Design considerations of wing stabilized free-fall vehicles

Abstract

Analytical design considerations and the measured behavior of a freely-falling, self-rotating oceanographic instrument using hydrodynamic airfoil wings to control vertical fall rate and enhance stability are presented.

Oceanic measurements of a vehicle of payload 30 kg, wing length 2 m, wing chord 0.16 m, and overmass of 5 kg (in seawater) show tilts from the vertical of order 2 × 10⁻³ radians and a fall velocity of 0.114 m s⁻¹ ±0.5%. The rotation rate is 21.8 s and perceptibly constant. Vertical velocity gradients measured on one drop are compared with vertical and horizontal accelerometer records, documenting the tilt and fall rate constancy. The fall rate and rotation rate compare well with the analytically derived formula.