SHAPE OPTIMIZATION PRINCIPLES FOR LONG-RANGE UNMANNED VEHICLES

Background. Optimization of unmanned vehicles needs improvement of their shapes in order to reduce aero- or hydrodynamic drag. In particular, long-range vehicles must have high economical efficiency, i.e. large values of the drag-to-weight ratio. This journal had published corresponding ideas and formulae several years before. Nevertheless, high interest in unmanned vehicles needs a brief presentation of basic principles and illustrative examples, which can be available for wide groups of engineers and managers. Objective. The purpose of the paper is to systematize the author’s contribution to the methods of the commercial efficiency improvement, unseparated bodies of revolution and wings of low drag and to discuss areas of applications for the long-rage terrestrial, airborne and water vehicles. Methods. Analytic formulae for the commercial efficiency (obtained before and taking into account the aerodynamic drag on hulls and the drag connected with the support of the vehicle weight) are used for the laminar and turbulent flow patterns. Results. A simple relationship between the speed, volume and the hull length of the optimal vehicle providing the laminar flow and maximum rage was obtained. Froude number ranges for the effective dynamic weight support were determined. Characteristics of optimal wings for corresponding airplanes and gliders were calculated. An example of the optimal underwater vehicle and a perspective boat hull shape are presented. Conclusions. The hull shapes must be similar to the unseparated bodies of revolution, which were proposed before or can be calculated according to particular needs. The proposed relationship between volume and length of a hull, speed of steady motion and kinematic viscosity of air or water has to be used. The elongation and the angle of attack of optimal wings have to be as large as possible. High values of the commercial efficiency open prospects for achievement of long ranges even with the use of electrical engines, 410–850 km for airplanes, 420–750 km fog gliding bombs released at the attitude of 10 km, 800–1200 km for underwater and floating boats, and practically unlimited flight time for airships using solar energy.