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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 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
NASA NTRS1979

Electrical Evaluation of RCA MWS5001D Random Access Memory, Volume 3, Appendix B

The electrical characterization and qualification test results are presented for the RCA MWS5001D random access memory. The tests included functional tests, AC and DC parametric tests, AC parametric worst-case pattern selection test, determination of worst-case transition for setup and hold times, and a series of schmoo plots. The test values for the output voltage, average input current, the supply current and the leakage current are presented.

Klute, A.↗
NASA NTRS1979

Electrical Evaluation of RCA MWS5001D Random Access Memory, Volume 4, Appendix C

The electrical characterization and qualification test results are presented for the RCA MWS5001D random access memory. The tests included functional tests, AC and DC parametric tests, AC parametric worst-case pattern selection test, determination of worst-case transition for setup and hold times, and a series of schmoo plots. Statistical analysis data is supplied along with write pulse width, read cycle time, write cycle time, and chip enable time data.

Klute, A.↗
NASA NTRS1979

Electrical Evaluation of RCA MWS5001D Random Access Memory, Volume 5, Appendix D

The electrical characterization and qualification test results are presented for the RCA MWS 5001D random access memory. The tests included functional tests, AC and DC parametric tests, AC parametric worst-case pattern selection test, determination of worst-case transition for setup and hold times, and a series of schmoo plots. Average input high current, worst case input high current, output low current, and data setup time are some of the results presented.

Klute, A.↗
NASA NTRS2013

Qualification of UHF Antenna for Extreme Martian Thermal Environments

The purpose of this development was to validate the use of the external Rover Ultra High Frequency (RUHF) antenna for space under extreme thermal environments to be encountered during the surface operations of the Mars Science Laboratory (MSL) mission. The antenna must survive all ground operations plus the nominal 670 Martian sol mission that includes summer and winter seasons of the Mars thermal environment.The qualification effort was to verify that the RUHF antenna design and its bonding and packaging processes are adequate to survive the harsh environmental conditions. The RUHF is a quadrifilar helix antenna mounted on the MSL Curiosity rover deck. The main components of the RUHF antenna are the helix structure, feed cables, and hybrid coupler, and the high-power termination load. In the case of MSL rover externally mounted hardware, not only are the expected thermal cycle depths severe, but there are temperature offsets between the Mars summer and winter seasons. The total number of temperature cycles needed to be split into two regimes of summer cycles and winter cycles. The qualification test was designed to demonstrate a survival life of three times more than all expected ground testing, plus a nominal 670 Martian sol missions. Baseline RF tests and a visual inspection were performed prior to the start of the qualification test. Functional RF tests were performed intermittently during chamber breaks over the course of the qualification test. For the RF return loss measurements, the antenna was tested in a controlled environment outside the thermal chamber with a vector network analyzer that was calibrated over the antenna s operational frequency range. A total of 2,010 thermal cycles were performed. Visual inspection showed a dulling of the solder material. This change will not affect the performance of the antenna. No other changes were observed. RF tests were performed on the RUHF helix antenna, hybrid, and load after the 2,010 qualification cycles test. The RF performance of the RUHF antenna, hybrid, and load were almost identical before and after the complete test. Therefore, the developed design of RUHF is qualified for a long-duration MSL mission. The RUHF antenna has not been used for long-duration missions such as MSL in the past. The state-of-the-art technology of the RUHF antenna is used to develop the antennas for MSL mission survivability. This developmental test data provides the confidence in using this RUHF antenna for future NASA missions to Mars.

Ramesham, Rajeshuni↗
NASA NTRS2014

Gradient Calculation Methods on Arbitrary Polyhedral Unstructured Meshes for Cell-Centered CFD Solvers

A survey of gradient reconstruction methods for cell-centered data on unstructured meshes is conducted within the scope of accuracy assessment. Formal order of accuracy, as well as error magnitudes for each of the studied methods, are evaluated on a complex mesh of various cell types through consecutive local scaling of an analytical test function. The tests highlighted several gradient operator choices that can consistently achieve 1st order accuracy regardless of cell type and shape. The tests further offered error comparisons for given cell types, leading to the observation that the "ideal" gradient operator choice is not universal. Practical implications of the results are explored via CFD solutions of a 2D inviscid standing vortex, portraying the discretization error properties. A relatively naive, yet largely unexplored, approach of local curvilinear stencil transformation exhibited surprisingly favorable properties

Meshes↗
DOE OSTI2019

SuperCam Body Unit Flight Model Vibration Test Report (Rev.A)

This report describes the vibration tests that were applied to the SuperCam Body Unit (SCBU) Flight Model (FM) at Protoflight levels. These tests were performed November 28 and 29, 2018, at the Los Alamos National Laboratory ISR-5 Shock and Vibration Environmental Test Facility, at TA-3, Building 502 Room E102. The test environments shown below were obtained from the SuperCam FM test plan, which is the overarching document for all testing. The vibration results from all testing are shown below. An anomaly was identified during the FM functional testing at the conclusion of the X-Axis. It was decided to re-test at -6 dB to determine if the anomaly progressed or remained the same. Functional testing did not show any changes after the -6 dB random vibration. It was then decided to re-test at -3 dB. Once again functional testing after the -3 dB vibration did not show any changes. Low-level random vibration signature surveys were performed before and after the -6 dB and -3 dB retests. This test series met the vibration requirements to qualify the SuperCam Body Unit FM for flight without any significant anomalies.

42 ENGINEERING↗
NASA NTRS2002

Coupling Finite Element and Meshless Local Petrov-Galerkin Methods for Two-Dimensional Potential Problems

A coupled finite element (FE) method and meshless local Petrov-Galerkin (MLPG) method for analyzing two-dimensional potential problems is presented in this paper. The analysis domain is subdivided into two regions, a finite element (FE) region and a meshless (MM) region. A single weighted residual form is written for the entire domain. Independent trial and test functions are assumed in the FE and MM regions. A transition region is created between the two regions. The transition region blends the trial and test functions of the FE and MM regions. The trial function blending is achieved using a technique similar to the 'Coons patch' method that is widely used in computer-aided geometric design. The test function blending is achieved by using either FE or MM test functions on the nodes in the transition element. The technique was evaluated by applying the coupled method to two potential problems governed by the Poisson equation. The coupled method passed all the patch test problems and gave accurate solutions for the problems studied.

Chen, T.↗
NASA NTRS2003

Functional Flight Test Report for Positive Systems' ADAR System 5500 Sensor SN8 Linear

This report describes results of the functional flight test conducted with the Positive Systems' ADAR 5500 sensor system (serial number 8, linear configuration) near Winslow, Arizona on June 30 and July 1, 1999. The in-flight test is one component of the NASA Scientific Data Purchase (SDP) Validation and Verification (V&V) process. It allows to measure characteristics of the entire sensor system affected by both performance of the sensor during a flight and post-flight image processing. The following characteristics were analyzed: changes of dark digital numbers (DN's), radiometric linearity, signal-to-noise ratio (SNR), spatial resolution, and geolocation accuracy. The measured characteristics were compared with the image product specifications defined in the Positive Systems' SDP contract. Dependence of the dark DN's on several factors was analyzed, but no significant correlation was found. However, the observed changes in dark DN's were relatively small, which justifies usage of a constant value in the dark DN subtraction procedure during post-processing. Dependence of measured at-sensor, in-band radiance (in arbitrary units) on measured in-band ground reflectance is very well described by a linear function - The sensor fulfills the linearity requirement. Measured SNR values lower than the contract specifications, but accuracy of that test was possibly affected by non-uniformity of the employed gray-scale panels. The SNR values are generally sufficiently high for most applications. SNR can also be improved during standard flights by using longer exposure times. Full width at half maximum (FWHM) of an edge response derived line spread function was used as a measure of spatial resolution. FWHM was generally smaller than twice the ground sample distance (GSD), in agreement with the contract specifications. Accuracy of the geolocation information, which is provided for the particular images in a metadata file, was found to meet contract requirements as well.

Stanley, Tom↗
DOE OSTI2022

SPEL: Software tool for Porting E3SM Land Model with OpenACC in a Function Unit Test Framework

Most high-end computers adopt hybrid architecture, porting a large-scale scientific code onto accelerators is necessary. The paper presents a generic method for porting large-scale scientific code onto accelerators using compiler directives within a modularized function unit test platform. We have implemented the method and designed a software tool (SPEL) to port the E3SM Land Model (ELM) onto the GPUs in the Summit computer. SPEL automatically generates GPU-ready test modules for all ELM functions, such as CanopyFlux, SoilTemperature, and EcosystemDynamics. SPEL breaks the ELM into a collection of standalone unit test programs for easy code verification and further performance improvement. We further optimize several ELM test modules with advanced techniques, including memory reduction, reconstructed parallel loops, and asynchronous GPU kernel launch. We hope our study will inspire new toolkit developments that expedite large-scale scientific code porting with compiler directives.

Schwartz, Peter↗
DOE OSTI2019

General-Surrogate Adaptive Sampling Using Interquartile Range for Design Space Exploration

Abstract A surrogate model is a common tool to approximate system response at untested points for design space exploration. Adaptive sampling has been studied for improving the accuracy of surrogates iteratively by introducing additional samples (simulations and experiments). New samples are often selected based on the estimated uncertainty in the design space. While some surrogates such as kriging have readily available uncertainty models for their predictions, other surrogates do not. Consequently, there have been studies of using the process of leaving-samples-out (LSO) used in cross-validation tools to estimate prediction uncertainty, such as the universal prediction distribution (UPD). In this paper, an adaptive sampling scheme for general surrogates is proposed based on LSO, similar to cross-validation and interquartile range (IQR). Multiple submodels are first developed from LSO. The uncertainty is then estimated from the IQR of these surrogates at a given point. New samples are added iteratively at the point with maximum IQR for design space exploration. The proposed scheme is illustrated using kriging, radial basis function, and neural network surrogates. The proposed scheme is evaluated using four algebraic test functions. Multiple sets of initial samples were produced to account for randomness. For these test functions, the proposed scheme was found to be more accurate and robust than kriging with its own uncertainty model. The proposed scheme was more accurate than the UPD for three out of the four test functions. For a fixed number of samples, the IQR-based adaptive sampling also proved to be more accurate than all-at-once sampling in most cases even when the estimated uncertainty was only mildly correlated with prediction errors.

Engineering↗
NASA NTRS2010

Spaceflight-Induced Cardiovascular Changes and Recovery During NASA's Functional Task Test

Microgravity-induced physiological changes could impair a crewmember s performance upon return to a gravity environment. The Functional Task Test (FTT) is designed to correlate these physiological changes to performance in mission-critical tasks. The Recovery from Fall/Stand Test (RFST) simulates one such task, measuring the ability to recover from a prone position and the cardiovascular response to orthostasis. The purpose of this study was to evaluate spaceflight-induced cardiovascular changes during the FTT. METHODS: Five astronauts participated in the FTT before 10-15 day missions, on landing day (R+0), and one (R+1), six (R+6) and thirty (R+30) days after landing. The RFST consisted of a 2-minute prone rest followed by a 3-minute stand during which heart rate (HR, Holter) and continuous blood pressure (BP, Finometer) were measured. Spectral heart rate variability (HRV) was calculated during the RFST to approximate autonomic function. Statistical analysis was performed with two-factor repeated measures ANOVA. RESULTS: During RFST, HR was higher on R+0 than preflight (p<0.004). This increase in HR persisted on R+1 and R+6 during the stand portion of RFST (p<0.026). BP was well-regulated on all test days. Parasympathetic activity was diminished on R+0 (p=0.035). Sympathovagal balance tended to be affected by spaceflight (main effect, p=0.072), appearing to be slightly elevated during postflight RFST except on R+30. Additionally, analysis of HR during the functional tasks yielded a higher HR on R+0 than preflight during 8 of 11 tasks analyzed, where all tasks had HR return to preflight values by R+30 (p<0.05). CONCLUSION: Spaceflight causes an increase in HR, decrease in parasympathetic activity, and increase in sympathovagal balance, which we confirmed during RFST. These spaceflight-induced changes seen in the RFST, along with the increased postflight HR in most functional tasks, can be used to assess functional performance after short-duration spaceflight.

Arzeno, N. M.↗
DOE OSTI2022

Workhorse minimally empirical dispersion-corrected density functional with tests for weakly bound systems: r 2 SCAN + rVV 10

SCAN+rVV10 has been demonstrated to be a versatile van der Waals (vdW) density functional that delivers good predictions of both energetic and structural properties for many types of bonding. Recently, the r 2 SCAN functional was devised as a revised form of SCAN with improved numerical stability. In this work, we refit the rVV10 functional to optimize the r 2 SCAN+rVV10 vdW density functional and test its performance for molecular interactions and layered materials. Our molecular tests demonstrate that r 2 SCAN+rVV10 outperforms its predecessor SCAN+rVV10 in both efficiency (numerical stability) and accuracy. This good performance is also found in lattice-constant predictions. In comparison with benchmark results from higher-level theories or experiments, r 2 SCAN+rVV10 yields excellent interlayer binding energies and phonon dispersions for layered materials.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Identification of Differential Equations by Dynamics-Guided Weighted Weak Form with Voting

In the identification of differential equations from data, significant progresses have been made with the weak/integral formulation. In this paper, we explore the direction of finding more efficient and robust test functions adaptively given the observed data. While this is a difficult task, we propose weighting a collection of localized test functions for better identification of differential equations from a single trajectory of noisy observations on the differential equation. We find that using high dynamic regions is effective in finding the equation as well as the coefficients, and propose a dynamics indicator per differential term and weight the weak form accordingly. For stable identification against noise, we further introduce a voting strategy to identify the active features from an ensemble of recovered results by selecting the features that frequently occur in different weighting of test functions. Systematic numerical experiments are provided to demonstrate the robustness of our method.

97 MATHEMATICS AND COMPUTING↗
NASA NTRS2000

Discontinuous dual-primal mixed finite elements for elliptic problems

We propose a novel discontinuous mixed finite element formulation for the solution of second-order elliptic problems. Fully discontinuous piecewise polynomial finite element spaces are used for the trial and test functions. The discontinuous nature of the test functions at the element interfaces allows to introduce new boundary unknowns that, on the one hand enforce the weak continuity of the trial functions, and on the other avoid the need to define a priori algorithmic fluxes as in standard discontinuous Galerkin methods. Static condensation is performed at the element level, leading to a solution procedure based on the sole interface unknowns. The resulting family of discontinuous dual-primal mixed finite element methods is presented in the one and two-dimensional cases. In the one-dimensional case, we show the equivalence of the method with implicit Runge-Kutta schemes of the collocation type exhibiting optimal behavior. Numerical experiments in one and two dimensions demonstrate the order accuracy of the new method, confirming the results of the analysis.

Bottasso, Carlo L.↗
NASA NTRS2002

Ultimate Tensile Strength as a Function of Test Rate for Various Ceramic Matrix Composites at Elevated Temperatures

Ultimate tensile strength of five different continuous fiber-reinforced ceramic composites, including SiC/BSAS (2D 2 types), SiC/MAS-5 (2D), SiC/SiC (2D enhanced), and C/SiC(2D) was determined as a function of test rate at I 100 to 1200 'C in air. All five composite materials exhibited a significant dependency of ultimate strength on test rate such that the ultimate strength decreased with decreasing test rate, similar to the behavior observed in many advanced monolithic ceramics at elevated temperatures. The application of the preloading technique as well as the prediction of life from one loading configuration (constant stress rate) to another (constant stress loading) for SiC/BSAS suggested that the overall macroscopic failure mechanism of the composites would be the one governed by a power-law type of damage evolution/accumulation, analogous to slow crack growth commonly observed in advanced monolithic ceramics.

Choi, Sung R.↗
NASA NTRS1984

Comments on the MHD stability of coronal plasmas with line-tying

Reasonable boundary conditions and test functions for photospheric line-tying are discussed, and their effects on the ideal MHD stability of coronal loops are considered. It is concluded that the plasma at the footpoints of a loop may safely be assumed to be stationary. When a simple perturbed test function is used for the energy principle, the function should be helical in form. Constraints on the test function should be discarded because they overestimate stability.

An, C.-H.↗
NASA NTRSDate not supplied

Functional Task Tests in Partial Gravity During Parabolic Flight

- Understanding how functional tasks are performed in partial gravity (partial-g) is necessary to define effective and comprehensive countermeasure strategies for preserving crew performance during exploration-class missions, such as on the Moon or Mars. - Changes in 1G performance metrics before (Pre) and after (Post) 6-month stays on the ISS and 70-day bed rest.

TR Macaulay↗