This study deals with orbital transfer of a rigid satellite system into a specified orbit by using its inner force generated in the system. First, the governing equations of the system are shown, and their non-integrability is proven by applying a nonlinear control theory. Subsequently, it is also shown that the system is controllable except its pericenter and its apocenter in an elliptic orbit. Then, this paper proposes a two-step approach, combining a solution for a ‘chained’ system and numerical modification based on ‘motion planning.’ Finally, computational simulations verify that orbital transfer to a specified orbit is accomplished successfully by applying the proposed approach.
To estimate uncertainties of wind tunnel test data, it is necessary to characterize tunnel flow qualities. Thus at a supersonic wind tunnel, the flow fields were assessed by Mach numbers calculated from total pressures, test section pitot and wall pressures. Furthermore, for easy and accurate estimations of the uncertainties, end to end error evaluations should be done with appropriate treatments of small error contributors. The uncertainties about a model weight correction were then evaluated from no-wind actual end data. The flow field error propagations were also examined and the uncertainties of each component of aerodynamic coefficients were treated as the independent error contributors. The estimated uncertainties were finally validated by data obtained repeatedly in short and long terms with flow field variations.
The paper studies the effect of neighboring blade rows on flutter characteristics of cascading blades. For this purpose the computation program to calculate the unsteady blade loading based on the unsteady lifting surface theory for contra-rotating annular cascades was formulated and coded. Then a computation program to solve the coupled bending-torsion flutter equation for the contra-rotating annular cascades was also developed. Some results of the flutter analysis are presented. The presence of the neighboring blade row gives rise to significant change in the critical flutter condition when the main acoustic duct mode is of cut-on state.
In order to simulate the interaction between the solar wind and the artificially deployed magnetic field produced around a magnetic sail spacecraft, a laboratory simulator was designed and constructed inside the space chamber (2m in diameter) at ISAS. As a solar wind simulator, a high-power magnetoplasmadynamic arcjet is operated in a quasisteady mode of ∼0.8ms duration. It can generate a simulated solar wind flow that is a high-speed (above 20km/s), high-density (above 1017m-3) hydrogen plasma plume of ∼70cm in diameter. A small coil (18mm in diameter), which is to simulate a magnetic sail spacecraft and can obtain 1.9-T magnetic field strength at its center, was immersed inside the simulated solar wind. Using these devices, the formation of a magnetic cavity (∼8cm in radius) was observed around the coil, which indicates successful simulation of the plasma flow around the coil (simulated magnetic sail spacecraft) in the laboratory.
Our developed cm-sized helicopter is inclined with a large pitch angle by the nose down moment generated by the aft propeller when it goes forward and when it keeps its position against a wind. This is because the ratio of parasite drag to the gravitational force is larger for a smaller helicopter. And the horizontal component of aerodynamic force generated by the main rotors, which equals the parasite drag, should be larger. Then, a small and lightweight attitude sensor was newly developed to measure the large pitching angle of the helicopter and to control the rotational speed of the aft propeller. The principle is same as that of a solar sensor.
Hayabusa, launched May 2003, is the first Japanese spacecraft to explore the small asteroid Itokawa (1998SF36) and touched down on Itokawa twice to sample of the surface material. LIDAR (LIght Detection And Ranging) is an important navigation sensor for the asteroid explorer to measure distance between the spacecraft and the asteroid. Since it is carried in a planetary exploration spacecraft, the weight of LIDAR is very lightweight of 3.7kg. In the rendezvous and touchdown operation, LIDAR supplied the ranging data to the spacecraft navigation system to approach Itokawa down to 50m and its total shots number of laser pulse was more than 4 million. The composition and basic performance of LIDAR are explained and this paper also reports the ranging data at the time of landing to asteroid Itokawa of the autumn of 2005.
The characteristics of a small actuator with propellers have been studied. The generated force increases as the rotational speed of the propellers and the viscosity of the liquid inside the actuator increase. This can be predicted by a simple analysis using the characteristics of wings at the Reynolds numbers where they operate. The understanding of wing characteristics at low Reynolds numbers, which has recently become important for designing a MAV (Micro Air Vehicle), can contribute to developing a small fluid machinery such as this small actuator with propellers.