Height, seasonal, and short-period variations of lower stratospheric winds around 20km altitude, where aircraft for the stratospheric radio link system will fly, are analyzed based on the wind data obtained by the MU (middle and upper atmosphere) radar for three years. While the stratospheric jet stream was found to be weak enough in summer, it turned to be fairly strong in winter even at the so-called ‘zero-wind’ height of around 20km, sometime exceeding 40m/s over a period of two days. Random wind fluctuations of the order of 1m/s was found to exist in thin turbulent layers of 50-100m thickness.
The work reported herein describes the results of analytical design using thermal-barrier-type Functionally Gradient Material (FGM) to insulate Scramjet cooling structures. Heat transfer coefficient of coolant side of the FGM (hl), representing the mass of the coolant required to cool the main structure, and the thermal resistance parameter (tFGM/λFGM) for equations governing the heat transfer at steady state were determined as the objective function and design variables, respectively. Using the function and variables, heat transfer of the gas-FGM-coolant was numerically analyzed for a stabilized ZrO2/γ-TiAl FGM with a γ-TiAl cooling structure. The effective thermal conductivity (λFGM) for the stabilized ZrO2/γ-TiAl FGM was calculated from the temperatures of the heated and cooled surfaces of the FGM, and from the enthalpy difference of the coolant at the inlet and outlet manifolds of the cooling structure, which was measured utilizing the Xe are lamp heating test. Then the optimum tFGM-λFGM was found to be largely dependent upon the resistant temperatures of the high temperature and low temperature side materials of the FGM. In the cooling structure using ZrO2/γ-TiAl FGM with optimized thermal resistance parameters (tFGM/λFGM), the mass of coolant required to maintain the γ-TiAl cooling structure at temperatures below its resistant range was 35% of that of the cooling structure without FGM.