Abstract: A material whose permeability to a fluid, such as a gas, is to be measured, forms at least part of the wall of a chamber which is otherwise impervious to the fluid, and the fluid is located within the chamber at a reference pressure level. In one embodiment, after a given interval of time, sufficient fluid is returned to the chamber to restore the pressure to its reference level. The volume of fluid required is a measure of the permeability of the material.

Abstract: A tethered aeroform balloon having an inflated toroid tail structure secured to the balloon hull by means of a plurality of rope lines for supporting the drag forces and the weight and steering forces of the tail structure. The inflated tail structure has a substantially symmetrical air foil section with support diaphragms secured inside the tail structure. The tail structure is inflated by an electric motor powered fan supported on the tail structure. A pressure switch prevents over inflation of the tail structure. A check valve prevents the escape of air from the tail structure when the fan is not running.

Abstract: A process for non-destructive inspection of a fusion bonded laminated article comprises disposing a pattern of material on a fusible adhesive layer disposed between two layers of the article. The layers and adhesive are fused together wherein the fusing causes a distortion in the pattern. The article is examined for the presence of the distortion which presence manifests an acceptable bonded joint.