This paper deals with design procedure of online guidance law for future missiles that are required to have agile maneuverability. For the purpose, the authors propose to mount high power side-thrusters on a missile. The guidance law for such missiles is discussed from a point of view of optimal control theory in this paper. Minimum time problem is solved for the approximated system. It is derived that bang-bang control is optimal input from the necessary conditions of optimal solution. Feedback guidance without iterative calculation is useful for actual systems. Multiple design point method is applied to design feedback gains and feedforward inputs of the guidance law. The numerical results show the good performance of the proposed guidance law.
A small crack on body surface led to a tragic accident in 2003, which is the Columbia accident. During the shuttle's re-entry, high temperature gas penetrated crack on leading-edge of the left wing and melted the aluminum structure, finally the Columbia blew up. Since early times, there are many fundamental studies about simple cavity-flow formed on body surface in hypersonic speeds. However, an investigation of Shock/Boundary-Layer Interaction (SBLI) on crack has not been researched. For multistage space transportation vehicle such as TSTO, SBLI is an inevitable problem, and then SBLI on crack becomes a critical issue for TSTO development. In this study, the effects of crack, where SBLI occurs, were investigated for TSTO hypersonic speed (M∞ = 8.1). A square crack locates at SBLI point on the TSTO booster. Results show that a crack and its depth strongly effect on peak heat flux and aerodynamic interaction flow-field. In the cases of shallow crack (d/C ≤ 0.10), there exist two high heat flux regions on crack floor, which locates at a flow reattachment region and a back end wall of crack. In this case, a peak heat flux at flow reattachment region becomes about 2 times as large as the stagnation point heat flux, which value becomes larger compared with a peak heat flux in the case of No-Crack TSTO. While in the case of deep crack (d/C = 0.20), overall heat flux on crack floor decreases to below the stagnation point heat flux. These results provide useful data for a development of TSTO thermal protection system (TPS) such as thermal protection tile.
In general, small satellites must achieve relatively high performance in spite of their restricted resources. To contribute such developments of small satellites, in this paper, we propose a new method of attitude controller synthesis of small satellites. This method is developed by a strategic use of gain-scheduled controller synthesis from the viewpoint of simultaneous optimization of structural and control systems. It also includes some modification of the existing gain-scheduled controller synthesis to achieve fixed closed-loop property. A numerical example of a gravity-gradient stabilized satellite illustrates the effectiveness of the proposed method in a practical application.
Since the launch of Sputnik, orbital debris population continues to increase due to ongoing space activities, on-orbit explosions, and accidental collisions. In the future, it is expected that a great deal of fragments will be created by explosions and collisions. Thus, the number of space debris may increase exponentially (Kessler Syndrome). This paper analyzes the Kessler Syndrome using the Low Earth Orbital Debris Environmental Evolutionary Model (LEODEEM) developed at Kyushu University with collaboration from JAXA. The purpose of the study aims at understanding the issues related to space environment conservation. The results provide effective conditions of Active Debris Removal which is one of the space debris mitigation procedures.