Linear stability analysis of compressible three-dimensional boundary layers on a supersonic natural laminar flow wing, which has strong crossflow and wall curvature effect extremely near the leading edge, is conducted at the flight test condition by solving parabolized stability equations (PSE) as well as the eigenvalue problem in linear stability theory (LST). The effects of the non-parallelism and the wall curvature which the LST approach excludes, and the normalization condition of the PSE method on the stability are investigated, focusing on both stationary and traveling modes subject to crossflow instability and the first unstable mode. Subsequently, the so-called eN method is used as a transition prediction method coupled with the fixed β technique. Finally each N factor map on the wing based on the PSE approach is compared with the result by LST. It is found that stationary modes are very sensitive to the wall curvature compared with traveling modes, and that some shortcomings related to the pathological problem, which existed on the results by the LST approach, can be solved by the current PSE method.
A method to localize a rover on a small planetary body has been proposed based on measurements of the round-trip propagation delay between the rover and the mother spacecraft. It provides the accurate position of the rover by estimating the rotational parameters of the planetary body. It assumes that the rotational parameters of the planetary body are time invariant. Some planetary bodies may not satisfy this assumption. In this paper, the method has been expanded so that it can be applied to the rovers on planetary body with precessional motion. In order to express the precessional motion of the planetary body, the state vector and the equation for the time update are modified. Numerical simulations assuming the rover on Itokawa-size asteroid have been conducted. These results suggested that the expanded method can provide accurate position of the rover in case that the precessional period is longer than 25% of the rotational period.
The Japan Aerospace Exploration Agency launched the S-310-43 sounding rocket from the Uchinoura Space Center on Aug.04, 2014 for the purpose of investigating such behavior as boiling and flow of cryogenic liquid rocket propellant in an environment simulating coasting flight on orbit by using the sounding rocket's sub-orbital ballistic flight. In the low-gravity state, the cryogenic fluid (liquid nitrogen) was introduced into the test sections of similar shapes to the flow channels in the cryogenic propulsion systems. The boiling of liquid nitrogen inside the test-sections and the transition of flow regimes from gas/liquid two-phase flow to liquid mono-phase flow were visualized. The temperatures, pressures and void fractions of each channels were measured as well. Development of the experimental equipment for S-310-43 sounding rocket is described in this paper.
A microwave neutralizer composed of a cylindrical discharge chamber (18 mm in inner diameter) and an L-shaped antenna through which a microwave power of 8W is fed into a working gas was analyzed by a three-dimensional Hybrid-PIC solver to realize the simulation in ion's time/space scale. The microwave heating of electrons was analyzed with another electromagnetic PIC solver, and the obtained microwave power absorption rate was utilized in the Hybrid-PIC solver. Compared with the experimental result, the relative error of the simulated discharge current was about 2%, whereas the error depends on a coefficient in an anomalous resistivity model. The ion density has a peak about 3.34×1018m-3 near the antenna tip, which results in the high ion current (per unit area) into the antenna and the front yoke. Ion number density about 1018m-3 is also kept inside the orifice due to Townsend ionization processes, and it was found that the ions produced near the orifice exit are pushed back toward upstream region due to the potential gradient, and contribute to the electron extraction.
This study presents the algorithm of a numerical analysis for pursuit-evasion type's differential games under the Stackelberg equilibrium. The Semi-DCNLP method is introduced as the optimizer for the solution of the flight path optimization under the Stackelberg equilibrium. For optimal flight path of the evader for an optimally pursuit spacecraft under the Stackelberg equilibrium, the Semi-DCNLP finds the proper trajectories which are corresponded with the trajectories obtained using the direct shooting method.
Air traffic flow control strategies for trajectory based continuous descent operation are discussed. Through numerical simulations including disturbances such as initial flight time error, aircraft control and wind forecast error, the differences of the descent air traffic behavior are investigated. It is demonstrated that the schedule based traffic control achieves optimum traffic capacity with incomplete safety assurance, and that the interval based control results in the contrary. It is possible for aircraft during the trajectory based operation to estimate the extensible or reducible time even during descent. This enables the aircraft to safely reduce its flight time as possible. An algorithm is newly presented by introducing the safe time assurance into the schedule based control, which is equivalent to the time reducing introduction into the interval based control. Numerical simulation has clearly demonstrated its advantage in both safety assurance and traffic capacity.
For the investigation of UAV and MAV, development of wing section which has high aerodynamics performance at the low Reynolds numbers region is required. In addition, the aerodynamic characteristics of the airfoil are influenced by the flow separation which is affected by the wing section configuration. In this study, the influences of upper surface configuration on the aerodynamic characteristics of the Ishii airfoil at the Reynolds number of 50,000 are experimentally investigated. The results demonstrated the laminar separation near the trailing edge whose configuration was resembled to that of NACA0012 airfoil. The lift coefficients, which becomes negative values in the NACA0012 airfoil case because of the laminar separation at the trailing edge, increases almost liner with the increase in the angle of attack. Turbulent region which is increased by the formation of the laminar separation bubble near the leading edge increases drag coefficients. The desirable upper surface configuration of wing section maintains the re-attachment of the laminar separated flow near the trailing edge at high angle of attack condition.
The elasto--viscoplastic constitutive equation based on the concept of continuum damage mechanics was formulated for the niobium alloy (C103) which is used as a chamber material in a satellite's thruster. A tensile and a low cycle fatigue test (strain-controlled) were conducted with plate and round bar specimens made of the niobium alloy. The tests were conducted in air at a room temperature and stress-strain curves were obtained in each cycle. Obtained data from the tests were used to determine the material parameters employed in the constitutive equation. Stress-strain curves and damage-evolution curves were also simulated and the validity of material parameters was confirmed by comparing calculated values with test results. Fatigue life analysis was also conducted and the results were compared with the experimental values. From the results, it is expected that the developed constitutive equations and determined material parameters can be used effectively to predict the mechanical features and the life of low cycle fatigue for the niobium alloy.