The three-dimensional flow structure around a model of the MUSES-C capsule traveling at a speed of Mach 10 was observed by using various techniques of the electric discharge method. The shock shape ahead of the capsule was observed by a shock shape visualization technique, and the streamline after the shock wave was observed by a streamline visualization technique. Subsequently, the flow pattern including the re-circulation region such as the separation point, free shear layer, and rear stagnation location behind the capsule was observed by using a technique of the electric discharge method. These experiments have made clear the three dimensional flow structure around the capsule, which was very difficult to visualize.
Instability of a curved compressible shear layer was investigated by the use of linear stability analysis. If velocity of flow along a convex wall is larger than that of flow along a concave wall, flow field is unstable to purely spanwise disturbances and streamwise vortices are formed. Effects of parameters such as convective Mach number, velocity ratio and density ratio on growth rates were investigated. There are negligible effects of compressibility on growth rates of these disturbances, which indicates relatively effective mixing enhancement for flow fields where effects of compressibility is large. Study on viscous fluid showed that growth rates of spanwise disturbances with large wavenumber decrease in comparison to the case of inviscid fluid. As a result, a certain spanwise wavelength having maximum growth rates exists and control of wavelength can contribute to mixing enhancement.
The subsonic flow for a 45deg-swept delta wing is numerically simulated to see the effects of trailing edge jet on aerodynamic forces. Computation has been performed at an angle of attack of 20deg and a Reynolds number of 2.0×104 based on the wing root chord. Under these conditions, the flow is fully separated from the wing surface, so that no suction peaks due to leading edge vortices appear over the upper surface of the wing. Consequently, the delta wing cannot take advantage of a vortical lift. When a jet is emitted normal to the wing lower surface near the trailing edge, the flow along the wing lower surface is decelerated. That is, the circulation around the wing increases. In one of the cases studied here, the lift coefficient became more than 40% higher than that of the plain delta wing. By contrast, in the case of trailing edge jet parallel to the wing lower surface, the flow along the wing lower surface is accelerated, and the lift coefficient became lower than that of the plain delta wing.
A laminar separation bubble formed on a NACA 0012 airfoil at a chord Reynolds number of 1.3×105 has been investigated to discuss the bubble behavior near stall. The flow is oscillating between a small separation-reattachment bubble formed near the leading-edge and a large separated region extending over the airfoil surface at a frequency of about 2Hz. Phase averaged turbulent energy production term have been obtained. Results indicate that the behavior of growth and decay of the phase averaged turbulent stress has strong correlation with the behavior of the phase averaged turbulent energy production.
The purpose of developing NASDA’s Engineering Test Satellite (ETS) series is to acquire a common and base technologies of satellites. The ETS-VIII is being developed to establish and verify an advanced 3-ton-class spacecraft bus-system with a large-scale deployable reflector. The ETS-VIII will depend on battery power until the solar array panels are deployed. There are two battery units each of which consists of 18 battery cells in series. Thermal control of battery at the launch site is very important, because increasing of the battery’s temperature during charging brings inefficient charging performance, generating further heat. In advance, trial examinations, charging batteries and measuring the charged capacitance, were performed to make sure that ETS-VIII operation at the launch site can be completed. This paper describes the results of trial examinations, thermal analysis based on these examinations and proposals for launch operations about charging the battery.
The microwave discharge ion engine generates plasmas of the main ion source as well as the neutralizer using 4GHz microwave without discharge electrodes and hollow cathodes, so that long life and durability against oxygen and air are expected. MUSES-C “HAYABUSA” spacecraft installing four microwave discharge ion engines was launched into deep space by M-V rocket on May 9, 2003. After vacuum exposure and several runs of baking for reduction of residual gas the ion engine system established the continuous acceleration of the spacecraft toward an asteroid. The Doppler shift measurement of the communication microwave revealed the performance of ion engines, which is 8mN thrust force for a single unit with 3,200sec specific impulse at 23mN/kW thrust power ratio. At the beginning of December 2003 the accumulated operational time exceeded 7,000 hours and units.
This paper discusses the minimum energy maneuver of satellites using two reaction wheels. The problem is a rest-to-rest maneuver around an axis without wheel by two wheels mounted on other perpendicular axes. The trajectory of the maneuver is described using new parameters that are presented by Tsiotras et al. The parameter is useful to present attitude of satellites with two wheels. The optimal attitude trajectories for satellites with isotropic moments of inertia were shown numerically. This paper proposes a simple optimal algorithm that needs no optimizing calculations. The proposed controller satisfies the necessary condition in terms of required maneuver with quasi-minimum-energy.