This paper investigates the nonlinear modeling of the liquid hydrogen turbopump for rocket engine. The degree of freedom of ball is introduced and its contact/separation from the inner or outer race is considered. The dynamic response of the turbopump shaft in the unsteady condition with fast acceleration which reaches more than third critical speed is numerically investigated, and the occurrence of the asynchronous vibration component is observed, and the characteristic of the asynchronous vibration component is discussed. This result is compared with the experimental result, and it shows the capability of the explanation of occurrence of the specific asynchronous vibration component observed in the experimental data.

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We have proposed a deployable-wing airplane for Mars exploration. In the present study, wind tunnel experiments have been carried out to clarify high-speed aerodynamic characteristics of the airplane. The result shows that the wing deployment is effective to improve the lift to drag ratio (L/D) of the airplane in flow regime less than Mach number of 3.0. In transonic flow regime, a peculiar stall characteristic can be seen for the deployable wing with the sweptback angle of 45 degrees. This is considered to be caused by the vortex breakdown occurred on the wing. Due to the stall, the pitching moment coefficient (C_M) shows a nonlinear characteristic. The C_M tends to decrease as the sweptback angle of the deployable wing decreases, showing that the wing deployment has a great influence on the longitudinal stability of the airplane. A canard has a characteristic of transiting the angle of attack where the stall occurs to higher ranges, increasing the lift coefficient (C_L) and L/D. At the same time, it has a characteristic of transiting the angle of attack where the nonlinear characteristic of the C_M occurs to higher ranges. Therefore, the use of the canard enables us to obtain high C_L and L/D as well as to improve the nonlinear characteristics of the C_M.

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CARATS (Collaborative Actions for Renovation of Air Traffic Systems) is a Japanese long-term vision of the future ATM (Air Traffic Management) which was planned to promote the research and development of the Japanese ATM system. CARATS Open Data released by the Japanese government in 2015 are operating data of RDP (Radar Data Processing) system actually used in four ACCs (Area Control Center) in Fukuoka FIR (Flight Information Region). Accuracy of the longitude and latitude of CARATS Open Data is evaluated by using GPS data measured in the airliner cabin. Results show that the longitude error of CARATS Open Data increases with the distance from Tokyo ACC and discontinuous changes occur when a reference radar site is handed over to another radar site. The effect of longitudinal and latitude errors of CARATS Open Data to flight parameters estimation is also studied, where it reveals that appropriate data processing is necessary to estimate parameters such as air speed and fuel flow.

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A method for autonomous path planning for disaster monitoring such as Fukushima nuclear power station accident in 2011 using a small rotorcraft UAV is proposed. In this method, a rotorcraft can search around damaged buildings without specifying the waypoints by an operator. Airspace including obstacles is assumed to be composed of 3D cells, and the vertexes of 3D cells become the candidates for waypoints. The waypoints through which the UAV can pass are obtained as flyable waypoints by searching and avoiding the position of 3D cells which include the objects inside them using laser scanning. The UAV first chooses the waypoints suitable for taking images from the flyable waypoints using evolutionary computation, and then generates 3D flight path using A*-EC hybrid path planning method. A*-EC hybrid path planning method is a technique for generating flight path quickly considering obstacle avoidance. Path planning problem is solved while the number of waypoints and final destination is unknown and the waypoints are changing as the UAV moves. The result of the simulation shows that the flight path suited for monitoring and taking images is obtained by the method quickly.

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An experimental investigation on an opposing jet as a thermal protection system in high enthalpy flow has been conducted. The heat flux distributions on a hemispherical-cylindrical test model with and without the opposing jet have been measured in a free-piston shock tunnel. The test gas is air with Mach number of 7.5 or 7.9 with total enthalpy of 20 MJ/kg or 4.8 MJ/kg, respectively. Nitrogen as a coolant gas is injected directly against the test flow through a sonic nozzle at the nose tip of the test model. The effect of alleviating heat loads is investigated by changing total pressure of the opposing jet. A significant reduction of surface heat loads is observed in the case of relatively strong opposing jet under both test flow conditions. The result indicates that thermal protection with the opposing jet is effective in high enthalpy flow. In addition, parameters to characterize the cooling effect of the opposing jet are discussed.

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When a spacecraft lands, a large shock load can lead to undesirable responses such as rebound and tripping. The authors previously discussed the problem of controlling these shock responses using momentum exchange impact dampers (MEIDs). MEIDs are classified by momentum exchange directions as follows: Upper-MEID (U-MEID) that launches the damper mass upward, Lower-MEID (L-MEID) that drops the damper mass downward, and Generalized-MEID (G-MEID) consisting of U-MEID and L-MEID, and G-MEID-A (G-MEID-Advanced) that has both upward and downward launching effect on single damper mass, by introducing initial tension to the MEID spring. However, studies of these MEIDs are mainly based on one-dimensional motion. Two-dimensional motion analyses have been done for only U-MEID. This research aims to derive the generalized MEID design methodology for two-dimensional motions. G-MEID-A, that is the most effective one for shock response control in previous MEIDs in the one-dimensional motion, are applied to multi-legged landing gear system. There are two damper masses, one is released to control spacecraft attitude, and the other is released to reduce landing shock. Their parameter design and optimal release timing are discussed in this paper. The effectiveness and robustness against landing slope angle variation of the proposed design methodology are verified by simulations.

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Attitude control of a spacecraft using a variable-speed double-gimbal control moment gyro is considered in this paper. A steering law of this type of actuator has singular points where the rotation axis of the wheel coincides with that of the outer gimbal. Either the avoidance or passage of the singular states can be adopted in the steering law. In this paper, the steering law that selects the avoidance or passage of the singular states from the outer gimbal motion in the vicinity of the singular states is proposed. The usefulness of the steering law is examined by the ground experiments as well as the numerical simulations.

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After the laminar boundary layer separates from the surface of the airfoil, the flow can reattach to the surface downstream. The area between laminar separation and reattachment is called a laminar separation bubble. The breakdown of the laminar separation bubble affects the stall characteristics of the airfoil significantly. Previous studies indicated that the breakdown of the laminar separation bubble can be suppressed by attaching a rectangular plate at the leading edge of the airfoil and adjusting the height of the plate appropriately. In this study, an autonomous actuator system which automatically adjusts the height of the plate following to the increment or decrement of the angle of attack was created. The experiments to verify this system were conducted for NACA0012 airfoil at a chord Reynolds number of 1.3×10⁵. Here, verification results of the system are summarized and its effectiveness to suppress the airfoil stall is discussed.

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These days, Continuous Climb Operation (CCO) and Continuous Descent Operation (CDO) are one of the hot topics in the field of the Air Traffic Management (ATM). However, the CCO and the CDO have a problem with respect to conflict resolution. When aircraft with the CCO or the CDO resolve conflict with other aircraft, they are not able to continue the CCO or the CDO. To resolve the problem, the conflict resolution method for the CCO and the CDO is developed. The conflict resolution method is developed by employing the simultaneous optimization method for trajectory and sequence. To evaluate the conflict resolution method, the simulations are conducted with the actual conditions. By the simulations, it is confirmed that the conflict resolution method is useful for the practical ATM.

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Since a large number of debris exists in the low earth orbit (LEO), deorbiting of the debris is an important subject in the space development. Electro-dynamic tether (EDT) system is a promising method to remove the debris from the LEO. The EDT is cost-effective because the material of the tether is cheap and the propellant is not required. However, the diameter of the tether is thin and the length is very long. Then, the EDT has a high risk to be severed by small meteoroids and the other small debris. To assess the survivability of the EDT, sever criteria are needed and have been proposed. However, the previously proposed criteria are different from each other, and they are not well grounded. In this paper, we propose a new experimental method to determine sever criteria based on the experimental results. Then, we carry out hypervelocity impact experiments to determine the new criteria and compare them with the previous criteria. Moreover, we calculate the survivability of an EDT system on the basis of proposed sever criteria.

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A simple type non-diaphragm shock tube operated by quick action valve constructed from the single piston system was developed. As a result of the performance test experiment, this facility can generate the shock wave with Mach number from 1.6 to 2.0 by changing the initial pressure ratio from 50 to 150. The pressure history suggested that the flow duration (almost constant pressure region) behind the shock wave is more than 100 μsec from the shock wave arrival. The observed shock wave by the visualization suggested that the shock wave propagating on the wedge model is almost plane normal shock wave. Therefore, this developed facility has enough capability for the future experiment.

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The balloon-borne VLBI (very long baseline interferometry) is a radio telescope for space observation from the stratosphere in the submillimeter wave band. The primary reflector has an aperture of 3 m in diameter whose degradation of aperture efficiency is required to be less than 17 % under the deformation due to variations of elevation angle and temperature during observation.In order to alleviate the deterioration of the aperture efficiency, the sub-reflector is equipped with a focal position adjustment mechanism. However, the adjustment mechanism may fail during observation, so that the focal position will be fixed at the prescribed position.This study evaluates the effect of the adjustment mechanism failure on the aperture efficiency through multiobjective optimization approach. The design problem has thirteen objective functions that correspond to the nominal observation condition and the other six conditions considering elevation angles and temperatures with normal and failure cases of the adjustment mechanism.The design problem is solved using the satisficing trade-off method (STOM). As STOM can obtain the single Pareto solution corresponding to the user's preference for each objective function by introducing an aspiration level, the trade-off analysis is easily performed.

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The Lorentz force acts on electrostatically charged objects moving in the Earth's magnetic field. This implies charged space debris orbit can be controlled and debris may be removed by controlling its charge amount. In this paper, we propose various charge control sequences for debris removal and investigate their performance via numerical simulations. The proposed sequences focus on monotonically decreasing semi-major axis, increasing the eccentricity, and decreasing perigee distance. Finally, we optimized the charge control sequence by a combination of these sequences.

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In this paper, a method to derive the minimum-time for formation reconfiguration of cruising two fixed-wing aircraft is proposed. Conventionally, the optimal reconfiguration problem is formulated as an optimal control problem by treating the aircraft as one system. In this paper, it is shown that the solution for this problem is driven by solutions for optimal control problem of single aircraft. The terminal values of this problem, which mean reachable limits of each aircraft, are consolidated efficiently, providing the time for the reconfiguration.

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The underexpanded argon jet through an orifice, upstream stagnation pressure 101300 Pa and pressure ratio 4 or 50, is calculated in an axisymmetric flow field by the DSMC method using the intermolecular collision scheme U-system which enables coarse cell networks for calculations near atmospheric pressure condition. According to our recent analysis, it has been demonstrated that physical properties in each cell of the U-system alter in accordance with a location within the cell. Speedup of the DSMC calculation is also investigated by the parallel processing using a CPU with multiple cores or threads. At the pressure ratio 4, it becomes clear that the damping of shock cells is induced by fluidic vortex-like motion along the jet boundary. An effect of the upstream calculation region of the orifice is also examined at the pressure ratio 50.

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This paper proposes a simple estimation technique for drag-reducing performance of riblet applied to the whole body of an aircraft. The point of this technique is how to estimate the wall shear stress on the aircraft body covered with riblets. First, RANS analysis of flow around an aircraft which is not covered with riblets is conducted to obtain the whole-body distributions of wall shear stress. The distributions of wall shear stress of an aircraft covered with riblet are obtained from the combination of the RANS results and drag reduction rate graphs obtained from wind-tunnel test. Finally, drag reduction rates are estimated from surface integration of the wall shear stress on both the riblet surface and smooth surface. As a result, the estimated drag reduction rates are close to that obtained by the previous flight tests, which indicates that this technique is reasonable. As a future plan, the effects of pressure gradient, angle between riblet and local flow will be considered.

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This paper studies to apply model predictive control to spacecraft nonlinear attitude tracking control problems under input saturation constraints. We first propose to use LPV (linear parameter varying) model obtained by linearizing relative dynamical equations around the given reference trajectories so that the on-line optimization is tractable by on-board computers as well as control performance is achieved. Then we derive the closed-loop stability condition in the form of LMI (linear matrix inequalities). The obtained results are evaluated and compared with other approaches through numerical studies. Finally the closed-loop stability is examined when the control law is implemented using RCS (reaction control systems) with PWM (pulse width modulation).

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