A 10-year program to develop a stratospheric airship for telecommunication relays and ground observations at 20 km altitude has started in December 2000. The program consists of 3 Phases. In 1st Phase, a 50 m unmanned airship will be developed with basic research for stratospheric airship to secure technologies required for 2nd Phase development. During the 2nd Phase development, a prototype stratospheric airship will be launched for station keeping at 20 km. The 2nd Phase development plan will take concrete shape based on the result of the 1st Phase. Then, stratospheric airship will be commercialized through 3rd Phase development. KARI, Korea Aerospace Research Institute, has been developing a 50 m unmanned airship system as its 1st Phase Program during last 3 years. KARI finished design of the system, manufacturing of components and sub-systems, tests of components and sub-systems, and total system check for flight test. KARI's general plan and approach for developing stratospheric airship are described in this paper. The characteristics of KARI's 50 m unmanned airship system are briefly introduced with ground and flight test results. Also, some activities for the 2nd phase are described.

Design, wind tunnel test, computational fluid dynamics (CFD) analysis, and flight test data analysis are conducted for the propeller of EAV-3, which is a solar-powered high-altitude long-endurance unmanned aerial vehicle developed by Korea Aerospace Research Institute. The blade element momentum theory, in conjunction with minimum induced loss, is used as a basic design method. Airfoil data are obtained from CFD analysis, which takes into account the low Reynolds number effect. The response surface is evaluated for design variables by using design of experiment and kriging metamodel. The optimization is based on desirability function. A wind tunnel test is conducted on the designed propeller. Numerical analyses are performed by using a commercial CFD code, and results are compared with those obtained from the design code and wind tunnel test data. Flight test data are analyzed based on several approximations and assumptions. The propeller performance is in good agreement with the numerical and measurement data in terms of tendency and behavior. The comparison of data confirms that the design method, wind tunnel test, and CFD analysis used in this study are practically useful and valid for the development of a high-altitude propeller.

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Korea Aerospace Research Institute (KARI) is developing an electric-driven HALE UAV in order to secure system and operational technologies since 2010. Based on the flight tests and design experiences of the previously developed electricdriven UAVs, KARI has designed EAV-3, a solar-powered HALE UAV. EAV-3 weighs 53kg, the structure weight is 22kg, and features a flexible wing of 19.5m in span with the aspect ratio of 17.4. Designing the main wing and empennage of the EAV-3 the amount of the bending due to the flexible wing, 404mm at 1-G flight condition based on T-800 composite material, and side wind effects due to low cruise speed, Vcr = 6m/sec, are carefully considered. Also, unlike the general aircraft there is no center of gravity shift during the flight because of the EAV-3 is the solar-electric driven UAV. Thus, static margin cuts down to 28.4% and center of gravity moves back to 31% of the Mean Aerodynamic Chord (MAC) comparing with the previously designed the EAV-2 and EAV-2H/2H+ to upgrade the flight performance of the EAV-3.