The Project of Osaka Institute of Technology Electric-Rocket-Engine onboard Small Space Ship (PROITERES) was started at Osaka Institute of Technology in 2007. After successfully launching the 1st PROITERES satellite, the 2nd PROITERES satellite with electrothermal Pulsed Plasma Thrusters (PPTs) has been developed since 2010. The main mission is powered flight with longer distance, i.e. changing more than 10km in altitude on near-earth orbits by high power PPTs. In this research, a 30W-class PPT system was developed by experimental and numerical simulation. In the present paper, we examine the interior physical phenomena and the performance characteristics by numerical simulation when changing cavity length. As a result, calculated performances agreed with experimental ones, and the cavity lengths between 10mm and 50mm with a stored energy of 31.59J achieved a maximum total impulse of 67.1Ns.
10kW class Inductively Coupled Plasma (ICP) heater in JAXA/ISAS was developed to evaluate heating-durability of membrane materials for inflatable reentry aeroshell. To utilize the ICP heater as an experimental facility to investigate heating-durability, it is necessary to clarify characteristics of the plasma flow generated by the ICP heater. In this study, emission spectroscopic analysis of air plasma flow which is used for heating tests of the aeroshell was conducted. Spectra of the air plasma flow at plasma heating region were acquired. Moreover, molecular temperatures were estimated based on the spectra data by a spectrum fitting method using a radiation analysis code. It was indicated that molecular temperatures of nitric oxide (NO) bands are 4200--5800K at the plasma heating region assuming the local thermal equilibrium. In addition, the experimental results qualitatively reproduced numerical simulation results obtained by computational fluid dynamics approach.
The strong growth of air traffic demand in the Asia-Pacific region is expected to continue, and it will be necessary for Japan to increase capacity in the area of the North Pacific over which it has responsibility for Air Traffic Control. For such measures, the influence of wind on the most efficient operating routes must be considered, but the westerly jet stream varies during the year so it is difficult to consider its influence comprehensively. Currently, flexible route operations that consider winds aloft wind are implemented in the North Pacific oceanic area, and track information is published daily. This paper provides the result of trend analysis and classification of flexible routes in the North Pacific in preparation for a future efficient route study of the area. Published flexible route data for one year were analyzed, and k-means clustering was used for classification of the large volume of data. As a result, although the variation of tracks over a year was found to be large, classification showed a north-south trend: In the summer, when the westerly jet stream is relatively weak, a trend to take routes close to the Great Circle on its north side was indicated, whereas in the winter, when the jet stream is strong, routes tend to be south of the Great Circle.
Pyrotechnic is typically used in the separation system of the rocket payload fairing. The disadvantage of this system is large impact force caused by pyrotechnic, and reduction of the impact force is expected to enhance international competitiveness of rocket launch vehicle. In order to predict the impact fracture behavior and understand separation mechanism of notched bolt, the tests and numerical simulations were performed. The test was performed under impact environment using split Hopkinson bar method. The thermal and structural coupling analysis were conducted as numerical simulation, which was considered plastic heat, visco-plasticity and temperature dependence of Ti-6Al-4V. The computed results were in a good agreement with the test results under room and cryogenic temperature environments. From the SEM observation, it was clarified that the fracture surface changed from ductile into brittle when the displacement rate was increased and testing temperature was decreased. From the computed results, it was confirmed that the separation phenomena were fast crack propagation from notch surface and the separation impact force can be determined by the tensile force fracturing the notch surface. In addition, the employed methodology was confirmed to be an effective tool to estimate a separation force quantitatively and develop lower impact system.