Tools for the Conceptual Design of a Stratospheric Hybrid Platform 2020-01-0025

CIRA is currently designing a HAPS for Earth Observation and Telecommunications named High Altitude Hybrid Airship. The configurations considered, can generate both aerodynamic and aerostatic forces to balance the weight during the different phases of a mission. The design of a hybrid configuration for stratospheric platforms represents a novelty in itself in the aerospace sector while some hybrid platforms have been proposed only for tropospheric applications. In order to carry out the conceptual design, some design tools have been implemented to rapidly obtain a conceptual layout, which can be used to perform CFD, FEM and stability analysis and, at the same time, to compute the relative platform mass breakdown. The proposed conceptual design process is based on two steps. A first coarse exploration algorithm which, starting from some input parameters, determines the best buoyancy ratio and some overall platform parameters (among others: weight, volume and dimensions) using some semi-empirical formulas to define sub-systems masses, aerodynamic coefficients and structures sizing. The second step consists in a finer optimization around the geometry obtained at the previous step, based on a better definition of the layout, which provides, as final output, a 3-D CAD layout of the stratospheric platform and its main structural elements. Layout modification during the design conceptual process represents an innovative aspect, which allows improvements, since the beginning of the design, the results. This layout, finally, represents the input for CFD, flight stability and FEM analysis. In this paper, this innovative conceptual design process defined to obtain some conceptual configurations of a hybrid HAPS, and the implemented design tools will be described. Furthermore, some HAPS layouts and preliminary CFD analysis will be presented.