Tether nets, which are deployed in a manner similar to cast nets, exhibit significant potential for capturing space debris. However, a critical challenge remains: the retraction of the net following deployment, which reduces the capture success rate. In this study, analytical equations are derived to determine the optimal parameters for a previously proposed net retraction prevention mechanism utilizing double-tethered bullets. The validity of the equations is assessed through comparison with previously obtained numerical and experimental results. The proposed analytical formulation elucidates the combinatorial relationships among key parameters that contribute to high capture success rates, thereby facilitating the design of nets of various sizes and the establishment of operational guidelines.

So far, from this study, it is revealed that the dynamics of a Mars Airplane tend to transition to the backside region due to a high flight speed and inherent aerodynamic characteristics compared to conventional aircraft. However, from the viewpoint of atmospheric and ground observations, a Mars Airplane must be capable of proper low-speed autonomous flight in the backside region. In this paper, we attempted to apply an input-output linearization to the extended state space model by the concept of flatness. Additionally, an active disturbance rejection control was also applied to design a control system that can cope with uncertainty in the dynamic characteristics. Numerical simulations were performed to verify the effectiveness of the proposed flight control system.

One of the problems of spacecraft with flexible structure is that vibration is generated in the flexible structure due to the demand of attitude control of the spacecraft, and this vibration affects to the performance of the attitude control. A flexible structure has higher order modes which cannot be treated as controlled modes, and those modes can make the spacecraft unstable. Moreover, in a real spacecraft system, there are some time delays such as in the actuator. Time delay may destroy the stability of the control system. In this paper, two-degree-of-freedom (2DOF) control using the decoupled plant as a reference model is developed. It is shown that both three-axis attitude control and vibration suppression including higher order modes are achieved by the 2DOF control in the presence of spillover and time delay.

Activities for improvement of force measurement accuracy have been carried out in wind tunnels of the Japan Aerospace Exploration Agency (JAXA) for about two decades. For the high accuracy of force balance measurement, several balances have been designed by the JAXA original simple method and calibrated using the JAXA automatic balance calibration machine, which was built in 2010. Many efforts have been made to the calibration machine, improving the repeatability of calibration and optimizing load patterns. In parallel, a balance with small hysteresis has been developed, and the double standard deviation of the residual error for 6-component combined-load random patterns is achieved to be 0.05% or less of full-scale load in the axial force component. This result is expected to significantly reduce errors in wind tunnel testing. Furthermore, the accuracy is clarified with and without combined load calibration, and guidelines for balance calibration corresponding to the purpose of various wind tunnel tests are discussed.

In order to perform a large eddy simulation with a turbulent boundary layer mixed with mainstream turbulence, which is reproduced by the rescaling method, we investigated the method of generating the mainstream turbulence and the blend function to smoothly connect the mainstream and the boundary layer. The turbulence as the main flow turbulence was obtained by time evolving from the initial condition in a periodic box. The initial condition was obtained by solving the diffusion equation based on random numbers to obtain the velocity fluctuation, the temperature fluctuation based on the energy conservation law, and the density fluctuation based on the equation of state, respectively. The Blend function is based on trigonometric functions and is applied to the interior of the boundary layer.