This study proposes a feedback control law for orbital parameters of a coplanar rigid satellite system. The governing equations are denoted as ‘Symmetrical Affine System’ with three variables and two control inputs, which is guaranteed to be locally controllable. However, because of time-variant parameters included in the governing equations, previously proposed feedback control laws cannot be directly applied. Therefore, in this paper, a novel feedback control law to simultaneously control plural orbital parameters is proposed. Finally the effectiveness of the proposed control law is validated through numerical simulations.
To make space activities more brisk, TSTO (Two Stage To Orbit) has been investigated worldwide as an advanced space transportation system. TSTO vehicles, which have a booster and an orbiter, have to make flight in a wide range of flight speed from subsonic to hypersonic, where they undergo aerodynamic interactions due to their combined bodies. In hypersonic flow regime, aerodynamic heating is critical, which depends on aerodynamic interaction pattern. In the present study, a delta-wing is employed as a booster and a diagonally-cut circular cylinder as an orbiter to reduce the aerodynamic interaction between these two bodies. It was found as a result of experiment that the heat flux on the head part of the diagonally-cut circular cylinder becomes about 2.4 times as large as the stagnation heat flux, while that on the delta-wing becomes about 0.5 times as large. These two values are roughly half of those in the case of a baseline combination: hemisphere-cylinder and delta-wing, which suggests that the diagonally-cut circular cylinder is promising as an orbiter head shape.
As base drag accounts for most of the total drag for spacecraft with a large base area, reduction in the base drag improves its aerodynamic performance. In the present study, a method using a pair of tabs normal to the base surface is proposed to reduce the base drag, and its effects on drag reduction are experimentally examined for a two-dimensional, simple bluff body with a large base area, the cross-section of which consists of a circular forebody and a rectangular afterbody, by changing the tab’s position and length. In addition, the flow fields around the model with/without tabs were visualized by the schlieren method with a high speed video camera, and CFD analysis was also made to supplement the experimental results. It was found that the tab method can remarkably increase the base pressure, which leads to a large decrease in the base drag. In the case where a pair of tabs with a non-dimensional length of 0.38 are installed at the base edges, the total drag is reduced by about 20.6% at a Mach number of 0.6 compared with that in the baseline case without tabs. Even when short tabs with a non-dimensional length of 0.07 are employed, about 10.0% reduction in the base drag is achieved. Thus, it was made clear from this study that the tab method proposed here is effective to decrease base drag in the transonic flow.
Aerodynamic characteristics of a tail system which consists of a single wing was examined experimentally. Although many conventional airplanes are equipped with one or more vertical tail(s) and a pair of horizontal tail for longitudinal and directional control, respectively, a wind tunnel experiment revealed that an appropriately configured single wing can control pitch and yaw of an airplane. The windtunnel test was performed on a model which consists of a main wing and a single wing tail. Aerodynamic forces were measured by a force balance and oil-flow visualization was performed as well. In the windtunnel test, two different steering methods of a single wing tail system were examined and both of them were shown to work compatibly.
The taketombo is a traditional flying toy of Japan transmitted from old times. Since the taketombo is made of a bamboo, it is also called the bamboo dragonfly. The taketombo consists of two parts, the wing and the shaft. The wing generates the lift, and the shaft is for giving rotation to the taketombo. However, the take-off and aerodynamic characteristics are not yet studied. Then, to study the take-off and aerodynamic characteristics of a taketombo, free flight test and wind tunnel test were performed. Free flight test of the taketombo were carried out to obtain base line data to experiment in the wind tunnel test. Flight data of the taketombo at the take-off in free air was reduced by analyzing the flight path from the high speed video which recorded the take-off flights of the taketombo. A wind tunnel test was conducted using two wing section models, normal and super taketombos. Forces were measured to investigate aerodynamic characteristics of the wing section of two taketombos. The aerodynamic characteristics of normal and super taketombos were compared.
The fluid behavior and the performance of a pulse-detonation-driven magnetohydrodynamic (MHD) electrical power generator with a diverging-converging nozzle connected to a linear tube are examined by quasi-one dimensional numerical simulations. In particular, the effects of diverging nozzle angle and of linear tube length on the performance are investigated. It is found that the temporal evolution of power output in this MHD generator has two peaks. The first peak is caused by the passage of detonation wave in the MHD generator part, and the second peak is due to the nozzle expansion of the working fluid. Furthermore, the results show that there exists the optimal diverging angle, and the increase in the linear tube length improves the generation performance.
All the flapping-wing micro air vehicles which have succeeded in flying make the feathering motions generated passively by their flapping motions. Parameters determining the passive feathering motion are identified and it is discussed what are required in these parameters for enabling a flapping-wing micro air vehicle to fly.