The shape-from-shading technique is investigated for application to obstacle avoidance for lunar landing. Tsai and Shah’s algorithm is accurate, but it is time-consuming and sensitive to its boundary condition. Pentland’s algorithm is robust and fast; however, it produces artifacts in reconstruction. We propose a real-time scheme of extracting flat areas instead of obstacles using Pentland’s method with a domain evaluation.
A magneto-plasma sail produces the propulsive force due to the interaction between the artificial magnetic field around a spacecraft inflated by the plasma and the solar wind erupted from the Sun. The inflation of the magnetic field by the plasma was proposed by a group of the University of Washington and the basic research has just started. This paper summarizes the characteristics of the magneto plasma sail by comparing with the other low-thrust propulsion systems, and investigates its potential application to near future planetary missions. Finally, an engineering satellite to demonstrate the magneto-plasma sail is proposed as a first step.
The interaction of a reflected shock wave with the boundary layer in a shock tube has been numerically analyzed. In calculation, the same conditions as the experiment by Matsuo et al. regarding a rectangular shock tube have been employed. The numerical scheme employed here is the explicit-implicit hybrid scheme, which was developed at our laboratory, along with Godunov’s exact Riemann solver. The solution adaptive mesh refinement method and geometrical mesh refinement method were also used to increase the accuracy and efficiency of the calculation. The results clearly show a complicated flow field with a recirculation region enclosed by bifurcated shocks. Moreover, it was made clear that the total enthalpy of the stagnated gas is dissipated by the viscous interaction between the quasi-shock structure and the boundary layer.
We have been developing a spacecraft simulation environment based on object-oriented design. The system consists of models of the hardware components, numerical solvers such as for dynamics and thermal conditions, the simulation framework to control the modules, and a simulation environment including a DB and GUI. The system enables distributed simulations for distributed parallel developments between the core bus system modules and the mission system modules, or distributing the CPU load. Moreover, it can verify on-board models (on-board software, hardware-in-the-loop). We examined a distributed computing middleware, High-Level Architecture/Run-Time Infrastructure (HLA/RTI) to evaluate the functions and the performance in spacecraft simulations. HLA/RTI was proposed by Defense Modeling and Simulation Office (DMSO), USA, and approved as an open standard of distributed simulation as IEEE Standard 1516 in September 2000. The performance of two types of RTI that depend on a volume of data to transmit/receive and a number of distributed modules was observed in different network environments. The two types were applied to a simplified H-IIA Transfer Vehicle (HTV) simulator to study the feasibility.
An elastica is a mathematical model of a beam undergoing the large deformations and rotations. The central line of beam is assumed to be inextensible in order to make the analysis of the beam feasible. Since the extensional deformation is not included in the strain energy of beam, the variational theory for the inextensible elastica has not been developed. In the present paper, the principle of virtual work and the principle of stationary potential energy for the elastica, exclusively expressed in terms of bending deformations, are derived from the principle of virtual work in the three dimensional elasticity. And it is shown that the developed variational principles yield the exact equilibrium equations for the beam in the large deformations and rotations.
Recently, some countries have begun conducting feasibility studies and R&D projects on High Altitude Platform Systems (HAPS). Japan has been investigating the use of an airship system that will function as a stratospheric platform for applications such as environmental monitoring, communications and broadcasting. If pseudolites were mounted on the airships, their GPS-like signals would be stable augmentations that would improve the accuracy, availability, and integrity of GPS-based positioning systems. Also, the sufficient number of HAPS can function as a positioning system independent of GPS. In this paper, a system design of the HAPS-based positioning system and its positioning error analyses are described.
The Blended Wing Body (BWB) has been studied as a configuration of next-generation large-scale jet transport. The principal advantages of the BWB configuration are reduction in fuel consumption by improvement of lift-drag ratio and decrease in structural weight. In this study, the optimal number of passengers for the BWB is discussed by designing several BWB aircrafts for different numbers of passengers. Suitable number of passengers is found to be about 400 from the viewpoint of the cabin layout and airport facilities. Then, the BWB and a conventional aircraft have been designed by a conceptual design method under similar design requirements. By comparing the results, drastic reduction in fuel weight was confirmed.