野中 聡

© Published under licence by IOP Publishing Ltd. The knowledge of forced flow heat transfer characteristics of liquid hydrogen (LH2) is important and necessary for design and cooling analysis of high critical temperature superconducting devices. However, there are few test facilities available for LH2 forced flow cooling for superconductors. A test system to provide a LH2 forced flow (∼10 m/s) of a short period (less than 100 s) has been developed. The test system was composed of two LH2 tanks connected by a transfer line with a controllable valve, in which the forced flow rate and its period were limited by the storage capacity of tanks. In this paper, a liquid hydrogen recirculation system, which was designed and fabricated in order to study characteristics of superconducting cables in a stable forced flow of liquid hydrogen for longer period, was described. This LH2 loop system consists of a centrifugal pump with dynamic gas bearings, a heat exchanger which is immersed in a liquid hydrogen tank, and a buffer tank where a test section (superconducting wires or cables) is set. The buffer tank has LHe cooled superconducting magnet which can produce an external magnetic field (up to 7T) at the test section. A performance test was conducted. The maximum flow rate was 43.7 g/s. The lowest temperature was 22.5 K. It was confirmed that the liquid hydrogen can stably circulate for 7 hours.

© Published under licence by IOP Publishing Ltd. Liquid hydrogen has excellent physical properties, high latent heat and low viscosity of liquid, as a coolant for superconductors like MgB2. The knowledge of Departure from Nucleate Boiling (DNB) heat flux of liquid hydrogen is necessary for designing and cooling analysis of high critical temperature superconducting devices. In this paper, DNB heat fluxes of liquid hydrogen were measured under saturated and subcooled conditions at absolute pressures of 400, 700 and 1100 kPa for various flow velocities. Two wire test heaters made by Pt-Co alloy with the length of 200 mm and the diameter of 0.7 mm were used. And these round heaters were set in central axis of a flow channel made of Fiber Reinforced Plastic (FRP) with inner diameters of 8 mm and 12 mm. These test bodies were vertically mounted and liquid hydrogen flowed upward through the channel. From these experimental values, the correlations of DNB heat flux under saturated and subcooled conditions are presented in this paper.

Copyright © 2017 by the International Astronautical Federation (IAF). All rights reserved. Copyright © 2017 by the International Astronautical Federation (IAF). All rights reserved. Mitsubishi Heavy Industries, Ltd (MHI) has been contributed to the development and manufacture of liquid fuelled launch vehicles from early phase in Japan. MHI began providing launch services with H-IIA launch vehicle for both commercial and governmental missions in 2007. In 2013 H-IIB launch vehicle was added in the line-up of service launcher family. The latest success rate of H-IIA/B has reached to 97 percent. In addition, a new expendable launcher H3 is under development and its first flight is planned in FY2020. In parallel, aiming for the drastic reduction of space transportation cost, R&D for the reusable space transportation systems is in progress. Especially, reusable 40kN-thrust liquid hydrogen/oxygen engine has been developed and demonstrated successful firing test worth 100 flights duration in 2014 by Japan Aerospace Exploration Agency (JAXA) and MHI. For next step, we have agreed to collaboratively develop a reusable experimental vehicle which will be equipped with the reusable engine. The objective of this vehicle is to raise TRL of several key technologies required for reusable space transportation systems as system demonstration. Additionally, JAXA and MHI continue a conceptual study of space transportation system, in order to market the reusable system in the 2020s with reduced cost of space transportation.

Copyright © 2017 by the International Astronautical Federation (IAF). All rights reserved. To study a system architecture for reusable launch vehicle, we have proposed a reusable sounding rocket in ISAS/JAXA which makes the access to space for scientific researches much easier and make the opportunities of the rocket launches much frequent. Reusable sounding rocket is different from the present expendable rockets in 1) repeated operations, 2) returning flight / re-ignition of engine / vertical landing, that is, 3) fault tolerant / health management. Technology maturation studies as phase-A of reusable sounding rocket development have been conducted from 2010 to 2016 as follows, 1) proto-model engine development and repeated operation demonstration, 2) fuel/oxidizer management demonstration through planned flight, in-flight restart and turnaround ground operation, 3) detailed aerodynamic design and returning flight studies, 4) health monitoring subsystem demonstration, and 5) comprehensive preliminary system design and front loading studies for "flyable vehicle" including repeated flight operation architecture. As these technical demonstrations for reusable sounding rocket development have successfully completed, a study system level verifications by a flight demonstrator are in progress from 2016 as the next step. In this plan, a reusable rocket test vehicle will be established for repeated flight demonstrations. Objectives of the demonstration are 1) system architecture study for repeated flight operation such as quick turnaround operation and fault tolerant design method, 2) life controlled and frequently repeated use of cryogenic propulsion system and its flight demonstrations, 3) study for the advanced returning flight method of vertical landers and its flight demonstrations, and 4) demonstration of advanced technology for future RLVs such as more composite on board, in flight fuel management, GH2/GOX auxiliary propulsion, health management, long-life high performance engine. These system level studies by a reusable flight demonstrator will be conducted for next three years. In this paper, ISAS/JAXA activities for development reusable launch vehicle, that is, technical demonstrations for reusable sounding rocket and a plan and present status of flight demonstrations by reusable rocket demonstrator, are summarized and reported.

© 2002-2011 IEEE. Liquid hydrogen (LH2) has excellent properties such as large latent heat, low viscosity, and so on. Because of these properties, LH2 is expected to be used as a coolant for a high-critical-temperature superconductor (HTS), including MgB2. The over-critical-current properties of an HTS are important for the stable designs of HTS devices cooled by LH2; however, the temperature change of a sheathed superconducting wire cannot be revealed only by current-voltage properties beyond critical current, since the current-sharing ratio among MgB2 and sheath materials is not unknown. In this study, transient over-critical-current tests were performed on a short MgB2 sample cooled by LH2 under magnetic field, and the sample temperatures were calculated from test data. In addition, the test sample temperature based on the test was compared with that of the computer simulation result. It was found that the temperature change of the wire just after the transport current exceeds the critical current is affected by external magnetic fields.

Copyright © 2016 by the International Astronautical Federation (IAF). All rights reserved. Mitsubishi Heavy Industries, LTD. (MHI) has been contributed to the development and manufacture of liquid fuelled launch vehicles from early phase in Japan. MHI began providing launch services with H-IIA launch vehicle for both commercial and government missions in 2007. In 2013 the H-IIB was added in the line-up of service launcher family. The latest success rate of H-IIA/B has reached to 97 percent. In addition, the development of new expendable launcher H3 has started, and it's first flight is planned in FY2020. In parallel, aiming for the drastic reduction of space transportation cost, RD for the reusable space transportation systems are in progress. The fundamental technologies for reusable engine, landing gear, and propellant management devices needed during way back flight, has been developed with JAXA. Especially, reusable 40 kN thrust liquid hydrogen/oxygen engine has been developed and demonstrated successful firing worth 100 flights duration in 2014. Additionally, MHI has studied guidance, navigation and control technology for vertical landing rocket, and demonstrated the control law in the flight test by a subscale experimented vehicle. This paper describes the current RD status of reusable rocket and approach to future reusable space transportation system which MHI considers.

Copyright © 2016 by the International Astronautical Federation (IAF). All rights reserved. A fully reusable sounding rocket is proposed in ISAS/JAXA. This vehicle adopts single stage and VTVL(vertical takeoff and vertical landing). The vehicle is decelerated by aerodynamic resistance and turn over for vertical landing in return phase. After that, the vehicle is decelerated by the main engine for soft-landing. To return the vehicle, there is a problem that the study of the guidance control method and securing both the launch ability and the propellant for soft-landing in addition to the ability required of conventional vehicle. It is necessary to design the airframe shape and control method after studying the motion characteristics at the time of return to clear these problems. This paper shows the result of motion analysis about the return system under consideration, and considers from the point of view of the vehicle specifications and control system. And it indicates the guidelines of the airframe and control system that is suitable for the return of reusable sounding rocket.

The Reusable Sounding Rocket is a fully re-usable sub-orbital sounding rocket that takes-off and lands vertically from/on the same launch site. The Reusable Sounding Rocket recovers its payload: one can make repeated use of instruments, recover samples, have a big data storage onboard, and so on. The Reusable Sounding Rocket can be launched daily. The target cost for operation is 1/10 of the existing sounding rocket, S-310. The duration of g environment is about 3 minutes. The payload bay is in the nose-cone and its volume is 0.8m in diameter and 1m in height. The maximum mass of the payload is 100kg.

© 2016 Ayane Sato et al. The objective of this study is to experimentally verify a new aerodynamic control concept of a high-angle-of-attack slender body. In the concept, penetrating flow channels are installed to the apex of the slender body. The blowing or suction is generated at the channel exits in response to the surface pressure distribution. First, the effects of the flow channels on the aerodynamic characteristics are experimentally investigated in a low-speed wind tunnel. The result shows the Suction-Blowing type channel is the most effective because its control effect does not reduce even in higher mainstream flow velocity. The peak value of the side force and yawing moment can be reduced by up to 64% and 49%, respectively. In addition, visualization of the surface flow pattern by the oil flow method shows that the Suction-Blowing type channel makes not only the primary separation line on the body side but also the secondary separation line on the body back become symmetric.

© 2016 The Authors. High-Tc (HTC) superconductors including MgB2 will show excellent properties under temperature of Liquid Hydrogen (LH2:20K), which has large latent heat and low viscosity coefficient. In order to design and fabricate the LH2 cooled superconducting energy devices, we must clear the cooling property of LH2 for superconductors, the cooling system and safety design of LH2 cooled superconducting devices and electro-magnetic property evaluation of superconductors (BSCCO, REBCO and MgB2) and their magnets cooled by LH2. As the first step of the study, an experimental setup which can be used for investigating heat transfer characteristics of LH2 in a pool and also in forced flow (circulation loop with a pump), and also for evaluation of electro-magnetic properties of LH2 cooled superconductors under external magnetic field (up to 7 T). In this paper, we will show a short sketch of the experimental set-up, practical experiences in safety operation of liquid hydrogen cooling system and example test results of critical current evaluation of HTC superconductors cooled by LH2.