Rapid Prototyping as a Tool to Support Wind Tunnel Testing of Unconventional Unmanned Airships

Scaled models are often used to check the aerodynamic performance of full scale aircraft and airship concepts, which have gone through a conceptual and preliminary design process. Results from these tests can be quite useful to improve the design of unconventional airships whose aerodynamics might be quite different from classical configurations. Once the airship geometry has been defined, testing is required to acquire aerodynamic data necessary to implement the mathematical model of the airship needed by the flight control system to develop full autonomous capabilities. Rapid prototyping has the great potential of playing a beneficial role in unconventional autonomous airship design similarly to the success obtained in the design process of conventional aircrafts. By reducing model cost, build time, difficulty of construction, and maintaining acceptable surface quality and finish, designers have greater ability to analyze several configurations of airships and to change the geometry in order to increase stability, reduce drag, or fulfill mission requirements. This work presents aspects of unmanned airship design which are supported by the use of RP techniques: a test model of a multi-body, cruiser-feeder unconventional airship system has been developed using hot wire cutting and SST printing technology which helped to construct necessary parts for complex body shapes. Taking into account actual model shape and material properties, model verification checks were performed on the final products through FEM and CFD analysis to ensure structural strength and integrity during test procedures and to virtually simulate wind tunnel tests; experimental data from the wind tunnel campaigns are then used in the development of an unmanned airship flight simulator, which is of critical importance in multi-body concepts when cruiser/feeder configurations need to perform docking and rendezvous maneuvers. Results which assess the quality of the test models by comparison of wind tunnel results to CFD simulations are also presented; a final discussion of advantages obtained applying RP technique to the airship design cycle concludes the paper.