High stability of spiral jet issued from a nozzle, which was designed with an annular slit connected to a conical cylinder, has been clarified by measuring the radial turbulence level and analyzing linearly the amplitude of radial perturbation. The measurement by using laser doppler annemometer indicated that the level of spiral jet was much smaller than that of conventional jet. The linear analysis, which was carried out by difference equation obtained by substituting perturbation into continuity and Euler equation, indicated that the amplitude of the spiral jet was much smaller than that of the conventional jet at the each, radial point. This approximate solution was qualitatively consistent with the experimental results. This high stability of the spiral jet was caused by its steeper axial velocity and its larger radial gradient change of axial velocity near the boundary as compared to the conventional jet.
PPG+AP composite propellants have exhibited extinction behavior when the chamber pressure is increased to some value, Pext, extinction pressure. The extinction pressures were found to be 1) independent of the pressurization rates, 2) altered by addition of carbon powder and 3) diminished by using propellants with higher PPG ratios. By thermal analysis of the propellants used and microscopic observation of the extinguished surfaces it is presumed that these phenomena are due to the differences in decomposition rates between PPG and AP at various chamber pressures and their decomposition enhancement by carbon addition.
Equations of motion for such multibody flexible structures as space structures containing a large number of degree of freedom is formulated by using a system written in a Object-Oriented language C++. This paper aims to achieve the following two accomplishment: The first is a general formulation of the equations of motion for multibody flexible structures applying the extended Hamilton's principle; The second is the development of the system for the formulation and the multibody structures are analyzed by utilizing the approach of Object-Oriented analysis. The developed system constitutes a mathematical simulation program for dynamical system and is formatted in C/C++ or Mathematica or Matlab.
In this report several propulsion systems of air cushion vehicles are introduced, and a state feedback control law is proposed for the trajectory control of an air cushion vehicle. This control system has to be treated as a nonholonomic system when we consider that the air cushion vehicle does not drift sideways for a good driving performance. We discuss the controllability of the nonholonomic system and use a Lyapunov-like function to develop a nonlinear state feedback control law. Effectiveness of the nonlinear state feedback control law for an ACV model was verified through numerical simulations.
In this paper, minimum fuel consumption trajectories and histories of control actions on two different orbital plane change missions, the GEO-LEO mission and the LEO-LEO mission, with consideration of the constraint of aerodynamic heating and the viscous effects on AOTV aerodynamic characteristics, have been investigated. For results, it has been made clear that viscous effects for the fuel consumption on both missions are little. However the effects for optimal trajectories and histories of control actions were different for each mission. It has also been made clear that in the case of GEO-LEO mission the air viscosity is needed to be considered to do the guidance for the AOTV. However for the LEO-LEO mission the air viscosity is not necessary in order to do the guidance.
The influence of high-energy ion bombardment on chemical structures of non-metallic materials was investigated to clarify the mechanism of the material degradation in space. Polymers of polyimide, polyetherether-ketone and perfluoroalkoxy and glasses coated with MgF2 were exposed to ion beams of oxygen and nitrogen with energy levels of 600eV-5keV, which were generated using an electron cyclotron resonance discharge ion accelerator. For the polymers, X-ray photoelectron spectroscopic analysis showed that both addition reactions of oxygen or nitrogen atoms and separations of various structural compounds occurred. In the glass plate, the coating layer of MgF2 was sputtered drastically.