Special Coverage

Soft Robot “Walks” on Any Terrain
Defense Advanced Research Projects Agency
Using Microwaves to Produce High-Quality Graphene
Transducer-Actuator Systems for On-Machine Measurements and Automatic Part Alignment
Wide-Area Surveillance Using HD LWIR Uncooled Sensors
Heavy Lift Wing in Ground (WIG) Cargo Flying Boat
Technique Provides Security for Multi-Robot Systems
Bringing New Vision to Laser Material Processing Systems
NASA Tests Lasers’ Ability to Transmit Data from Space
Converting from Hydraulic Cylinders to Electric Actuators
Automating Optimization and Design Tasks Across Disciplines

Progress in Acoustic Transmission of Power Through Walls

A document presents updated information on implementation of the wireless acoustic-electric feed-through (WAEF) concept, which was reported in “Using Piezoelectric Devices To Transmit Power Through Walls” (NPO-41157), NASA Tech Briefs, Vol. 32, No. 6 (June 2008), page 70. To recapitulate: In a basic WAEF setup, a transmitting piezoelectric transducer on one side of a wall is driven at resonance to excite ultrasonic vibrations in the wall. A receiving piezoelectric transducer on the opposite side of the wall converts the vibrations back to an ultrasonic AC electric signal, which is then detected and otherwise processed in a manner that depends on the modulation (if any) applied to the signal and whether the signal is used to transmit power, data, or both.

Posted in: Briefs, TSP, Physical Sciences, Acoustics, Vibration, Acoustics, Vibration

Stochastic Analysis of Orbital Lifetimes of Spacecraft

A document discusses (1) a Monte-Carlo-based methodology for probabilistic prediction and analysis of orbital lifetimes of spacecraft and (2) Orbital Lifetime Monte Carlo (OLMC) — a Fortran computer program, consisting of a previously developed long-term orbit-propagator integrated with a Monte Carlo engine.

Posted in: Briefs, TSP, Information Sciences, Finite element analysis, Life cycle analysis, Spacecraft

Lightweight Carbon-Carbon High-Temperature Space Radiator

A document summarizes the development of a carbon-carbon composite radiator for dissipating waste heat from a spacecraft nuclear reactor. The radiator is to be bonded to metal heat pipes and to operate in conjunction with them at a temperature approximately between 500 and 1,000 K. A goal of this development is to reduce the average areal mass density of a radiator to about 2 kg/m2 from the current value of ≈10 kg/m2 characteristic of spacecraft radiators made largely of metals.

Posted in: Briefs, Mechanical Components, Mechanics, Composite materials, Lightweight materials, Radiators, Spacecraft

Transmissive Diffractive Optical Element Solar Concentrators

These would weigh and cost less than do mirror-type solar concentrators.

Solar-thermal-radiation concentrators in the form of transmissive diffractive optical elements (DOEs) have been proposed as alternatives to mirror- type solar concentrators now in use. In comparison with functionally equivalent mirror-type solar concentrators, the transmissive, diffractive solar concentrators would weigh and cost less, and would be subject to relaxed mechanical tolerances.

Posted in: Briefs, TSP, Physical Sciences, Optics, Optics, Solar energy

Nematic Cells for Digital Light Deflection

Smectic A (SmA) prisms can be made in a variety of shapes and are useful for visible spectrum and infrared beam steerage.

Smectic A (SmA) materials can be used in non-mechanical, digital beam deflectors (DBDs) as fillers for passive birefringent prisms based on decoupled pairs of electrically controlled, liquid crystalline polarization rotators, like twisted nematic (TN) cells and passive deflectors. DBDs are used in free-space laser communications, optical fiber communications, optical switches, scanners, and in-situ wavefront correction.

Posted in: Briefs, TSP, Materials, Optics, Optics, Materials properties

Ultra-Stable Beacon Source for Laboratory Testing of Optical Tracking

A prototype laser beacon assembly provides reference for testing tracking and pointing systems.

The ultra-stable beacon source (USBS) provides a laser-beam output with a very low angular jitter and can be used as an absolute angular reference to simulate a beacon in the laboratory. The laser is mounted on the top of a very short (≈1 m) inverted pendulum (IP) with its optical axis parallel to the carbon fiber pendulum leg. The 85-cm, carbon fiber rods making up the leg are very lightweight and rigid, and are supported by a flex-joint at the bottom (see figure). The gimbal-mounted laser is a weight-adjustable load of about 1.5 kg with its center of rotation co-located with the center of percussion of the inverted pendulum. This reduces the coupling of transverse motion at the base of the pendulum to angular motion of the laser at the top.

Posted in: Briefs, TSP, Physical Sciences, Lasers, Lasers, Vibration, Vibration, Mountings, Test equipment and instrumentation

Delaying Trains of Short Light Pulses in WGM Resonators

Delays would not be limited by resonator ring-down times.

Suitably configured whispering-gallery-mode (WGM) optical resonators have been proposed as delay lines for trains of short light pulses. Until now, it has been common practice to implement an optical delay line as a coiled long optical fiber, which is bulky and tends to be noisy. An alternative has been to implement an optical delay line as a coupled-resonator optical waveguide (a chain of coupled optical resonators), which is compact but limits the width of the pulse spectrum to the width of an optical resonance and thereby places a lower limit on the duration of a pulse. In contrast, a delay line according to the proposal could be implemented as a single WGM resonator, and the pulses delayed by the resonator could be so short that their spectral widths could greatly exceed the spectral width of any single resonance.

Posted in: Briefs, Physical Sciences, Fiber optics, Optics, Waveguides, Fiber optics, Optics, Waveguides

Improving the Optical Quality Factor of the WGM Resonator

New iterative annealing and polishing increases the resonator’s finesse over the fundamental limit.

Resonators usually are characterized with two partially dependent values: finesse (ℱ) and quality factor (Q). The finesse of an empty Fabry-Perot (FP) resonator is defined solely by the quality of its mirrors and is calculated as

ℱ = πR1/2/(1 – R).

Posted in: Briefs, Physical Sciences, Mirrors, Optics, Optics

Multiphysics Modeling Simplifies Analysis of Electrical and Electromagnetic Effects

Effects of lightning strikes and electromagnetic fields are simulated and modeled easily.

The Saab Group has 17 business units, which are split into defense and security, systems and products, and aeronautics. Over the years, the company has taken advantage of the many paradigm shifts that have taken place in engineering analysis. One example is implementing comprehensive engineering methodologies that combine traditional experiments and testing with newer tools such as computer modeling and simulation. In the 1980s, Saab began applying largescale computer simulations, which were used to verify the lightning-protection components in the wings of the Gripen fighter aircraft.

Posted in: Briefs, Software, Analysis methodologies, Simulation and modeling

Geophysical Wave Propagation Calculation Using Multiphysics

Geologists can conduct in-field calculations without the need for large computing resources.

The propagation of shear (S) and compression (P) waves within the Earth represents a critically important phenomenon for geologists. For many years, geologists have developed specialized computational programs to calculate wave propagation within complex geophysical regions. These programs have been instrumental in determining the location and characteristics of natural phenomena (e.g., earthquakes) and manmade activity (e.g., nuclear-blast tests).

Posted in: Briefs, Software, Computer software / hardware, Computer software and hardware, Computer software / hardware, Computer software and hardware, Research and development

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