Mechanical & Fluid Systems

Flight Tests of a Ministick Controller in an F/A-18 Airplane

Pilots' opinions were generally favorable. In March of 1999, five pilots performed flight tests to evaluate the handling qualities of an F/A-18 research airplane equipped with a small-displacement center stick (ministick) controller that had been developed for the JAS 39 Gripen airplane (a fighter/attack/ reconnaissance airplane used by the Swedish air force). For these tests, the ministick was installed in the aft cockpit (see figure) and production support flight control computers (PSFCCs) were used as interfaces between the controller hardware and the standard F/A-18 flight-control laws.

Posted in: Briefs, Mechanical Components, Mechanics, Architecture, Flight control systems, Human machine interface (HMI), Flight tests, Fixed-wing aircraft


Mirrors Containing Biomimetic Shape-Control Actuators

Local bending would be controlled to obtain desired surface figures. Curved mirrors of a proposed type would comprise lightweight sheets or films containing integral, biologically inspired actuators for controlling their surface figures. These mirrors could be useful in such applications as collection of solar energy, focusing of radio beams, and (provided sufficient precision could be achieved) imaging. These mirrors were originally intended for use in outer space, but it should also be possible to develop terrestrial versions.

Posted in: Briefs, TSP, Mechanical Components, Mechanics, Mirrors, Sensors and actuators, Biomechanics


Folded Resonant Horns for Power Ultrasonic Applications

Ultrasonic actuators can be made shorter.    Figure 1. Three Similar Power Ultrasonic Actuators are depicted partly in cross sections to illustrate a progression of designs from a straight stepped horn to a folded inverted stepped horn. Folded horns have been conceived as alternatives to straight horns used as resonators and strain amplifiers in power ultrasonic systems. Such systems are used for cleaning, welding, soldering, cutting, and drilling in a variety of industries. In addition, several previous NASA Tech Briefs articles have described instrumented drilling, coring, and burrowing machines that utilize combinations of sonic and ultrasonic vibrational actuation. The main advantage of a folded horn, relative to a straight horn of the same resonance frequency, is that the folded horn can be made shorter (that is, its greatest linear dimension measured from the outside can be made smaller). Alternatively, for a given length, the resonance frequency can be reduced. Hence, the folded-horn concept affords an additional degree of design freedom for reducing the length of an ultrasonic power system that includes a horn.

Posted in: Briefs, TSP, Mechanical Components, Mechanics, Downsizing, Amplifiers, Tools and equipment, Product development, Drilling, Industrial vehicles and equipment


Rollable Thin Shell Composite-Material Paraboloidal Mirrors

These lightweight focusing mirrors can be stored in fairly narrow cylinders. An experiment and calculation have demonstrated the feasibility of a technique of compact storage of paraboloidal mirrors made of thin composite-material (multiple layers of carbon fiber mats in a polymeric matrix) shells coated with metal for reflectivity. Such mirrors are under consideration as simple, lightweight alternatives to the heavier, more complex mirrors now used in space telescopes. They could also be used on Earth in applications in which gravitational sag of the thin shells can be tolerated.

Posted in: Briefs, TSP, Mechanical Components, Mechanics, Mirrors, Imaging and visualization, Composite materials, Lightweight materials, Materials properties


Cellular Pressure-Actuated Joint

Pockets in one of the sealing members would help maintain differential pressure. A modification of a pressure-actuated joint has been proposed to improve its pressure actuation in such a manner as to reduce the potential for leakage of the pressurizing fluid. The specific joint for which the modification is proposed is a field joint in a reusable solid-fuel rocket motor (RSRM), in which the pressurizing fluid is a mixture of hot combustion gases. The proposed modification could also be applicable to other pressure- actuated joints of similar configuration.

Posted in: Briefs, TSP, Mechanical Components, Mechanics, Sensors and actuators, Joining, Pneumatic systems, Rocket engines


Force-Measuring Clamps

Clamping forces can be measured easily and quickly. Force-measuring clamps have been invented to facilitate and simplify the task of measuring the forces or pressures applied to clamped parts. There is a critical need to measure clamping forces or pressures in some applications — for example, while bonding sensors to substrates or while clamping any sensitive or delicate parts. Many manufacturers of adhesives and sensors recommend clamping at specific pressures while bonding sensors or during adhesive bonding between parts in general.

Posted in: Briefs, Mechanical Components, Mechanics, Sensors and actuators, Joining, Adhesives and sealants, Test equipment and instrumentation


Multiple-Use Mechanisms for Attachment to Seat Tracks

These could serve as standard or universal seat-track clamps. A Seat Track Attach Mechanism (SAM) is a multiple-use clamping device intended for use in mounting various objects on the standard seat tracks used on the International Space Station (ISS). The basic SAM design could also be adapted to other settings in which seat tracks are available: for example, SAM-like devices could be used as universal aircraft- seat-track mounting clamps.

Posted in: Briefs, Mechanical Components, Mechanics, Seats and seating, Mountings, Spacecraft


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