In-flight replanning of penetration routes to avoid threat zones of circular shapes

In-flight replanning of a strike mission requires the capability of generating survivable penetration routes, quickly and efficiently, with limited computer resources on board the aircraft. Although dynamic programming (DP) has been used traditionally for route generation, it requires quantization of the state space into cells of specified dimensions, and places restrictions on the route to traverse the state space from cell center to cell center along one of the prescribed headings. The algorithm developed avoids threat zones of circular shapes, and is ideal for in-flight replanning of penetration routes. The algorithm is much faster than DP, it generates flyable routes that do not require smoothing, and the run time depends strictly on the number of threats to be avoided, rather than on cell size used for state space quantization. The algorithm uses geometric construction to synthesize routes with linear segments tangent to the threat periphery and circular segments along the threat periphery, and obtains the shortest route between a starting point and a destination point, by using the principle of optimality. The algorithm is validated in a high density threat environment with overlapping threat lethality envelopes of varying sizes, and used to generate various penetration routes.