We succeeded in determining a tri-axial ellipsoidal model of one LEO debris Cosmos 2082 rocket body, its rotational axis direction in the celestial sphere, a compositional parameter, its rotation period and its precession using only light curve data that was obtained by an optical telescope. The brightness of the LEO debris was monitored for 2 days. The method of the least squares fitting is applied to determine these values. The derived axial ratios of the LEO debris is 100:18:18, the coordinates of the rotational axis direction in the celestial sphere are R.A. = 305.8º and Dec. = 2.6º and its rotation period is 41 seconds. When the precession is considered, its amplitude and precession period are 30.5º and 29.4 minutes, respectively. These results show that optical light curve data are sufficient to determine the shape and the motion of LEO debris.
Capillary waves are radiated upstream from the liquid jet tip which contracts under the action of surface tension force from its upstream portion. The possible processes which change the upstream propagating capillary waves to unstable waves moving downstream with the liquid flow are explored on the basis of the one-dimensional governing equations which are derived to describe the temporal surface deformation along the liquid jet. It is found that the reflection of the capillary waves at the nozzle exit, the gas pressure action due to the velocity difference between the ambient gas and the deformed liquid jet and the local destabilization of superposed capillary waves are main candidates responsible for the liquid disintegration involved in turbulent atomization and liquid jet breakup.
Disintegration mechanism through a liquid-phase feedback loop is explored for a circular liquid jet issued into an otherwise quiescent gas. An asymptotic analysis of capillary waves radiating from the liquid jet tip is used to derive analytical expression for the feed back loop for the regular axisymmetric liquid jet disintegration occurring at a large distance from the nozzle exit for various Weber numbers. The calculation results predict the breakup characteristics which are consistent with the experimental observations. The role of turbulence contained in the issued jet and the change in atomization feature at large Weber numbers are also discussed briefly.
Spectroscopic measurements of microwave-discharged low-pressure nitrogen plasmas were made in a tube with a diameter of 9.5mm and length of 42mm. Intense radiation of N2 2+ bands and weak radiations of N2+ 1-, N2 1+, and NO γ bands were observed. Unique intensity distribution of N2 2+ bands with high vibrational levels was observed as in the arc-discharged micro-air plasma-jets. Rotational and vibrational temperatures were determined by a spectral matching method with N2 2+ (0, 2) and (1, 3) bands. The vibrational state of the plasma was also investigated by the N2 2+ band intensity. As the experimental spectra could not be reconstructed by a usual equilibrium radiation theory with one rotational temperature, the theoretical spectra were constructed with the effects of predissociation and theoretical non-Boltzmann rotational population distribution, and were compared with the experimental ones. As a result, it was found that the vibrational and rotational temperatures were dependent on the theoretical model for rotational population distribution, that the rotational temperature was dependent on the vibrational states, and that the plasmas were in the vibrational non-equilibrium state.
Flight tests were carried out to obtain aerodynamic characteristics of the low altitude stationary flight test airship. The deceleration test method was used in a flight experiment to obtain the drag coefficient. Combining with the deceleration test result, the minimum drag coefficient was acquired by equating a thrust force with the corresponding drag force at the steady level flight. As a result, 0.044±0.002 were obtained on the minimum drag coefficient of the airship. Modifications of the deceleration test data analysis are proposed to be applicable to test data obtained under non-zero attack angle etc. in the paper.
Ignition tests of methane fuel under supersonic air streams were conducted with the methane/oxygen combustion jets as an ignition source. The ignition capability of the combustion jets differed with their equivalence ratio φ; ignition at Mach 2 was successful at 2.4kW calorific input power with φ=0.3 jets while 6.5kW power was needed at stoichiometry (φ=1.0). Numerical calculations revealed the relative effectiveness on shortening the ignition delay times for methane/air mixture between active radicals such as H, O, and OH and ordinary oxygen gas O2 abundantly contained in the lean combustion jets. These results overall suggest that ignition by the methane/oxygen combustion jets has an advantage in simplicity from the practical viewpoint over the plasma jet method which needs a heavy electrical power source.
We proposed the new optimization method based on stochastic process. The characteristics of this method are to obtain the approximate solution of the optimum solution as an expected value. In numerical calculation, a kind of Monte Carlo method is used to obtain the solution because of stochastic process. Then, it can obtain the probability distribution of the design variable because it is generated in the probability that design variables were in proportion to the evaluation function value. This probability distribution shows the influence of design variables on the evaluation function value. This probability distribution is the information which is very useful for the system design. In this paper, it is shown the proposed method is useful for not only the optimization but also the system design. The flight trajectory optimization problem for the hang-glider is shown as an example of the numerical calculation.