Mechanical & Fluid Systems

Single-Vector Calibration of Wind-Tunnel Force Balances

Improved data quality with an order of magnitude reduction in cost and calibration cycle time over prior methods. An improved method of calibrating a wind-tunnel force balance involves the use of a unique load application system integrated with formal experimental design methodology. The Single-Vector Force Balance Calibration System (SVS) overcomes the productivity and accuracy limitations of prior calibration methods.

Posted in: Briefs, Mechanical Components

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Microgyroscope With Vibrating Post as Rotation Transducer

Unlike in prior vibratory microgyroscopes, there is no cloverleaf structure. The figure depicts a micromachined silicon vibratory gyroscope that senses rotation about its z axis. The rotation-sensitive vibratory element is a post oriented (when at equilibrium) along the z axis and suspended at its base by thin, flexible silicon bands oriented along the x and y axes, respectively. Unlike in the vibratory microgyroscopes described in the immediately preceding article ["Cloverleaf Vibratory Microgyroscope With Integrated Post" (NPO-20688)] and other previous articles in NASA Tech Briefs, the rotation-sensitive vibratory element does not include a cloverleaf-shaped structure that lies (when at equilibrium) in the x-y plane.

Posted in: Briefs, TSP, Mechanical Components

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Cloverleaf Vibratory Microgyroscope With Integrated Post

Modifications should lead to greater unit-to-unit consistency. A modified design and fabrication sequence has been devised to improve the performance of a cloverleaf vibratory microgyroscope that includes an axial rod or post rigidly attached to the center of the cloverleaf structure. The basic concepts of cloverleaf vibratory microgyroscopes, without and with rods or posts, were described in two prior articles in NASA Tech Briefs, Vol. 21, No. 9 (September 1997): "Micromachined Planar Vibratory Microgyroscopes" (NPO-19713), page 68 and "Planar Vibratory Microgyroscope: Alternative Configuration" (NPO-19714), page 70. As described in more detail in the second-mentioned prior article, the cloverleaf-shaped structure and the rod or post are parts of a vibratory element that senses rotation via the effect of the Coriolis force upon its vibrations.

Posted in: Briefs, TSP, Mechanical Components

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Ultrasonic/Sonic Mechanisms for Drilling and Coring

These mechanisms imitate burrowing actions of gophers and crabs. Two apparatuses now under development are intended to perform a variety of deep-drilling, coring, and sensing functions for subsurface exploration of rock and soil. These are modified versions of the apparatuses described in "Ultrasonic/Sonic Drill/Corers With Integrated Sensors" (), NASA Tech Briefs, Vol. 25, No. 1 (January 2001), page 38. In comparison with the drilling equipment traditionally used in such exploration, these apparatuses weigh less and consume less power. Moreover, unlike traditional drills and corers, these apparatuses function without need for large externally applied axial forces.

Posted in: Briefs, TSP, Mechanical Components

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Advances in Thrust-Based Emergency Control of an Airplane

It should be possible to land safely after a primary-flight-control failure. Engineers at NASA's Dryden Flight Research Center have received a patent on an emergency flight-control method implemented by a propulsion-controlled aircraft (PCA) system. Utilizing the pre-existing auto-throttle and engine-pressure-ratio trim controls of the airplane, the PCA system provides pitch and roll control for landing an airplane safely without using aerodynamic control surfaces that have ceased to function because of a primary-flight- control-system failure. The installation of the PCA does not entail any changes in pre-existing engine hardware or software. [Aspects of the method and system at previous stages of development were reported in "Thrust-Control System for Emergency Control of an Airplane" (DRC-96-07), NASA Tech Briefs, Vol. 25, No. 3 (March 2001), page 68 and "Emergency Landing Using Thrust Control and Shift of Weight" (DRC-96-55), NASA Tech Briefs, Vol. 26, No. 5 (May 2002), page 58.]

Posted in: Briefs, TSP, Mechanical Components

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Neutral-Axis Springs for Thin-Wall Integral Boom Hinges

A document proposes the use of neutral-axis springs to augment the unfolding torques of hinges that are integral parts of thin-wall composite-material booms used to deploy scientific instruments from spacecraft. A spring according to the proposal would most likely be made of metal and could be either flat or curved in the manner of a measuring tape. Under the unfolded, straight-boom condition, each spring would lie along the neutral axis of a boom. The spring would be connected to the boom by two supports at fixed locations on the boom. The spring would be fixed to one of the supports and would be free to slide through the other support. The width, thickness, and material of the spring would be chosen to tailor the spring stiffness to provide the desired torque margin to assist in deployment of the boom. The spring would also contribute to the stiffness of the boom against bending and torsion, and could contribute some damping that would help suppress unwanted vibrations caused by the deployment process or by external disturbances.

Posted in: Briefs, TSP, Mechanical Components

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Shields for Enhanced Protection Against High-Speed Debris

A report describes improvements over the conventional Whipple shield (two thin, spaced aluminum walls) for protecting spacecraft against high-speed impacts of orbiting debris. The debris in question arise mainly from breakup of older spacecraft. The improved shields include exterior "bumper" layers composed of hybrid fabrics woven from combinations of ceramic fibers and high-density metallic wires or, alternatively, completely metallic outer layers composed of high-strength steel or copper wires. These shields are designed to be light in weight, yet capable of protecting against orbital debris with mass densities up to about 9 g/cm3, without generating damaging secondary debris particles. As yet another design option, improved shields can include sparsely distributed wires made of shape-memory metals that can be thermally activated from compact storage containers to form shields of predetermined shape upon arrival in orbit. The improved shields could also be used to augment shields installed previously.

Posted in: Briefs, TSP, Mechanical Components

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