Attitude synchronization is a key technology in the capture of tumbling satellites. The inertia ratio of the satellite is a dominant parameter of the motion. Estimation of the inertia ratio of tumbling satellites is thus an important function for a chaser satellite in order to synchronize its attitude motion with the tumbling satellite motion. This paper proposes a new control scheme named “Smooth Reference Model Adaptive Sliding-Mode Control”(SRMASMC) algorithm for attitude tracking maneuvers. The adaptive law installed on the sliding mode control (SMC) algorithm is employed to estimate the inertia ratio of the tumbling satellite. A smooth reference model is introduced to reduce the control torques at the beginning of the tracking maneuver by the SMC method. The attitude tracking performance of the SRMASMC method is evaluated numerically in comparison to a quaternion feedback control method and a SMC method.
The effects of attack angle on side jet aerodynamic interaction were experimentally investigated. Experiments were conducted by using the ISAS supersonic wind tunnel. A model used in this study is a 10deg half-angle blunt cone with a circular sonic jet injected at right angles to the body surface on the leeward side. Force and surface pressure measurements were performed as well as schlieren and oil flow visualizations. As a result, it is found that the aerodynamic interaction promotes the jet reaction force with increasing attack angle. Furthermore, the flowfields with aerodynamic interaction at high attack angles were clarified.
Laboratory-model low-power Hall thrusters, named the THT-III-series, were operated in order to examine influences of ceramics species of the acceleration channel walls, and shape and strength of radial magnetic field in the acceleration channels on the operational characteristics. For the THT-IIIA-BN thruster both with acceleration channel walls made of boron nitride and with more intensive concentration of magnetic field lines near the acceleration channel exit, a higher thrust efficiency was achieved with a lower discharge current and a higher thrust for an optimum magnetic field strength regardless of discharge voltage at a constant xenon mass flow rate. Accordingly, both the thrust and the specific impulse ranged from 10 to 70mN and from 1,200 to 2,300s, respectively, at discharge voltages of 200–500V with mass flow rates of 1–3mg/s in a wide input power range of 250–1,800W. The thrust efficiency ranged from 30 to 45%.
Low-frequency discharge current oscillation in the 20kHz range is a phenomenon to be solved for stability operation of Hall thrusters. In our previous work based on theoretical and numerical analyses, possibility of amplitude mitigation by raising the neutral species temperature incoming to an ionization-zone was predicted. In the present work, its experimental verification is conducted, where the physical mechanism of controlling oscillation amplitude is studied.
This paper presents the development of a multi-functional and miniature GPS receiver in NASDA. The investigation for the design and implementation method for the spaceborne GPS receiver has been conducted. And a bread-board model of parallel signal search on matched filtering technique, which is an essential technique of the multi-functional GPS receiver, was manufactured. And time to acquisition (TTA) of GPS signal was measured using GPS simulator. The test results of the trial product show that TTA is 60ms and time to first fix (TTFF) of the navigation calculation in a low-altitude orbit is within 5.3min in worst case.
The flight of Spaceplane is always under accelarating in the assent way and always under decelarating in the desent way and yet cruising in the return way. Besides, its flight envelope is considerably wider than that of airplane. Thus the integrated design method is required to build the best transportation system optimized taking into account the propulsion system and the airframe under the entire flight conditions. In this paper it is shown an optimization method on TSTO spaceplane system. Genetic algorithm (GA) was applied to optimize design parameters of engine, airframe, and trajectory simultaneously. Several types of engine were quantitatively compared using payload ratio as an evaluating function. It was concluded that precooled turbojets is the most promising engine for TSTO among Turbine Based Combined Cycle (TBCC) engines.