The antenna system with shape control mechanism, which includes both radiation pattern analysis and structural control of its surface, is expected to be useful for space antennas. Testing is carried out to verify the system is effective even for inflatable antennas with strong nonlinearity. Deformed surface due to disturbance is measured, and its radiation patterns are calculated, instead of measuring the radiation patterns. Antenna surface error is estimated from these radiation patterns and it is reduced by controlling tensions of supporting cables. The effectiveness of the system is clearly shown from the controlled radiation pattern.
A one-dimensional theoretical method for an evaluation of the net thrust of a scramjet engine is presented. To calculate the thrust performance of the engine analytically, an efficiency characterizing compression process, such as recovery factor in total pressure or kinetic energy efficiency etc., is necessary. In the previous theoretical method, this efficiency was roughly assumed. Although the effect of aerodynamic parameters and configuration parameters on the thrust can be investigated with this rough assumption, the net thrust evaluated with this method was not enough accurate to be compared with the measured thrust in experiments. The total pressure loss is chosen as the efficiency in this paper. This total pressure loss is evaluated from the engine internal drag with the wind tunnel experiment, which is due to irreversible process through the engines. The theoretical maximum thrust of the engines can be calculated with this new method.
An airship has usually two or three ballonets in its envelope in which air is contained. Its buoyancy and attitude control is performed by changing the air content of each ballonet. It is said that ballonet slosh may influence airship’s stability or ride quality. However, no quantitative treatment has been performed so far to investigate this phenomenon. In this paper the coupled equations of an airship longitudinal motion are formulated by modeling the ballonets as cylindrical containers. Some numerical calculations are performed for a 25m class airship and it has been shown that the ballonet slosh may become a design issue when the shape of the ballonet is thinner or when the size becomes larger.
Forebody and aftbody radiative heating rates of the MUSES-C asteroid sample return capsule have been assessed along the reentry trajectory from an engineering standpoint. Nonequilibrium hypersonic flows around the capsule with ablation of the thermal protection system involved were determined by CFD calculations, while the radiative heat transfer was computed by the radiation code SPRADIAN in a non-coupled manner with the flow analysis. In order to take into account much uncertainty in the thermal relaxation, chemical reaction, and ablation models used in the flow analysis, parametric studies were performed by changing these models to obtain the conservative estimation of the radiative environments. The radiative heat flux was found to be considerably affected by the ablation model, especially in the aftbody region of the capsule.
This paper describes a collision avoidance problem of aircraft. In a conventional avoidance problem, there is an assumption that target information is certain. However, information may not be always certain in reality, and handling of uncertain information has not been discussed. Therefore, new control law is proposed to deal with uncertain information and to get correct information. The uncertainty depending on position, which is defined in the inertial or relative coordinate system, is dealt with in this paper. To cover each coordinate system, proposed control law is applied to ‘corner problem’ and ‘in-fog problem’, respectively. Several elements are defined in order to express uncertainty of target information. Simulation results show that the severe avoidance by conventional law is improved and to be obtained satisfactory performance by dealing with uncertain information.
To clarify the hovering performance of the rotor whose disk is partly outside the edge of a finite inclined ground plane, a hovering test was conducted with a model rotor and a ground effect plate. At a chain of the flight environment from out-of-ground effect to full ground effect cases, the thrust, torque, and blade flap angle of the rotor hovering above the inclined ground plane were measured. Such flight environment was simulated altering the horizontal distance from the rotor hub center to the ground edge, i.e., center-to-edge distance, at a constant rotor height and ground inclination angle. As a result, it is shown that the hovering performance of the rotor in the inclined and partial ground effect remarkably depends on the combinations of the center-to-edge distance, the ground inclination angle, and the rotor height, and that the hovering performance of the rotor in the partial ground effect on the mountain side of the inclined ground plane is very different from that on the valley side.
The present paper treats the flutter and divergence characteristics of composite plate wings with various sweep angles. In the first report of this paper, the effect of laminate configuration on the flutter and divergence characteristics is investigated for composite plate wings. Aeroelastic analysis of composite plates is based on the finite element method and the subsonic unsteady lifting surface theory. To examine the effect of laminate configuration, the flutter and divergence characteristics are represented on the lamination parameter plane, instead of using the composite fiber angle or the non-dimensional cross-coupling parameter. The representation gives a comprehensive explanation of the effects of principal-axis stiffness and bending-torsional coupling on the flutter and divergence characteristics.
The present paper treats the flutter and divergence characteristics of composite plate wings with various sweep angles. In the second report of this paper, a minimum weight design of composite plate wings under the flutter and divergence velocity constraints is conducted by using a genetic algorithm in which lamination parameters are used as design variables. Aeroelastic analysis of composite plates is based on the finite element method and the subsonic unsteady lifting surface theory. The effectiveness of aeroelastic tailoring, which improves the aeroelastic characteristics of composite wings by the layup optimization, is demonstrated through the optimal results.
Compressive property degradation of the composite laminated plates due to a characteristic damage state (CDS) in quasi isotropic laminates ([45°/90°/-45°/0°]n ) subjected to a transverse impact is studied numerically, which consist of a spiral array of inter-connected transverse cracks and delaminations, separating a laminates into sublaminates. The results are compared with those of laminated plates having circular delaminations of an equivalent number and size. The compressive property degradation due to the spiral array damage is found to be insignificant compared to the circular delaminations. It is because the portion around the center axis connected each other through the thickness constrains relative movements of the separated ligaments. It can be said that some other factors of the impact damage neglected in the present model must contribute to the property degradation.