A structural sizing tool in conjunction with the FEM code Nastran was developed to predict wing structural weight of a subsonic aircraft. The tool has a capability to efficiently perform the sizing process with several features including automatic meshing, setup for the optimization problem and analysis job management. Additionally, to save computational cost, buckling strength criterions of theoretical analysis method were introduced as a constraint of the optimization problem instead of the full buckling simulation. The result of a test case is presented and compared with the empirical weight prediction method. The present method shows comparable result with the empirical method than the result without consideration for the buckling related criterions.
The microwave-discharge miniature ion thrusters were installed and demonstrated on HODOYOSHI-4 and PROCYON. The ion thruster on PROCYON had some troubles and its lack of robustness was exposed. In this study, we conducted three ground experiments to reveal the important controlled parameters or external factors on the performance of the ion thruster. The dependence on the controlled parameters, the mass flow rates and the microwave power inputs, was investigated using an ion thruster which was designed as same as the flight model. The effect of two external factors, the structure inference and the temperature, was also tested using the structure and thermal model of PROCYON. As a result, we reported some knowledge which should be considered on the small-satellite development with an ion thruster.
This paper presents a navigation optimal powered descent landing guidance for autonomous precision planetary landing. High precision navigation is required for precision landing and use of terrain relative navigation (TRN) is being studied. Since the navigation accuracy of the TRN depends on the landing trajectory, we propose the navigation optimal trajectory to improve landing accuracy. This paper defines the optimal control problem which minimizes the navigation error at landing by using the estimated error covariance of the Kalman filter of the navigation algorithm. By assumption and approximation, around reference trajectory, trace of covariance matrix is linearized with respect to the landing trajectory, and the trajectory is discrete linearized with respect to the dynamics and non-convex constraints. The problem is convexified by these discrete-linearizations and formulated to sub-problem of Second-order cone programming (SOCP). Therefore, this problem is solved by iterative convexification and convex-optimization. The effectiveness of the algorithm is confirmed by Monte Carlo simulation on Mars landing problem. In this simulation, the accuracy of TRN depends on the line of sight distance of the image sensor. The proposed guidance algorithm by using convex programming can potentially be implemented in spacecraft as onboard real-time applications.
This paper investigates the influence on aerodynamic performance of a winged compound helicopter due to change of the lift share ratio between a rotor and a wing through a numerical simulation. The lift share ratio is defined by the wing incidence angle. A compound helicopter model is constructed with the UH-60A helicopter rotor and the fuselage configuration, which is based on the JAXA scaled down model. The fuselage model combines the body with a rectangular wing of an aspect ratio of 10. Flight condition at a cruising speed corresponding to an advance ratio of 0.703 is simulated, where the rotor speed is reduced to 75% RPM. Numerical simulation results show that the aerodynamic performance degrades significantly by rotor/wing aerodynamic interaction, where a decreasing wing lift relates to a rotor thrust increase. To minimize the aerodynamic drag caused by the rotor/wing interaction, it is found that the wing should be installed at an incidence angle of the highest lift to drag ratio, and the wing area should be adjusted to satisfy the optimal rotor/wing lift ratio.