To estimate uncertainties of wind tunnel test data, it is necessary to analyze statistical uncertainties of tunnel flow conditions. The tunnel flow field should be calibrated at many points in time and space. At a blow-down type hypersonic wind tunnel, this multipoint calibration of the flow field has to be divided in many tests. Among these many tests, random error limits estimated from statistical assessments of Mach number measurements were applied to judge the measurement repeatabilities including liquefaction free flow. The uncertainties of the flow conditions were validated through comparisons of standard model test data in/out of two calibration ranges across the years. Methodology to represent hypersonic wind tunnel performances has been established for data quality assurances by applying the statistical uncertainty assessments.
The influence of module connection appeared in the changes in the internal force during deployment motion. When the internal force arises in a deployable structure during deployment, two major resistance factors affect the deployable characteristics. One is friction in each hinge portion. Another is strain energy due to structural deformation. To evaluate the influence of module connection on deployment characteristics, we performed deployment experiments under micro gravity. The changes in deployment force were measured for given tolerance of connection points. We concluded that the major resistance factor was strain energy due to structural deformation.
TSTO (Two Stage To Orbit) is a candidate for advanced space transportation system, which is required to fly over a wide region from subsonic to hypersonic speed with an orbiter connected with a booster. The hypersonic flow field with aerodynamic interaction around a TSTO model, which consists of a delta wing as a booster and a hemisphere-cylinder as an orbiter, has been investigated. The temperature distribution is measured by the Temperature Sensitive Paint (TSP) method, and the heat flux with thermo-couples. As a result, the flow field has been significantly affected by the clearance between the two bodies. In the case of a small clearance, heat flux on the head of the hemisphere-cylinder becomes about 3.1 times as large as the stagnation heat flux for the hemisphere-cylinder alone. On the other hand, at a large clearance, heat flux on the delta wing becomes about 1.1 times as large as the stagnation heat flux. In addition, a new thermal protection system (TPS) to reduce the aerodynamic heating due to shock/shock interaction and shock/boundary-layer interaction is also investigated in this paper. A triangular prism installed on the delta wing can change the aerodynamic heating, depending on its location. It was found that a small device installed upstream is effective, where the heat flux has been reduced by about 48%.
Twin underexpanded impinging jets are experimentally and numerically studied in this paper. The experiments were performed by two dimensional wall static pressure measurements and by the schlieren method. Numerical calculations were also conducted by solving three dimensional compressible Navier-Storkes equations in generalization curvilinear coordinate. The main parameters for the twin jets are the nondimensional distance between the two nozzle centers H/D covering 1.5 and 2.0, the nozzle to plate separation L/D 2.0 and 3.0 and the pressure ratio defined by p0/p 2.5–5.0, where D is the diameter of each nozzle exit, p0 the stagnation pressure and p the back pressure. It is found that, so called, a fountain flow which occurs at the middle position between the two jets breaks jets boundaries due to its unsteadiness. Comparison between the experiments and the calculations shows that in case of shorter distancce between two nozzle and higher pressure ratio, two jets interact before they reach the impinging wall causing clear pressure peak at the middle position between the jets.
Arcing on satellite solar array due to interaction with space plasma may cause permanent loss of satellite power, once the arc becomes permanent sustained arc. An arc on solar array becomes a secondary arc when solar array circuit is short-circuited and provides energy to the arc plasma. The permanent sustained arc, the final stage of the secondary arc, destroys a solar array string or the complete power circuits at the worst case. To investigate the threshold conditions for the secondary arc formation, laboratory tests are carried out in a xenon plasma chamber simulating LEO plasma environment with an external circuit simulating a spacecraft power system. Solar array coupon panels simulating the hot and return ends of a string circuit are tested for various combinations of string voltage and string current. Experimental results show that formation of secondary arc strongly depends on the string voltage and duration of secondary arc depends on the string current.
The safety problem of aircraft that encounters wind shear during the final approach flight phase is addressed using a game theoretic approach. The game consists of two players, an aircraft and wind shear. The control scheme is composed of non-cooperative game between players. In the game, aircraft tries to fly to avoid crashing to ground and down burst attempts to force the aircraft to crash. A new control strategy based on nonlinear receding horizon control is applied to the game. It is shown by simulation that this control strategy is effective against wind shear.
Aerodynamic performances of a rectangular intake were investigated experimentally. After a tradeoff study of rectangular intakes whose operative Mach number is from 0 to 6, 20% external compression intake is selected as the best intake from the viewpoint of low number of actuators. Intake performances such as total pressure recovery and mass flow ratio are evaluated by wind tunnel tests. The free stream Mach number of the wind tunnel was M5.1. The size of the intake was 75mm in cowl capture height. Low ramp driving force was achieved by connecting links of the second ramp and third ramp. After the first wind tunnel test that is performed to evaluate the basic performance of the intake, the configuration of the intake is modified. Ramp length of the first ramp and the second ramp were changed to improve the total pressure recovery. Bleed from the second ramp is added. Seal mechanism between the variable ramps and the sidewall is modified. Total pressure recovery is improved from 9.9% to 21.7% by the modifications.