Ryojiro Akiba

Control of omni-directional rendezvous trajectories

Abstract A range-rate control algorithm for spacecraft rendezvous was proposed by the authors elsewhere. The algorithm used only one in-sight-line propulsion and led to the stable, stationary and straight line trajectory only in a certain area in the orbital plane. The rendezvous process was not so rapid. Now, another propulsion across the sight-line is implemented. The process becomes quicker. The stable, stationary and straight line trajectory can be placed anywhere in the whole orbital plane. The phase plane method is adopted to stability analysis. Computer simulation of three-dimensional motion shows the simplicity and good quality of the algorithm.

International edition of iaa multilingual dictionary coordinated through computer network

Abstract This paper proposes a procedure for editing the “IAA Multilingual Space Dictionary”. The dictionary is constructed through international cooperation. Therefore, assignment of the work to each country and international information exchange methods should be discussed. To ensure efficient editorial work, active use of a computer network is proposed. Some anticipated difficulties of editing based on a computer system are also described.

A concept of the energy storable orbital power station (ESOPS)

Abstract To save foreseeable difficulties and risks associated with large scale development of the Space Power Station on GEO at a remote distance, the Energy Storable Orbital Power Station (ESOPS) placed in a near earth orbit is proposed. Most promising orbit for ESOPS is a fixed periapsis pseudo sun synchronous orbit. A thermodynamical power generation is preferable owing to its inherent insensitive nature against radiation suffered on the medium altitude orbit. Thermal energy storage using latent heat of fusion seems the best choice for this system. The power transmission from ESOPS to ground station presents most critical problems due to non-stationary characteristics.

Motion Analysis of Captive Platform System Constructed from Airship and Tether

The existence of a platform at the stratosphere is expected to be the role to gain a foothold in space. When the platform is employed airship in, it is transported by advection due to its lighter-than-air body. Thereupon, a mooring of platform is reasonable in order to incarnate fixed-point platform. Conception of a captive platform system is similar to the Rockoon one which rendered remarkable services for the space observation of the early days. Therefore, the application of captive platform system to the launch site is highly expected in order to realize the space transportation system with a large quantity and high frequency. In this study, the motion of a captive platform system constructed from an airship and tethers is analyzed in order to ensure that the motion of a captive platform system is practically incarnated. Moreover, the sensitivities of aerodynamic performance and buoyancy of the airship is observed. Consequently, the practically incarnated motion of a captive platform system has been identified under the condition of the storm environment. Furthermore, the reduction of the advection distance driven away by the storm has been quantitatively indicated under the different conditions of aerodynamic performance and buoyancy of the airship. The sensitivities of the lift and buoyancy of the airship for the motion of a system has been revealed in order to conceptually design airship geometry.

Orbital design and technological feasibility of Halley mission

Abstract Missions to Halleys comet in 1985–1986 are discussed. They include pre-perihelion encounter, post-perihelion encounter, the utilization of Venus swing-by, one round mission in which the spacecraft goes the round of the Sun before the encounter and missions to the point beneath the perihelion of Halleys orbit. Technological feasibility of the small spacecraft is also discussed on the basis of the use of the improved version of M-3S launch vehicle.

Feasibility Studies on a High-Altitude Captive Lighter-Than-Air Platform System

A station-keeping platform in the stratosphere can be a novel foothold toward spaceactivities. If the platform is conformed as free-ight LTA vehicles, there are possibilitiesthat they may be blown away by the atmospheric advection due to its free-ight nature.Therefore, mooring this type of platform to the ground by a cable will be much easierto hold it in position. This concept of a captive platform system looks somewhat similarto rockoon systems which provided remarkably good services for the space observation inthe past days. Namely, application of a captive platform system to a rocket launch padis well expected to realize a space transportation system of ample payload capacity withmuch frequent services. In addition, this newly conceived system will have a wide spectrumrange of application elds such as agriculture, meteorology, communication, etc. However,several technical issues are identi ed to materialize such a captive stratospheric platform.In these studies, summary results are presented for each of these technical issue itemsregarding ight tests, tether system operation, and wireless communication experiment.Consequently, useful knowledge has been empirically acquired concerning the above issuesin order to construct a captive LTA stratospheric platform.

A development of a balloon made of fiber reinforced film

In present ballooning missions, as payloads increasingly become heavier and more sophisticated, much higher reliability is required in the balloon itself and in the launch operational technique. Hence, ISAS (the Institute of Space and Astronautical Science) has developed a balloon made of relatively thick films reinforced with high-strength fiber fabric (ref. 1 to 3). In order to verify structural properties and manufacturing quality, partial strength tests together with a trial production of small scale balloons have been car ied 5 . out. In 1990, a sub-scale B5 (5,000 m In volume) size balloon was produced, and a full inflation test on the ground prior to a flight experiment was implemented on account of demonstrating the basic capability of the fiber reinforced balloon. This paper describes research and development of the proposed balloon associated with selection and verification study of the high-strength fiber reinforced film.

DEVELOPMENT STUDY OF LOX/LH2 PROPULSION SYSTEMS

ABSTRACT The national development program of a LOX/LH2 propulsion system, which is intended to be used as the second stage of the future Japanese launch vehicle called H-1, is being performed cooperatively by the three representative organizations relating to rocket technology in Japan: the National Space Development Agency of Japan (NASDA), the National Aerospace Laboratory (NAL) and the Institute of Space and Aeronautical Science (ISAS), University of Tokyo. The development study of LOX/LH2 propulsion system has started at the ISAS in 1975 according to its own program. By 1980 have almost finished the development tests of major components for the engine of 7,000 kg thrust level. The thrust chamber is of the tubular wall type and has the nominal design performance of 7,000 kg thrust level and 433 seconds specific impulse in vacuum. The gas generator is of the side-outlet reverse-flow type and composed of a spherical combustion chamber, 12 coaxial injectors and a start valve. The turbopump has the very unique configuration to have never been developed for rocket engine. A LOX and a LH2 pump are arranged at each end and a turbine at center of the turbopump. Each of the two pumps is mounted on each of the two rotor shafts which is not interconnected and rotate in opposite direction of each other because of no stator between two rotors. The solid propellant gas generator is used for the turbine spinner. The engine system assembled together with these components is to be tested in the middle of 1980. In parallel with the development of tubular wall thrust chamber, the channel wall thrust chamber is also being developed in the ISAS to aim at the future high performance engine, which is manufactured with use of the diffusion bonding technique. The present paper describes the status of the development study on the LOX/LH2 propulsion system being conducted by the ISAS.

Recent development of scientific satellites and their launch vehicles

Abstract The Institute of Space and Aeronautical Science (ISAS), University of Tokyo, has been engaged in the development of scientific satellites and their launch vehicles of Mu series. ISAS has conducted the first flight test of M-3S, the newest version of Mu series, and launched a technology test satellite MS-T4 into an orbit. The objectives were to verify the overall performance of the vehicle and to perform various experiments on the satellite technology to be applied to the following scientific satellites. Technological aspects of M-3S and MS-T4 are reviewed in reference to the recent trend in the scientific satllite program.