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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 307 records · Page 17
All sourcesNASA NTRSDOE OSTI
NASA NTRS2000

Fluid flow releases fibroblast growth factor-2 from human aortic smooth muscle cells

This study tested the hypothesis that fluid shear stress regulates the release of fibroblast growth factor (FGF)-2 from human aortic smooth muscle cells. FGF-2 is a potent mitogen that is involved in the response to vascular injury and is expressed in a wide variety of cell types. FGF-2 is found in the cytoplasm of cells and outside cells, where it associates with extracellular proteoglycans. To test the hypothesis that shear stress regulates FGF-2 release, cells were exposed to flow, and FGF-2 amounts were measured from the conditioned medium, pericellular fraction (extracted by heparin treatment), and cell lysate. Results from the present study show that after 15 minutes of shear stress at 25 dyne/cm(2) in a parallel-plate flow system, a small but significant fraction (17%) of the total FGF-2 was released from human aortic smooth muscle cells. FGF-2 levels in the circulating medium increased 10-fold over medium from static controls (P<0.01). A 50% increase in FGF-2 content versus control (P<0.01) was found in the pericellular fraction (extracted by heparin treatment). Furthermore, a significant decrease in FGF-2 was detected in the cell lysate, indicating that FGF-2 was released from inside the cell. Cell permeability studies with fluorescent dextran were performed to examine whether transient membrane disruption caused FGF-2 release. Flow cytometry detected a 50% increase in mean fluorescence of cells exposed to 25 dyne/cm(2) versus control cells. This indicates that the observed FGF-2 release from human aortic smooth muscle cells is likely due to transient membrane disruption on initiation of flow.

Non-NASA Center↗
NASA NTRS1997

High-Temperature Superconducting/Ferroelectric Structures for Tunable Microwave Components

At the NASA Lewis Research Center, ferroelectric films, such as SrTiO3 and Ba(x)Sr(1-x)TiO3, are being used in conjunction with YBa2Cu3O(7-delta) high-temperature superconducting (HTS) thin films to fabricate tunable microwave components, such as filters, varactors, and local oscillators. These structures capitalize on the variation of the dielectric constant of the ferroelectric film upon the application of a dc electric field as well as on the low microwave losses exhibited by the high-temperature superconducting films relative to their conventional conductor counterparts. (For example, the surface resistance for a YBa2Cu3O(7-delta) thin film at 10 GHz and 77 K is more than two orders of magnitude lower than that of copper at the same frequency and temperature.) SrTiO3 and Ba(x)Sr(1-x)TiO3 films are used because their crystal structure and lattice parameters are similar to those of YBa2Cu3O(7-delta), thus enabling the growth of highly textured YBa2Cu3O(7-delta) films with high critical current densities on the underlying ferroelectric film, or alternatively, of highly textured ferroelectric film on the underlying YBa2Cu3O(7-delta) film. Our efforts have been concentrated so far in determining the deposition parameters required for optimal ferroelectric thin-film growth (i.e., maximum tunability and lowest loss) and in investigating different varactor configurations to determine which geometry is the most advantageous in terms of tunability, losses, and required bias for a given communication application. For example, we have observed that for optimized SrTiO3 films in a parallel plate capacitor, tunabilities of up to 47 percent and dissipation losses (tan d) of 0.05 are attainable at 1 MHz , 80 K, and within the 0- to 5-V bias range. In contrast, for an interdigital configuration, tunabilities of up to 70 percent and tan d ranging from 0.015 to 0.001 (depending on bias) have been observed at 1 MHz and 77 K within the 0- to 100-V bias range. Efforts are underway to use these results in developing tunable receiver front-end preselect filters as well as in low-phase noise, tunable local oscillators for K-band applications. These components represent a hitherto unavailable technology to meet the stringent performance requirements of foreseeable satellite and wireless communication systems (e.g., bandwidth, in-band insertion losses, out-of-band rejection, and noise, amongst others) in a more advantageous fashion than with currently available technology (e.g., dielectric-filled cavity and waveguide filters, and dielectric resonator oscillators). Prototypes of high-temperature superconducting/ferroelectric tunable components such as a low-phase noise K-band local oscillator, a preselect C-band filter, and a low-loss K-band phase shifter are under development at NASA Lewis.

Miranda, Felix A.↗
NASA NTRS2003

Numerical Studies of Properties of Confined Helium

We carry out state of the art simulations of properties of confined liquid helium near the superfluid transition to a degree of accuracy which allows to make predictions for the outcome of fundamental physics experiments in microgravity. First we report our results for the finite-size scaling behavior of heat capacity of superfluids for cubic and parallel-plate geometry. This allows us to study the crossover from zero and two dimensions to three dimensions. Our calculated scaling functions are in good agreement with recently measured specific heat scaling functions for the above mentioned geometries. We also present our results of a quantum simulation of submonolayer of molecular hydrogen deposited on an ideal graphite substrate using path-integral quantum Monte Carlo simulation. We find that the monolayer phase diagram is rich and very similar to that of helium monolayer. We are able to uncover the main features of the complex monolayer phase diagram, such as the commensurate solid phases and the commensurate to incommensurate transition, in agreement with the experiments and to find some features which are missing from the experimental analysis.

Manousakis, Efstratios↗
NASA NTRS1999

Finite Ground Coplanar (FGC) Waveguide: Characteristics and Advantages Evaluated for Radiofrequency and Wireless Communication Circuits

Researchers in NASA Lewis Research Center s Electron Device Technology Branch are developing transmission lines for radiofrequency and wireless circuits that are more efficient, smaller, and make lower cost circuits possible. Traditionally, radiofrequency and wireless circuits have employed a microstrip or coplanar waveguide to interconnect the various electrical elements that comprise a circuit. Although a coplanar waveguide (CPW) is widely viewed as better than a microstrip for most applications, it too has problems. To solve these problems, NASA Lewis and the University of Michigan developed a new version of a coplanar waveguide with electrically narrow ground planes. Through extensive numerical modeling and experimental measurements, we have characterized the propagation constant of the FGC waveguide, the lumped and distributed circuit elements integrated in the FGC waveguide, and the coupling between parallel transmission lines. Although the attenuation per unit length is higher for the FGC waveguide because of higher conductor loss, the attenuation is comparable when the ground plane width is twice the center conductor width as shown in the following graph. An upper limit to the line width is derived from observations that when the total line width is greater than ld/2, spurious resonances due to the parallel plate waveguide mode are established. Thus, the ground plane width must be less than ld/4 where ld is the wavelength in the dielectric. Since the center conductor width S is typically less than l/10 to maintain good transverse electromagnetic mode characteristics, it follows that a ground plane width of B = 2S would also be electrically narrow. Thus, we can now treat the ground strips of the FGC waveguide the same way that the center conductor is treated.

Ponchak, George E.↗
NASA NTRS1999

Atomic Oxygen Lamp Cleaning Facility Fabricated and Tested

NASA Lewis Research Center's Atomic Oxygen Lamp Cleaning Facility was designed to produce an atomic oxygen plasma within a metal halide lamp to remove carbon-based contamination. It is believed that these contaminants contribute to the high failure rate realized during the production of these lamps. The facility is designed to evacuate a metal halide lamp and produce a radio frequency generated atomic oxygen plasma within it. Oxygen gas, with a purity of 0.9999 percent and in the pressure range of 150 to 250 mtorr, is used in the lamp for plasma generation while the lamp is being cleaned. After cleaning is complete, the lamp can be backfilled with 0.9999-percent pure nitrogen and torch sealed. The facility comprises various vacuum components connected to a radiation-shielded box that encloses the bulb during operation. Radiofrequency power is applied to the two parallel plates of a capacitor, which are on either side of the lamp. The vacuum pump used, a Leybold Trivac Type D4B, has a pumping speed of 4-m3/hr, has an ultimate pressure of <8x10-4, and is specially adapted for pure oxygen service. The electronic power supply, matching network, and controller (500-W, 13.56-MHz) used to supply the radiofrequency power were purchased from RF Power Products Inc. Initial test results revealed that this facility could remove the carbon-based contamination from within bulbs.

Sechkar, Edward A.↗
NASA NTRS2000

Radio Frequency (RF) Micro-Electromechanical Systems (MEMS) Switches for Space Communications

Micro-electromechanical systems (MEMS) is an emerging technology for radio frequency (RF) systems because it has the potential to dramatically decrease loss and improve efficiency. In this paper, we address the design and fabrication of novel MEMS switches being developed at NASA Glenn Research Center. Two types of switches are being developed: a microstrip series single pole single throw (SPST) switch and a coplanar waveguide (CPW) series SPST and single pole double throw (SPDT) switches. These are being fabricated as an integral part of 50 Ohm microstrip and CPW RF integrated circuits using microfabrication techniques. The construction of the switch relies on a cantilever beam that is partially supported by a dielectric post. The cantilever beam is electro-magnetically actuated. To decrease stiction, a Si3N4 thin film is deposited over the contact area. Thus, when the switch is closed, the ON-state insertion loss is governed by the parallel plate capacitance formed by the two contacts. The isolation in the OFF-state is governed by the parasitic capacitance when the cantilever is in the up position. RF MEMS switches have been demonstrated with 80% lower insertion loss than conventional solid state devices (GaAs Metal Semiconductor Field Effect Transistors (MESFETs) and Silicon PIN diodes) based switches. For example, a conventional GaAs five-bit phase shifter which is required for beam steering in a phased array antenna has approximately 7 dB of insertion loss at 26.5 GHz where as a comparable MEMS based phase shifter is expected to have only 2 dB of insertion loss. This translates into 56% lower power dissipation and therefore decreases the thermal load on the spacecraft and also reduces the power amplifier requirements. These benefits will enable NASA to build the next generation of deep space science crafts and micro/nano satellites.

Simons, Rainee N.↗
NASA NTRS2005

Spectrometer Technology Development for Far-Infrared Line Surveys

The objective of this proposal was to build and demonstrate a new direct-detection diffraction grating concept and couple it to an array of bolometers. The spectrometer was to be built around a parallel-plate waveguide diffraction grating, WaFIRS: Waveguide Far-InfraRed Spectrometer. The grating is two dimensional in nature, which provides a compact configuration to suit NASA s needs for cryogenic spectrometers for future opportunities, such as infrared/submillimeter spectrometers for a suborbital balloon platform, for SOFIA, for SPICA (a Japanese satellite), and for SAFIR. Our goal was to build a spectrometer (Z-Spec) for 1.0 - 1.5 mm and demonstrate spectral resolution, throughput, and background-limited performance. This grant would partially cover the expenses and we were subsequently awarded a second grant, NAGS-12788, to complete the project. We have one-year received a no-cost extension on NAG.5-12788, to be completed in 3/31/06.

Glenn, Jason↗
NASA NTRS2005

A Ka-Band Wide-Bandgap Solid-State Power Amplifier: Architecture Performance Estimates

Motivated by recent advances in wide-bandgap (WBG) gallium nitride (GaN) semiconductor technology, there is considerable interest in developing efficient solidstate power amplifiers (SSPAs) as an alternative to the traveling-wave tube amplifier (TWTA) for space applications. This article documents the results of a study to investigate power-combining technology and SSPA architectures that can enable a 120-W, 40 percent power-added efficiency (PAE) SSPA. Results of the study indicate that architectures based on at least three power combiner designs are likely to enable the target SSPA. The proposed architectures can power combine 16 to 32 individual monolithic microwave integrated circuits (MMICs) with >80 percent combining efficiency. This corresponds to MMIC requirements of 5- to 10-W output power and >48 percent PAE. For the three proposed architectures [1], detailed analysis and design of the power combiner are presented. The first architecture studied is based on a 16-way septum combiner that offers low loss and high isolation over the design band of 31 to 36 GHz. Analysis of a 2-way prototype septum combiner had an input match >25 dB, output match >30 dB, insertion loss <0.02 dB, and isolation >30 dB over the design band. A 16-way design, based on cascading this combiner in a binary fashion, is documented. The second architecture is based on a 24-way waveguide radial combiner. A prototype 24-way radial base was analyzed to have an input match >30 dB (under equal excitation of all input ports). The match of the mode transducer that forms the output of a radial combiner was found to be >27 dB. The functional bandwidth of the radial base and mode transducer, which together will form a radial combiner/divider, exceeded the design band. The third architecture employs a 32-way, parallel-plate radial combiner. Simulation results indicated an input match >24 dB, output match >22 dB, insertion loss <0.23 dB, and adjacent port isolation >20 dB over the design band. All three architectures utilize a low-loss MMIC amplifier module based on commercial MMIC packaging and a custom microstrip-to-rectangular-waveguide transition. The insertion loss of the module is expected to be 0.45 dB over the design band.

Epp, L.↗
NASA NTRS2007

A Microfabricated Segmented-Involute-Foil Regenerator for Enhancing Reliability and Performance of Stirling Engines

An actual-size microfabricated regenerator comprised of a stack of 42 disks, 19 mm diameter and 0.25 mm thick, with layers of microscopic, segmented, involute-shaped flow channels was fabricated and tested. The geometry resembles layers of uniformly-spaced segmented-parallel-plates, except the plates are curved. Each disk was made from electro-plated nickel using the LiGA process. This regenerator had feature sizes close to those required for an actual Stirling engine but the overall regenerator dimensions were sized for the NASA/Sunpower oscillating-flow regenerator test rig. Testing in the oscillating-flow test rig showed the regenerator performed extremely well, significantly better than currently used random-fiber material, producing the highest figures of merit ever recorded for any regenerator tested in that rig over its approximately 20 years of use.

Ibrahim, Mounir↗
NASA NTRS2008

Simulation of a Miniature, Low-Power Time-of-Flight Mass Spectrometer for In Situ Analysis of Planetary Atmospheres

We are implementing nano- and micro-technologies to develop a miniaturized electron impact ionization mass spectrometer for planetary science. Microfabrication technology is used to fabricate the ion and electron optics, and a carbon nanotube (CNT) cathode is used to generate the ionizing electron beam. Future NASA planetary science missions demand miniaturized, low power mass spectrometers that exhibit high resolution and sensitivity to search for evidence of past and present habitability on the surface and in the atmosphere of priority targets such as Mars, Titan, Enceladus, Venus, Europa, and short-period comets. Toward this objective, we are developing a miniature, high resolution reflectron time-of-flight mass spectrometer (Mini TOF-MS) that features a low-power CNT field emission electron impact ionization source and microfabricated ion optics and reflectron mass analyzer in a parallel-plate geometry that is scalable. Charged particle electrodynamic modeling (SIMION 8.0.4) is employed to guide the iterative design of electron and ion optic components and to characterize the overall performance of the Mini TOF-MS device via simulation. Miniature (less than 1000 cubic centimeters) TOF-MS designs (ion source, mass analyzer, detector only) demonstrate simulated mass resolutions greater than 600 at sensitivity levels on the order of 10(exp -3) cps/molecule N2/cc while consuming 1.3 W of power and are comparable to current spaceflight mass spectrometers. Higher performance designs have also been simulated and indicate mass resolutions approximately 1000, though at the expense of sensitivity and instrument volume.

King, Todd T.↗
NASA NTRS2007

Wirelessly Interrogated Position or Displacement Sensors

Two simple position or displacement sensors based on inductance-capacitance resonant circuits have been conceived. These sensors are both powered and interrogated without use of wires and without making contact with other objects. Instead, excitation and interrogation are accomplished by means of a magnetic-field-response recorder. Both of the present position or displacement sensors consist essentially of variable rectangular parallel-plate capacitors electrically connected in series with fixed inductors. Simple inductance-capacitance circuits of the type used in these sensors are inherently robust; their basic mode of operation does not depend on maintenance of specific environmental conditions. Hence, these sensors can be used under such harsh conditions as cryogenic temperatures, high pressures, and radioactivity.

Woodard, Stanley E.↗
NASA NTRS2006

Nearly Direct Measurement of Relative Permittivity

A recently conceived technique for determining the relative permittivity of a material sample at a given frequency is more nearly direct than are prior techniques that involve measurement of such related non-electrical quantities as the size, shape, and/or weight of the specimen. The present technique involves only measurement of two voltages at the frequency in question, followed by calculation of the ratio between the voltages. The technique requires two circuits a test circuit and a reference circuit that are identical except as described below. Each circuit includes a capacitor C1 connected in series with a much larger capacitor C2 to form a voltage divider (see figure). C1 is a parallel-plate capacitor. The top electrode of C1 is connected to an AC signal source of voltage Va at the frequency of interest. The top electrode of C1 is surrounded by a guard electrode that, in turn, is surrounded by a grounded electrode. The bottom electrode of C1 is connected to the top electrode of C2. The bottom electrode of C2 is grounded. The volume enclosed by the top, bottom, and guard electrodes of C1 constitutes a sample cell. A material sample, having relative permittivity k at the frequency of interest, is placed in the sample cell. The exact shape and size of the sample volume is not critical and can be chosen to fit the material sample. What is critical is that (a) C2 in both circuits be identical and (b) the sample cell in the test circuit have the same size and shape as that in the reference circuit, so that the capacitances of the two sample cells are proportional to the permittivities of their contents.

Calle, Carlos I.↗
NASA NTRS2010

Fabrication of an Absorber-Coupled MKID Detector and Readout for Sub-Millimeter and Far-Infrared Astronomy

We have fabricated absorber-coupled microwave kinetic inductance detector (MKID) arrays for sub-millimeter and far-infrared astronomy. Each detector array is comprised of lambda/2 stepped impedance resonators, a 1.5 micrometer thick silicon membrane, and 380 micrometer thick silicon walls. The resonators consist of parallel plate aluminum transmission lines coupled to low impedance Nb microstrip traces of variable length, which set the resonant frequency of each resonator. This allows for multiplexed microwave readout and, consequently, good spatial discrimination between pixels in the array. The Al transmission lines simultaneously act to absorb optical power and are designed to have a surface impedance and filling fraction so as to match the impedance of free space. Our novel fabrication techniques demonstrate high fabrication yield of MKID arrays on large single crystal membranes and sub-micron front-to-back alignment of the microstrip circuit.

Brown, Ari-David↗
NASA NTRS2010

NASA Tech Briefs, September 2010

Topics covered include: Instrument for Measuring Thermal Conductivity of Materials at Low Temperatures; Multi-Axis Accelerometer Calibration System; Pupil Alignment Measuring Technique and Alignment Reference for Instruments or Optical Systems; Autonomous System for Monitoring the Integrity of Composite Fan Housings; A Safe, Self-Calibrating, Wireless System for Measuring Volume of Any Fuel at Non-Horizontal Orientation; Adaptation of the Camera Link Interface for Flight-Instrument Applications; High-Performance CCSDS Encapsulation Service Implementation in FPGA; High-Performance CCSDS AOS Protocol Implementation in FPGA; Advanced Flip Chips in Extreme Temperature Environments; Diffuse-Illumination Systems for Growing Plants; Microwave Plasma Hydrogen Recovery System; Producing Hydrogen by Plasma Pyrolysis of Methane; Self-Deployable Membrane Structures; Reactivation of a Tin-Oxide-Containing Catalys; Functionalization of Single-Wall Carbon Nanotubes by Photo-Oxidation; Miniature Piezoelectric Macro-Mass Balance; Acoustic Liner for Turbomachinery Applications; Metering Gas Strut for Separating Rocket Stages; Large-Flow-Area Flow-Selective Liquid/Gas Separator; Counterflowing Jet Subsystem Design; Water Tank with Capillary Air/Liquid Separation; True Shear Parallel Plate Viscometer; Focusing Diffraction Grating Element with Aberration Control; Universal Millimeter-Wave Radar Front End; Mode Selection for a Single-Frequency Fiber Laser; Qualification and Selection of Flight Diode Lasers for Space Applications; Plenoptic Imager for Automated Surface Navigation; Maglev Facility for Simulating Variable Gravity; Hybrid AlGaN-SiC Avalanche Photodiode for Deep-UV Photon Detection; High-Speed Operation of Interband Cascade Lasers; 3D GeoWall Analysis System for Shuttle External Tank Foreign Object Debris Events; Charge-Spot Model for Electrostatic Forces in Simulation of Fine Particulates; Hidden Statistics Approach to Quantum Simulations; Reconstituted Three-Dimensional Interactive Imaging; Determining Atmospheric-Density Profile of Titan; Digital Microfluidics Sample Analyzer; Radiation Protection Using Carbon Nanotube Derivatives; Process to Selectively Distinguish Viable from Non-Viable Bacterial Cells; and TEAMS Model Analyzer.

Source record↗
NASA NTRS1995

NASA Tech Briefs, November 1995

The contents include: 1) Mission Accomplished; 2) Resource Report: Marshall Space Flight Center; 3) NASA 1995 Software of the Year Award; 4) Microbolometers Based on Epitaxial YBa2Cu3O(sub 7-x) Thin Films; 5) Garnet Random-Access Memory; 6) Fabrication of SNS Weak Links on SOS Substrates; 7) High-Voltage MOSFET Switching Circuit; 8) Asymmetric Switching for a PWM H-Bridge Power Circuit; 9) Better Ohmic Contacts for InP Semiconductor Devices; 10) Low-Bandgap Thermovoltaic Materials and Devices; 11) Digital Frequency-Differencing Circuit; 12) Imaging Magnetometer; 13) Computer-Assisted Monitoring of a Complex System; 14) Buffered Telemetry Demodulator; 15) Compact Multifunction Inspection Head; 16) Optical Detection of Fractures in Ceramic Diaphragms; 17) Eddy-Current Detection of Cracks in Reinforced Carbon/Carbon; 18) Apparent Thermal Conductivity of Multilayer Insulation; 19) Optimizing Misch-Metal Compositions in Metal Hydride Anodes; 20) Device for Sampling Surface Contamination; 21) Probabilistic Failure Assessment for Fatigue; 22) Probabilistic Fatigue and Flaw-Propagation Analysis; 23) Windows Program for Driving the TDU-850 Printer; 24) Subband/Transform MATLAB Functions for Processing Images; 25) Computing Equilibrium Chemical Compositions; 26) Program Processes Thermocouple Readings; 27) ICAN-Second-Generation Integrated Composite Analyzer; 28) Integrated Composite Analyzer with Damping Capabilities; 29) Computing Efficiency of Transfer of Microwave Power; 30) Program Calculates Power Demands of Electronic Designs; 31) Cost-Estimation Program; 32) Program Estimates Areas Required by Electronic Designs; 33) Program to Balance Mapped Turbopump Assemblies; 34) BiblioTech; 35) Controlling Mirror Tilt With a Bimorph Actuator; 36) Burst-Disk Device Simulates Effect of Pyrotechnic Device; 37) Bearing-Mounting Concept Accommodates Thermal Expansion; 38) Parallel-Plate Acoustic Absorbers for Hot Environments; 39) Adjustable-Length Strut Withstands Large Cyclic Loads; 40) Tool Indicates Contact Angles in Bearing Raceways; 41) Gravity Slides With Magnetic Braking; 42) High-Torque, Lightweight, Pneumatically Driven Wrench for Small Spaces; 43) Device for Testing Compatibility of an O-Ring; 44) Magnetic Heat Pump Containing Flow Diverters; 45) Variable-Tilt Helicopter Rotor Mast; 46) "Beach-Ball" Robotic Rovers; 47) Apparatus Would Measure Temperatures of Ball Bearings; 48) Flexible Borescope for Inspecting Ducts; 49) Texturing Copper To Reduce Secondary Emission of Electrons; 50) Automated Laser Cutting in Three Dimensions; 51) Algorithm Helps Monitor Engine Operation; 52) Flexible Revision of Data-Processing Communications; 53) Software for Managing the Use of Land; 54) Thermal Strap Increases Cryocooling Efficiency; 55) Reversible Nut With Engagement Indication; 56) Control Algorithms for Kinematically Redundant Manipulators; 57) Computed Hydrogen-Flow Splits in a Rocket Engine; 58) Pressure and Thermal Modeling of Rocket Launches; 59) Field of View of a Spacecraft Antenna: Analysis and Software; 60) Digital Controller for Laser-Beam-Steering Subsystem; 61) More About Beam-Steering Subsystem for Laser Communication; 62) Digital Controller for Laser-Beam-Steering Subsystem: Part 2; 63) Interface Circuit Board for Space-Shuttle Communications; 64) Automated Planning of Spacecraft Telecommunications; 65) Artifacts of Spectral Analysis of Instrument Readings; 66) Neural-Network Controller for Vibration Suppression; 67) Adaptive Finite-Element Computation in Fracture Mechanics; 68) Attitude Control for the Cassini Spacecraft; 69) Analytical Model for Fluid Dynamics in a Microgravity Environment; 70) Study of Rocket-Engine Joints Bonded by NVCU/NARloy-Z; 71) Improved Silicon Nitride for Advanced Heat Engines; 72) Parameters for Welding Aluminum/Lithium Alloys; 73) Lightweight Composite Intertank Structure; 74) Foil Patches Seal Small Vacuum Leaks; 75) Data Base on Cables and Connectors; 76) Effect of Clock Mode on Radiation Hardnessf an ADC; and 77) Fault-Tolerant Control for a Robotic Inspection System.

Source record↗
NASA NTRS2011

Development of Sample Verification System for Sample Return Missions

This paper describes the development of a proof of-concept sample verification system (SVS) for in-situ mass measurement of planetary rock and soil sample in future robotic sample return missions. Our proof-of-concept SVS device contains a 10 cm diameter pressure sensitive elastic membrane placed at the bottom of a sample canister. The membrane deforms under the weight of accumulating planetary sample. The membrane is positioned in proximity to an opposing substrate with a narrow gap. The deformation of the membrane makes the gap to be narrower, resulting in increased capacitance between the two nearly parallel plates. Capacitance readout circuitry on a nearby printed circuit board (PCB) transmits data via a low-voltage differential signaling (LVDS) interface. The fabricated SVS proof-of-concept device has successfully demonstrated approximately 1pF/gram capacitance change

Electrodes↗
NASA NTRS2011

High precision electric gate for time-of-flight ion mass spectrometers

A time-of-flight mass spectrometer having a chamber with electrodes to generate an electric field in the chamber and electric gating for allowing ions with a predetermined mass and velocity into the electric field. The design uses a row of very thin parallel aligned wires that are pulsed in sequence so the ion can pass through the gap of two parallel plates, which are biased to prevent passage of the ion. This design by itself can provide a high mass resolution capability and a very precise start pulse for an ion mass spectrometer. Furthermore, the ion will only pass through the chamber if it is within a wire diameter of the first wire when it is pulsed and has the right speed so it is near all other wires when they are pulsed.

Sittler, Edward C.↗
NASA NTRS2004

Highly Efficient Vector-Inversion Pulse Generators

Improved transmission-line pulse generators of the vector-inversion type are being developed as lightweight sources of pulsed high voltage for diverse applications, including spacecraft thrusters, portable x-ray imaging systems, impulse radar systems, and corona-discharge systems for sterilizing gases. In this development, more than the customary attention is paid to principles of operation and details of construction so as to the maximize the efficiency of the pulse-generation process while minimizing the sizes of components. An important element of this approach is segmenting a pulse generator in such a manner that the electric field in each segment is always below the threshold for electrical breakdown. One design of particular interest, a complete description of which was not available at the time of writing this article, involves two parallel-plate transmission lines that are wound on a mandrel, share a common conductor, and are switched in such a manner that the pulse generator is divided into a "fast" and a "slow" section. A major innovation in this design is the addition of ferrite to the "slow" section to reduce the size of the mandrel needed for a given efficiency.

Rose, Franklin↗