Special Coverage

Self-Healing Wire Insulation
Thermomechanical Methodology for Stabilizing Shape Memory Alloy (SMA) Response
Space Optical Communications Using Laser Beams
High Field Superconducting Magnets
Active Response Gravity Offload and Method
Strat-X
Sonar Inspection Robot System
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Measuring Low Concentrations of Liquid Water in Soil

Electrical-impedance measurements serve as sensitive indications of moisture content. An apparatus has been developed for measuring the low concentrations of liquid water and ice in relatively dry soil samples. Designed as a prototype of instruments for measuring the liquid-water and ice contents of Lunar and Martian soils, the apparatus could also be applied similarly to terrestrial desert soils and sands. The high sensitivity of this apparatus is best appreciated via a comparison: Whereas soil moisture contents of agricultural interest range between 3 and 30 weight percent, this apparatus is capable of measuring moisture contents from 0.01 to 10 weight percent (at room temperature). Moreover, it has been estimated that optimization of the design of the apparatus could enable measurement of moisture contents as low as 1 part per million by weight.

Posted in: Briefs, TSP, Physical Sciences

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Compact Microwave Fourier Spectrum Analyzer

Large delays needed for time-domain autocorrelations would be realized photonically. A compact photonic microwave Fourier spectrum analyzer [a Fourier-transform microwave spectrometer, (FTMWS)] with no moving parts has been proposed for use in remote sensing of weak, natural microwave emissions from the surfaces and atmospheres of planets to enable remote analysis and determination of chemical composition and abundances of critical molecular constituents in space.

Posted in: Briefs, TSP, Physical Sciences

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Non-Contact Measurement of Density and Thickness Variation in Dielectric Materials

An improved nondestructive inspection method uses terahertz energy for density and thickness mapping in dielectric, ceramic, and composite materials. This non-contact, single-sided terahertz electromagnetic measurement and imaging method characterizes micro-structural (e.g., spatially-lateral density) and thickness variation in dielectric (insulating) materials. This method was demonstrated for space shuttle external tank sprayed-on foam insulation and has been designed for use as an inspection method for current and future NASA thermal protection systems and other dielectric material inspection applications where no contact can be made with the sample due to fragility and it is impractical to use ultrasonic methods (the latter methods require the sample under test to be immersed in liquid).

Posted in: Briefs, TSP, Physical Sciences

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The Mars Science Laboratory Touchdown Test Facility

In the Touchdown Test Program for the Mars Science Laboratory (MSL) mission, a facility was developed to use a full-scale rover vehicle and an overhead winch system to replicate the Skycrane landing event. A driving requirement for the testing facility was the need to support a load of 5,000 lb (2,268 kg) at a minimum height of 13 m. Few facilities at JPL qualify with enough height, leaving the Building 280 Static Test Tower as the logical choice. However, this facility is popular, so an additional requirement was that the MSL test facility be temporary, and be able to be disassembled in a matter of a week or two, be stored for a period of time, and then be reassembled again quickly for V&V (verification and validation) testing.

Posted in: Briefs, Physical Sciences

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Combinatorial Generation of Test Suites

Testgen is a computer program that generates suites of input and configuration vectors for testing other software or software/hardware systems. As systems become ever more complex, often, there is not enough time to test systems against all possible combinations of inputs and configurations, so test engineers need to be selective in formulating test plans. Testgen helps to satisfy this need: In response to a test-suite-requirement-specification model, it generates a minimal set of test vectors that satisfies all the requirements.

Posted in: Briefs, TSP, Software

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InP Heterojunction Bipolar Transistor Amplifiers to 255 GHz

These amplifiers can be used in millimeter-wave imaging systems for weapons detection and airport security, and for radar instruments. Two single-stage InP heterojunction bipolar transistor (HBT) amplifiers operate at 184 and 255 GHz, using Northrop Grumman Corporation’s InP HBT MMIC (monolithic microwave integrated circuit) technology. At the time of this reporting, these are reported to be the highest HBT amplifiers ever created. The purpose of the amplifier design is to evaluate the technology capability for high-frequency designs and verify the model for future development work.

Posted in: Briefs, Semiconductors & ICs

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Composite Layer Manufacturing With Fewer Interruptions

An improved version of composite layer manufacturing (CLM) has been invented. CLM is a type of solid freeform fabrication (SFF) — an automated process in which a three-dimensional object is built up, point-by-point, through extrusion of a matrix/fiber composite-material precursor. The elements of SFF include (1) preparing a matrix resin in a form in which it will solidify subsequently, (2) mixing fibers and matrix material to form a continuous preimpregnated tow (also called “towpreg”), and (3) dispensing the towpreg from a nozzle onto a base while moving the nozzle to form the dispensed material into a series of patterned layers of controlled thickness.

Posted in: Briefs, Manufacturing & Prototyping

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