The Galileo spacecraft exploration has shown a probability that Europa has a large amount of water under its icy surface, as well as that some kinds of life may be present on Europa. In the present study, feasibility analysis for Japan’s Europa exploration is carried out in terms of interplanetary and Jupiter atmospheric flight trajectories. First, three types of interplanetary trajectories from the Earth to Jupiter, i.e. direct, Mars gravity-assisted, and Venus-Earth gravity-assisted, are calculated and the case of the minimum Jovian insertion energy, i.e. the maximum deliverable mass, is selected in each type of the trajectories. Second, flight trajectories in the Jovian atmosphere for decelerating and deploying spacecraft to Europa are calculated and the required mass of the ablator is evaluated. It is clearly shown that aerobraking is much more advantageous for enhancement of deliverable mass than applying chemical propulsion alone, and that the combination of H-IIA Augmented Launch Vehicle, gravity assists, and aerobraking will enable Europa biological explorations.
A new measurement by using a catalytic reaction on a platinum wire was conducted spatially to evaluate a mixing condition in a supersonic flow field. A spatial mixing field was created by a transverse hydrogen jet injected into a cold supersonic cross flow (Mach 1.81) through a wedge shaped injector. The half-vertical angles of 8° or 18° were chosen as that of the wedge shaped injector. These results were compared with that of a circular injector case. The results showed that this method could evaluate a spatial mixing condition. The results also clarified that a jet plume in the cases of wedge injectors penetrated higher than that of the circular injector case and separate from the lower wall when going downstream. To observe jet/supersonic flow interaction, Schlieren visualization and oil flow visualization were carried out. It was shown that the extent of the separation region around the 8° wedge injector was the smallest among those injectors. Pitot pressure measurements were also conducted. These indicated that a wedge injector scheme was more beneficial than that of a circular injector for the supersonic combustion and combustor wall cooling.
Since the ICAO decided to adopt the GNSS-based CNS/ATM as a future standard navigation system, there has been much research to guarantee the required navigation performance of CNS/ATM sub-systems (GBAS, SBAS, etc.), mainly in the integrity or continuity aspect. However, it is also important to study the interoperability and natural transition between the old and new nav-aids because of their very different features. Therefore, we focused on the verification of the performance of the new systems, especially GBAS, through comparison with conventional aircraft landing guidance systems such as ILS. For performance verification, we developed the GBAS system and conducted three types of ground tests and several flight tests. In the analysis of the test data, we compared the GBAS navigation solutions with the data collected from the ILS inspection device — Theodolite. From the analysis, we concluded that the developed GBAS system satisfied the Precision Approach Category I requirements in the aspect of accuracy, and was consistent with the conventional aircraft precision approach guidance system.
In this paper, wing-body configurations for a next generation Supersonic Transport are designed by means of Multiobjective Evolutionary Algorithms. SST wing-body configurations are designed to reduce the aerodynamic drag and the sonic boom for supersonic flight. To lower the sonic boom intensity, the present objective function is to satisfy the equivalent area distribution for low sonic boom proposed by Darden. Wing and fuselage is defined by 131 design variables and optimized at the same time. Structured multiblock grids around SST wing-body configuration are generated automatically and an Euler solver is used to evaluate the aerodynamic performance of SST wing-body configuration. Compromised solutions are found as Pareto solutions. Although they have a variety of fuselage configurations, all of them have a similar wing planform due to the imposed constraints. The present results imply that a lifting surface should be distributed innovatively to match Darden’s distribution for low boom.
Wind tunnel experiments were conducted to obtain a comprehensive understanding of the aerodynamic characteristics of two-dimensional stepped-nose obstacles. In our previous numerical study on the flow around stepped-nose obstacles at a zero angle of attack, the following favorable properties have been found for such step configuration that the flow separating from the front corners reattaches to the leading edges of the side surfaces. (1) The strong vortices trapped in the step region produce the suction forces acting on the step walls to cancel the drag force acting the front surface. (2) The suppression of large-scale flow separation on the obstacle’s sides reduces not only the suction force acting on the back surface, but also the lateral force fluctuation to a great degree. (3) The resulting net drag coefficient is much smaller than that of square/rectangular obstacles. In the present experimental study, the drag coefficient of stepped-nosed obstacles with various step height and length, at zero angle of attack, was measured to identify the optimum step configuration for large drag reduction. The effect of attack angle on drag, lift and moment coefficients was examined to gain insight into the static and dynamic stability of stepped-nose obstacles. The effect of step configuration on the Strouhal number was also examined. It was found that the stepped nose brought about static stability to the obstacle with a rather large step length-to-height ratio, but neither static nor dynamic stability was derived for the optimal step configuration with maximum drag reduction.
The unsteady flow oscillation caused by the wake vortices generated from a number of objects is a meaningful theme for fluid dynamics and aeroacoustics. The discrete vortex method has been used for a variety of incompressibly high Reynolds number flows as a simple numerical simulation method, and this method has merit as an easy treatment for wake vortices. So the discrete vortex method is often used for cascade flow, but it has difficulty in being directly applied to stator-rotor interaction because it could cause a locally unnatural flow through the interaction between wake vortices and bounded vortices expressing the surface of objects. In this paper, a suitable method using a sub-element method is applied not to spoil the basic algorithm and the essential merit of the discrete vortex method, and an investigation of the basic mechanism of interaction between stator and rotor is performed.
This paper proposes a new collision avoidance control law for aircraft. RCPA (Range of Closest Point of Approach), representing risk in the future, and TCPA (Time to CPA), representing current risk, are used as risk functions. Furthermore, fuzzy logic is introduced in order to achieve human maneuvering and to settle singular point and chattering problems that are discussed in previous studies. Avoidance strategy consists of four main phases, maintaining course, avoidance, parallel flight and recovery phase, and three transition phases. The parallel flight phase and three transition phases are introduced to achieve moderate avoidance and smooth phase transition, respectively. Simulation results show that the proposed control law settles the past problems and achieves smooth and adequate avoidance. This paper also discusses the fuzzy evaluation method.
This paper reports the flutter investigation of a winged reentry space vehicle having rotational modes in dynamic deflection due to an elastic attachment between a vehicle and a booster rocket. The elastic rotational mode is taken into consideration as an elastic rolling mode or an elastic yawing mode. Flutter experiments have been conducted in a transonic wind tunnel. The doublet-point method (DPM) is used to calculate flutter boundaries for this model. It is shown that an elastic rolling mode may lower the critical speed of anti-symmetric mode flutter because its existence alters the natural vibration mode of anti-symmetric bending which causes flutter. On the other hand, a coupling between an elastic yawing mode and an anti-symmetric bending one becomes critical in the different model.