This paper reports results of fundamental experiments using a continuous-wave CO2 laser thruster. The Laser-Sustained Plasma (LSP) was maintained under a pressure range from 2 to 7 atm with a laser power level of more than 300W. The location of LSP can be controlled by adjusting power level and focus position of the 1aser beam. Thruster performance was evaluated by measuring thrust using a load-cell sensor. Energy balance in the thruster was clarified by measuring heat loss and transparent laser loss.
Plasma velocity measurement of quasi-steady MPD thrusters was carried out to investigate the dependence of the exhaust plasma velocity characteristics on the discharge chamber configurations. The velocities at the exit of MPD channels and PF-series MPD arcjets, which were designed to generate a high axial current, were measured by a Fabry-Perot interferometer. Plasma velocities exhausted from the MPD channel exit were above a sonic velocity in this operational conditions. However, for a large cathode radius, it is inferred that the effect of the friction between the plasma and the cathode surface could not be ignored. On the other hand, the velocity profiles for PF arcjets were dependent on the anode radius and the mass flow rates, and the experimental velocities were larger than the theoretical ones derived from the electromagnetic thrust.
In order to investigate mechanisms of ignition promotion by a plasma jet igniter in the supersonic flow, asymptotic analysis and ignitian experiment were carried out. As the results of an asymptotic analysis, the maximum temperature and ternperature distributions in a plasma jet igniter have been obtained. Then, a bulk temperature and a bulk degree of dissociation in the plasma jet igniter were estimated quantitatively. From these results, ignition promotion effects of plasma tarch and microburner (H2/O2 combustion gas torch) could be estimated analytically. The results represented that both igniters have almost the same effects of ignition promotion. An experimental comparison between their effects showed the same result as the analytical one. Furthermore, ignition promotion effects of radical addition and temperature increase by an igniter were compared analytically. The results showed that the effect of radical addition was greater than that of temperature increase.
The use of overset concept for the unstructured grid method is relatively unexplored. However, the overset approach can extend the applicability of the unstructured grid method for real engineering problems without much efforts in code developments. Multiple moving-body problem is one of those applications. In this paper, the overset unstructured grid method is applied to a flow simulation about an experimental supersonic airplane separation from a rocket booster. Two unstructured grids, each of which covers the airplane and the rocket booster respectively, are used for the simulation. The grid around the rocket booster moves with time in the stationary grid about the airplane. The computed result clearly simulates the shock wave patterns between two bodies. Comparisons with the experimental results show good agreements in the lift and pitching moment coefficients of the airplane and booster during the separation process.
The turbulent structure and the growth rate of the supersonic double shear layer were investigated experimentally. Subsonic air was in parallel injected into Mach 1.78 airstream. In order to contort the spanwise vortex, two configurations of curved injector were used. A new optical measurement that employs schlieren technique and a Pitot pressure measurement were conducted. The optical measurement revealed the existence of the contarted spanwise vortex. In case that spanwise vortex is cantorted, the contorted part of the spanwise vortex is considered to behave like a vortex pair. The spanwise averaged shear layer thickness was estimated from Pitot pressure measurement. Only asymmetric curved injector was effective in increasing the spanwise averaged shear layer thickness. For asymmetric curved injector, vortex pairs of upper and lower shear layers, rotating in the same direction, were considered to induce rib structures.