TENSAIRITY CONCEPT APPLIED TO LIGHTER-THAN-AIR VEHICLES FOR LIGHT-WEIGHT STRUCTURES

摘要

Airships have the intrinsic advantages of Lighter-Than-Air (LTA) vehicles: minimal energy consumption and Vertical Take-Off and Landing (VTOL) characteristics. Due to these advantages, significant efforts are being taken in order to investigate new applications and technical improvements. More specifically, there is a renewed interest in large airships for heavy payload transportation and for stratospheric airships. The design of large airships is a big challenge, especially when considering the structural point of view, since big volumes imply high loads, and since light weight is a major requirement for this type of vehicles. In this context, a light-weight structure is proposed by applying the structural Tensairity concept. A Tensairity beam consists of a rigid air beam designed on the basis of complete functional separation of the different structural elements, allowing for a maximum optimization. In this paper, the justification of the feasibility of applying Tensairity components in airships is discussed based on two criteria. The first criterion is the justification of the need of a lightweight structure by a state of the art analysis and a study of the principal characteristics of the existing types of LTA vehicles structures. The second criterion is a preliminary technical analysis, which aims to clarify if the load bearing behavior of airships is suited for the application of the Tensairity concept. Moreover, the bases for the development of the concept for the LTA vehicles structures are established. The advantages and drawbacks of the traditional rigid airships structure in comparison with a non-rigid structure has been analyzed, which conclusion is that the use of a rigid structure is convenient for large airships, since it reduces significantly the stresses of the envelope, but at the same time decreases the payload efficiency due to the addition of the structure's weight. Moreover, the analysis of the load bearing behavior suggests the technical feasibility of applying Tensairity components, since airships have to withstand high bending moments and Tensairity structures are appropriate for withstanding such loads. Finally, the principal guidelines for defining the various load cases and for modeling Tensairity beams have been defined. In order to confirm the hypothesis of the suitability of Tensairity structures on airships, extensive research on design, analysis and optimization of Tensairity beam grids in typical airship loading conditions is needed.