Patent ID: 8646721

Claim:
An airborne craft incorporating a fluid dynamic device for directing fluid flow to generate thrust, the fluid dynamic device comprising a thrust control shroud disposed about a central axis of said fluid dynamic device for directing a fluid flow between an upstream fluid intake region and a downstream fluid exit region, forming a fluid exit area, of said shroud to generate thrust wherein the degree of flexibility of said shroud is sufficient to enable displacement of said fluid exit region of said shroud with respect to said central axis resulting in a translation of said fluid exit area, the fluid dynamic device further comprising at least a powered fan for generating air flow that enters said fluid intake region of the shroud, is directed by the shroud, and exits the shroud at the fluid exit region, wherein said fluid exit region of said shroud is defined by a plurality of shroud portions and each of said shroud portions is configured such that a translation of said fluid exit region results in a radial displacement of each said shroud portion with respect to said central axis, such displacement being in a predominantly inward or outward direction; and wherein said shroud portions are in the form of flexible, independently movable petals, such that the level of shear stress induced in that part of the shroud disposed parallel to the direction of translation of the shroud is minimized wherein said petals are actuated by an actuation means and said actuation means comprises an actuating ring and a plurality of actuators, at least one actuator allowing control of rotation of said actuating ring about said central axis.