ANALYSIS OF LOW FLYING MISSILES VERSUS VARIOUS SEA STATES

A PROGRAM OF WORK IS PROPOSED LEADING TO THE PREDICTION AND UNDERSTANDING OF THE AERODYNAMICS ACTING ON A MISSILE OR AN AIRPLANE FLYING AT LOW ALTITUDE OVER THE SEA SURFACE. IT APPEARS THAT CLOSE TO THE SEA SURFACE, THE UNSTEADY NATURE OF THE AMBIENT AIR IS OF SUFFICIENTLY HIGH FREQUENCY TO CAUSE LAGS IN THE AERODYNAMIC RESPONSE OF THE MISSILE DUE TO THE GUSTS ACTING ON IT. THIS PHENOMENON CAN ONLY BE REPRESENTED BY AN UNSTEADY AERODYNAMIC ANALYSIS. SPECIFICALLY, THE UNSTEADY AERODYNAMIC EFFECTS INDUCED BY VARIOUS SEA STATES WILL BE INVESTIGATED FOR A VEHICLE FLYING AT SUBSONIC, TRANSONIC, OR SUPERSONIC SPEEDS ABOVE THE SEA WAVES. IN THE PHASE I WORK, THE FLYING VEHICLE WILL BE SIMPLIFIED TO ONE AIRFOIL OR TO TWO AIRFOILS A SHORT DISTANCE APART. A TWO-DIMENSIONAL, UNSTEADY TRANSONIC SMALL DISTURBANCE CODE WILL BE MODIFIED TO INCLUDE THE VEHICLE GUSTS AND WAVY WALL EFFECTS INDUCED BY THE SEA WAVES ON THE AERODYNAMICS OF THE VEHICLE. IT IS ANTICIPATED THAT THE RESULTS OF THE PHASE I WORK WILL INCLUDE THE UNSTEADY AERODYNAMIC FORCES AND MOMENTS (IN THE PITCH PLANE) AND PHASE LAGS FOR VARIOUS COMBINATIONS OF SEA STATES AND MISSILE/VEHICLE VELOCITIES. LEVEL FLIGHT AND PLUNGING VEHICLE MOTION WILL BE CONSIDERED. CONDITIONS FOR WHICH QUASI-STEADY AERODYNAMIC ANALYSIS IS VALID WILL BE DEFINED.