successfully nished, JAXA has been conducting intensive researches on a next generation Epsilon to launch a more powerful and lower cost version of Epsilon (Evolved Epsilon). In order to minimize technical risks and to keep up with demand of future payloads, JAXA plans to take a step-by-step approach toward Evolved Epsilon. As the first upgrade toward Evolved Epsilon, JAXA has started the development of Enhanced Epsilon. The Enhanced Epsilon is required to enhance launch capability by ERG satellite mission which have decided to change an orbit to be put into to farther and also to improve on-board capability in size and in weight by ASNARO2 satellite mission. The development of Enhanced Epsilon is mainly the renewal of the second stage, and also includes the each subsystem's improvement. The main change of the solid propulsion system is exposure of the second motor M-35. Currently, the design has been finished. The outside diameter of the motor case is expanded into approximately 2.5 m in order to increase the amount of the solid propellant and the outer shell of the motor case is used as the outer shell of the launch vehicle. Solid propellant which can the high-performance equal to a conventional upper-stage motor developed newly, reducing the cost. A general front ignition system is adopted instead of the rear ignition system of the throw-away type which was adopted for the previous motor. A new development material is applied to the case lining. An expansible nozzle is not adopted because compatibility of high-performance and cost reduction. In order to verify the design, the static firing test of the second motor M-35 on condition of vacuum has been conducted. This paper describes overview of development of the solid propulsion system for Enhanced Epsilon and the results of the M-35 static firing test.

The Epsilon Launch Vehicle, the newest version of Japan's solid propulsion rocket, has been further developed under the name of "Enhanced Epsilon" since its first flight in September 2013. The development of Enhanced Epsilon includes the increase of the launch capacity and payload usable volume by the development of the new second stage motor and the arrangement of the second stage outside the nose fairing, the application of our new "Low Shock Separation System" for payload environment improvement, and the modification of the avionics system for the operational simplification. This development will make the vehicle much more versatile and user-friendly. This development of Enhanced Epsilon will finish in the spring of 2016. We completed the ground firing test of a real-scale new second stage in the winter of 2015 and are now testing the prototype model with totally improved structures. Enhanced Epsilon will be applied to the coming launches of small payloads. In 2016, we will conduct a flight demonstration of its second launch in the basic configuration without PBS, or Post Boost Stage with liquid propulsion system. Then the third launch will be demonstrated in the optional configuration with PBS. This paper describes the results of Enhanced Epsilon's development on the total system, subsystems and components and the preparation status of Epsilon's second launch.

Copyright © 2016 by the International Astronautical Federation. All rights reserved. Although reusable launch vehicle's necessity and significance, being cost-effective, eco-friendly and reliable, have been recognized in a long time, practical system still has never been realized except the Space Shuttle. There are two main reasons in this. One reason is that reusable vehicle's recurring cost is high. The other reason is that reusable vehicle, especially that upper stage, have the problem of aerodynamic heating during re-entry. We are considering new upper stage reusable launch vehicle with solid rocket booster, which clear these problems concerning reusable launch vehicle. For the first problem on the recurring cost, the application of the auto inspection system which is cultivated in solid rocket motor's development and launch operation is being considered. That is expected to reduce the inspection cost drastically after the vehicle flight. For the second problem on the re-entry, challenging technologies are applied in the upper stage. Those are material and structure with heat tolerance and lightness, active-cooling system to share the hydrogen with the liquid propulsion system, advanced guidance and control system, and so on. On the other hand, to the lower stage or booster, application of solid rocket is considered. Since the challenging upper stage's size is expected to vary through the iteration of design cycles, the lower stage should be stable and flexible with the thrust level in development phase. Because solid motors of various sizes are developed in JAXA/ISAS since the first small solid motor started to be developed in 1954, those development method has been efficiently accumulated. Then this legacy's utilization for the new system is expected to be quite beneficial. On these technological backgrounds, this paper describes the system study for new upper-stage reusable launch vehicle with the solid rocket booster.

<p>As a replacement for hydrazine, ammonium-dinitramide-based ionic liquid propellant (ADN-based ILP) has been developed by JAXA and Carlit Holdings Co., Ltd. This propellant is made by mixing three solid powers: ADN, monomethylamine nitrate, and urea. The propellant's theoretical specific impulse is 1.2 times higher than that of hydrazine, and its density is 1.5 times higher at a certain composition. Although ionic liquids were believed to be non-flammable for a long time owing to their low-volatility, recently combustible ILs have been reported. The combustion mechanism of ILs is not yet understood. The objective of this paper is to understand the combustion wave structure of ADN-based ILP. The temperature distribution of the combustion wave in a strand burner test shows a region of constant temperature. This region would indicate boiling in a gas-liquid phase. Thus, the combustion wave structure consists of liquid, gas-liquid, and gas phases. The dependence of boiling point on pressure would identify chemical substances in the gas-liquid phase. The dependence of combustion and ignition characteristics on ADN content is also discussed. </p>

資料番号: PA1510016000

The Epsilon Launch Vehicle, the newest version of Japan's solid propulsion rocket, has been further developed since its first flight in 2013. This development succeeds to the original Epsilon's design philosophy that providing small satellite manufactures with the efficient launch system and allowing them to have more flexible designs will increase space activities. As the first step toward this purpose, the effective development is carried out in the short term. That includes the development of the new second stage motor, the compactification of the avionics component, and the optimization of the liquid propulsion system in the post boost stage. The development will increase the launch capacity and payload usable volume, while simplifying the system configuration. The development of Enhanced Epsilon will be finished in 2016.

The Epsilon launch vehicle, the newest version of Japan's solid propulsion rocket, made its maiden flight in September of 2013 and successfully deployed the extreme ultra-violet planetary telescope satellite, "Hisaki". It should be emphasized that JAXA appreciates the advantages of the combined power of standardized small satellites and Epsilon's highly efficient launch system to increase space activities. The purpose of the Epsilon rocket is to provide small satellites with responsive launching with low-cost, user-friendly and efficient launch system. Now that the first flight was successfully finished, the most important thing is what the next step will be. JAXA has been conducting intensive researches on a next generation Epsilon to launch a more powerful and lower cost version of Epsilon (E-l). In order to minimize technical risks and to keep up with demand of future payloads, JAXA plans to take a step-by-step approach toward E-l through lowering the cost and enhancing the launch system performance. As the first upgrade toward E-l, the renewal of the second stage , the simplification of launch operation, and the improvement of the liquid propulsion system are considered. As the second upgrade, the improvement of the solid motor for the first and third stages, the reconstruction of the avionics system, and synergy with Japanese Next Flagship Launcher are considered. Completion of the two-step upgrade will lead to accomplishment of the purpose of the Epsilon rocket.

The development of the Epsilon launch vehicle, Japan's next generation solid rocket launcher, has just moved to the final stretch for its first launch scheduled in the summer of 2013 to carry the planetary telescope satellite SPRINT-A. The JAXA appreciates the advantages of combined benefits of the standardized small satellites and the Epsilon's highly efficient launch system in order to increase the level of space activities. The primary purpose of Epsilon is to provide small satellites with a responsive launch that means "Small, Low cost, Fast and Reliable". The attention should be directed toward the innovative design concept of Epsilon, which aims at developing the next generation technologies such as the highly intelligent autonomous checkout system and the mobile launch control. Now that the full-scale development is about to be finished, the most important is what the next step should be beyond the Epsilon. This paper deals with the significance of the Epsilon launch vehicle and how it contributes to the possible evolution of future space transportation systems.

The Epsilon launch vehicle, the newest version of Japan's solid propulsion rocket, has successfully had its maiden flight in this September carrying the extreme ultra-violet planetary telescope satellite SPRINT- A. It should be emphasized that the JAXA appreciates the advantages of combined power of the standardized small satellites and the Epsilon's highly efficient launch system, both developed by JAXA, to increase the level of space activities. Although the launch site of the Epsilon rocket, the Uchinoura Space Center (USC), was originally considered a highly compact launch complex, some modifications were made to become more efficient. The efficient launch vehicle and the compact USC established one of the most powerful tools that contribute to small missions (tentatively, maximum 1.2 ton into LEO and 450kg into SSO, as of the first flight). The purpose of the Epsilon rocket is to provide small satellites with a responsive launching, which means in this study we focus on a low cost, user friendly and ultimately efficient launch system. To realize this, the design concept of the Epsilon involves various innovative next generation technologies such as the highly intelligent autonomous checkout system and the mobile launch control. Owing to these endeavors, it was proved that the lift-off can be executed in less than 6 days after the first stage motor stand-on although the first flight took longer for extra tests and operations to complete the entire development. Another aspect that small satellites will most welcome is more user-friendly character involving: A reduction in the acoustic vibration level by refined ground facilities an attenuation of the sinusoidal vibration environment by a special vibration attenuator and a highly accurate orbit injection by a liquid propelled upper stage. Their effectiveness was well demonstrated. Now that the first flight was finished, the most important is what the next step will be in the future. JAXA has been conducting intensive researches on a next generation Epsilon to launch a more powerful and lower cost version Epsilon (El) in 2017 (TBD). In order to minimize the level of technical risks, JAXA plans to take a step by step approach to improve the cost and performance of the launch system toward El. According to this strategy, the second flight will be conducted in 2015 with an enhanced launch capacity of more than 500kg into SSO. This paper provides the results of the first flight of the Epsilon and reveals its evolution plan. Copyright© (2013) by the International Astronautical Federation.

The Epsilon launch vehicle has two main objectives. One is to evolve the highly efficient launch vehicle using the solid rocket system technologies that we have obtained for more than fifty years. The other is to meet the needs of the small satellites whose market will grow in the near future definitely. The needs and the demands of the small satellites have been flowdowned to the requirements of the Epsilon launch vehicle. As a next generation launch system, the Epsilon launch vehicle has several special features. The level of user friendliness is increased including more accurate orbit insertion precision, lower acoustic environment and lower separation shock level. It is optimized from the point of view of both cost and performance. This paper describes the system design of the Epsilon launch vehicle.

A new small solid launcher named Epsilon is currently under development in JAXA. The Epsilon launch vehicle is normally three stage rocket system and can be added an optional liquid propulsion system to the third stage for the missions requiring precision orbit insertion. The SRB-A motor boosting the H-IIA vehicle and the H-IIB vehicle will be shared as the first stage motor. Upper-stage motors are inherited from the fifth M-V launch vehicle, from the viewpoints of development cost reduction, performance increase, and advanced technology succession. The solid motor side jet (SMSJ) system, which is used for the roll control during the first stage powered flight and the three-axis control after the SRB-A burnout, will be newly developed based on the technology of the SMSJ for the M-V vehicle. A maiden flight of the first Epsilon is scheduled in the summer of 2013. A successive concept of the advanced propulsion technologies for next-gen Epsilon are also described in the present paper. There are many technical challenges, such as new propellants and mass reduction of nozzle liner, to be tackled with for the next couple of year. © 2012 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.

The development of the Epsilon launch vehicle, Japan's next generation solid rocket launcher, has just moved on to the final stretch for its first launch scheduled in summer of 2013 carrying the planetary telescope satellite SPRINT-A. It should be emphasized that the JAXA appreciates the advantages of combined power of the standardized small satellites and the Epsilon's highly efficient launch system, both developed by JAXA. The launch site of the Epsilon rocket is the Uchinoura Space Center (USC), the home of Japan's solid rockets, which will be modified to become more efficient although it is already a highly compact launch complex. The efficient launch vehicle and the compact USC will establish one of the most powerful tools that contribute to small missions (maximum 1.2 ton into LEO and 450kg into SSO as of the first flight). The purpose of the Epsilon rocket is to provide small satellites with a responsive launching, which means in this study we focus on a low cost, user friendly and ultimately efficient launch system. To realize this, the design concept of the Epsilon involves various innovative next generation technologies such as the highly intelligent autonomous checkout system and the mobile launch control. Owing to these endeavors, the lift-off will be executed in less than 6 days after the first stage motor stand-on. Another aspect that small satellites will most welcome is more user-friendly characteristics involving improvements in: The acoustic vibration level at ignition by refined ground facilities the sinusoidal vibration environment by a special vibration attenuator and the orbit injection accuracy by a liquid propelled upper stage. Now that the full-scale development is about to be finished, the most important is what the next step should be beyond the Epsilon. JAXA has already announced the post Epsilon development to launch a low cost version Epsilon (El) in 2017. Note that the strategy taken to lower the cost will be mainly based on using lighter and lower cost materials, thus resulting in higher performance as well. In order to minimize the level of technical risks, JAXA plans to take a step by step approach to improve the cost and performance of the launch system toward El and the second flight will be conducted in 2015 with an enhanced launch capacity of more than 500kg into SSO. This paper provides the details of the final phase of the Epsilon development and reveals its evolution plan. Copyright © (2012) by the International Astronautical Federation.

イプシロンロケット二段階開発の最初のステップでは,本質的な低コスト化と即応性の向上を目指す革新的機体システム技術の開発に重きを置いている.推進系の開発においては,H-IIAやM-Vの開発で培われた技術を最大限活用することによって,期間,コスト,リスクを抑え,革新的機体システム技術の早期実証及び近い将来の小型衛星打上げの要求に応える.第1段モータには基幹ロケットのSRB-Aモータを共用し,第2段,第3段にはM-V-5号機の第3段モータ,キックモータをほぼそのまま流用してM-Vをしのぐ輸送効率を達成する.推進系の新しい開発課題は,多様なミッションへの対応能力を高めるPBSの小型液体推進系,そして第1段推力飛行中のロール制御と同コースティング中の3軸制御を担うSMSJ装置である.2013年度の初飛行を目指すイプシロンの推進系開発は,2011年度内に詳細設計を完了して初号機製造に進む見通しである.

The Epsilon rocket, formerly called Advanced Solid Rocket (ASR) launcher, proceeded to the full development phase in August 2010 and its launch site was officially declared to be the Uchinoura Space Center (USC), the home of Japanese solid propellant rocket. The primary purpose of Epsilon is to provide small satellites with a responsive launch that means a low cost, user-friendly and ultimately efficient launch system. The slogan is "Small, Cheap, Fast and Reliable". This outcome is also a result of the excellent endeavors of those who devoted themselves to the next generation solid propellant rocket. However, this is not the final destination. Now that the development was approved, the most important is what the next step should be beyond Epsilon. This paper deals with the significance of the development of Epsilon launch vehicle and how it contributes to the possible evolution of future space transportation systems.

In January, 2011, the launch site of the Epsilon rocket was officially declared to be the Uchinoura Space Center (USC), the home of Japanese solid propellant rockets since the Japan's first satellite was launched in 1970. The development of the Epsilon launch vehicle is now about to advance to its detailed design level to prepare for its first flight, scheduled to be carried out in 2013. The primary purpose of Epsilon is to provide small satellites with a responsive launch that means a low cost, user-friendly and ultimately efficient launch system. The innovative design concept of the Epsilon launch vehicle will greatly contribute to increase the level of the space transportation technologies. However, this is not the final destination. Equally important is what the next step should be beyond Epsilon. This paper deals with the current development status of the Epsilon launch vehicle and its intended evolution. Copyright ©2011 by the International Astronautical Federation. All rights reserved.

イプシロンロケットの目的は,小型衛星に対して即応性豊かな打ち上げシステム,すなわち自在性と機動性に富みユーザーフレンドリな輸送手段を構築,宇宙への敷居を下げて宇宙科学や宇宙利用の裾野を拡大することにある.一方,これを輸送系の視点でみると,打ち上げシステムの革新というひと言に尽きる.すなわち,今後のロケット開発にあたっては,射場設備と運用はもとより,製造プロセスから搭載系に至るまで,およそロケットの打ち上げに必要な設備や運用をとことんコンパクトで身軽なものにしていこう,それが未来への扉を開く鍵であるという理念である.イプシロンロケットでは,このような壮大なビジョンを実現する第一歩として,ロケットのインテリジェント化やモバイル管制などの超革新技術を開拓,これを世界に先駆けて実証するために,初号機を2013年度に打ち上げる計画である.

ISAS activities for reusable rocket technology and architecture including flight demonstration by the RVT (Reusable Vehicle Testing) have shown various progresses in technical areas such as frequent-flight propulsion systems, reusable rocket engines, returning flight and vertical landing techniques and demonstrations, composite cryogenic LH2 tank studies, new architectures for reusable and repeated flights with quick turnaround and so on. Following these basic studies of reusable rocket, mission definition and system requirement synthesis of the reusable sounding rocket are completed. In addition to the technical and performance related issues, its operational aspects and requirements for the frequent and repeated flight were given stressed. Throughout the studies, technical readiness to the reusable rocket technique and for the system synthesis for the reusable sounding rocket vehicle are in progress. For the sounding rocket's system definition and requirement analysis, research of the flight demand such as the number-of-flight per year and its frequency by the potential user communities. These requirements are from the needs of the middle to upper atmosphere research, studies from micro-gravity community, engineering community which may use this repeated flight opportunity. Copyright ©2010 by the International Astronautical Federation. All rights reserved.

A micro solid propellant thruster for simple attitude control of a 10 kg class small spacecraft is currently under development. The prototype has 0.8 mm micro rocket elements, arrayed at a pitch of 1.2 mm on a 22 × 22 mm substance. Initially, solid propellants were used, obtaining only 20% ignition probability with a very long ignition delay (e.g. 1000 ms) as well as very high ignition energy. While observing the tested prototype sample, it became apparent that the main cause of these problems was a gap between the solid propellants and ignition heater. So, the thruster system was improved so that the propellants adhered to the heater. In addition, an ignition charge was used that starts to burn at 210°C, which was acetone having the form of slurry. As a result, a better ignition probability of over 80% in vacuum and half thrust of expectation were gained.

無毒で常温貯蔵可能な液体推進剤として亜酸化窒素(N_2O)/エタノールの組合せに着目し,それによる扱い易い液体推進系の実証研究を進めている.当面の目標として大気吸い込み式極超音速推進系の飛行試験に用いる加速用ロケットエンジンへの適用を目指しているが,その低温環境順応性を活かす衛星・探査機搭載推進系への応用も視野に入れている.これまでに,推力700N級の要素試験供試体を用いた燃焼試験を2シリーズ行って,エンジン噴射器設計のための有用なデータと運用特性を取得してきた.併せて,水冷式燃焼器による燃焼器壁面熱流束分布の測定や厚肉のシリカ繊維強化プラスチックSFRP製燃焼器を用いた燃焼試験によって燃焼器への耐熱複合材料適用の可能性も探っている.