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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 1,117 records · Page 62

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NASA NTRS1999

Testing of the International Space Station and X-38 Crew Return Vehicle GPS Receiver

This paper discusses the process and results of the performance testing of the GPS receiver planned for use on the International Space Station (ISS) and the X-38 Crew Return Vehicle (CRV). The receiver is a Force-19 unit manufactured by Trimble Navigation and Modified in software by the NASA Goddard Space Flight Center (GSFC) to perform navigation and attitude determination in space. The receiver is the primary source of navigation and attitude information for ISS and CRV. Engineers at GSFC have developed and tested the new receiver with a Global Simulation Systems Ltd (GSS) GPS Signal Generator (GPSSG). This paper documents the unique aspects of ground testing a GPS receiver that is designed for use in space. A discussion of the design and tests using the GPSSG, documentation, data capture, data analysis, and lessons learned will precede an overview of the performance of the new receiver. A description of the challenges of that were overcome during this testing exercise will be presented. Results from testing show that the receiver will be within or near the specifications for ISS attitude and navigation performance. The process for verifying other requirements such as Time to First Fix, Time to First Attitude, selection/deselection of a specific GPS satellite vehicles (SV), minimum signal strength while still obtaining attitude and navigation, navigation and attitude output coverage, GPS week rollover, and Y2K requirements are also given in this paper.

Simpson, James↗

NASA NTRS2008

Design, Fabrication, and Performance of Foil Gas Thrust Bearings for Microturbomachinery Applications

A methodology for the design and construction of simple foil thrust bearings intended for parametric performance testing and low marginal costs is presented. Features drawn from a review of the open literature are discussed as they relate to bearing performance. The design of fixtures and tooling required to fabricate foil thrust bearings is presented, using conventional machining processes where possible. A prototype bearing with dimensions drawn from the literature is constructed, with all fabrication steps described. A load-deflection curve for the bearing is presented to illustrate structural stiffness characteristics. Start-top cycles are performed on the bearing at a temperature of 425 C to demonstrate early-life wear patterns. A test of bearing load capacity demonstrates useful performance when compared with data obtained from the open literature.

Dykas, Brian↗

NASA NTRS1972

Investigation of a mixed compression axisymmetric inlet at Mach number 5.3

The hypersonic diffuser portion of an uncooled high performance mixed compression, axisymmetric inlet suitable for subsonic burning engines was designed and tested. Performance of a model with a 25.4-cm capture diameter was measured in a wind tunnel and the results were compared with theoretical predictions calculated by a comprehensive computer program. All tests were conducted at a Mach number of 5.3 at a total temperature of 667 K and a total pressure of 11.57 atm. The angle of attack ranged from 0 to + or - 3 deg. Performance at angle of attack remained high. Reasonably high performance in the throat (maximum throat pitot-pressure recovery of 77 percent and an average value of 58 percent) was obtained at 0 deg angle of attack with relatively large amounts of boundary-layer bleed (11 to 22 percent of the capture mass flow). The computer program used in the design of this inlet is considered marginally adequate for predicting hypersonic inlet flow fields. Although the program as it now exists is very useful, an improved computer program that more accurately predicts the boundary layer and the shock-wave-boundary-layer interaction and accounts for boundary-layer bleed should be developed for reliability predicting hypersonic inlet flow fields.

Latham, E. A.↗

NASA NTRS2016

Hollow Cathode Assembly Development for the HERMeS Hall Thruster

To support the operation of the HERMeS 12.5 kW Hall Thruster for NASA's Asteroid Redirect Robotic Mission, hollow cathodes using emitters based on barium oxide impregnate and lanthanum hexaboride are being evaluated through wear-testing, performance characterization, plasma modeling, and review of integration requirements. This presentation will present the development approach used to assess the cathode emitter options. A 2,000-hour wear-test of development model Barium Oxide (BaO) hollow cathode is being performed as part of the development plan. Specifically this test is to identify potential impacts cathode emitter life during operation in the HERMeS thruster. The cathode was operated with a magnetic field-equipped anode that simulates the HERMeS hall thruster operating environment. Cathode discharge performance has been stable with the device accumulating 743 hours at the time of this report. Observed voltage changes are attributed to keeper surface condition changes during testing. Cathode behavior during characterization sweeps exhibited stable behavior, including cathode temperature. The details of the cathode assembly operation of the wear-test will be presented.

Propulsion Technology↗

DOE OSTI2023

Extended Bandwidth Spread Spectrum Time Domain Reflectometry Cable Test for Thermal Aging, Low Resistance Fault, and Water Detection

In 2022, researchers at Pacific Northwest National Laboratory (PNNL) used the Accelerated and Real-Time Environmental Nodal Assessment (ARENA) cable and motor test bed to characterize spread spectrum time domain reflectometry (SSTDR) and compare the responses of an SSTDR instrument to those of a frequency domain reflectometry (FDR) instrument. Results showed both techniques could detect and locate cable anomalies such as phase-to-phase low resistance and shorts, thermal insulation damage, mechanical insulation damage, and the presence or absence of water in some conditions. The SSTDR tests used a commercial instrument provided by LiveWire Innovations Inc. This commercial instrument performed tests at 6, 12, 24, and 48 MHz bandwidth. The results of these tests were compared to FDR tests where bandwidths could be extended up to 1.3 GHz, although the best responses for cable tests were from 100 to 500 MHz. Lower bandwidth signals can propagate better along the cable while higher bandwidths have higher resolution for impedance change reflections allowing more precise indication of location and separation of anomalies. The 2022 research found that FDR responses were clearer than SSTDR and speculated that a higher bandwidth SSTDR could more successfully detect and locate cable anomalies. One advantage of the SSTDR system investigated was that it was designed for energized online use up to 1,000 volts, which may be a significant advantage for nuclear power plant use. The LiveWire SSTDR instrument is an established product in the rail and aircraft industry and updating the SSTDR hardware parameters is difficult to justify without more conclusive testing. Therefore, a software adjustable laboratory SSTDR instrument was developed by PNNL and was used to test extended bandwidth SSTDR cable tests. Within the ARENA test bed, 42 cable conditions were tested with the PNNL SSTDR, FDR, and the LiveWire SSTDR—each operating at four different bandwidths. Observations and conclusions regarding the relative performance of the three instruments over different bandwidths are note below. Responses of the PNNL SSTDR (at 50 MHz) and the LiveWire SSTDR (at 48 MHz) were similar. The PNNL SSTDR higher frequency bandwidths behaved as expected showing sharper peaks and higher noise. This validated the PNNL SSTDR as a reasonable implementation of the SSTDR technology. Lower bandwidth SSTDR responses (particularly 6 and 12 MHz) may have increased value for use within longer cables but were not particularly effective at identifying anomalous cable behavior in the 100 ft cables tested here. The higher bandwidths of the PNNL SSTDR (50, 100, 200, and 400 MHz) did not provide substantially clearer cable reflectometry responses, but having the higher frequency responses available did add to the cable test evaluation. Strong responses to shorts and low impedance faults between phases were particularly evident in the higher bandwidth PNNL SSTDR and the FDR data. Measurements were repeatable, with similar responses obtained from a thermally aged cable for tests taken a month apart. Signal noise was affected in the unshielded cable by the local in-tray cable arrangement including proximity to metal edges and rungs of the cable tray. Foam isolation of the cable from the tray metal reduced in both FDR and SSTDR responses. Cable condition monitoring in nuclear power plants will likely benefit from both more informative off-line testing methods and from the development of on-line methods for continuous monitoring of cables in use. The LWRS-funded ARENA test bed was a valuable resource for this development and direct comparison of nuclear electrical cable condition monitoring technologies. Test results are targeted to guide industry advancement of testing and monitoring tools for cable aging management.

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗

DOE OSTI2022

Evaluation of bifacial module technologies with combined–accelerated stress testing

In view of the increasing interest and market share of bifacial cells and modules, suitable substrates such as glass and transparent backsheets along with ethylene vinyl acetate (EVA) and polyolefin elastomer (POE) encapsulants were examined in combined-accelerated stress testing (C-AST) to evaluate and compare degradation modes. Testing with both monofacial and bifacial cells, we found glass-glass modules with monofacial cells led to greater grid finger breakage than those with polymeric backsheets. Furthermore, this is attributed to previous X-ray topography and modeling work showing higher stress in cells and interconnections in glass-glass modules than glass-backsheet modules. Consistent with the objectives of C-AST, which stresses modules at levels corresponding to the limits seen in the natural environment, we observed the UV-fluorescence signatures of modules tested in C-AST (considering the degradation associated with developing chromophores, moisture penetration and photobleaching effects) to be like those in fielded modules, more so than other chamber stress testing implemented for comparison. We found light-induced degradation (LID) in module types with regenerated (inactive) cells with C-AST, suggesting the possibility of LID destabilization in some field conditions. We could also distinguish potential-induced degradation (PID) on the back of the bifacial passivated emitter and rear cells (PERC) in C-AST. Confirming with ex-situ tests, we found polarization-type PID most prevalent in glass-glass modules with EVA as would be anticipated considering the greater leakage current through such module encapsulation. Unlike PID tests performed in the dark, which can lead to false positive PID test results, field-representative illumination is experienced by the modules on the front and back side while –1200 V system voltage is applied in C-AST, supporting the conclusion that this module type with glass-glass construction would be susceptible to PID in the field.

14 SOLAR ENERGY↗

DOE OSTI2020

Stellar population models based on the SDSS-IV MaStar library of stellar spectra – I. Intermediate-age/old models

ABSTRACT We use the first release of the SDSS/MaStar stellar library comprising ∼9000, high S/N spectra, to calculate integrated spectra of stellar population models. The models extend over the wavelength range 0.36–1.03 µm and share the same spectral resolution ($R\sim 1800$) and flux calibration as the SDSS-IV/MaNGA galaxy data. The parameter space covered by the stellar spectra collected thus far allows the calculation of models with ages and chemical composition in the range $\rm {\mathit{ t}\gt 200 \,Myr, -2 \lt = [Z/H] \lt = + 0.35}$, which will be extended as MaStar proceeds. Notably, the models include spectra for dwarf main-sequence stars close to the core H-burning limit, as well as spectra for cold, metal-rich giants. Both stellar types are crucial for modelling λ > 0.7 µm absorption spectra. Moreover, a better parameter coverage at low metallicity allows the calculation of models as young as 500 Myr and the full account of the blue horizontal branch phase of old populations. We present models adopting two independent sets of stellar parameters (Teff, log g, [Z/H]). In a novel approach, their reliability is tested ‘on the fly’ using the stellar population models themselves. We perform tests with Milky Way and Magellanic Clouds globular clusters, finding that the new models recover their ages and metallicities remarkably well, with systematics as low as a few per cent for homogeneous calibration sets. We also fit a MaNGA galaxy spectrum, finding residuals of the order of a few per cent comparable to the state-of-art models, but now over a wider wavelength range.

Maraston, C.↗

DOE OSTI2023

High-Temperature Creep Behavior of Thin-Walled FeCrAl Alloy Tubes

This report summarizes measured creep properties for FeCrAl alloy C26M measured using subsized specimens machined from prototypic thin-walled tubes. A representative tube fabricated in a previous large batch production effort was machined into dual-gauge axial specimens using electrical-discharge machining. Creep tests, comprising strain-rate jump tests (SRJ), jump stress (JS) and constant-stress (CS) tests, were conducted at temperatures ranging from 600-900ºC to determine creep mechanisms (elucidated from stress exponents) and activation energies to compare with prior data available in the literature at temperatures up to 650ºC. It was found that the results from the SRJ tests indicated that the highest stress exponent of 5.8 occurred at 600ºC, which decreased to the lowest stress exponent of 2.5 at 700ºC. At higher temperatures, the stress exponents increased slightly to a range of 2.9 to 4.3 between 750ºC and 900ºC. The high stress exponent value of 5.8 suggested dislocation glide creep mechanisms dominated creep deformation at 600ºC since high stress values were measured. The low stress exponent of 2.5 at 700ºC suggested diffusional creep mechanisms start to occur that aid in dislocation cross-slip and climb mechanisms. The slightly higher stress exponents of 2.9 to 3.9 may suggest different contributions of creep deformation mechanisms based on diffusional processes associated with Nabarro-Herring and Coble creep and dislocation creep that involve thermally activated cross-slip and climb mechanisms. These deformation mechanisms could have also been affected by the development of recovery and/or recrystallization processes in the microstructure of the C26M2 specimens. From the SJ and single CS tests, two sets of creep activation energies were calculated. The steady state creep values obtained from the SJ tests showed several abnormalities especially with the data at 850ºC. The comparison of the creep activation energies between the data from the SJ and CS tests showed higher creep rates for the SJ tests than the CS tests, indicating microstructure softening occurred in the C26M2 specimens during the SJ tests that led to the higher creep rates at stresses above the initial stress of 10 MPa. For the CS tests, the results showed steady increases in MCR with increasing temperature at each stress. The best linear fit to the MCR values at each stress was with data obtained at 800ºC, 850ºC and 900ºC. The lowest Q c value of 130.8 KJ/mole was observed with the highest stress of 25 MPa. As stress was lowered, the Q c values increased continuously to the highest value of 188.2 KJ/mole at 10 MPa. This trend suggests that the dominant creep mechanism is diffusional based dislocation climb since the decreasing activation energies with increasing stress promotes easier dislocation climb around obstacles. The comparison between the SJ and CS tests indicates that the best type of creep test performed on FeCrAl alloys such as C26M2 is the single CS test.

36 MATERIALS SCIENCE↗

NASA NTRS1971

Design, fabrication, and testing of an external fuel (UO2), full-length thermionic converter

The development of a full-length external-fuel thermionic converter for in-pile testing is described. The development program includes out-of-pile performance testing of the fully fueled-converter, using RF-induction heating, before its installation in the in-pile test capsule. The external-fuel converter is cylindrical in shape, and consists of an inner, centrally cooled collector, and an outer emitter surrounded by nuclear fuel. The term full-length denotes that the converter is long enough to extend over the full height of the reactor core. Thus, the converter is not a scaled-down test device, but a full-scale fuel element of the thermionic reactor. The external-fuel converter concept permits a number of different design options, particularly with respect to the fuel composition and shape, and the collector cooling arrangement. The converter described was developed for the Jet Propulsion Laboratory, and is based on their concept for a thermionic reactor with uninsulated collector cooling as previously described. The converter is double-ended, with through-flow cooling, and with ceramic seals and emitter and collector power take-offs at both ends. The design uses a revolver-shaped tungsten emitter body, with the central emitter hole surrounded by six peripheral fuel holes loaded with cylindrical UO2 pellets.

Schock, A.↗

NASA NTRS1974

Space shuttle OMS helium regulator design and development

Analysis, design, fabrication and design verification testing was conducted on the technological feasiblity of the helium pressurization regulator for the space shuttle orbital maneuvering system application. A prototype regulator was fabricated which was a single-stage design featuring the most reliable and lowest cost concept. A tradeoff study on regulator concepts indicated that a single-stage regulator with a lever arm between the valve and the actuator section would offer significant weight savings. Damping concepts were tested to determine the amount of damping required to restrict actuator travel during vibration. Component design parameters such as spring rates, effective area, contamination cutting, and damping were determined by test prior to regulator final assembly. The unit was subjected to performance testing at widely ranging flow rates, temperatures, inlet pressures, and random vibration levels. A test plan for propellant compatibility and extended life tests is included.

Wichmann, H.↗

NASA NTRS1972

Precision Pointing Control System (PPCS) star tracker test

Tests performed on the TRW precision star tracker are described. The unit tested was a two-axis gimballed star tracker designed to provide star LOS data to an accuracy of 1 to 2 sec. The tracker features a unique bearing system and utilizes thermal and mechanical symmetry techniques to achieve high precision which can be demonstrated in a one g environment. The test program included a laboratory evaluation of tracker functional operation, sensitivity, repeatibility, and thermal stability.

Source record↗

NASA NTRS1979

Nonlinear structural crash dynamics analyses

Presented in this paper are the results of three nonlinear computer programs, KRASH, ACTION and DYCAST used to analyze the dynamic response of a twin-engine, low-wing airplane section subjected to a 8.38 m/s (27.5 ft/s) vertical impact velocity crash condition. This impact condition simulates the vertical sink rate in a shallow aircraft landing or takeoff accident. The three distinct analysis techniques for nonlinear dynamic response of aircraft structures are briefly examined and compared versus each other and the experimental data. The report contains brief descriptions of the three computer programs, the respective aircraft section mathematical models, pertinent data from the experimental test performed at NASA Langley, and a comparison of the analyses versus test results. Cost and accuracy comparisons between the three analyses are made to illustrate the possible uses of the different nonlinear programs and their future potential.

Hayduk, R. J.↗

NASA NTRS1979

Test results of the DOE/Sandia 17 meter VAWT

A review is given of the test program of a 17 meter Vertical Axis Wind Turbine VAWT. Performance test results are discussed including difficulties encountered during the VAWT operation along with ways of solving these problems.

Nellums, R. O.↗

NASA NTRS1989

Cable coupling lightning transient qualification

Simulated lightning strike testing of instrumentation cabling on the redesigned solid rocket motor was performed. Testing consisted of subjecting the lightning evaluation test article to simulated lightning strikes and evaluating the effects of instrumentation cable transients on cables within the system tunnel. The maximum short-circuit current induced onto a United Space Boosters, Inc., operational flight cable within the systems tunnel was 92 A, and the maximum induced open-circuit voltage was 316 V. These levels were extrapolated to the worst-case (200 kA) condition of NASA specification NSTS 07636 and were also scaled to full-scale redesigned solid rocket motor dimensions. Testing showed that voltage coupling to cables within the systems tunnel can be reduced 40 to 90 dB and that current coupling to cables within the systems tunnel can be reduced 30 to 70 dB with the use of braided metallic sock shields around cables that are external to the systems tunnel. Testing also showed that current and voltage levels induced onto cables within the systems tunnel are partially dependant on the cables' relative locations within the systems tunnel. Results of current injections to the systems tunnel indicate that the dominant coupling mode on cables within the systems tunnel is not from instrumentation cables but from coupling through the systems tunnel cover seam apertures. It is recommended that methods of improving the electrical bonding between individual sections of the systems tunnel covers be evaluated. Further testing to better characterize redesigned solid rocket motor cable coupling effects as an aid in developing methods to reduce coupling levels, particularly with respect to cable placement within the systems tunnel, is also recommended.

Cook, M.↗

NASA NTRS1999

Elimination of High-Frequency Combustion Instability in the Fastrac Engine Thrust Chamber

A series of tests were conducted to stabilize the combustion of the Fastrac engine thrust chamber. The first few stability tests resulted in unstable combustion due ineffective acoustic cavity designs. The thrust chamber exhibited unstable combustion in the first-tangential mode and its harmonics. Combustion was stabilized by increasing the volume of the acoustic cavities and by plugging the dump-cooling orifices so that the cavities were uncooled. Although the first few stability tests resulted in unstable combustion, prior and subsequent long-duration performance tests of the Fastrac thrust chamber were spontaneously stable. Stability considerations during the injector faceplate design were based on the Hewitt correlation.

Rocker, Marvin↗

NASA NTRS1999

Elimination of High-Frequency Combustion Instability in the Fastrac Engine Thrust Chamber

Rocker, Marvin↗

NASA NTRS2006

An Assessment of NASA Glenn's Aeroacoustic Experimental and Predictive Capabilities for Installed Cooling Fans: Aerodynamic Performance - Part 1

Driven by the need for low production costs, electronics cooling fans have evolved differently than the bladed components of gas turbine engines which incorporate multiple technologies to enhance performance and durability while reducing noise emissions. Drawing upon NASA Glenn's experience in the measurement and prediction of gas turbine engine aeroacoustic performance, tests have been conducted to determine if these tools and techniques can be extended for application to the aerodynamics and acoustics of electronics cooling fans. An automated fan plenum installed in NASA Glenn's Acoustical Testing Laboratory was used to map the overall aerodynamic and acoustic performance of a spaceflight qualified 80 mm diameter axial cooling fan. In order to more accurately identify noise sources, diagnose performance limiting aerodynamic deficiencies, and validate noise prediction codes, additional aerodynamic measurements were recorded for two operating points: free delivery and a mild stall condition. Non-uniformities in the fan s inlet and exhaust regions captured by Particle Image Velocimetry measurements, and rotor blade wakes characterized by hot wire anemometry measurements provide some assessment of the fan aerodynamic performance. The data can be used to identify fan installation/design changes which could enlarge the stable operating region for the fan and improve its aerodynamic performance and reduce noise emissions.

VanZante, Dale E.↗

NASA NTRS2012

Ice Growth Measurements from Image Data to Support Ice-Crystal and Mixed-Phase Accretion Testing

This paper describes the imaging techniques as well as the analysis methods used to measure the ice thickness and growth rate in support of ice-crystal icing tests performed at the National Research Council of Canada (NRC) Research Altitude Test Facility (RATFac). A detailed description of the camera setup, which involves both still and video cameras, as well as the analysis methods using the NASA Spotlight software, are presented. Two cases, one from two different test entries, showing significant ice growth are analyzed in detail describing the ice thickness and growth rate which is generally linear. Estimates of the bias uncertainty are presented for all measurements. Finally some of the challenges related to the imaging and analysis methods are discussed as well as methods used to overcome them.

Struk, Peter, M↗