In this paper, supersonic dusty shock-layer flow over a blunt body is numerically studied by the Eulerian and Lagrangian hybrid approach. For the gas phase, the axisymmetric Navier-Stokes equations are solved by the finite difference method, while the particle phase is analyzed by the method of particle tracing. The bounce of particles at the body surface is considered. The gas-particle interaction is taken into account by evaluating the momentum and energy exchange between the particle and the ambient fluid. The numerical results show that the presence of particles in the flow causes the reduction in the shock-layer thickness and the augmentation of the wall pressure and wall heating rate. These effects strongly depend on the size of the particles.
Band-sealer machines, which seal long polyethylene-film gores continuously, are used to produce big plastic balloons. The machines are designed to operate in long factories and can not stop sealing in a middle of long gores. This paper describes a new belt-sealer that we have developed for producing big polyethylene balloon. The machine is designed such that it can stop and re-start in any middle point of sealing. The sealer removes handling difficulties of the usual-type band-sealer and can be operated even in factories with small area. A thin polyethylene balloon with a volume of 120, 000 m3 was made by the new type belt-sealer. This balloon (BT 120) was launched successfully on January 27, 1997. The balloon ascended normally and reached the altitude of 50.2 km after 3 hrs.. The altitude is the highest balloon altitude ever in Japan.
We discuss the mechanism of energy transfer between rotation and revolution of a satellite through the gravity gradient. We assume the earth to be a homogeneous sphere and regard the satellite as an ellipsoid of inertia, not point mass. On the condition, the satellite experiences not only the gravitational force acting on the point mass at the center of mass, but also the force and torque due to the gravity gradient. In addition to the rotational energy and the orbital energy, the satellite has the potential energy generated by the gravity gradient, which performs the energy transfer. Utilizing the principle, we derive the optimal attitude of the satellite for raising the orbital energy. Additional energy is supplied to the rotation by the attitude control and transfers to the orbital motion through the mechanism. Fainally, we numerically examine the effect of the proposed method to raise the orbital energy by attitude motion.
Noise and oscillatory behavior of a plasma column produced in front of the microwave discharge neutralizer developed for MUSES-C mission were experimentally investigated. Radiated electric field emissions were measured following to MIL-STD-461 E. The average noise level exceeded the narrowband specification by 30 dBμV/m at frequencies less than 5 MHz. Noise in electron emission current was also measured by using a current probe and a spectrum analyzer, and was compared with the noise of a hollow cathode. The microwave discharge neutralizer generates a broadband noise and oscillations which have a fundamental frequency of about 160 kHz and are accompanied by its harmonics up to the 5th. Considering the dependence on the diameter of the plasma column, they are probably the radial oscillation modes of ion acoustic waves. Although the hollow cathode shows nearly the same noise level at frequencies less than 1 MHz, intense oscillation exists in the 1-10 MHz range, which is generated by the keeper plasma.
This paper is devoted to optimize the trajectory of the end-effector of space robot to suppress the attitude variation of the main body and to reduce impulsive force at capturing a target as well as to preserve the manipulability during manipulator motions. The B spline curve is applied to represent the trajectory shape. Constrained parameters of the manipulation include relative velocities and attitude between the target and the end-effector and the approach direction to the target at the capture. The knot vectors and control points of the curve at the end of the trajectory are determined to meet the constraints. By discretizing states variables, the problem is formulated as the non-linear optimization problem. The optimal trajectories for five approach directions are obtained by using Sequential Quadratic Programming (SQP) method. Effect of difference of the approaching direction on the manipulability, impulsive forces, attitude variation and optimal trajectory is investigated, and a basic strategy for planning the end-effector trajectory is discussed to conclude the present result of study.