The motion of a kite is simulated using an in-house numerical simulation code, where aerodynamics are coupled with flight dynamics. In the present study aerodynamic forces, attitude and stability are examined for a kite with camber and string lines. The results reveal that the kite shows stable flight; specifically, it keeps a constant altitude, moving from side to side periodically. The reason for this is the restoring forces produced by strings on the kite, which generate simple harmonic motion of the kite. The motion obtained by the present method shows good agreement with experimental results. Thus, the numerical method used here is found to be effective in the simulation of a kite. Furthermore, based on the data obtained from the present numerical simulation, a model is proposed to analyze the characteristic motion in the flight of a kite using its aerodynamic properties, and the period of the kite’s periodical motion in the lateral direction is explained.

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The space solar power system (SSPS) transfers enormous amounts of electrical energy through microwaves. When high-power microwaves are irradiated from an antenna in a LEO plasma environment, there is a concern about discharge caused by interaction between the plasma and the microwaves. There has been no experimental observation of such an interaction phenomenon. Verification experiments are essential for SSPS to become a reality. We examine whether discharge or related phenomena occur or not on patch antennas under various conditions in the laboratory. We verify the hypothesis of discharge inception that the discharge is caused by multipactoring and breakdown of the outgas product. We compute the minimum electric field for the discharge inception.

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A high-order aerodynamics simulation code for the Reynolds-averaged Navier-Stokes (RANS) equations is developed using the spectral volume (SV) method for unstructured tetrahedral meshes. A nonlinear LU-SGS implicit scheme is used to enhance convergence to the steady state solution, and a novel reconstruction limiter for the SV method is developed to improve the accuracy and the convergence property for flows with shock waves. The turbulent viscosity is modeled by the Spalart-Allmaras (SA) one-equation model. The developed code is validated for turbulent flow over a flat plate and assessed for a transonic flowfield over a wing studied in the third AIAA drag prediction workshop (DPW-3). Computations of a turbulent flow over high-lift devices are performed, and the ability to predict complicated flowfields is demonstrated favorably via comparison with the reference data. The developed code is fully parallelized for application to large-scale industrial problems by using domain decomposition and MPI.

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Commercial off-the-shelf (COTS) technologies are increasingly used to realize compact, low-cost and high-performance on-board equipment. Before a COTS technology can be adopted in orbit, its performance must be verified in the orbit environment, where factors such as radiation must be considered. This paper presents the irradiation test results of SD cards exposed to gamma ray and proton irradiation. During the testing, we find breakdown phenomena specific to proton irradiation whereas extreme gamma ray irradiation exerts no significant effect. Moreover, the proton phenomena occurs even when the target is switched off throughout the irradiation. The anomalies induced by the irradiation are irreversible.

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The development of an efficient and flexible guidance system is one of the most important aspects of studies on reusable space transportation systems such as winged rockets. A guidance system that can generate several good trajectories instantly is required for responding to sudden changes in trajectories that may lead to accidents. We therefore propose a flight trajectory optimization method that uses a dynamically distributed genetic algorithm (DGA). DGA optimizes solutions by dynamically dividing and merging the individuals using the convergence situation of population. In most conventional studies on distributed genetic algorithms, the population has been divided into a fixed number of groups. This constraint sometimes deteriorates the growth of the solution because the number of groups and individuals in each group is closely related to the convergence of the solution. Our proposed dynamically DGA, which uses hierarchical clustering, was verified by a computer simulation.

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The International Space Station (ISS) is the single largest and most complex scientific and engineering space structure in human history. Its orbital parameters make it extremely vulnerable to atmospheric drag force. The complex interactions between the atmosphere's molecular structure, solar energetic particles, extreme ultraviolet (EUV) radiation and the geomagnetic field cause heating and subsequent expansion of the upper atmosphere. This condition increases drag on low Earth orbit satellites and varies with current space weather conditions. In this work we applied empirical atmospheric density model as a function of space environmental parameters, to model drag force impact on a model LEO Satellite during variation of solar activity. Applying the resulting drag model on a model ISS satellite we found that depending on the severity of solar events, stage of the solar cycle and orbital parameters, a massive artificial satellite could experience orbit decay rate of up to 2.95 km/month during solar maximum and up to 1km/month during solar minimum.

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We develop a progressive wireless system for structural health monitoring of isolated space structures such as satellites and space stations. The system can wirelessly communicate the monitored data using the energy harvested from structural vibrations. To construct the wireless monitoring system, we present a built-in piezoelectric energy harvester. The harvester is controlled by a microprocessor, which enhances the transduction of vibrational energy to electrical energy. Consequently, the harvester generates a larger amount of electrical energy than that of a conventional passive harvester. The harvested energy is used to drive the microprocessor and also used to transmit radio waves for wireless communication. In this system, the structural vibration is regarded as an energy source for energy harvesting as well as a monitoring target for structural health monitoring. The experimental results demonstrate that our wireless monitoring system can autonomously monitor the structural health of a vibrating system and wirelessly communicate the data without requiring an external energy supply.

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A new boundary-layer sensor for drag decomposition of computational subsonic flow fields is introduced. Boundary-layer detection is the key technology for the drag decomposition method to compute profile drag precisely because it calculates the profile drag integrating the drag produced only in the boundary-layer. The new sensor is based on the boundary-layer thickness determination concept of the Baldwin-Lomax turbulence model. It is shown that the new sensor has advantages over the conventional boundary-layer sensor, such as dispensing with parametric studies and geometric extensions. Additionally, the new method showed less dependency on the computational grid size. This means that it may require less computational resources because it should be able to estimate the converged value of the profile drag using less computational grid. In this paper, the advantages of the new sensor are both visually and numerically inspected. The influence of approximating the order of the drag equation is also examined.

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In order to design the natural laminar flow nose for the high Reynolds number condition suppressing the increase of pressure drag, “local” and “non-axisymmetric” deformation is applied to a base shape. Through the analysis for low Reynolds number cases, it is confirmed that the localized deformation suppresses the increase of pressure drag, and that non-axisymmetric deformation reduces pressure gradient in the azimuthal direction effectively in order to extend the laminar region. It is also shown that there is a capability of more extension of the natural laminar flow effect to the high Reynolds number condition corresponding to the real civil supersonic transport suppressing the increase of pressure drag.

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An error elimination method for surface shape measurement results obtained using the grating projection method is proposed to establish a precise surface shape measurement method for space structures with a high spatial resolution. By measuring the surface shape of a spherical mirror model, it is clarified that measurement errors can be divided into systematic errors depending on the projected grating patterns and random errors, which are affected by the optical properties of the object and the measurement system. Proposed is an error elimination method incorporating bandpass filter to remove the systematic errors and averaging procedures to reduce the random errors. By demonstrating the surface shape measurement of a spherical mirror model and a white plate model, it was shown that the proposed method can remove measurement errors by more than 50%. The effectiveness of the proposed method is presented by the results.

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The aim of this research is to investigate the thermal nonequilibrium state of CO₂-N₂-Ar plasma flows generated in an arc-heated wind tunnel using spectroscopic analysis. An area intensity method that uses molecular band spectra is applied to accurately evaluate the thermal nonequilibrium state of the plasma flows. The radiation from CO₂-N₂-Ar arc plasma flows around a disk model is observed using spectroscopic measurements. The flow temperatures are evaluated by applying the area intensity method to the CN Violet bands dominantly observed in the measured spectra. In the freestream, the vibrational temperature is higher than the rotational temperature due to the vibrational nonequilibrium process. In the shock layer, a faster vibrational relaxation process can be observed because the vibrational temperature starts to decrease after reaching its maximum value. However, the vibrational temperature is still higher than the rotational temperature. Therefore, the vibrational nonequilibrium state is present in the shock layer. In conclusion, we clarify the thermal nonequilibrium state of CO₂-N₂-Ar arc plasma flows along the stagnation streamline around the disk model.

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