In this paper, on-orbit joint flexibility experiments using ETS-VII (Engineering Test Satellite VII) robotic arm are discussed. Considering manipulability of the robotic arm, the arm vibration due to the joint stiffness may influence on the berthing manipulation. The vibration of the robotic arm mounted on a satellite is characterized as follows, 1) coupling between the arm and the satellite attitude vibration, and 2) transition of the arm natural frequency according to its posture changes with the inertial parameter variation. The experiments are planned to evaluate these vibration disturbance. Using telemetry data detected by FTS (Force Torque Sensor) attached to the end-effector, the arm natural frequencies and the transitions of the arm vibration amplitude are analyzed. And the validity of the simulation results is demonstrated.
An arc-heated wind tunnel has been used to produce nitrogen gas flow with high enthalpy to investigate physical phenomena along the stagnation streamline of a hemi-sphere cylinder with a diameter of 10 mm. The rotational and vibrational temperatures were measured by a spectroscopic method. The rotational temperature took a maximum value of 800 K at a location 2 mm upstream of the stagnation point, while the vibrational temperature showed a nearly constant value of 5, 500 K, which was much higher than the rotational temperature. This means that the present flow is in the state of thermal nonequilibrium. For comparison, the flow was numerically simulated by using the measured data as boundary conditions. As a result the calculated translational-rotational temperature was 80 K higher than the experimental data. Vibrational temperature had a tendency to decrease along the centerline of the wind tunnel, due to insufficient energy exchange between translational-rotational and vibrational energy.
Parametric study is conducted to find the optimum condition of water rocket for long flight, provided that the tank volume is prescribed. The parameters considered in the present study are the initial air pressure, water volume fraction, empty rocket mass, launching angle and bottle diameter which significantly affect the flight performance of water rocket. First, we calculate the temporal changes in tank pressure, water and air issue speeds and thrust, on the basis of a simple physical model which has been experimentally validated. Then, this model is incorporated into the equation of motion to calculate the ballistic flight of water rocket with various parameter values. As a result, it is found that PET bottles in the market are one of the most suitable for use as the pressure tank of water rocket.
This paper discusses a static stability theory for airplanes. The conventional definitions of static stability are neither clear nor systematic. For example, the aerodynamic characteristics that play an important part for obtaining static stability are used just like the definition of static stability. And, although the static stability concepts for flight-velocity and three rotary motions are discussed, the static stability concepts for heaving velocity (or angle of attack) and sliding velocity (or sideslip angle) are almost not discussed. On the basis of these situations, a system of definitions for 6 static stability concepts is proposed in this paper. In the first report of this paper, the static flight-velocity stability and the static angle of attack stability of these 6 stability concepts are discussed, and each stability criteria are obtained using the aerodynamic characteristics of airframe.
This paper discusses a static stability theory for airplanes. The conventional definitions of static stability are neither clear nor systematic. On the basis of these situations, in the first report of this paper, a system of definitions on 6 static stability concepts was proposed, and the static flight-velocity stability and the static angle of attack stability were discussed. In this second report, static pitch stability or longitudinal static stability of aircrafts is discussed. This paper proposes that “dM/dθ<0” should be used as the fundamental definition. A general criterion for static pitch stability is deduced from this definition. From this criterion, “Cma<0” is obtained as the requirement in the case of normal low subsonic flight conditions. Furthermore, this criterion gives the conditions that “flight-path divergence” phenomenon in high angle of attack region and “tuck-under” phenomenon in transonic flight region occur.
Combustion and unstart processes of a scramjet engine in Mach 4 flight condition were investigated experimentally focusing on the changes of the engine internal flow structures under the ‘weak’ and ‘intensive’ combustion modes. Cold flow tests were carried out using a 1/5-scale model of the scramjet engine examined in the firing tests at Ramjet Engine Test Facility (RJTF). Pressure rise due to combustion was successfully simulated by a flow-plug installed in the engine nozzle section to demonstrate good agreement with the wall pressure distributions of the engine under ‘weak’ and ‘intensive combustion’ modes. Especially, upper limit of the combustor maximum pressure at which engine fell into unstart was exactly simulated. This limit value was revealed to be the separation pressure of the turbulent boundary layer in the isolator. Shadowgraph visualization demonstrated that in the intensive combustion mode large-scale boundary layer separation was formed over the isolator, backward facing step and constant area combustor.