Mechanical & Fluid Systems

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: Briefs, TSP, Mechanical Components, Mechanics

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Algorithm Computes Kinematics of a Rover on Rocky Terrain

This algorithm is efficient enough for use in a real-time simulation. The Rover Analysis Modeling and Simulation (ROAMS) algorithm is to solve the kinematics of a wheeled mo- bile robot (rover) traversing on a rocky terrain. The rover is constructed using a “rocker-bogey-differential” type suspension and steering system as shown in the figure. By exploring the mechanical symmetry and the wheeled-terrain contact characteristics on a rough terrain profile, we developed a novel algorithm to carry out the rover’s configuration, including the vehicle’s wheels, steering and suspension linkages, and the position and orientation of the chassis. Because of its efficient and reliable numerical results, the ROAMS algorithm is well suited for the real-time simulation test bed, e.g., a simulation software system, of the mobile robotic vehicles in the planetary surface exploration missions. Currently, it is used to support the development of simulation and operation tools for the Mars Exploration Rover (MER) in the Mars ‘03 mission.

Posted in: Briefs, TSP, Mechanical Components, Mechanics

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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.

Posted in: Briefs, TSP, Mechanical Components, Mechanics

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Pressure-Balanced, Low-Hysteresis Finger Seal

Pressure balance would be altered to reduce a hysteretic variation of leakage. A second-generation design for a finger seal has been proposed to reduce a hysteretic effect that gives rise to increased leakage in a first-generation finger seal. As explained below, the second-generation design provides for balancing of pressure drops along the flow paths within the seal in such a way as to reduce a friction force believed to cause the hysteresis.

Posted in: Briefs, TSP, Mechanical Components, Mechanics

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Instrument for Measuring Extreme Winds

This rugged instrument has no moving parts. An instrument is undergoing development for use in measuring both the horizontal direction and the horizontal speed of wind in the speed range from 60 to 300 mph (about 27 to 134 m/s) at a rate of at least 50 samples per second. The speed range of this instrument greatly exceeds that of conventional anemometers, encompassing speeds observed in hurricanes and tornadoes. Unlike conventional anemometers, this instrument has a small exposure profile and contains no rotating mechanisms and, hence, is more rugged.

Posted in: Briefs, TSP, Mechanical Components, Mechanics

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Mechanized Harvesting of Plants in a Controlled Environment

The proposed Plant Harvesting Mechanization System (PHARMS) would comprise machinery and controls for semiautomated harvesting of plants grown in a controlled environment. The PHARMS was conceived as a prototype of harvesters to be incorporated into life-support systems of spacecraft and remote planetary bases, wherein plants would provide food and contribute to recycling of air and water. On Earth, PHARMS-like systems could reduce the labor of harvesting plants from protected agricultural systems in which special fruits and vegetables, herbs, ornamental plants, and mushrooms are grown. At harvest time, the PHARMS would be moved from storage to a location near the plantgrowth chamber. There, it would be unfolded from a compact configuration, then prepared for operation by setting of control parameters and mechanical alignment with the chamber and plants. In operation, the PHARMS would pull plant trays out of the chamber and remove plants from the trays. Then it would subject the plants to a variety of other processes, depending on the crop: Examples of such processes include drying, cutting, chopping, stripping of seeds from stalks, threshing, separation of roots from stalks or vines, breaking pods to extract seeds, and pneumatic separation of seeds from chaff.

Posted in: Briefs, Mechanical Components, Mechanics

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Emergency Landing Using Thrust Control and Shift of Weight

Landing with control surfaces and engines on one side inoperative may be possible. Normally, the damage that results in a total loss of the primary flight control of a transport airplane, including all the engines on one side, would be catastrophic. Dryden Flight Research Center has conceived of a method of responding to a total loss of hydraulic pressure and failure of engines on one side: An emergency controller would utilize the engines that are still working on the other side, along with transfers of fuel among tanks to effect lateral shift of the center of gravity (CG), in order to steer the airplane to an emergency landing.

Posted in: Briefs, Mechanical Components, Mechanics

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