A new variable termed the ejector drive parameter was proposed as a dominant parameter of the pressure recovery ratio of constant-area mixing tubes. It was derived from the one-dimensional analysis of a zero-secondary flow mode. This parameter represented the strength of the normal shock wave generated in the rocket exhaust that is spreading to the entire cross section of mixing tubes under the zero-secondary-flow condition. Parametric studies were carried out for investigating the pressure recovery ratios of the constant-area mixing tubes, and the analytical results were plotted against the ejector drive parameter or several other parameters. It was determined that the influences of each parameter on the pressure recovery ratios were minimized by using the ejector drive parameter. In order to validate the results of the parametric studies, cold flow experiments were conducted by using supersonic-subsonic ejectors with cylindrical or rectangular constant-area mixing tubes. The measured pressure recovery ratios were in good agreement with the pressures predicted by the one-dimensional analysis.
The influences of the molecular weight and total temperature of a primary gas on the flow fields of constant-area mixing tubes for ejector-jets were investigated. First, in order to investigate the exit choke, parametric studies were carried out for the exit-choke phenomena in the constant-area mixing tubes by using a one-dimensional model. The effects of the incoming Mach number, wall friction, expansion ratio of a primary nozzle, and specific heat ratio on the exit-choke phenomena were reported. Moreover, flow fields having primary flows with high total temperatures were investigated by CFD. The transition points from the exit-choke mode to the free-jet choke mode obtained by CFD were in good agreement with those obtained by the one-dimensional model. The pressure recovery performances in both choke modes were compared. The decrease in the static pressure at the exit of the subsonic diffuser attached downstream of the mixing tube was observed.
Gas adsorption onto optical surfaces equipped in satellites is one of the causes of signal degradation occurred in orbit and water is one of the most potent ad-molecules. To estimate the degradation caused by water adsorption onto optical glass surface, the transmittance measurements were carried out in UV-VIS (200--800nm) and IR (1.7--20μm) wavelength ranges. Five kinds of glasses, SiO2, BK7, Al2O3, CaF2, and ZnSe, which are typically used for satellite optics, were selected as glass samples. In IR wavelength range, a local absorption feature was appeared at λ=3.1μm when a glass temperature was below 200K. The phase change of adsorbed water from vapor to solid may account for the newly appeared absorption. In UV-VIS region, there was no local absorption feature but broad transmittance decrease. BK7 and ZnSe, which are hydrophobic, showed little transmittance decrease and it was hard to find the wavelength dependence for their transmittance spectra. On the other hand, the transmittance spectra of hydrophilic glasses, SiO2, Al2O3, and CaF2, showed wavelength dependence and had the local minimal value. From our computation, it is found that the growth of ice grains on a glass surface makes it possible to reproduct the spectral transmittance degradation detected for hydrophilic glasses.
REIMEI/INDEX (INnovative-technology Demonstration EXperiment) is a 70kg class small satellite which the Institute of Space and Astronautical Science, Japan Exploration Agency, ISAS/JAXA, has developed for observation of auroral small-scale dynamics as well as demonstration of advanced satellite technologies. An important engineering mission of REIMEI is integrated satellite control using commercial RISC CPUs with a triple voting system in order to ensure fault-tolerance against radiation hazards. Software modules concerning every satellite function, such as attitude control, data handling, and mission applications, work cooperatively so that highly sophisticated satellite control can be performed. In this paper, after a concept of the integrated satellite control is introduced, the Integrated Controller Unit (ICU) is described in detail. Also unique topics in developing the integrated control system are shown.
The supersonic biplane is well known as the airfoil that has zero wave drag at the supersonic speed. This paper investigates aerodynamic characteristics of the supersonic biplane with the finite span length and effects of the aspect and taper ratios by comparing with the two-dimensional supersonic biplane which has the infinite span length using the computational fluid dynamics. The rectangular wing was employed to examine the effect of the aspect ratio and tapered wing was employed to inspect the effect of the taper ratio. Both the rectangular wing and the two-dimensional supersonic biplane choke at the high angle of attack. The drag of the three-dimensional wing becomes smaller when it has a higher aspect ratio. The drag polar curve of the three-dimensional wing approaches asymptotically to the drag polar curve of the two-dimensional supersonic biplane when it has a higher taper ratio. The drag of the tapered wing becomes smaller when it has an adequate taper ratio.
In this research, CFRP scarf repair panels were tested to evaluate the tensile mechanical properties and impact characteristics. CFRP scarf repair panels were prepared to simulate the assumed three different situations. These situations consist of two different scarf repair methods and impact damage case which are autoclave repair, heat blanket repair, and impact damage case. As the result, these strengths are not recovered in all situations, however, stiffness was recovered in all situations. Moreover, the strength of heat blanket repair and impact damage case were reduced compared with autoclave repair.