Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “probing”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 757 records · Page 42
All sourcesNASA NTRSDOE OSTI
NASA NTRS1993

Total temperature probes for high-temperature hypersonic boundary-layer measurements

The design and test results of two types of total temperature probes that were used for hypersonic boundary-layer measurements are presented. The intent of each design was to minimize the total error and to maintain minimal size for measurements in boundary layers 1.0 in. thick and less. A single platinum-20-percent-rhodium shield was used in both designs to minimize radiation heat transfer losses during exposure to the high-temperature test stream. The shield of the smaller design was flattened at the flow entrance to an interior height of 0.02 in., compared with 0.03 in. for the larger design. The resulting vent-to-inlet area ratios were 60 and 50 percent. A stainless steel structural support sleeve that was used in the larger design was excluded from the smaller design, which resulted in an outer diameter of 0.059 in., to allow closer placement of the probes to each other and to the wall. These small design changes to improve resolution did not affect probe performance. Tests were conducted at boundary-layer-edge Mach numbers of 5.0 and 6.2. The nominal free-stream total temperatures were 2600 degrees and 3200 degrees R. The probes demonstrated extremely good reliability. The best performance in terms of recovery factor occurred when the wire-based Nusselt number was at least 0.04. Recommendations for future probe designs are included.

Albertson, Cindy W.↗
NASA NTRS1993

Probe impedance measurements for millimeter-wave integrated horn antennas

In order to achieve an impedance-matched millimeter-wave integrated horn antenna mixer array, the characteristics of the antenna probes inside the horn must be known. This paper describes impedance measurements for various probes in low-frequency model horns of two different types: (1) a 3 x 3 array made of aluminum by electric discharge machining and (2) a half horn made of copper sheet placed on a big copper-clad circuit board that was used as an image plane. The results of measurements indicate that the presence of the horn increases the effective length of the probe element, in agreement with reports of Guo et al. (1991) and theoretical analysis of Eleftheriades et al. (1991). It was also found that the resonant frequencies can be controlled by changing the length of the probes or by loading the probes.

Guo, Yong↗
NASA NTRS1993

Probe shapes that measure time-averaged streamwise momentum and cross-stream turbulence intensity

A method and apparatus for directly measuring the time-averaged streamwise momentum in a turbulent stream use a probe which has total head response which varies as the cosine-squared of the angle of incidence. The probe has a nose with a slight indentation on its front face for providing the desired response. The method of making the probe incorporates unique design features. Another probe may be positioned in a side-by-side relationship to the first probe to provide a direct measurement of the total pressure. The difference between the two pressures yields the sum of the squares of the cross-stream components of the turbulence level.

Rossow, Vernon J.↗
NASA NTRS1995

More About Pressure Probes For Turbulent Flows

Array of probes yields data on static and total pressures and cross-stream turbulence. Is combination of separate pressure-probe arrays described in "Measuring Streamwise Momentum and Cross-Stream Turbulence" (ARC-11934), and "Probe Rakes To Measure Static Pressure and Turbulence" (ARC-12973). Equations that express directional responses of various probes in array solved together to eliminate unknown quantities; makes it possible to process digitized time-averaged probe readings together to obtain time-averaged static, stagnation, and cross-stream-turbulence pressures.

Rossow, Vernon J.↗
NASA NTRS1961

Wind-Tunnel Tests of Seven Static-Pressure Probes at Transonic Speeds

Wind-tunnel tests have been conducted to determine the errors of 3 seven static-pressure probes mounted very close to the nose of a body of revolution simulating a missile forebody. The tests were conducted at Mach numbers from 0.80 to 1.08 and at angles of attack from -1.7 deg to 8.4 deg. The test Reynolds number per foot varied from 3.35 x 10(exp 6) to 4.05 x 10(exp 6). For three 4-vane, gimbaled probes, the static-pressure errors remained constant throughout the test angle-of-attack range for all Mach numbers except 1.02. For two single-vane, self-rotating probes having two orifices at +/-37.5 deg. from the plane of symmetry on the lower surface of the probe body, the static-pressure error varied as much as 1.5 percent of free-stream static pressure through the test angle-of- attack range for all Mach numbers. For two fixed, cone-cylinder probes of short length and large diameter, the static-pressure error varied over the test angle-of-attack range at constant Mach numbers as much as 8 to 10 percent of free-stream static pressure.

Capone, Francis J.↗
NASA NTRS1999

0.4 Microns Spatial Resolution with 1 GHz (lambda = 30 cm) Evanescent Microwave Probe

In this article we describe evanescent field imaging of material nonuniformities with a record resolution of 0.4 microns at 1 GHz (lambda(sub g)/750000), using a resonant stripline scanning microwave probe. A chemically etched tip is used as a point-like evanescent field emitter and a probe-sample distance modulation is employed to improve the signal-to-noise ratio. Images obtained by evanescent microwave probe, by optical microscope, and by scanning tunneling microscope are presented for comparison. Probe was calibrated to perform quantitative conductivity measurements. The principal factors affecting the ultimate resolution of evanescent microwave probe are also discussed.

Tabib-Azar, M.↗
NASA NTRS2001

Evaluation of Forces on the Welding Probe of the Automated Retractable Pin-Tool (RPT)

The NASA invention entitled 'The Hydraulic Controlled Auto-Adjustable Pin Tool for Friction Stir Welding' (US Patent 5,893,507), better known as the Retractable Pin-Tool (RPT), has been instrumented with a load-detecting device allowing the forces placed on the welding probe to be measured. As the welding probe is plunged into the material, the forces placed on the probe can now be characterized. Of particular interest are those forces experienced as the welding probe comes within close proximity to the back-up anvil. For a given material, it is believed that unique forces are generated relative to the distance between the welding probe and the anvil. The forces have been measured and characterized for several materials, and correlations have been made between these forces and the pin's position relative to the backside of the weld material.

Ding, R. J.↗
NASA NTRS1999

Evaluation of Forces on the Welding Probe of the Retractable Pin-Tool (RPT)

NASA invention entitled, "The Hydraulic Controlled Auto-Adjustable Pin Tool for Friction Stir Welding" (U.S. Patent 5,893,5 07), better known as the Retractable Pin-Tool (RPT) has been instrumented with a load detecting devise allowing the forces placed upon the welding probe to be measured. As the welding probe is plunged into the material, the forces placed upon the probe can now be charactefized. Of particular interest are those forces experienced as the welding probe comes within close proximity to the back-up anvil. For a given material, it is believed that unique forces are generated relative to the distance between the welding probe and the anvil. The forces have been measured and characterized for several materials, and correlations have been made between these forces and the pin's position relative to the backside of the weld material.

Ding, R. Jeffrey↗
NASA NTRS2001

Performance Evaluation of Particle Sampling Probes for Emission Measurements of Aircraft Jet Engines

Considerable attention has been recently received on the impact of aircraft-produced aerosols upon the global climate. Sampling particles directly from jet engines has been performed by different research groups in the U.S. and Europe. However, a large variation has been observed among published data on the conversion efficiency and emission indexes of jet engines. The variation results surely from the differences in test engine types, engine operation conditions, and environmental conditions. The other factor that could result in the observed variation is the performance of sampling probes used. Unfortunately, it is often neglected in the jet engine community. Particle losses during the sampling, transport, and dilution processes are often not discussed/considered in literatures. To address this issue, we evaluated the performance of one sampling probe by challenging it with monodisperse particles. A significant performance difference was observed on the sampling probe evaluated under different temperature conditions. Thermophoretic effect, nonisokinetic sampling and turbulence loss contribute to the loss of particles in sampling probes. The results of this study show that particle loss can be dramatic if the sampling probe is not well designed. Further, the result allows ones to recover the actual size distributions emitted from jet engines.

Lee, Poshin↗
NASA NTRS1996

Overview of the Galileo Probe Mission to Jupiter

The Galileo Probe entered the atmosphere of Jupiter on December 7, 1995, for the first time directly sampling the atmosphere of one of the outer planets. The entry was the most difficult ever attempted in terms of heat and deceleration loads. The probe and all scientific instruments functioned successfully, and returned data on composition, clouds, thermal structure, winds, energy balance, lightning, and inner radiation belts. A probe mission overview is presented, highlighting the key mission events and major science objectives. The purpose of the overview is to set the stage for the following papers which describe findings from the probe scientific investigations and discuss implications of the probe results.

Young, Richard E.↗
NASA NTRS2004

Large-Scale Fabrication of Carbon Nanotube Probe Tips For Atomic Force Microscopy Critical Dimension Imaging Applications

Carbon nanotube (CNT) probe tips for atomic force microscopy (AFM) offer several advantages over Si/Si3N4 probe tips, including improved resolution, shape, and mechanical properties. This viewgraph presentation discusses these advantages, and the drawbacks of existing methods for fabricating CNT probe tips for AFM. The presentation introduces a bottom up wafer scale fabrication method for CNT probe tips which integrates catalyst nanopatterning and nanomaterials synthesis with traditional silicon cantilever microfabrication technology. This method makes mass production of CNT AFM probe tips feasible, and can be applied to the fabrication of other nanodevices with CNT elements.

Ye, Qi Laura↗
NASA NTRS1994

Self-Nulling Eddy Current Probe for Surface and Subsurface Flaw Detection

An eddy current probe which provides a null-signal in the presence of unflawed material without the need for any balancing circuitry has been developed at NASA Langley Research Center. Such a unique capability of the probe reduces set-up time, eliminates tester configuration errors, and decreases instrumentation requirements. The probe is highly sensitive to surface breaking fatigue cracks, and shows excellent resolution for the measurement of material thickness, including material loss due to corrosion damage. The presence of flaws in the material under test causes an increase in the extremely stable and reproducible output voltage of the probe. The design of the probe and some examples illustrating its flaw detection capabilities are presented.

Wincheski, B.↗
NASA NTRS1994

Application of Self Nulling Eddy Current Probe Technique to the Detection of Fatigue Crack Initiation and Control of Test Procedures

A major part of fracture mechanics is concerned with studying the initiation and propagation of fatigue cracks. This typically requires constant monitoring of crack growth during fatigue cycles and the knowledge of the precise location of the crack tip at any given time. One technique currently available for measuring fatigue crack length is the Potential Drop method. The method, however, may be inaccurate if the direction of crack growth deviates considerably from what was assumed initially or the curvature of the crack becomes significant. Another popular approach is to optically view the crack using a high magnification microscope, but this entails a person constantly monitoring it. The present proposed technique uses an automated scheme, in order to eliminate the need for a person to constantly monitor the experiment. Another technique under development elsewhere is to digitize an optical image of the test specimen surface and then apply a pattern recognition algorithm to locate the crack tip. A previous publication showed that the self nulling eddy current probe successfully tracked a simulated crack in an aluminum sample. This was the impetus to develop an online real time crack monitoring system. An automated system has been developed which includes a two axis scanner mounted on the tensile testing machine, the probe and its instrumentation and a personal computer (PC) to communicate and control all the parameters. The system software controls the testing parameters as well as monitoring the fatigue crack as it propagates. This paper will discuss the experimental setup in detail and demonstrate its capabilities. A three dimensional finite element model is utilized to model the magnetic field distribution due to the probe and how the probe voltage changes as it scans the crack. Experimental data of the probe for different samples under zero load, static load and high cycle fatigue load will be discussed. The final section summarizes the major accomplishments of the present work, the elements of the future R&D needs and the advantages and disadvantages of using this system in the laboratory and field.

Namkung, M.↗
NASA NTRS2005

Effective Radius of Ice Cloud Particle Populations Derived from Aircraft Probes

The effective radius(r(sub e)) is a crucial variable in representing the radiative properties of cloud layers in general circulation models. This parameter is proportional to the condensed water content (CWC) divided by the extinction (sigma). For ice cloud layers, parameterizations for r(sub e), have been developed from aircraft in-situ measurements 1) indirectly, using data obtained from particle spectrometer probes and assumptions or observations about particle shape and mass to get the ice water content (IWC) and area to get sigma, and recently 2) from probes that measure IWC and sigma directly. This study compares [IWC/sigma] derived from the two methods using data sets acquired from comparable instruments on two aircraft, one sampling clouds at mid-levels and the other at upper-levels during the CRYSTAL-FACE field program in Florida in 2002. The sigma and IWC derived by each method are compared and evaluated in different ways for each aircraft data set. Direct measurements of sigma exceed those derived indirectly by a factor of two to two and a half. The IWC probes, relying on ice sublimation, appear to measure accurately except when the IWC is high or the particles too large to sublimate completely during the short transit time through the probe. The IWC estimated from the particle probes are accurate when direct measurements are available to provide constraints and useful information in high IWC/large particle situations. Because of the discrepancy in sigma estimates between the direct and indirect approaches, there is a factor of 2 to 3 difference in [IWC/sigma] between them. Although there are significant uncertainties involved in its use, comparisons with several independent data sources suggest that the indirect method is the more accurate of the two approaches. However, experiments are needed to resolve the source of the discrepancy in sigma.

Heymsfield, Andrew J.↗
NASA NTRS1999

Cone-Probe Rake Design and Calibration for Supersonic Wind Tunnel Models

A series of experimental investigations were conducted at the NASA Langley Unitary Plan Wind Tunnel (UPWT) to calibrate cone-probe rakes designed to measure the flow field on 1-2% scale, high-speed wind tunnel models from Mach 2.15 to 2.4. The rakes were developed from a previous design that exhibited unfavorable measurement characteristics caused by a high probe spatial density and flow blockage from the rake body. Calibration parameters included Mach number, total pressure recovery, and flow angularity. Reference conditions were determined from a localized UPWT test section flow survey using a 10deg supersonic wedge probe. Test section Mach number and total pressure were determined using a novel iterative technique that accounted for boundary layer effects on the wedge surface. Cone-probe measurements were correlated to the surveyed flow conditions using analytical functions and recursive algorithms that resolved Mach number, pressure recovery, and flow angle to within +/-0.01, +/-1% and +/-0.1deg , respectively, for angles of attack and sideslip between +/-8deg. Uncertainty estimates indicated the overall cone-probe calibration accuracy was strongly influenced by the propagation of measurement error into the calculated results.

Won, Mark J.↗
NASA NTRS2005

Design, Fabrication, and Testing of Emissive Probes to Determine the Plasma Potential of the Plumes of Various Electric Thrusters

A significant problem in the use of electric thrusters in spacecraft is the formation of low-energy ions in the thruster plume. Low-energy ions are formed in the plume via random collisions between high-velocity ions ejected from the thruster and slow-moving neutral atoms of propellant effusing from the engine. The sputtering of spacecraft materials due to interactions with low-energy ions may result in erosion or contamination of the spacecraft. The trajectory of these ions is determined primarily by the plasma potential of the plume. Thus, accurate characterization of the plasma potential is essential to predicting low-energy ion contamination. Emissive probes were utilized to determine the plasma potential. When the ion and electron currents to the probe are balanced, the potential of such probes float to the plasma potential. Two emissive probes were fabricated; one utilizing a DC power supply, another utilizing a rectified AC power source. Labview programs were written to coordinate and automate probe motion in the thruster plume. Employing handshaking interaction, these motion programs were synchronized to various data acquisition programs to ensure precision and accuracy of the measurements. Comparing these experimental values to values from theoretical models will allow for a more accurate prediction of low-energy ion interaction.

Chen, Erinna M.↗
NASA NTRS2006

Solar Probe: Close Encounter with the Sun

The Solar Probe Science and Technology Definition Team (STDT) recently completed a detailed study of the Solar Probe Mission based on an earliest launch date of October 2014. Solar Probe, when implemented, will be the first close encounter by a spacecraft with a star (i.e., 3 Rs above the Sun s photosphere). The report and its executive summary were published by NASA (NASA/TM-2005-212786) in September 2005 and can be found at the website http://solarprobe.gsfc.nasa.gov/. A description of the science is being prepared for publication in Reviews of Geophysics by McComas et al. [2006]. For this talk, we will be presenting the consensus view of the STDT including a brief description of the scientific goals, a description of the overall mission, including trajectory scenarios, spacecraft description and proposed scientific payload. We will discuss all these topics and the importance of flying the Solar Probe mission both with regard to understanding fundamental issues of solar wind acceleration and coronal heating near the Sun and Solar Probe s unique role in understanding the acceleration of Solar Energetic Particles (SEPs), which is critical to future Human Exploration.

Sittler, E. C., Jr.↗
NASA NTRS2005

[Now, The Time for Probes and In-Situ Science]

A viewgraph explaining the need for probes and in situ measurements to understand data from extra solar planet studies is shown. The topics include: 1) To explore the universe and search for life: Probes in Context; 2) What is a probe?; 3) NASA Ames Research Center-founded 1939; 4) Past & Present: Successful Probes and Fly-by's; 5) Thermal Protection Materials and Arc-Jet Facility; 6) Mars Exploration Rovers-Spirit & Opportunity; 7) Bio/Info/Nanotechnology; 8) Technology for Exploration; 9) Award Winning NASA Research Park; 10) Where we need to go; and 11) The Future: Pico Probes

Hubbard, G. Scott↗