• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.30 no.8
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• pp.148-155
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• 2002

A study on the installation angle of solar panels is conducted as a conceptual study on solar-RFC(regenerative fuel cell) system for stratospheric airships. The airship heads for the west in winter days and the east in summer days according to wind directions. Considering this, it is found that when the solar panel is installed with the center angle of 30 degree the energy output of solar panels is maximized on winter solstice and satisfies the required energy of summer days as well. Although with the optimized solar panel installation angle, efficiency of the regenerative power system needs be improved to 47% to provide required energy of a 170m-long airship. And the required amount of efficiency improvement decreases as the airship size increases.

• Proceedings of the KSME Conference
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• 2002.08a
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• pp.799-802
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• 2002

Korea Aerospace Research Institute has been developing a 50-meter class airship to demonstrate the technology to be used in the development of a stratospheric airship, and importance of accurate prediction of the dynamic behavior of an airship before flight test is widely conceived. The added mass has large impact on the dynamic characteristics of an airship unlike for an airplane and the added mass of the airship with empennage is predicted in this paper. At first, the usability of the strip theory is examined which integrates the analytic two dimensional results in the cross section along the longitudinal axis. A panel method with the surface distribution of sources is developed and its validity is also examined. Finally, the panel method with both source and doublet distributions is implemented, and it is validated and applied for the calculation of the added mass of a 50-meter class airship. Using the methods developed, the influence of empennage and control surface deflection on the added mass property of the airship is studied.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.37 no.1
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• pp.42-54
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• 2009

Contrast to the 6-DOF nonlinear dynamic modeling of nonlinear tracking problem, 3-DOF point-mass modeling of flight mechanics is efficient and adequate for applying the trajectory optimization problem. There exist limitations to apply an optimal trajectory from point-mass modeling as a reference trajectory directly to conduct the nonlinear tracking control, In this paper, new matching trajectory optimization scheme is proposed to compensate those differences of mismatching. To verify performance of proposed method, full ascent three-dimensional flight trajectories are obtained by reflecting the real constraints of flight conditions and airship performance with and without jet stream condition. Then, they are compared with the optimal trajectories obtained from conventional method.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2005.11a
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• pp.103-106
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• 2005

The material properties of membrane for stratospheric airship is experimentally investigated. Mechanical tensile properties of the membrane material at room, high and low temperature are measured using instron with thermal chamber. Experimentaly, material non-linearity is observed at room and high temperature. In order to simulate material non-linearity caused by the uniaxial extension curve of a woven fabric, the nonlinear hyperelastic problem is considered with finite clement program of ABAQS. Numerical results are compared with experimental results.

• International Journal of Aeronautical and Space Sciences
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• v.16 no.4
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• pp.500-509
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• 2015

The numerical simulation of two-dimensional moving blade row interactions is conducted by CFD means to investigate the interactions between the front and rear propeller in a stratospheric airship contra-rotating open propeller configuration caused by different rotational speeds. The rotational speed is a main factor to affect the propeller Reynolds number which impact the aerodynamic performance of blade rows significantly. This effect works until the Reynolds number reaches a high enough value beyond which the coefficients become independent. Additionally, the interference on the blade row has been revealed by the investigation. The front blade row moves in the induced-velocity field generated by the rear blade row and the aerodynamic coefficients are influenced when the rear blade row has fast RPMs. The rear blade row moving behind the front one is affected directly by the wake and eddies generated by the front blade row. The aerodynamic coefficients reduce when the front blade row has slow RPMs while increase when the front blade row moves faster than itself. But overall, the interference on the front blade row due to the rear blade row is slight and the interference on the rear blade row due to the front blade row is much more significant.

• Journal of Institute of Control, Robotics and Systems
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• v.11 no.3
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• pp.214-221
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• 2005

For decades, airships have being developed in Europe (especially German) and America. Airships are planning to be used for advertisements and airliners as well. In Korea, KARI (Korea Aerospace Research Institute) is developing stratospheric communication airship and the similar research is carried out in Japan. Among them, Zeppelin of German has the cutting-edge airship technology with Zeppelin NT. In this paper, the flight performance and stability were evaluated by comparing mathematical theory and the real test. The stability was examined through dynamic modeling and assured by designing controllers at each flight mode. Elevator angle, rudder angle, magnitude of thrust and tilting angle of thrust vector were used as control inputs. Moreover, after measuring the airship velocity, flight direction, magnitude and direction of the wind, attitude angles and trajectories of the airship at each flight mode, the results were compared with the simulation. To get the reasonable data, low-pass filter and band-stop filter were designed to get rid of the sensor noise and engine vibration. The test was accomplished at cruise mode, turning mode, and deceleration. To conclude, with comparing the simulation data and flight test data, it could be known that the dynamic model used in this paper was reasonable.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.31 no.7
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• pp.127-135
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• 2003

• International Journal of Aeronautical and Space Sciences
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• v.7 no.2
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• pp.56-69
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• 2006

For a relatively small country like Korea, a radionavigation system using airships can be considered, which is to provide the navigation service utilizing the stratospheric airships that are deployed in the stratosphere at the altitude of around 20-23km, and which is an independent or a back-up radionavigation system other than current GPS or GLONASS. In this paper, a feasibility study on the constellation of stratospheric airships for the navigation system has been performed. A measure of a geometrical condition between a receiver and navigation transmitters. called the DOP (Dilution of Precision), determines the resulting positioning error of the navigation system, if the error of range measurement is predictable. Therefore, with assumption that the range measurement error of the stratospheric airship navigation system is quite similar to GPS. the several DOP values have been used to evaluate the performance of the navigation system with comparing with the DOP values of GPS as the reference values. To provide the position information of the navigation transmitters to users, a receiver cluster system fixed on the ground, called an IGPS (inverted GPS), is proposed, and the error is also evaluated using the DOP values. Five areas around five major cities in South Korea have been selected, and then by numerical simulations the DOP values are compared those of GPS to assess the performance of the proposed navigation system using stratospheric airships. The possible frequency bands have been proposed. and then link budget of the navigation transmitter has been analyzed for the proposed navigation system.

• International Journal of Aeronautical and Space Sciences
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• v.6 no.2
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• pp.64-75
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• 2005

The Stratospheric Airship Platform (SAP) has a capability of performing the autonomous and guidance flight to satisfy given missions. To be used as the High Altitude Platforms (HAPs), the capabilities of controlling platform's accurate position and keeping the station point are the most important features. Under this circumstances Autonomous Flight Control System (AFCS) is a critical system and plays a key role in achieving the given requirements and succeeding in missions. In this paper, the design and analysis results of the AFCS algorithms and controller are presented. The brief summary of the AFCS hardware structure is also explained. The autopilot controller and guidance logics were designed based on the linear dynamics of the unmanned airship platform and the full nonlinear dynamics was considered to evaluate and verify their performances.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2004.04a
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• pp.87-90
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• 2004

In this paper, geometrically non-linear finite element analyses were performed to study the mechanical behavior of the material system of the envelope of stratospheric airships. The microstructure of the load­bearing plain weave layer was identified and modeled. The Updated Lagrangian formulation was employed to consider the geometric non-linearity as well as the induced structural non-linearity for the fiber tows. The stress-strain behavior was predicted and the effective elastic modulus was calculated by numerical experiments. It was found the non-linear stress-strain curves were largely different from those by linear analysis with much higher non-linear elastic moduli. The difference was more distinguishable when the tow waviness was smaller.