The future multi beam satellite communication systems require high antenna pointing accuracy of about 0.015 degree. In geostationary orbit, several disturbance torques, such as gravity gradient torque, solar pressure torque, affect the antenna pointing accuracy. In the multi beam communication satellites, large diameter antenna reflectors and large solar paddles, which are scheduled to be used, cause large solar pressure torque. In this paper, at first the solar pressure torque of the 2-ton class satellite with two anti symmetric antenna reflectors was calculated, then, the structure which causes large solar pressure torque was considered numerically. Based on the results, especially the secular and periodical component of the roll/yaw plane solar pressure torque, it was revealed, how to decide the magnitude of the bias momentum of the bias momentum attitude control system from the point of yaw error requirement. Finally it was confirmed that simulation values agree well with the theoretical results.
Evaporation of a hydrocarbon fuel droplet in high pressure and high temperature environments was studied experimentally and theoretically. It is found that the pressure dependency of evaporation constant is divided into three patterns, which correspond to the ambient temperature. At the lower ambient temperature, the evaporation constant decreases with the increase of the ambient pressure, and reaches a minimum value at a certain ambient pressure, beyond which the evaporation constant increases as the ambient pressure increases. At the intermediate ambient temperature, the evaporation constant increases monotonically. At the higher ambient temperature, the evaporation constant increases with increasing the ambient pressure and reaches a maximum value at a certain pressure, beyond which the evaporation constant decreases. The theoretical study was performed by using the film mass and heat transfer model. By comparing the theoretical and experimental results, it is found that the variations of the evaporation constant for the lower and intermediate temperature are attributable to the variation of material properties, but that for the higher ambient temperature, the variation of the evaporation constant is inferred to be attributable not only to the variation of the material properties but also to the time dependency of the droplet temperature.
The weak form statement for equilibrium equations is derived for the quasi-three-dimensional free edge problem of laminates with anisotropic layers under uniform axial extension which was originally studied by Pipes and Pagano. Based on this statement, conventional finite element method is formulated to evaluate interlaminar stresses due to delamination growth from the free edge of the laminates. Utilizing the finite element method, strain energy release rates are obtained by the use of stiffness method or crack closure integral method. Numerical examples for the delamination growth in carbon-epoxy composite laminates are shown. The-oretical predictions for location of delamination onset are discussed, taking into account the size of initial defects, loading directions and delamination crack modes.
In the previous paper, a discrete vortex method was applied to a two-dimensional arc-shaped ACV with an external air supply in order to investigate the outer flow around it. It was confirmed from the numerical results that the vortices were concentrated near the front part of the ACV and the low pressure due to the concentration of vortices generated thrust force. In the present paper, adopting the gate-shaped ACV which may be significantly subjected to the low pressure due to the concentration of vortices, the effect of the height of the ACV on both the outer flow behaviors and the drag characteristics is investigated. The concentration of vortices is distinguished into two flow patterns according to the height of the ACV. From the point of view of the drag characteristics, if the concentration of vortices is formed near the front surface of the ACV, to increase the height of the ACV is more effective for the reduction of the drag force, otherwise vice versa.
A lifting-surface theory of oscillating high-speed propellers has already been formulated by the author in a form of integral equations. The purpose of this note is to propose a method for solution of these integral equations. An adjoint variational principle, equivalent to the integral equations for direct and reverse flows as well as to the Kutta conditions in both the flows, is derived. It is shown that the generalized aerodynamic forces acting on the propeller blades will be computed advantageously by applying a Rayleigh-Ritz type method to the variational principle.