A system to measure gaseous fuel distribution was devised, which is based on infra-red light absorption by carbon-hydrogen stretch mode of vibration and the computed tomography method (IR-CT method). Since the incident light intensity from an infra-red laser fluctuated temporally, the effect was diminished by dividing the beam to two, one of which was monitored for better measurement accuracy. It was found that the error due to the laser fluctuation was within 0.8% and the feasibility of the IR-CT method was confirmed by applying the system to the measurements of the methane fuel concentration in an internal combustion engine model and a burner with diffusion flame. Furthermore, calibration to determine absorptivity was undertaken, which was used for the conversions from the measured line absorption coefficients to spatial fuel concentration in the combustion field.
In the present analysis, the cycle of pulse detonation engine (PDE) operation, such as combustion, exhaust and filling phases, was performed by 2-dimensional calculations. A 2nd-order MacCormack-TVD scheme is used to solve Navier-Stokes equations where a simplified two-step chemical reaction model is introduced. Model PDEs have various tube lengths with a constant cross section, containing an Ar-diluted stoichiometric oxyhydrogen mixture. The performance of PDE was estimated and compared with the result of Endo-Fujiwara theoretical analysis. In the present PDE performance estimation, useful formulas for impulse per unit area that are in good agreement with theoretical analysis are derived. Through the cycle analysis of PDE operation, the thrust density of each Model PDE was also estimated and essential aspects of the PDE cycle were obtained.
Plasma contactors are proposed as making good electrical contact between spacecraft and ambient ionospheric plasma. Especially, it has been studied as the one of key components of electrodynamic tether for electron emitter and collector. In this study, the experiments were conducted to understand the plasma contacting process. Hollow cathodes were used for plasma contactor to establish a low impedance electrical contact. The results show the simultaneous operation of the plasma contactors for current collection and emission from and to an ambient plasma at the current levels of the order of five ampere. We obtained a performance curve, potential profile and the appearance of a bright luminous cloud that typically extends some tens of centimeters from the collector and confirmed closed current loop formation via simulated plasma between the emitter and the collector.
A Neural Network (NN) model of a human operation is tried to construct to analyze pilot behavior. The flight data obtained by simulator operation are utilized to teach the NN model. The input data to the model are visual cues from the cockpit and the pilot column deflection history, and the output is the elevator angle. The Genetic Algorithms (GA) optimizes the NN model in order to obtain the appropriate structure and its parameters. It can be seen that the sensitivity analysis and the threshold analysis of the obtained NN model reveal the human pilot behavior.
Double discharge operation for a pulsed plasma thruster (PPT) was proposed and the preliminary experiments were conducted to improve the lower propellant utilization efficiency of PPTs that is attributable mainly to a late-time vaporization problem. In the double discharge operation, two successive discharges were produced with a microseconds-order interval to accelerate the late-time vaporization gas generated in a primary discharge by the electromagnetic interaction in a secondary one. Experimental results showed by adopting the double discharge operation the effective exhaust velocity was increased compared with the one in the ordinary PPT operation. This velocity increment indicated that the ratio of electromagnetically accelerated propellant gas to total propellant consumption was risen in the double discharge operation. Furthermore, when the time interval between the two discharges was shorter than the single discharge duration, it was observed that the impulse bit, specific impulse and thruster efficiency were higher than those in the ordinary operation.
It’s important to predict the free motion of uncontrolled spacecrafts for concerning the capturing mission. In this paper, free motion of the Engineering Test Satellite-VII (ETS-VII) is analyzed through numerical simulations with consideration of various disturbance torques. Simulation results are compared with the actual free motion telemetry data during the attitude control loss.