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A Reactive-Ion Etch for Patterning Piezoelectric Thin Film

Gaseous mixtures BCl3 and Cl2 are highly selective for etching PbZr1-xTixO3 films. Reactive-ion etching (RIE) under conditions described below has been found to be a suitable means for patterning piezoelectric thin films made from such materials as PbZr1-xTixO3 or BaxSr1-xTiO3. In the original application for which this particular RIE process was developed, PbZr1-xTixO3 films 0.5 μm thick are to be sandwiched between Pt electrode layers 0.1 µm thick and Ir electrode layers 0.1 μm thick to form piezoelectric capacitor structures. Such structures are typical of piezoelectric actuators in advanced microelectromechanical systems now under development or planned to be developed in the near future.

Posted in: Manufacturing & Prototyping, Briefs, TSP

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Numerical Modeling of Nanoelectronic Devices

Nanoelectronic Modeling 3-D (NEMO 3-D) is a computer program for numerical modeling of the electronic structure properties of a semiconductor device that is embodied in a crystal containing as many as 16 million atoms in an arbitrary configuration and that has overall dimensions of the order of tens of nanometers. The underlying mathematical model represents the quantum-mechanical behavior of the device resolved to the atomistic level of granularity. The system of electrons in the device is represented by a sparse Hamiltonian matrix that contains hundreds of millions of terms. NEMO 3-D solves the matrix equation on a Beowulf-class cluster computer, by use of a parallel-processing matrix×vector multiplication algorithm coupled to a Lanczos and/or Rayleigh-Ritz algorithm that solves for eigenvalues. In a recent update of NEMO 3-D, a new strain treatment, parameterized for bulk material properties of GaAs and InAs, was developed for two tight-binding submodels. The utility of the NEMO 3-D was demonstrated in an atomistic analysis of the effects of disorder in alloys and, in particular, in bulk InxGal–xAs and in In0.6Ga0.4As quantum dots.

Posted in: Software, Briefs, TSP

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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: Mechanical Components, Briefs, TSP

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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: Mechanical Components, Briefs, TSP

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Analysis of Designs of Space Laboratories

A report presents a review of the development of laboratories in outer space, starting from the pioneering Skylab and Salyut stations of the United States and the former Soviet Union and progressing through current and anticipated future developments. The report includes textual discussions of space-station designs, illustrated with drawings, photographs, and tables. The approach taken in the review was not to provide a comprehensive catalog of each space laboratory and every design topic that applies to it, but, rather, to illustrate architectural precedents by providing examples that illustrate major design problems and principles to be applied in solving them. Hence, the report deemphasizes information from the most recent space-station literature and concentrates on information from original design reports that show how designs originated and evolved. The most important contribution of the review was the development of a methodology, called "units of analysis," for identifying and analyzing design issues from the perspectives of four broad domains: laboratory science, crew, modes of operations, and the system as a whole.

Posted in: Mechanical Components, Briefs, TSP

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Bio-Inspired Engineering of Exploration Systems

Exploration systems with capabilities imbibed from nature enable new operations that were otherwise very difficult or impossible to accomplish. The multidisciplinary concept of "bioinspired engineering of exploration systems" (BEES) is described, which is a guiding principle of the continuing effort to develop biomorphic explorers as reported in a number of articles in the past issues of NASA Tech Briefs. The intent of BEES is to distill from the principles found in successful nature-tested mechanisms of specific "crucial functions" that are hard to accomplish by conventional methods but that are accomplished rather deftly in nature by biological organisms. The intent is not just to mimic operational mechanisms found in a specific biological organism but to imbibe the salient principles from a variety of diverse bio-organisms for the desired "crucial function." Thereby, we can build explorer systems that have specific capabilities endowed beyond nature, as they will possess a combination of the best nature-tested mechanisms for that particular function. The approach consists of selecting a crucial function, for example, flight or some selected aspects of flight, and develop an explorer that combines the principles of those specific attributes as seen in diverse flying species into one artificial entity. This will allow going beyond biology and achieving unprecedented capability and adaptability needed in encountering and exploring what is as yet unknown. A classification of biomorphic flyers into two main classes of surface and aerial explorers is illustrated in the figure, with examples of a variety of biological organisms that provide the inspiration in each respective subclass.

Posted in: Mechanics, Mechanical Components, Briefs, TSP

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Hybrid Aerial/Rover Vehicle

This robotic vehicle would combine features of balloons and "beach-ball" rovers. A proposed instrumented robotic vehicle called an "aerover" would fly, roll along the ground, and/or float on bodies of liquid, as needed. The aerover would combine features of an aerobot (a robotic lighter-than-air balloon) and a wheeled robot of the "rover" class. An aerover would also look very much like a variant of the "beach-ball" rovers described in "Lightweight 'Beach- Ball' Robotic Vehicles" (NPO-20283), NASA Tech Briefs, Vol. 22, No. 7 (July 1998), page 74. Although the aerover was conceived for use in scientific exploration of Titan (the largest moon of the planet Saturn), the aerover concept could readily be adapted to similar uses on Earth.

Posted in: Mechanical Components, Briefs, TSP

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