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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 325 records · Page 18

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NASA NTRS1993

TOPEX Microwave Radiometer Thermal Control: Post-System-Test Modifications and On-Orbit Performance

The Topex Microwave Radiometer has had an excellent thermal performance since launch. The instrument, however, went through a hardware modification right before launch to correct for athermal design inadequacy that was uncovered during the spacecraft thermal vacuum test. This paper reports on how the initially obscure problem was tracked down, and how the thermal models were revised, validated, and utilized to investigate the solution options and guide the hardware modification decisions. Details related to test data interpretation, analytical uncertainties, and model-prediction vs. test-data correlation, are documented. Instrument/spacecraft interface issues, where the problem originated and where in general pitfalls abound, are dealt with specifically. Finally, on-orbit thermal performance data are presented, which exhibit good agreement with flight predictions, and lessons learned are discussed.

Lin, Edward I.↗

NASA NTRS1980

Improvement of analytical dynamic models using modal test data

A method developed to determine maximum changes in analytical mass and stiffness matrices to make them consistent with a set of measured normal modes and natural frequencies is presented. The corrected model will be an improved base for studies of physical changes, boundary condition changes, and for prediction of forced responses. The method features efficient procedures not requiring solutions of the eigenvalue problem, and the ability to have more degrees of freedom than the test data. In addition, modal displacements are obtained for all analytical degrees of freedom, and the frequency dependence of the coordinate transformations is properly treated.

Berman, A.↗

NASA NTRS1952

Dynamic Response of Turbine-blade Temperature to Exhaust-gas Temperature for Gas-turbine Engines

The frequency of blade temperature to exhaust gas temperature is presented for two locations in the blade and at several operating conditions. The frequency response was determined by Fourier analysis of transient data. Two analytical methods are presented, and results are compared with experimental data. Dynamic response of turbine-blade temperature to exhaust-gas temperature exhibited the form of an approximate first-order lag. The results are used to predict blade temperature for a typical controlled and uncontrolled gas-turbine engine.

HEAT TRANSFER THEORY AND EXPERIMENT↗

NASA NTRS2016

Climate Analytics as a Service

Exascale computing, big data, and cloud computing are driving the evolution of large-scale information systems toward a model of data-proximal analysis. In response, we are developing a concept of climate analytics as a service (CAaaS) that represents a convergence of data analytics and archive management. With this approach, high-performance compute-storage implemented as an analytic system is part of a dynamic archive comprising both static and computationally realized objects. It is a system whose capabilities are framed as behaviors over a static data collection, but where queries cause results to be created, not found and retrieved. Those results can be the product of a complex analysis, but, importantly, they also can be tailored responses to the simplest of requests. NASA's MERRA Analytic Service and associated Climate Data Services API provide a real-world example of climate analytics delivered as a service in this way. Our experiences reveal several advantages to this approach, not the least of which is orders-of-magnitude time reduction in the data assembly task common to many scientific workflows.

big data↗

NASA NTRS1972

Geological material discrimination from Nimbus satellite data

An analysis was made of Nimbus satellite data to determine its suitability in determining the physical properties of surface materials. Attempts were also made to use these data in developing analytical techniques for handling data from other earth resources and meteorological satellites.

Pohn, H. A.↗

NASA NTRS1976

Experimental-analytical correlation of optimum duct acoustic liner performance

Mode matching and segmented duct analytical models have been developed to take advantage of relative placement of liner segments in the design of optimal duct acoustic liners of one, two, and three segments. This paper presents experimental results which were obtained for liners installed in a rectangular duct for the case with no mean airflow through the duct. Excellent correlation is shown between the analytical and experimental data, thus verifying the analytical procedures used to design the optimum segmented lining configurations.

Patterson, J. D.↗

NASA NTRS2007

Curved Duct Noise Prediction Using the Fast Scattering Code

Results of a study to validate the Fast Scattering Code (FSC) as a duct noise predictor, including the effects of curvature, finite impedance on the walls, and uniform background flow, are presented in this paper. Infinite duct theory was used to generate the modal content of the sound propagating within the duct. Liner effects were incorporated via a sound absorbing boundary condition on the scattering surfaces. Simulations for a rectangular duct of constant cross-sectional area have been compared to analytical solutions and experimental data. Comparisons with analytical results indicate that the code can properly calculate a given dominant mode for hardwall surfaces. Simulated acoustic behavior in the presence of lined walls (using hardwall duct modes as incident sound) is consistent with expected trends. Duct curvature was found to enhance weaker modes and reduce pressure amplitude. Agreement between simulated and experimental results for a straight duct with hard walls (no flow) was excellent.

Dunn, M. H.↗

NASA NTRSDate not supplied

In-Situ Consolidation Automated Fiber Placement of Thermoplastic Composites for High-Rate Aircraft Manufacturing

The National Aeronautics and Space Administration (NASA) initiated the Hi-Rate Composites Aircraft Manufacturing (HiCAM) project in 2021 with the goal of significantly increasing composite structures manufacturing rate in the commercial aircraft industry. The technologies currently under investigation include resin infusion and automated fiber placement (AFP) of novel thermoset materials and thermoplastic composites. Thermoplastic composites offer attractive solutions to rapid manufacturing due to their ability to be formed and consolidated quickly. NASA is particularly focused on assessing composite structure manufacturing utilizing an in-situ consolidation AFP of thermoplastics (ICAT) process employing a recently developed laser heating system. Two semi-crystalline polyaryletherketone thermoplastic tape materials were characterized to ascertain the ICAT process parameters at AFP placement speeds approaching 423 mm/s. The required laser power settings were determined at Electroimpact, measuring material temperatures utilizing a forward looking infrared (FLIR) thermal imaging camera and thermocouples. The material temperature, tool temperature, and placement speed were varied for resulting consolidation quality assessment. The resulting temperature data were also utilized to calibrate thermal analysis models under development at NASA. The experimental temperature data confirmed analytical results. An overview of the HiCAM project as well as initial data from ICAT process characterizations are described.

thermoplastic composites↗

NASA NTRS2020

Structural Model Tuning Tool: User's Reference Manual

This report presents an efficient approach for tuning finite element models to match the measured ground vibration test and static test data. Frequencies, mode shapes, total weight, location of the center of gravity, and static deformation computed from the finite element model are matched to the measured data. The model tuning procedure used in this work is based on solving an optimization problem in which the errors for the considered metrics, between the finite element prediction and the measured data, are minimized. Analytical sensitivity values of performance indices are computed using the NASTRAN-generated sensitivity values together with the in-house computer codes, which allow for faster computational time and the use of gradient-based optimizers. The method is applied to the Aerostructures Test Wing IV model. The study shows that the military standard and the National Aeronautics and Space Administration standard for comparing analytical and experimental modal data are all satisfied. The final finite element model correlates well with the test data. The flutter speed decreases by 8.91 percent after model tuning compared with the original Aerostructures Test Wing IV design.

Chan-gi Pak↗

NASA NTRS2022

In-Situ Consolidation Automated Fiber Placement of Thermoplastic Composites for High-Rate Aircraft Manufacturing

laser heating↗

NASA NTRS1986

Comparison of analytical and experimental performance of a wind-tunnel diffuser section

Wind tunnel diffuser performance is evaluated by comparing experimental data with analytical results predicted by an one-dimensional integration procedure with skin friction coefficient, a two-dimensional interactive boundary layer procedure for analyzing conical diffusers, and a two-dimensional, integral, compressible laminar and turbulent boundary layer code. Pressure, temperature, and velocity data for a 3.25 deg equivalent cone half-angle diffuser (37.3 in., 94.742 cm outlet diameter) was obtained from the one-tenth scale Altitude Wind Tunnel modeling program at the NASA Lewis Research Center. The comparison is performed at Mach numbers of 0.162 (Re = 3.097x19(6)), 0.326 (Re = 6.2737x19(6)), and 0.363 (Re = 7.0129x10(6)). The Reynolds numbers are all based on an inlet diffuser diameter of 32.4 in., 82.296 cm, and reasonable quantitative agreement was obtained between the experimental data and computational codes.

Shyne, R. J.↗

NASA NTRS1975

Additional experiments with a four-bladed cyclic pitch stirring model rotor, part 2 of second yearly report

The four bladed pitch stirring rotor model was used in a rotor dynamic wake survey at zero advance ratio, covering 2 deg, 5 deg and 8 deg collective pitch settings. Dynamic wake data were taken in planes .12 and .20 radii below the rotor disk and are to be compared with analytical wake data with parameters to be identified from pitch stirring transients. The model was modified to perform such transients. The instrumentation developed for this purpose is described together with the method of data acquisition and with the test procedures. The hardware and software for several data handling systems are discussed. These systems extract from pitch stirring transients the parameters of analytical dynamic rotor wake models.

Hohenemser, K. H.↗

NASA NTRS1974

Comparison of flight data and analysis for hingeless rotor regressive inplane mode stability

Analytical and experimental data obtained during the development of the AH-56A covering stability of the regressive inplane mode, including coupling with other modes such as body and rotor plunge are reported. Data were obtained on two distinctly different control systems; both gyro controlled, but one with feathering moment feedback and the other with direct flapping feedback. A review was made of analytical procedures employed in investigating the stability of this mode and a comparison was made of the analytical and experimental data. The effect of certain parameters including blade droop, sweep, delta 3, alpha 1, vehicle roll inertia, inplane frequency, and rpm and forward speed on the mode were also reviewed. It was shown that the stability of this mode is treatable by analysis and that adequate stability is achievable without recourse to auxiliary inplane damping devices.

Anderson, W. D.↗

NASA NTRS1994

Integrated active and passive control design methodology for the LaRC CSI evolutionary model

A general design methodology to integrate active control with passive damping was demonstrated on the NASA LaRC CSI Evolutionary Model (CEM), a ground testbed for future large, flexible spacecraft. Vibration suppression controllers designed for Line-of Sight (LOS) minimization were successfully implemented on the CEM. A frequency-shaped H2 methodology was developed, allowing the designer to specify the roll-off of the MIMO compensator. A closed loop bandwidth of 4 Hz, including the six rigid body modes and the first three dominant elastic modes of the CEM was achieved. Good agreement was demonstrated between experimental data and analytical predictions for the closed loop frequency response and random tests. Using the Modal Strain Energy (MSE) method, a passive damping treatment consisting of 60 viscoelastically damped struts was designed, fabricated and implemented on the CEM. Damping levels for the targeted modes were more than an order of magnitude larger than for the undamped structure. Using measured loss and stiffness data for the individual damped struts, analytical predictions of the damping levels were very close to the experimental values in the (1-10) Hz frequency range where the open loop model matched the experimental data. An integrated active/passive controller was successfully implemented on the CEM and was evaluated against an active-only controller. A two-fold increase in the effective control bandwidth and further reductions of 30 percent to 50 percent in the LOS RMS outputs were achieved compared to an active-only controller. Superior performance was also obtained compared to a High-Authority/Low-Authority (HAC/LAC) controller.

Voth, Christopher T.↗

NASA NTRS1991

Analysis of materials from MSFC LDEF experiments

In preparation for the arrival of the Long Duration Exposure Facility (LDEF) samples, a material testing and handling approach was developed for the evaluation of the materials. A configured lab was made ready for the de-integration of the LDEF experiments. The lab was prepared to clean room specifications and arranged with the appropriate clean benches, tables, lab benches, clean room tools, particulate counter, and calibrated and characterized analytical instrumentation. Clean room procedures were followed. Clean room attire and shoe cleaning equipment were selected and installed for those entering. Upon arrival of the shipping crates they were taken to the lab, logged in, and opened for examination. The sample trays were then opened for inspection and test measurements. The control sample measurements were made prior to placement into handling and transport containers for the flight sample measurements and analysis. Both LDEF flight samples and LDEF type materials were analyzed and tested for future flight candidate material evaluation. Both existing and newly purchased equipment was used for the testing and evaluation. Existing Space Simulation Systems had to be upgraded to incorporate revised test objectives and approaches. Fixtures such as special configured sample holders, water, power and LN2 feed-throughs, temperature measurement and control, front surface mirrors for reflectance and deposition, and UV grade windows had to be designed, fabricated, and installed into systems to achieve the revised requirements. New equipment purchased for LDEF analysis was incorporated into and/or used with existing components and systems. A partial list of this equipment includes a portable monochromator, enhanced UV System, portable helium leak detector for porosity and leak measurements, new turbo pumping system, vacuum coaster assembly, cryopumps, and analytical and data acquisition equipment. A list of materials tested, equipment designed, fabricated and installed, systems used, and analytical research accomplished on both LDEF flight samples and on similar materials which were lab tested for a comparative analysis to the LDEF flight samples is presented.

Johnson, R. Barry↗

NASA NTRS1993

Orbital Signature Analyzer (OSA): A spacecraft health/safety monitoring and analysis tool

Fixed or static limit sensing is employed in control centers to ensure that spacecraft parameters remain within a nominal range. However, many critical parameters, such as power system telemetry, are time-varying and, as such, their 'nominal' range is necessarily time-varying as well. Predicted data, manual limits checking, and widened limit-checking ranges are often employed in an attempt to monitor these parameters without generating excessive limits violations. Generating predicted data and manual limits checking are both resource intensive, while broadening limit ranges for time-varying parameters is clearly inadequate to detect all but catastrophic problems. OSA provides a low-cost solution by using analytically selected data as a reference upon which to base its limits. These limits are always defined relative to the time-varying reference data, rather than as fixed upper and lower limits. In effect, OSA provides individual limits tailored to each value throughout all the data. A side benefit of using relative limits is that they automatically adjust to new reference data. In addition, OSA provides a wealth of analytical by-products in its execution.

Weaver, Steven↗

NASA NTRS1984

Steady internal flow and aerodynamic loads analysis of shuttle thermal protection system

An analytical model for calculation of ascent steady state tile loading was developed and validated with wind tunnel data. The analytical model is described and results are given. Results are given for loading due to shocks and skin friction. The analysis included calculation of internal flow (porous media flow and channel flow) to obtain pressures and integration of the pressures to obtain forces and moments on an insulation tile. A heat transfer program was modified by using analogies between heat transfer and fluid flow so that it could be used for internal flow calculation. The type of insulation tile considered was undensified reusable surface insulation (RSI) without gap fillers, and the location studied was the lower surface of the orbiter. Force and moment results are reported for parameter variations on surface pressure distribution, gap sizes, insulation permeability, and tile thickness.

Petley, D. H.↗

NASA NTRS1977

Evaluation of the F-8 DFBW analytic redundancy sensor FDI algorithm using telemetry data

In this paper we present a reliable technique for failure detection and identification (FDI) for dual redundant flight control sensors aboard the NASA F-8 digital fly-by-wire (DFBW) aircraft, and we discuss the successful application of the technique to identifying failures injected on test flight telemetry data. The technique exploits the analytic redundancy which exists as relationships among variables being measured by dissimilar instruments. With straightforward modification the technique may be extended to provide failure monitoring of a single remaining sensor after the identified failure of its companion sensor.

Deckert, J. C.↗