A panel discussion was held to discuss the technical challenges in orbital transfer vehicle (OTV) development using electric propulsion. Electric propulsion is advantageous in the transportation of SSPS if the solar array panel in the payload can be used in the OTV. Argon is the candidate for the propellant, and the technical issues for the development of high-power argon-propellant thruster are discussed. The collaboration with the ground launch vehicle is indispensable to attain the SSPS, in addition to the cross-field collaboration for the optimization of the OTV. The necessity of technology demonstration missions and technical roadmap is reconfirmed to promote the collaboration among the researchers.
Microwave Rocket obtains an impulsive thrust by utilizing millimeter-wave supported detonation induced by a millimeter-wave beam oscillator, gyrotron. To design a thruster, it is necessary to reproduce its thrust generation process quantitatively. Therefore, in order to conduct detailed measurement on millimeter supported detonation, a new gyrotron, specially designed for atmospheric millimeter-wave discharge, has been developed. This paper summarizes its specifications.
This paper describes a unified design theory both for high-efficiency power amplifiers and high-efficiency rectifiers base on the time reversal duality principle. In high efficiency power amplifier design, optimization for time domain drain voltage and drain current waveforms can be transformed into load impedance optimization problem, where DC input power and RF output power at fundamental frequency are balanced by nulling harmonic output power. Class-F and Class-R (Reactive harmonic load) amplifiers are their good examples. These high-efficiency power amplifiers can be used as rectifiers with appropriate gate switch timing. Using this principle, a developed GaN-HEMT smart module which can be used both as a high-efficiency power amplifier and a high-efficiency rectifier is demonstrated.
The magnetic nozzle RF plasma thruster simply consists of a radiofrequency (RF) discharge and a magnetic nozzle. The high density plasma produced by inductively-coupled and/or helicon-wave-coupled discharge is transported along the axial magnetic field lines to the open source exit; the spontaneous plasma acceleration and momentum conversion processes seem to contribute to enhance the thrust generation. Current status of the studies on the fundamental physics and the performance improvement will be shown here.
The space solar power systems require large surfaces in space, therefore they should be stored in small volumes during the launch phase and be deployed on orbits. Thus, the improvement of the power to volume ratio is important. This paper proposes space deployable “textile” membrane structures with the flasher folding pattern, to achieve high storage efficiency. This structure consists of a textile membrane, flexible boards, and thin-film solar cells. This study provides some solutions that satisfies the mechanical and electrical design issues related to the storage of the integrated structures, and verify the effectiveness by prototyping.
This study evaluates the thermal deformation of an ultralight antenna panel structure made of CFRP thin plate to examine its applicability to the 30m class Geostationary Precipitation Radar (GPR) satellite. This GPR satellite is a midway target to realize the future space solar power systems. The proposed antenna structure is made of three layers of materials; copper foil, dielectric, and CFRP. To design this structure ensuring the flatness required for the electromagnetic performance, the finite element model was established. The validity of the model was tested against the thermal test of the coupon specimen with a single antenna patch or strip. The thermal deformation of the antenna unit which consist of hundreds of antenna patches was then numerically examined. Furthermore, sensitivity studies regarding the layer thickness and the loading condition were conducted to improve the flatness of the proposed antenna structure.
In order to realize the launch of a spacecraft using laser propulsion, a propulsion system using donut-mode beam and a spherical capsule that solves the problem of its position and attitude stability has been proposed. The purpose of this research is to verify the feasibility of the system by performing a launch test on a laboratory scale. As a result of experiments using a spherical target with a diameter of about 14 mm, hovering was possible at an altitude of about 3 mm. We also confirmed the expected restoring force by using donut-mode beam.
When implementing wireless power transmission systems in society, two important issues need to be considered. One is that it can coexist with existing communication systems, another is to minimize the impact on humans and animals. For the first task, the author proposed the use of a two-sided retrodirective system. This is because radio wave leakage is minimized and interference with the communication system can be expected to be avoided. In order to solve the latter problem, it is necessary to develop a technology in which a power transmission beam can instantaneously avoid an intruder when a person or an animal accidentally enters the beam. The authors accidentally discovered that a two-sided retrodirective scheme that solves the first problem also solves the latter problem at the same time. Here the behavior of the beam to avoid the radio wave absorber in the transmission space is described.
This research aims to unravel the mechanism of heat transfer phenomena in the flow inside a heat exchanger made of porous carbon, and to enhance the energy efficiency of the continuous wave laser propulsion system using heat exchanger. We measured the temperature distribution of the heat exchanger. Furthermore, we proposed a one dimensional model considering conduction and radiation heat transfer and verified it comparing the model and experimental result.
Laser beams are propagated to the sky in various wavelength and power levels for laser light show, astronomical observations, weather-monitoring, etc., and the application has been expanding. Our company has a track record of the safety high power laser beam propagation in the atmosphere through R&D programs, the high power laser system for MOD and L-SSPS for JAXA. In this paper, I introduce the regulations of laser beam propagation to the sky in U.S.A. where the legislation has been progressed, and propose the need for drawing up Japanese ground rules in order to continue safe laser beam propagation to the sky into the future.
At present, a demonstration experiment using small satellites is planned to realize solar power generation (SPS). In the demonstration experiment, it is necessary to accurately evaluate the beam shape transmitted from the satellites. The beam shape was reproduced using a two-dimensional least-squares pattern processing technique. In this paper, we showed that by using this satellite as a LEO and arranging the receiving stations in one dimension, simpler and more accurate measurements can be performed than before.
Recently, research and development of hall thruster cluster system as a high-power electric propulsion system for inter-orbit transportation are underway. In the cluster system, the plumes from the heads interfere with each other. Thus, evaluations of the interference are required. In this study, we constructed a Side By Side (SBS) system consisting of two hall thrusters and a hollow cathode. We evaluated the effects of plume interference on propulsion performance and operating characteristics of the SBS system.