Abstract: The invention relates to the propulsion of transport vehicles in air or water, which involves the new use of a nozzle comprising an internal surface, a curved surface merging into the internal surface, a narrowed throat in the internal surface located towards the leading edge of the nozzle, a jacket surrounding the internal surface, an annular internal slot located in the internal surface between the curved surface and the narrowed throat and communicating with the jacket. The fluid under pressure is supplied through the slot the arrangement of the slot being such that the fluid is ejected at an acute angle of under 45.degree. to the direction of the exit flow tangentially to the curved surface.