A unified design methodology for unmanned airships: from preliminary sizing to flying qualities

Among the most versatile lighter-than-air platforms, unmanned airships are currently being designed mostly for either low-altitude missions for close-distance surveillance, in competition with multi-copter drones, or for high-altitude missions in the stratospheric layer, thus ideally complementing the role of space satellites. Correspondingly, algorithms to automatically compute global values like the volume and mass of an airship, for a desired mission performance and for assumed technologies of the components (like the materials employed for the envelope or the construction of the gondola), have been experimented with and are already documented in the literature.

Building on this base, this research proposes a method where not just the parameters mostly typical to preliminary design are solved, but a unified automatic approach is employed for taking into account requirements on static balance as well as dynamic performance. This modular method links three original tools, developed in-house respectively for preliminary sizing, lofting and inertial modeling, and dynamic analysis. The synergistic use of the first two allows the simultaneous computation of not just the weight and volume of the machine for a specific mission, but also a detailed static balance problem, by suitably arranging the masses of the components onboard. The last module further tweaks the positioning of selected components to obtain better flying qualities. The latter are measured by means of damping and the characteristic time of specific eigenmodes of the system, in turn obtained after drawing a linearized model of airship dynamics from a fully non-linear one.

The outcome of the overall unified sizing procedure, numerically configured as an automatically solved optimal problem, accounts not just for the requirements of the mission profile, but also potentially for static balance and for a desired level of flying qualities. The full procedure is demonstrated on the data of an existing small-scale airship prototype.