Haruo Kawasaki

Development of Flat Plate Heat Pipe and the Project of On-orbit Experiment

Because of the advancement of satellite systems which leads to an intensified heat dissipation requirement, the development of a thin heat transport device is needed. We noted oscillating heat pipes (OHPs) with check valves, and have developed flat plate heat pipes (FHPs), which are 3 millimeters thick and can transport or diffuse more than 100 W of heat. Applying FHP to the spacecraft, the heat transfer characteristic of FHP under microgravity conditions should be examined. The “FHP On-orbit Experiment (FOX)” is a project to conduct the performance evaluation experiment of FHP under microgravity environment, and the FOX’s component will be mounted on Small Demonstrate Satellite-4 (SDS-4), which is developed by JAXA. This paper describes the ground performance of FHP and the substance of FOX.

A study of oven magnetrons toward a transmitter for space applications

The objective of the present study is to evaluate 2.45GHz and 5.8GHz oven magnetrons, toward a transmitter for space applications. Dc-rf efficiency and frequency spectrum of the oven magnetrons were measured. Significant improvement of efficiency and reduction of back bombardment energy must be necessary for the present 5.8GHz oven magnetron to facilitate thermal management in space and to improve the frequency spectrum, respectively. Thermal vacuum tests of a 2.45GHz oven magnetron were also conducted. From experimental results, the dc-rf efficiency was mainly dependent on magnet temperature. Therefore, thermal control of the magnets and pole pieces is essential for the highly-efficient magnetron operation in space.

Effect of Size on Thermal Performance of Limited Size Multilayer Insulation

Multilayer insulation blankets are used in various sizes for thermal control of space systems. These multilayer insulation blankets are processed, usually by being seamed and patched. It is qualitatively understood that the thermal performance of small size multilayer insulation is more or less deteriorated. The effects of size of space use multilayer insulation blankets on thermal performance are known qualitatively, but not quantitatively. In this study, the thermal performance of limited size multilayer insulation blankets was measured by using the boil-off calorimeter method with liquid nitrogen. The temperature distribution on a rectangular multilayer insulation was also measured in order to investigate the nonuniformity of the local heat flux across the rectangular multilayer insulation. Thermal performance declines with the decrease of multilayer insulation area. This is because the local heat flux drastically increases in the hem region and the gap between the edge of blanket and base plate. Based...

Temperature Dependence of Thermal Performance in Space Using Multilayer Insulation

T = temperature , K t = thickness, m V = volume flow rate, L min -1 Subscripts av = average temperature , K B = boil-off tank or base plate g = vapor Hem = hem of MLI blanket l = liquid MLI = MLI outermost surface, Test MLI N = number of layers, number of test MLI n = number of control MLI blanket (masking MLI blanket) S = outermost surface of MLI Total = total into the boil-off tank, measured from evaporation rate by experiment V = vacuum chamber

Influence of Processing on Thermal Performance of Space Use Multilayer Insulation

Most spacecrafts flown today are covered with multilayer insulation blankets as the most efficient thermal control element. This study was performed to investigate the influence of various processing methods for space use multilayer insulation on thermal performance. The latter was measured by the calorimetric method using a liquid nitrogen cryostat and it was verified that the thermal performance of the multilayer insulation blankets that were processed in the most conventional manner for space use was found to be deteriorated considerably by hem processing such as overlap, seam, and patch. An estimation of the deterioration of the thermal performance of processed multilayer insulation blankets is given in this report.

Characteristics of Reservoir Embedded Loop Heat Pipe in Deployable Radiator on ETS-VIII at Beginning of the Experiment under Orbital Environment

A deployable radiator (DPR) on the Engineering Test Satellite-VIII (ETS-VIII) was launched to a geo stationary orbit using H-IIA rocket on 18 Dec. 2006, carrying a deployable radiator (DPR). Deployable radiators are anticipated for extension of the radiator area on satellites to mitigate increased heat generation. The DPR is an experimental apparatus on the ETSVIII; it has a reservoir-embedded loop heat pipe (RELHP) for heat transfer from the experimental heat load to the DPR radiator. The RELHP reservoir is embedded in the evaporator for reliable function of the Loop Heat Pipe (LHP). This paper describes the DPR and the RELHP characteristics on the ETS-VIII from its launch operation to the beginning of the test under an orbital environment.

ISS experiments for the clarification of boiling and two-phase flow in microgravity and for the development of high-performance space cold plates

Inflow boiling, gravity effects on the distribution of both phases are observed in a heated tube and heat transfer coefficients due to two-phase forced convection is deteriorated in microgravity. In narrow channels between heated and unheated plates, the increase in subcooling enlarges a size of flattened bubble and reduces the frequency of detachment under microgravity conditions resulting the emphasis of heat transfer deterioration. To clarify reasons for the unknown behaviors of interfacial distribution and corresponding characteristics in heat transfer not easily be clarified through the experiments on ground, the opportunity on the experiments utilizing long-term microgravity duration realized in ISS is required. The experiments on microgravity boiling and two-phase flow are proposed by the collaboration of researchers in five countries. A common test loop is designed to conduct multiple experiments by the interchangeable structures of test sections; a transparent heated tube for the visualized flow boiling, a stainless tube for the measurement of CHF data, a copper surface for the heat transfer data of nucleate boiling with superimposed liquid flows in a duct, a glass heated plate with multiple array of small temperature sensors and transparent heaters for the clarification of mechanisms in nucleate boiling heat transfer, and one or two models of cold plates for practical applications. A direction of researches in the present discipline is proposed based on the existing experimental results and on the idea developed by the present authors.

Conceptual Study on Heat Transfer System for Space Solar Power System

It is estimated that the energy consumption all over the world will increase to nearly 3 times in 2050 and that the total amount of CO2 exhaust will increase 3 times also. Hence, it is expected the lack of energy resource and severe green house effect by CO2 may emerge in future. Space Solar Power System (SSPS) is one of the candidates with potential, among the various future power sources, because of almost eternal power supply with almost no emission of CO2. After a pioneering work by NASA in USA, some reference models are proposed and investigated by DLR in Germany, ISAS, and NEDO both in Japan, in which the power spectrum are underlying from 250MW to 1GW respectively. The conceptual design of System for Space Solar Power System has been developed actively in NASDA. Today, SSPS is supposed feasible, if economical rationality will be solved by promising technical scenario. In the report, the results from present survey of heat transfer system for SSPS reference model in NASDA is mentioned, in the view of technical criticality to realize the total system not only for the technical demonstration but also the commercial plant.

Characteristics Variation of Reservoir Embedded Loop Heat Pipe under the Orbital Environment in Three Years

A deployable radiator (DPR) on the Engineering Test Satellite-VIII (ETS-VIII) was launched to a geo stationary orbit by the H-IIA rocket on 18 Dec. 2006. The DPR, an experimental apparatus on ETS- VIII; it has a Reservoir-Embedded Loop Heat Pipe (RELHP) for heat transfer from the experimental heat load to the DPR radiator. The RELHP reservoir is embedded in the evaporator for reliable function of the Loop Heat Pipe (LHP). This paper describes the characteristics of the DPR and the RELHP under an orbital environment over three years.

The DC-RF Conversion Efficiency Change of Magnetron with Thermal Condition

Converters that change DC power to microwave power are applied in various industries. Such converters can be categorized as magnetrons, traveling wave tubes (TWTs), and semiconductor converters. The magnetron has merits of high power and small size. The magnetron, as depicted in figure 1, can be a high- power transmitter for a space satellite, since the magnetron is a low-cost device and that is in mass produced ground use (Mitani et al., 2004; and Kitagawa et al., 1989). The magnetron, however, has demerits of in poorly stabilized output frequency spectra and variations in efficiency. The purpose of this study is to investigate the DC-RF conversion efficiency change of magnetrons with thermal condition.