Thrust performances of scramjet engines were compared with theoretical values to quantify the progress in engine performances (defined as “achievement factors”, or “factors”) from Mach (termed as “M”) 4 to M8 flight conditions. An engine with a ramp produced an experimental thrust of 215 N under the M8 tests and a comparison of a theoretical thrust yielded a thrust achievement factor of 51%. By excluding boundary layer, an engine with a thick strut delivered a net thrust of 560 N and showed a thrust factor of 92% and a net thrust factor of 45%. The thrusts was limited by flow separation caused by engine combustion (termed as “engine unstart”). The starting characteristics was improved by boundary layer controls in M6 and M4 conditions. An engine with a thin strut doubled the thrust from 1620N to 2460N by the boundary layer bleeding in the M6 tests. The improved thrust factor was 60% at the stoichiometric H2 condition. Under M4 tests, the net thrust was tripled by the bleed and a two-staged injection of H2. As results, the thrust factor was raised from 53% to 70%, the net thrust factor was increased from 32% to 55%. Studies required for improving the net performance was addressed.
As a feasible welding method in space, the authors have previously proposed the space GHTA (Gas Hollow Tungsten Arc) welding process. The space GHTA welding with high frequency power source for the arc starting may cause the electro-magnetic noise problems of computer equipments placed on the ISS. Therefore, in this paper the welding experiments of aluminum alloy by the space GHTA welding with DC high voltage power source for the arc starting was carried out in the ISS orbital pressure 10-5Pa. It is made clear that there is the shifting phenomenon in which the spark discharge changes to the glow or arc discharge at starting phenomenon of the space GHTA welding in high vacuum condition, and the features of those starting phenomenon are demonstrated. And the space GHTA welding with DC high voltage power source can be used for welding in the ISS orbital pressure.
Mixing of twin swirling helium jets injected from a ramp into a supersonic airstream was experimentally investigated to clarify the interaction between the vortices introduced by the ramp and the swirl. The direction and strength of the swirl were changed by replacing cylindrical chambers through which the injectant was introduced to the injector. The direction of the swirl was either same as or opposite to that of the ramp vortex. Helium concentration distributions were measured in three cross sections. The swirl in the same direction brought the injectant to the center plane of the two jets and merged to a single one, while that in the opposite direction kept each jet apart. However, there was no significant difference in the maximum concentration of helium observed in the tests with different directions and strength of the swirl.
Recently, earth observation satellite missions are becoming more demanding and diversified to note 3-dimensional map production, disaster observation, earth resource exploration, and so on. As a result, the pointing or tracking requirements of mission instruments such as CCD camera or Rader to the ground target are decisive factors in designing the Attitude and Orbit Control System (AOCS). In this paper, the relation between AOCS capability of the satellite main body and the ground tracking accuracy is strictly defined and a new determination method of attitude and attitude rate specifications to meet these requirements is proposed. Assuming an AOCS with a star tracker unit and GPS, the validity of the proposed method is demonstrated by numerical simulations.
The results of experimental studies and numerical simulations on the characteristics of a rectangular membrane made from elastic material in supersonic flow are presented. These experiments were conducted using the supersonic wind tunnel at ISAS. The characteristics of deformation, aerodynamic forces, and oscillation of the membrane are investigated experimentally. It was found that the membrane deformation and aerodynamic forces depend mainly on the aeroelasticity parameter (the ratio of aerodynamic force to elastic force), and that severe oscillation of the membrane is not observed in the experiments. A computational model, in which the membrane is described by a finite number of virtual particles, is also proposed, and their motion is computed in a Lagrangian manner. In the present study, two-dimensional calculations are performed. For the flow simulation, Newtonian flow analysis and compressible Navier-Stokes analysis are used. The results are compared with the experimental data, and good agreement is obtained.
An experimental study on reduction of aerodynamic heating due to opposing jet in supersonic flow has been conducted. Experiments are conducted by using a conventional blowdown type wind tunnel. A hemisphere model is installed into supersonic free stream of Mach number of 4 and coolant gas is injected through a sonic nozzle at the top of the model. Significant decrease of surface heat flux distribution is observed and opposing jet is proved to be quite effective on the reduction of aerodynamic heating at the nose region of the blunt body. The effect of total pressure ratio of opposing jet to the free stream on the reduction of aerodynamic heating is also investigated.