This paper presents an obstacle detection method for a soft landing on the moon. Instead of modeling the obstacles on the moon we model the safe landing region on the moon as a horizontal and flat region. To find the safe landing region we propose a method using a quantity named local second-order moment of the image intensity, which is a second-order moment in a small region of the image. The ability of the proposed method is evaluated using the real images of the Apollo program and CAD images.
An efficient methad to handle entropy correction parameters in a TVD scheme is praposed for the computational estimate of aerodynamic heating around a hypersonic vehicle. The whole flowfield is divided into two regions: one region includes shack waves, and the other covers the baundary layer. Different constant values of entropy conection parameters are suitably chosen in the two regions. This simple setting of parameters substantially reduces trialand-aiter computations in comparison with other existing methods. The application to the OREX qreentry vehicle problem demonstrates the advantage of the present method.
Laser propulsion powered by a CW laser has been studied. Thruster performance and energy balance in the thruster were numerically computed. Laser beam optics, inverse-Bremsstrahlung absorption, ionization/recombination reactions, radiation, heat conduction, and convection have been modeled. Computational stiffness due to its quite small flow speed has been overcome by using a Flux Vector Splitting implicit scheme with a large CFL number. The computed positions of Laser Sustained Plasma (LSP) in the thruster show a good agreement with measured ones. The estimated energy conversion efficiency was 23%, and the rest of input power was lost as the radiation from the LSP and as the laser beam passing through the LSP.
An efficient and user-friendly system for constructing unstructured surface grid directly from a CAD-defined surface data has been developed. Key features of the system are; 1) adoption of the advancing-front surface triangulation method, which eliminates the necessity to divide the surface into a number of patches, 2) graphical user interface (GUI) using OpenGL and Microsoft Visual C++ for controlling the surface mesh generation, where mouse operations are used for fixing the ill-defined background grid as well as the control of grid density by inserting source lines and points on the surface. The capability of this method is demonstrated for several airplane configurations. A significant reduction of time required for the surface grid generation is achieved. The quality of the generated surface grids is evaluated by computing the flow field.
Separated and reattaching flows produced by an axial sudden expansion have been studied experimentally. The flow fields were produced by an axisymmetric sudden enlargement from an orifice of diameter 30mm to a pipe of diameter 80mm. Mean velocities and turbulent intensities were measured by a hot-wire anemometry. The Reynolds number based on the orifice diameter was 25, 000. Flow visualization tests were also done. It was shown that large-scale vortices are produced at the orifice. These vortices begin to pair each other, but soon they lose their axisymmetry, i.e. breakdown occurs. The streamwise position where this breakdown occurs is located at much more upstream position when compared with that of an orifice free-jet flow under the same inlet condition.