Abstract: A low-cost fiber-optic sensor system for composite pressure tanks detects structural degradation of composite material pressure tanks. Light power attenuation in embedded optical fiber simulates tank volume change and replaces hydrostatic tank testing. Current U.S. Department of Transportation rules require that all pressure tanks be hydrostatically tested to verify structural integrity. Tanks do not have to be removed from service for testing. With the invention, testing can be done in-situ. For composite LNG tanks used on vehicles or emergency inflation devices used on aircraft for escape ramps, in-situ testing offers substantial maintenance cost savings. because of the simplicity of the test procedure, more frequent structural checks can be made economically to improve the safe operation of composite tanks.

Abstract: The highly-stiffened, dual-axle antenna tracking pedestal improves tracking performance, reduces manufacturing and installation costs and increases safety during field assembly, maintenance and operation of the pedestal. The reinforced concrete counterweights affect the natural frequency of the pedestal system and reduce vibrational effects from wind loads during antenna slew. Reduction of the number of structural components and pouring concrete counterweights at the job site simplifies fabrication, as well as reducing shipping and handling costs. The use of a dual-axle mount provides antenna slewing without problems associated with conventional azimuth-elevation pedestal systems. The pedestal mount has a structure and drive system that is simple and inexpensive. The drive system has two orthogonal rotational axes, one oriented east-west and the other north-south. The two rotational degree-of-freedom arrangement allows smooth tracking over the entire sky.

Abstract: A structure for a pressure and buckling resisting hull has an undulated shell body with flat, plural, polyhedral faces, shell caps at the ends, and transition sections attaching the shell caps to the shell body. The shell body polyhedral faces may be generally triangular or generally trapezoidal and are truncated triangular in shape for reducing material stress and for increasing buckling resistance. The top-to-base length ratios of the truncated triangular shapes are selected to optimize structural performance so that differences between maximum stress-depth and buckling-depth curves are minimized. Transition sections are conoidal in shape or are formed by portions having alternating flat triangular faces with curved triangular faces. Buckling strength and material stress are reduced or increased by using transition sections which are longer or shorter than the polyhedral faces in the shell body.

Abstract: A collapsible chair has a sheet of flexible mesh material supported by four arms extending in a tetrahedral pattern from a self-locking, gravity-operated base joint. The outward ends of the front arms are angled upwardly. U-shaped stabilizing legs pivot outwardly from the front arms to a forwardly extended position. The support arms are received in pockets in the flexible sheet to permit detachment thereof. The arms are pivotally connected to the base joint to permit them to be folded parallel to each other. The hollow rectangular lower ends of the arms telescopically receive similiarly shaped guide arms on the base joint to permit axial movement between an upward position in which the arms are freely pivotable and a downward position in which the arms are automatically locked in the tetrahedral position.

Abstract: A structure is disclosed for resisting pressure, such as external and internal hydrostatic pressure loading. A plurality of flat polyhedral plates are sealed together along their edges to provide an undulated cylindrical shell. An inner cylinder (and end enclosures for transferring axial loading from the outer shell to the inner cylinder) provides axial restraint. A dome over the inner cylinder may form a part of the end structure of the shell. Inner beams, rods and stiffened plates may also be employed for additional radial restraint.