Mechanical & Fluid Systems

Apparatus for Friction Stir Welding of Pipes

FSW heads would move circum- ferentially and pipes would be supported against FSW loads. A proposed apparatus would effect friction stir welding (FSW) along a circumferential path to join two pipes. The apparatus is denoted an “orbital FSW system” because the circum- ferential motion of the FSW head would be similar to the motions of welding heads in commercial orbital fusion welding systems.

Posted in: Mechanics, Briefs

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Mechanisms for Reliable One-Time Deployment of Panels

These mechanisms overcome the disadvantages of both pyrotechnic and thermal release mechanisms. Mechanisms denoted restraint/ release/deployment-initiation (RRDI) devices have been invented to enable the rapid, reliable, one-time deployment of panels that have been hinged together and stowed compactly by folding them together at the hinges. Although the RRDI devices were originally intended for use in deploying the solar photovoltaic panels that generate electric power for a spacecraft, they are also suitable for deploying other, similarly hinged panel arrays (including solar photovoltaic panels) in terrestrial applications. The RRDI devices overcome the disadvantages (shock and the consequent potential for damage) of explosive release devices as well as the disadvantages (slowness and high power demand) of electrically actuated thermal release devices.

Posted in: Mechanics, Briefs, TSP

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Hexfoil Rotary Flexures

These devices would afford high accuracy of centration. Hexfoil rotary flexures have been proposed as pivots suitable for use in precise optical instruments. In the application that inspired the hexfoil concept, there is a requirement for a limited-rotation mirror gimbal that would maintain, with unprecedented accuracy, coincidence among the axes of rotation and a fiducial mark on the mirror, over the entire range of rotation. Theoretically, a hexfoil rotary flexure could satisfy this requirement.

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Improvements in the Use of Water Washes in Testing for NVR

Effectiveness of washing and sensitivity of detection are increased. Some improvements have been made to enhance the role of water as a test solvent for determining the amount of hydrocarbon nonvolatile residue (NVR) present on an item of hardware that is required to be totally or nearly devoid of such residue. Water is now used as an NVR-testing solvent because (1) even highmolecular- weight hydrocarbon greases are at least slightly soluble in water, (2) water is safer and less expensive than are chlorofluorocarbon solvents [in particular, 1,1,2- trichloro-1,2,2-trifluoroethane (also known as CFC-113), which was used previously in testing for hydrocarbon NVR], and (3) CFC solvents are expensive and are now recognized as environmentally harmful.

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Improved Flange Design for Cryogenic Vacuum O-Ring Seals

Spring-loaded joints could be made less bulky. A compact spring-loading design has been proposed to increase the reliability of seals in the joints of vacuum cryogenic systems. Heretofore, such joints have been, variously, compact or reliable, but not both, for the following reasons: In all such joints, sealing is effected by compression of soft metal (typically, indium or alloys of indium) O rings between flanges. Over time, the soft O-ring metal flows, with consequent reduction of preload, sometimes leading to loss of seal. To ensure reliable seals, it is necessary to spring-load the flanges to maintain compression of the O rings. However, spring-loaded joints of traditional design are not compact.

Posted in: Mechanics, Briefs, TSP

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Crowned Races for Crossed Roller Bearings

Scuffing would be reduced. Crowned races have been proposed for crossed roller bearings. Crowning of the races   is expected to reduce scuffing of the cylindrical rollers. Crowning of the races is expected to be especially beneficial in bearings made of polymers (instead of metals) to reduce weight.

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Flight Research on Supersonic Laminar Flow

Flow over a suitably designed airfoil can remain largely laminar, even at supersonic speed. Some airfoil designs have been shown by theory and small-scale tests to be capable of passively maintaining laminar flow at super -sonic speeds. More recently, flight tests have proven that these designs can maintain large runs of laminar flow at higher Reynolds numbers in harsh flight environments. The flight tests were conducted for the purposes of observing laminar flow at speeds up to mach 2.0 and determining the conditions under which laminar flow breaks down.

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