Inflatable kites using the concept of Tensairity

Inflatable structures have very interesting properties such as low weight, compact transport volume and easy set up. Both manned and unmanned aircraft have been built using inflatable wings. However, a severe drawback of inflatable wings is the small load-bearing capacity of such structures which limits the aspect ratio of this wing type. Introducing the structural concept of Tensairity overcomes this deficiency. Tensairity combines an inflatable structure with struts and cables and thus increases the stiffness and maximal load of the inflatable structure tremendously. A further improvement of the stiffness and ultimate load of Tensairity can be achieved by introduction of fabric webs into the airbeam. In this work, the concept of web-Tensairity was further developed into curved girders to be able to build wings with dihedral, sweep and twist. A comparison between a curved and a straight web-Tensairity girder proved that their load deflection behaviour was very similar and superior to a curved and straight airbeam with the same dimensions and internal pressure. The stiffness of the web-Tensairity girder was estimated analytically. To demonstrate the concept of Tensairity wings, the goal was set to build a Tensairity kite which flies stable on a single tether. The latest kite prototype has a span of almost 8 m and a projected area of 11 m2. Results of structural and aerodynamic tests of this kite are presented.