INFLATED parachutes and other high-drag objects often travel along trajectories that are far from being characterized by a constant velocity and constantdrag coeffi cient. 1; 2 During ight or cruise they may undergo unsteady motions such as during a turn maneuver, or during oscillationscaused by accumulated excess air spilling from alternate sides. 3¡ 16 Time-dependent speeds are of course seen duringparachutein ationandalsorightafterin ationwhenthefully in atedcanopythendeceleratestotheterminalvelocityregime. 17¡ 20 This means that, even at constant surface area, these objects may feature a ratio FD. t/= V. t/2 that is not only time dependent but also motion-and trajectory-dependent. In other words, defi ning the drag force of a moving body of constant surface area S through21