For repairing broken-down satellites or removing space debris, autonomous capturing of tumbling objects in space is recognized as one of the most important technologies in future space activities. This paper proposes a novel capturing method that adjusts the chaser's attitude motion to the target's one before grasping it. This method can solve the problem that the manipulator alone can not grasp a target with fast or complicated rotational motion. Several required techniques are mentioned too, such as motion estimation, chaser's structure, etc. The validity of this method is demonstrated by same computational simulations.
The objective of the present study is to experimentally make clear the mechanism of aerodynamic interaction, in particular pressure interaction, due to a jet located off-center at the base of a blunt body with angle of attack in subsonic to transonic flow. The correlation between change in pressure drag and local pressure distribution by issuing the jet toward the downstream is obtained in terms of four parameters: the jet deflection angle, the jet mass flow rate, the freestream Mach number, and the angle of attack of model. Results indicate that the interacted flow field is characterized by three components: jet entrainment, vortex, and turn of main flow round the corner of the model base. At lower angle of attack than 15 degrees, the interacted flow shows different mechanisms between the inner and the outer regions at the base. In the inner region, pressure increases due to a vortex produced by jet entrainment, in which the circulated flow yields a stagnation point at the base. This is a favorable effect in terms of thrust. However, larger deflection of jet decreases the pressure in this region due to breakdown of the vortex. On the other hand, in the outer region, pressure decreases due to disappearance of a vortex produced in the case of no jet. At higher angle of attack than 15 degrees, more main flow comes to turn to the base round its corner. Consequently, the base pressure tends to have a uniform distribution with increasing the angle of attack. Moreover, increase in the jet mass flow rate makes this trend prominent, where the pressure in the outer region decreases to a certain level. Meanwhile, this pressure interaction increases with the freestream Mach number, which is caused by two effects:turn of more main flow to the base due to compressibility and jet expansion due to decrease in the ambient pressure.
A wind tunnel test was conducted to study the mechanism of a flight of a flying disc which flies while rotating. A Flying disc is a rotating disc without blades, being different from the rotor of a helicopter and the like and its cross sectional shape is a unique upward convex. Using a production flying disc used at an official game, wind tunnel tests were performed. Forces were measured to investigate aerodynamic characteristics of an object of such a shape. In addition, a flat disc was also experimented for a comparison. Free flight tests of the flying disc were carried out to obtain base line data to experiment in the wind tunnel test. Flight data of the flying disc in free air was reduced by analyzing the flight path from the video tapes which recorded the flights of the flying disc. Smoke visualization tests were also made to visualize the flow pattern around the flying disc.
Many criteria for longitudinal short term flying qualities of higher-order-system (HOS) airplanes have been proposed, but these are based on the response characteristics to pilot's control input. However, the response to gust input, which is independent of the feed-forward loop in the flight control system, will also influence the flying qualities. Not only the response characteristics to pilot's input, but also the response characteristics to gust input should be included as one of evaluation parameters in the criteria. Simple application of this idea to Neal-Smith criterion is shown as example.
We calculate the two-dimensional unsteady reactive flow to study the body-force effect on the lateral movement of cellular flames. The equation used is the compressible Navier-Stokes equation including an exothermic one-step irreversible chemical reaction, where the hydrodynamic effect caused by thermal expansion is taken into account. We superimpose the disturbance with the peculiar wavelength on a stationary plane flame and simulate the evolution of the disturbed flame front. The disturbance superimposed grows initially with time, and then the flame front changes from a sinusoidal to a cellular shape. After the formation of a cellular flame, cells on the flame move laterally when the Lewis number is lower than unity. Because, the diffusive-thermal effect and the nonlinear effect of the flame front play a primary role in the appearance of the lateral movement of cells. The body-force effect has a great influence on the lateral velocity of cells. When the flame is propagated upward, i.e., the body-force effect has a destabilizing influence, the lateral velocity becomes smaller as the acceleration increases. When the flame is propagated downward, on the other hand, the lateral velocity takes the maximum value at the specific acceleration and becomes smaller with an increase in the acceleration. The change in the lateral velocity is due to the increase and decrease in high-temperature regions and to the variation of the maximum flame temperature at the convex flame front toward the unburned gas.