Inflated mobile lifting structures analysis of generator-cord construction for circular planforms

Abstract

An inflatable lifting system basically consists of a flexible membrane attached to the periphery of a base containing an orifice. A load is suspended from the inner surface of the membrane and the base rests in contact with the ground; on inflating the device the load is raised and with suitable design and a continuous pressure supply the structure can lose ground contact and hover. An equilibrium configuration is said to have been reached when air is about to escape from the base orifice and ground contact is lost. A model of a system is considered in which the load is carried in a set of cords attached to the periphery of an annular base. These cords.are shorter than the length of fabric gore which lies between them and bows outwards under the excess pressure. The statics of the structure are analysed and it is shown that for practical design purposes the base orifice area should be less than half the projected area of the canopy below the load suspension points. Possible equilibrium configurations are investigated and a method for calculating the fabric gore shape is given. Formulae for designing an actual system are included.