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.

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A nine node finite element model has been developed for analysis of geometrically non-linear laminatelt composite shells. The formulation is based on the degenerate solid shell concept and utiliLes a set of assumed strain fields as well as assumed dkplacement. Two different local orthogonal co-ordinate systems were used to maintain invariance of the element stiffness matrix. The formulation assumes strain and the determinant of the Jacobian matrix to be linear in the thickness direction. This allow~s analytical integration in the thickness direction regardless of ply layups. The formulation also allows the reference plane to be different from the shell midsurface. The results of numerical tests demonstrate the validity and the effectiveness of the present approach.

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A nonlinear aircraft tracking filter using a point mass flight dynamics model with three degrees of freedom is presented. While the models used by conventional air traffic control tracking filters are based on simple kinematics, the model for the present filter is based not only on kinematic relations but also on three-dimensional aircraft translational force equations and control variables. This allows for practical and sophisticated implementation of the attitude effects on translational acceleration. The control variables, which consist of the angle of attack, roll angle, and thrust setting, are treated as states with random processes. Tracking with simulation data indicates that the present filter is superior to other single and multiple model-based filters in terms of position and course accuracy, and the model associated with it is insensitive to flight motion types and design parameters. The results of tracking with real flight data also correspond well with those found by tracking with the simulation data.