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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 523 records · Page 29
All sourcesNASA NTRSDOE OSTI
NASA NTRS2023

Finite Element Simulation of Three Full-Scale Crash Tests for Cessna 172 Aircraft

The NASA Emergency Locator Transmitter Survivability and Reliability project was initiated in 2013 to assess the crash performance standards for the next generation of emergency locator transmitter (ELT) systems. Three Cessna 172 aircraft were acquired to perform crash testing at the NASA Langley Research Center Landing and Impact Research Facility. Full-scale crash tests were conducted in the summer of 2015, and each test article was subjected to severe, but survivable, impact conditions including a flare-to-stall during emergency landing and two controlled-flight-into-terrain scenarios. Finite element analyses were performed to numerically simulate the aircraft response to the crash tests. The first test simulated impacting a concrete surface represented analytically by a rigid plane. Tests 2 and 3 simulated impacting a dirt surface represented analytically by an Eulerian grid of brick elements using a Mohr–Coulomb material model. The objective of this paper is to summarize the test and analysis results for the three full-scale crash tests. Simulation models of the airframe that correlate well with the tests are needed for future studies of alternate ELT mounting configurations.

Finite Element Analysis↗
NASA NTRS1969

Hot-cracking studies of Inconel 718 weld- heat-affected zones

Hot ductility tests, gas-tungsten-arc fillerless fusion tests, and circle patch-weld-restraint tests were conducted on Inconel 718 to better understand and correlate the weldability /resistance to hot cracking/ of the alloy. A correlation of the test results with composition, heat-treat condition, grain size, and microstructure was made.

Thompson, E. G.↗
NASA NTRS1972

Investigation of GH2-GO2 combustion

Data from prototype GO2-GH2 injection elements were obtained and analyzed. The bulk of the testing was conducted with nonreacting propellants, N2 to simulate the O2 and H2. A limited number of tests were conducted in combusting environment, with the purpose of this testing being to evaluate the effects of combustion on cold flow mixture ratio and mass profiles. The cold flow testing was completed in 223 tests. Analytical model correlations of these data are under way. The hot flow testing was completed in 36 tests. These data have been reduced and are documented in the report.

Calhoon, D. F.↗
NASA NTRS1973

Analyses of flight model spacecraft performance during thermal-vacuum tests

Malfunction data from the thermal-vacuum tests of 39 flight-model spacecraft have been analyzed. The results are interpreted in terms of the test variables and the spacecraft performance. The malfunction data are correlated with the test time as a single variable, and also with the composite variable of time plus temperature. The improvement in spacecraft performance is examined by means of malfunction rates, malfunctions per spacecraft, and the probability of no failure related to test time. The minimum thermal-vacuum test profile required for Goddard Space Flight Center spacecraft is verified, and the probability of a defect remaining undetected is estimated.

Timmins, A. R.↗
NASA NTRS1992

Design and analysis of seals for extended service life

Space Station Freedom is being developed for a service life of up to thirty years. As a consequence, the design requirements for the seals to be used are unprecedented. Full scale testing to assure the selected seals can satisfy the design requirements are not feasible. As an alternative, a sub-scale test program has been developed by MSFC to calibrate the analysis tools to be used to certify the proposed design. This research has been conducted in support of the MSFC Integrated Seal Test Program. The ultimate objective of this research is to correlate analysis and test results to qualify the analytical tools, which in turn, are to be used to qualify the flight hardware. This research is totally focused on O-rings that are compressed by perpendicular clamping forces. In this type of seal the O-ring is clamped between the sealing surfaces by loads perpendicular to the circular cross section.

Bower, Mark V.↗
NASA NTRS1993

Viscoelastic analysis of seals for extended service life

The space station is being developed for a service life of up to thirty years. As a consequence, the design requirements for the seals to be used are unprecedented. Full scale testing to assure the selected seals can satisfy the design requirements are not feasible. As an alternative, a sub-scale test program (2) has been developed by MSFC to calibrate the analysis tools to be used to certify the proposed design. This research has been conducted in support of the MSFC Integrated Seal Test Program. The ultimate objective of this research is to correlate analysis and test results to qualify the analytical tools which in turn, are to be used to qualify the flight hardware. Seals are simple devices, in wide spread use. The most common type of seal is the O-ring. O-ring seals are typically rings of rubber with a circular cross section. The rings are placed between the surfaces to be sealed, usually in a groove of some design. The particular design may differ based on a number of different factors. This research is focused on O-rings that are staticly compressed by perpendicular clamping forces, commonly referred to as face seals. In this type of seal the O-ring is clamped between the sealing surfaces by loads perpendicular to the circular cross section.

Bower, Mark V.↗
NASA NTRS2016

Digital Image Correlation Techniques Applied to Large Scale Rocket Engine Testing

Rocket engine hot-fire ground testing is necessary to understand component performance, reliability and engine system interactions during development. The J-2X upper stage engine completed a series of developmental hot-fire tests that derived performance of the engine and components, validated analytical models and provided the necessary data to identify where design changes, process improvements and technology development were needed. The J-2X development engines were heavily instrumented to provide the data necessary to support these activities which enabled the team to investigate any anomalies experienced during the test program. This paper describes the development of an optical digital image correlation technique to augment the data provided by traditional strain gauges which are prone to debonding at elevated temperatures and limited to localized measurements. The feasibility of this optical measurement system was demonstrated during full scale hot-fire testing of J-2X, during which a digital image correlation system, incorporating a pair of high speed cameras to measure three-dimensional, real-time displacements and strains was installed and operated under the extreme environments present on the test stand. The camera and facility setup, pre-test calibrations, data collection, hot-fire test data collection and post-test analysis and results are presented in this paper.

Gradl, Paul R.↗
NASA NTRS2017

Modeling the Extremely Lightweight Zerodur Mirror (ELZM) Thermal Soak Test

Exoplanet science requires extreme wavefront stability (10 pm change/10 minutes), so every source of wavefront error (WFE) must be characterized in detail. This work illustrates the testing and characterization process that will be used to determine how much surface figure error (SFE) is produced by mirror substrate materials' CTE distributions. Schott's extremely lightweight Zerodur mirror (ELZM) was polished to a sphere, mounted, and tested at Marshall Space Flight Center (MSFC) in the X-Ray and Cryogenic Test Facility (XRCF). The test transitioned the mirror's temperature from an isothermal state at 292K to isothermal states at 275K, 250K and 230K to isolate the effects of the mirror's CTE distribution. The SFE was measured interferometrically at each temperature state and finite element analysis (FEA) has been completed to assess the predictability of the change in the mirror's surface due to a change in the mirror's temperature. The coefficient of thermal expansion (CTE) distribution in the ELZM is unknown, so the analysis has been correlated to the test data. The correlation process requires finding the sensitivity of SFE to a given CTE distribution in the mirror. A novel hand calculation is proposed to use these sensitivities to estimate thermally induced SFE. The correlation process was successful and is documented in this paper. The CTE map that produces the measured SFE is in line with the measured data of typical boules of Schott's Zerodur glass.

Brooks, Thomas E.↗
NASA NTRS1976

Analysis of the Learjet 35/36 Wing and Correlation with Experimental Results

Two NASTRAN models of the Gates Learjet Corporation Model 35/36 Wing were developed. The models and the problems encountered in their development are discussed. A skin buckling analysis used for the ultimate loading conditions is presented. A discussion of the static tests and the correlation of the static test with the NASTRAN results and the results of a supplementary semimonocoque beam analysis are also included.

Abla, M. H.↗
NASA NTRS2013

Lessons Learned During Instrument Testing for the Thermal Infrared Sensor (TIRS)

The Themal InfraRed Sensor (TIRS) instrument, set to launch on the Landsat Data Continuity Mission in 2013, features a passively cooled telescope and IR detectors which are actively cooled by a two stage cryocooler. In order to proceed to the instrument level test campaign, at least one full functional test was required, necessitating a thermal vacuum test to sufficiently cool the detectors and demonstrate performance. This was fairly unique in that this test occurred before the Pre Environmental Review, but yielded significant knowledge gains before the planned instrument level test. During the pre-PER test, numerous discrepancies were found between the model and the actual hardware, which were revealed by poor correlation between model predictions and test data. With the inclusion of pseudo-balance points, the test also provided an opportunity to perform a pre-correlation to test data prior to the instrument level test campaign. Various lessons were learned during this test related to modeling and design of both the flight hardware and the Ground Support Equipment and test setup. The lessons learned in the pre-PER test resulted in a better test setup for the nstrument level test and the completion of the final instrument model correlation in a shorter period of time. Upon completion of the correlation, the flight predictions were generated including the full suite of off-nominal cases, including some new cases defined by the spacecraft. For some of these ·new cases, some components now revealed limit exceedances, in particular for a portion of the hardware that could not be tested due to its size and chamber limitations.. Further lessons were learned during the completion of flight predictions. With a correlated detalled instrument model, significant efforts were made to generate a reduced model suitable for observatory level analyses. This proved a major effort both to generate an appropriate network as well as to convert to the final model to the required format and yielded additional lessons learned. In spite of all the challenges encountered by TIRS, the instrument was successfully delivered to the spacecraft and will soon be tested at observatory level in preparation for a successful mission launch.

Peabody, Hume L.↗
NASA NTRS1986

Thermal Control Working Group report

The Thermal Control Working Group limited its evaluation to issues associated with Earth orbiting and planetary spacecraft with power levels up to 50 kW. It was concluded that the space station technology is a necessary precursor but does not meet S/C 2000 needs (life, high heat flux, long term cryogenics, and survivability). Additional basic and applied research are required (fluid/materials compatibility and two phase system modeling). Scaling, the key issue, must define accelerated life test criteria. The two phase systems require 0g to 1 g correlation. Additional ground test beds are required and combined space environment tests of materials.

Haslett, Robert↗
NASA NTRS1992

Thermal analysis and test of SUNLITE reference cavity for laser frequency stabilization

SUNLITE is a space-based experiment which uses a reference cavity to provide a stable frequency reference for a terahertz laser oscillator. Thermal stability of the cavity is a key factor in attaining a stable narrow-linewidth laser beam. This paper describes the thermal stability requirements on the cavity design and detailed thermal analysis performed, as well as thermal testing that was performed on a prototype. Analytical thermal models were correlated to the test data and additional modeling of the current design is presented. Suggestions for improving similar high-precision thermal tests are given.

Amundsen, R. M.↗
NASA NTRSDate not supplied

A Method for Validating Causal Diagrams of Human Health Risk in Space Flight

The complexity of cause-and-effect relationships between spaceflight hazards and resulting health conditions clouds understanding of the totality of human system risk in space. In response, NASA has introduced Directed Acyclic Graphs (causal diagrams) into the human systems risk management process. These diagrams allow for a common understanding of the mechanisms that lead from unique hazards of spaceflight to the health outcomes important to agencies and astronauts. However, the paucity of available biomedical data from spaceflight creates a need for methods of validating causal models that can accommodate data from spaceflight model analogs. Here we outline one approach utilizing open-access rodent bone datasets from the Ames Life Sciences Data Archive. The properties of directed acyclic graphs themselves can provide an epistemological and statistical framework for validation of a priori causal representations of human system risk in space flight. The assumed causal connections on the graph creates sets of logical implications: variables that – if the causal diagram is correct – should be correlated, as well as sets that should be conditionally independent. By testing these implied correlations and conditional independencies both statistically and heuristically, we can provide evidence for or against specific causal pathways on the causal diagram. In addition to validation of expert-generated causal diagrams, machine learning techniques can learn the most likely structure of a causal diagram from a given dataset. Comparison with and reconciliation between machine-learned causal diagrams and expert-generated diagrams is another technique for challenging assumptions and improving our understanding of causal mechanisms. Accurately representing complex causation is essential to systemic understanding of human health risks in space travel. Having a robust system of validating causal diagrams helps us arrive at more accurate representations of causal systems. This process will be integral to developing the countermeasures necessary for extended exploration of the moon and Mars.

Robert Reynolds↗
NASA NTRS2019

Large Male Anthropomorphic Test Device (ATD) Finite Element Model (FEM) Correlation Improvement

As part of an activity for the Commercial Crew Program (CCP), a NASA Engineering and Safety Center (NESC) team conducted tests of small female, medium male, and large male Hybrid III anthropomorphic test device (ATD) head-neck complexes. The results were compared to simulation results from ATD finite element model (FEM) predictions to determine the validity and fidelity of ATD models for use in certifying CCP vehicles. The NESC was requested to help improve the large male ATD FEM to better represent physical responses. This report contains the outcome of the NESC assessment.

Kelly, Michael J.↗
NASA NTRS1985

Critical joints in large composite primary aircraft structures. Volume 1: Technical summary

A program was conducted at Douglas Aircraft Company to develop the technology for critical joints in composite wing structure that meets all the design requirements of a 1990 commercial transport aircraft. In fulfilling this objective, analytical procedures for joint design and analysis were developed during Phase 1 of the program. Tests were conducted at the element level to supply the empirical data required for methods development. Large composite multirow joints were tested to verify the selected design concepts and for correlation with analysis predictions. The Phase 2 program included additional tests to provide joint design and analysis data, and culminated with several technology demonstration tests of a major joint area representative of a commercial transport wing. The technology demonstration program of Phase 2 is discussed. The analysis methodology development, structural test program, and correlation between test results and analytical strength predictions are reviewed.

Bunin, Bruce L.↗
NASA NTRS1973

Average correlation functions in on-line testing of linear systems

This paper is a report on new methods for on-line testing of single-input/single-output linear and time-invariant systems. No interruption of system operation is necessary, since the signals used in this test procedure are the normal operating signals. Test results indicate that detectable system errors using finite amounts of data are well within tolerance for normal operation in all but the most stringent applications.

Mix, D. F.↗
NASA NTRS1976

Correlation of AH-1G airframe test data with a NASTRAN mathematical model

Test data was provided for evaluating a mathematical vibration model of the Bell AH-1G helicopter airframe. The math model was developed and analyzed using the NASTRAN structural analysis computer program. Data from static and dynamic tests were used for comparison with the math model. Static tests of the fuselage and tailboom were conducted to verify the stiffness representation of the NASTRAN model. Dynamic test data were obtained from shake tests of the airframe and were used to evaluate the NASTRAN model for representing the low frequency (below 30 Hz) vibration response of the airframe.

Cronkhite, J. D.↗
NASA NTRS1978

Development of base pressure similarity parameters for application to space shuttle launch vehicle power-on aerodynamic testing

A base pressure data correlation study was conducted to define exhaust plume similarity parameters for use in Space Shuttle power-on launch vehicle aerodynamic test programs. Data correlations were performed for single bodies having, respectively, single and triple nozzle configurations and for a triple body configuration with single nozzles on each of the outside bodies. Base pressure similarity parameters were found to differ for the single nozzle and triple nozzle configurations. However, the correlation parameter for each was found to be a strong function of the nozzle exit momentum. Results of the data base evaluation are presented indicating an assessment of all data points. Analytical/experimental data comparisons were made for nozzle calibrations and correction factors derived, where indicated for use in nozzle exit plane data calculations.

Sulyma, P. R.↗