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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 397 records · Page 22
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Shared mooring system designs and cost estimates for wave energy arrays

For floating renewable energy devices to become more cost-efficient and commercially scalable, their mooring system designs must be low-cost and suited for large-scale installations. Large arrays of floating devices, such as wave energy converters (WECs), will likely be designed with an individual mooring system for each device in the array. However, new mooring technology advancements provide options to use shared mooring lines to connect adjacent devices to one another, reducing the total number of anchors in the array, thereby reducing material use and cost. Here, this paper explores the design, modeling, and cost analysis of shared mooring systems for various sizes of arrays consisting of heaving oscillating water column (OWC) WECs. Shared mooring systems for WEC arrays sized in 2 x N and N x N grid layouts are designed to meet the relevant design standards, checking their performance with a nonlinear time-domain dynamic simulation, and the costs of each are calculated and compared. Several assumptions are taken in the design process to produce efficient results, providing a preliminary optimization for guidance on design decisions rather than a full, detailed design analysis. Mooring system costs per WEC were found to decrease as the number of WECs in the array increase, up to certain array sizes. The 2 x 3 array had the lowest mooring system cost per WEC out of all arrays considered, with a 60% cost reduction relative to using individual mooring systems. The 3 x 3 and 4 x 4 arrays achieved a 50% cost per WEC reduction. In addition to these significant cost reductions, the shared mooring system designs can provide advantages through smaller mooring system footprints, lower installation times, and less seabed disturbance.

16 TIDAL AND WAVE POWER↗
NASA NTRS1976

Oso 7 measurements of atomic oxygen and molecular nitrogen densities in the earth's upper atmosphere

Densities of molecular nitrogen and monatomic oxygen are presented as a function of altitude for selected intervals of March-May 1972 Oso 7 satellite data. Results on atmospheric attenuation of solar extreme UV radiation at 200-400 A, at heights from 250 to 500 km, are of particular interest. Satellite sunrise measurements above 330 km are not consistent with the Jacchia (1971) atmospheric model, and may constitute evidence for dynamic phenomena occurring in the heated upper levels. Density and temperature variations are considered mainly responsible for the sunrise anomaly observed. Checks were made for possible errors in the satellite pointing system and other instrumental effects.

Modali, S. B.↗
NASA NTRS1986

Free vibration and dynamic response analysis of spinning structures

The proposed effort involved development of numerical procedures for efficient solution of free vibration problems of spinning structures. An eigenproblem solution procedure, based on a Lanczos method employing complex arithmetic, was successfully developed. This task involved formulation of the numerical procedure, FORTRAN coding of the algorithm, checking and debugging of software, and implementation of the routine in the STARS program. A graphics package for the E/S PS 300 as well as for the Tektronix terminals was successfully generated and consists of the following special capabilities: (1) a dynamic response plot for the stresses and displacements as functions of time; and (2) a menu driven command module enabling input of data on an interactive basis. Finally, the STARS analysis capability was further improved by implementing the dynamic response analysis package that provides information on nodal deformations and element stresses as a function of time. A number of test cases were run utilizing the currently developed algorithm implemented in the STARS program and such results indicate that the newly generated solution technique is significantly more efficient than other existing similar procedures.

Source record↗
NASA NTRS1986

Event time recorder

Accurate timing of sounding rocket payload events is critical for successful missions. The payload event timers used must be checked numerous times to verify proper settings. A cost-effective time event recorder was developed which will store up to 32 time events and provide a hard copy printout. The event recorder consists of an AIM 65 microcomputer with a custom hardware interface and assembly language software. The 32 input lines can be triggered by voltage changes or current sensing.

Stuchlik, D. W.↗
NASA NTRS1989

A global climatology of albedo, roughness length and stomatal resistance for atmospheric general circulation models as represented by the Simple Biosphere Model (SiB)

Components of the Simple Biosphere Model (SiB) of Sellers et al. (1986) were used to generate global monthly fields of surface albedo (0.4-4.0 microns), roughness length and minimum surface (stomatal) resistance. SiB consists of three submodels which describe the roles of radiative transfer, turbulent transfer and surface resistance in determining the energy balance of the vegetated land surface. These three submodels were detached from SiB and used on the SiB parameter set (total and green leaf area index, leaf angle orientation, canopy dimensions, etc.) to calculate global monthly fields of albedo, roughness length and minimum stomatal resistance at 1 x 1 deg resolution. Time series of various parameters are also displayed for each vegetation type for specified grid points. The SiB results compare reasonably well with appropriate measurements obtained from the literature and have the additional merit of being mutually consistent; the three submodels use many common parameters, which ensures that, for each grid area, the calculated surface properties are closely interrelated as is the case in nature. The derived fields provide a check on the operation of the submodels and the correctness of the parameter set. They can also be used as prescribed fields for GCMs that do not have biophysically based land surface parameterizations.

Dorman, J. L.↗
NASA NTRS1997

RL10A-3-3A Rocket Engine Modeling Project

Two RL10A-3-3A rocket engines comprise the main propulsion system for the Centaur upper stage vehicle. Centaur is used with bod Titan and Atlas launch vehicles, carrying military and civilian payloads from high altitudes into orbit and beyond. The RL10 has delivered highly reliable service for the past 30 years. Recently, however, there have been two in-flight failures which have refocused attention on the RL10. This heightened interest has sparked a desire for an independent RL10 modeling capability within NASA and th Air Force. Pratt & Whitney, which presently has the most detailed model of the RL10, also sees merit in having an independent model which could be used as a cross-check with their own simulations. The Space Propulsion Technology Division (SPTD) at the NASA Lewis Research Center has developed a computer model of the RL10A-3-3A. A project team was formed, consisting of experts in the areas of turbomachinery, combustion, and heat transfer. The overall goal of the project was to provide a model of the entire RL10 rocket engine for government use. In the course of the project, the major engine components have been modeled using a combination of simple correlations and detailed component analysis tools (computer codes). The results of these component analyses were verified with data provided by Pratt & Whitney. Select modeling results and test data curves were then integrated to form the RL10 engine system model The purpose of this report is to introduce the reader to the RL10 rocket engine and to describe the engine system model. The RL10 engine and its application to U.S. launch vehicles are described first, followed by a summary of the SPTD project organization, goals, and accomplishments. Simulated output from the system model are shown in comparison with test and flight data for start transient, steady state, and shut-down transient operations. Detailed descriptions of all component analyses, including those not selected for integration with the system model, are included as appendices.

Binder, Michael↗
NASA NTRS2013

Verification of the H2O Linelists with Theoretically Developed Tools

Two basic rules (i.e., the pair identity and the smooth variation rules) resulting from the properties of the energy levels and wave functions of H2O states govern how the spectroscopic parameters vary with the H2O lines within the individually defined groups of lines. With these rules, for those lines involving high j states in the same groups, variations of all their spectroscopic parameters (i.e., the transition frequency, intensity, pressure broadened half-width, pressure-induced shift, and temperature exponent) can be well monitored. Thus, the rules can serve as simple and effective tools to screen the H2O spectroscopic data listed in the HITRAN database and verify the latter's accuracies. By checking violations of the rules occurring among the data within the individual groups, possible errors can be picked up and also possible missing lines in the linelist whose intensities are above the threshold can be identified. We have used these rules to check the accuracies of the spectroscopic parameters and the completeness of the linelists for several important H2O vibrational bands. Based on our results, the accuracy of the line frequencies in HITRAN 2008 is consistent. For the line intensity, we have found that there are a substantial number of lines whose intensity values are questionable. With respect to other parameters, many mistakes have been found. The above claims are consistent with a well known fact that values of these parameters in HITRAN contain larger uncertainties. Furthermore, supplements of the missing line list consisting of line assignments and positions can be developed from the screening results.

spectroscopy↗
NASA NTRS2017

Pressure-Fed LOX/LCH4 Reaction Control System for Spacecraft: Transient Modeling and Thermal Vacuum Hotfire Test Results

An integrated cryogenic liquid oxygen, liquid methane (LOX/LCH4) reaction control system (RCS) was tested at NASA Glenn Research Center's Plum Brook Station in the Spacecraft Propulsion Research Facility (B-2) under vacuum and thermal vacuum conditions. The RCS is a subsystem of the Integrated Cryogenic Propulsion Test Article (ICPTA), a pressure-fed LOX/LCH4 propulsion system composed of a single 2,800 lbf main engine, two 28 lbf RCS engines, and two 7 lbf RCS engines. Propellants are stored in four 48 inch diameter 5083 aluminum tanks that feed both the main engine and RCS engines in parallel. Helium stored cryogenically in a composite overwrapped pressure vessel (COPV) flows through a heat exchanger on the main engine before being used to pressurize the propellant tanks to a design operating pressure of 325 psi. The ICPTA is capable of simultaneous main engine and RCS operation. The RCS engines utilize a coil-on-plug (COP) ignition system designed for operation in a vacuum environment, eliminating corona discharge issues associated with a high voltage lead. There are two RCS pods on the ICPTA, with two engines on each pod. One of these two engines is a heritage flight engine from Project Morpheus. Its sea level nozzle was removed and replaced by an 85:1 nozzle machined using Inconel 718, resulting in a maximum thrust of 28 lbf under altitude conditions. The other engine is a scaled down version of the 28 lbf engine, designed to match the core and overall mixture ratios as well as other injector characteristics. This engine can produce a maximum thrust of 7 lbf with an 85:1 nozzle that was additively manufactured using Inconel 718. Both engines are film-cooled and capable of limited duration gas-gas and gas-liquid operation, as well as steady-state liquid-liquid operation. Each pod contains one of each version, such that two engines of the same thrust level can be fired as a couple on opposite pods. The RCS feed system is composed of symmetrical 3/8 inch lines that tap off of the main propellant manifold to send LOX and LCH4 outboard to the RCS pods. A Thermodynamic Vent System (TVS) is used to condition propellants at each pod by venting through an orifice and then routing the cold expansion products back through tubing that is welded along a large portion of the main RCS feed lines. Prior to final installation on the ICPTA, the RCS engines were tested in a small vacuum chamber at the Johnson Space Center (JSC) Energy Systems Test Area (ESTA) to verify functionality of the new COP ignition system and check out operation of the vacuum nozzles. After engine-level testing, the RCS engines were installed on the vehicle and a series of integrated hot-fire tests were performed at JSC consisting of various pulsing and steady-state firings as well as integrated main engine/RCS operation. The ICPTA was then integrated into the Plum Brook B-2 facility for vacuum and thermal/vacuum testing. Testing in the B-2 facility was composed of multiple thermal and pressure environments. The first set of tests were performed under ambient temperature and altitude pressure conditions. These tests consisted of a range of minimum impulse bit (MIB) pulsing sequences with low duty cycle, analogous to a coast phase in which the RCS is primarily used for station keeping. The primary goal of this sequence is to understand how propellant conditions were effected without an active TVS. In this scenario, consistent gas-gas operation is desirable since it results in a smaller MIB and more efficient propellant consumption. Multiple skin thermocouples are mounted on the feedlines, in addition to a submerged thermocouple on each commodity, in order to gather thermal data on the system. Higher duty cycle pulsing tests were then performed, analogous to an ascent or landing mission phase. The primary goal of this sequence was to examine how well the engines self-conditioned without active TVS when starting from a quiescent state. The TVS was then activated during some tests to demonstrate the capability to quickly condition the engines for higher pulsing demand scenarios. A thermocouple at the TVS outlet allows for the calculation of energy absorbed by the vented propellant. Lastly, tests with longer pulses and multiple engines firing either in sequence or simultaneously were run in order to gather transient system response data on waterhammer. Six total high-speed pressure transducers are installed on the RCS system, one sensor at the end of each propellant manifold line on the pods, and one at the tap-off location for each commodity. This will allow for the accurate characterization of waterhammer in the system under various propellant conditions and firing sequences. Other instrumentation for this test series includes nozzle throat thermocouples, chamber pressure measurement, heat soakback measurement, and tank wall plume impingement temperature measurement. The next set of tests were performed to demonstrate simultaneous main engine and RCS operation. Data from this test will be used to examine if there is any change to nominal operation of the RCS as a result of feed system interaction or other phenomenon. Some of these tests began under high vacuum conditions (target ambient pressure less than 1x10(exp -3) torr) and others began at altitude conditions. The last set of tests were performed with the B-2 cold wall active. Under these tests, many of the same low duty cycle MIB tests were repeated in order to characterize how propellant conditions changed with the lower heat leak. In this scenario the RCS manifold experiences much less heat leak, resulting in a change to how well the engines self-condition. As a result, an increase in maximum waterhammer pressures and a change in natural frequency of the system was expected due to higher density propellants. The lower heat leak should also result in a change to the MIB pulse profile, and data will be examined to understand how MIB repeatability is affected in the different operating environments. Parallel to the test efforts, a set of transient model development efforts were made to predict RCS performance. The primary effort was aimed at producing a SINDA/FLUINT model to predict propellant conditioning up to the engine inlet as a function of different environmental and operating parameters, with the goal of predicting chamber pressure, TVS performance, and propellant consumption over time. Preliminary results for this effort will be presented in comparison with test data. Additional modeling efforts were made using SINDA/FLUINT to predict waterhammer in the system since the software is capable of handling multiphase transient fluid dynamics. These results will be compared with the high-speed pressure transducer test data for validation purposes.

Atwell, Matthew J.↗
NASA NTRS1982

Long term variability of transmission of thin In-Sn and Sn-C films for EUV instrumentation

The transmission variability is reported for two filters in the EUV, where the filters were supported on an 80% transmission nickel mesh and fabricated by means of a vacuum deposition technique. The first film consisted of 2500 A-thick indium, deposited on 500 A-thick tin, and had its primary bandpass in the 740-960 A range. The second consisted of 1800 A-thick tin and 2000 A-thick carbon, with a bandpass of 500-750 A. At the end of 10 months, the transmission of both filters was measured to check variations. It is demonstrated that the EUV transmission of such filters can change over the typical lifetime of satellite missions, and that such variation depends on the storage environment. The use of vacuum, rather than dry nitrogen storage is recommended.

Chakrabarti, S.↗
NASA NTRS1992

Precipitable water and surface humidity over global oceans from special sensor microwave imager and European Center for Medium Range Weather Forecasts

Global fields of precipitable water W from the special sensor microwave imager were compared with those from the European Center for Medium Range Weather Forecasts (ECMWF) model. They agree over most ocean areas; both data sets capture the two annual cycles examined and the interannual anomalies during an ENSO episode. They show significant differences in the dry air masses over the eastern tropical-subtropical oceans, particularly in the Southern Hemisphere. In these regions, comparisons with radiosonde data indicate that overestimation by the ECMWF model accounts for a large part of the differences. As a check on the W differences, surface-level specific humidity Q derived from W, using a statistical relation, was compared with Q from the ECMWF model. The differences in Q were found to be consistent with the differences in W, indirectly validating the Q-W relation. In both W and Q, SSMI was able to discern clearly the equatorial extension of the tongues of dry air in the eastern tropical ocean, while both ECMWF and climatological fields have reduced spatial gradients and weaker intensity.

Liu, W. T.↗
NASA NTRS1995

An Image Processing Algorithm Based On FMAT

Information deleted in ways minimizing adverse effects on reconstructed images. New grey-scale generalization of medial axis transformation (MAT), called FMAT (short for Fuzzy MAT) proposed. Formulated by making natural extension to fuzzy-set theory of all definitions and conditions (e.g., characteristic function of disk, subset condition of disk, and redundancy checking) used in defining MAT of crisp set. Does not need image to have any kind of priori segmentation, and allows medial axis (and skeleton) to be fuzzy subset of input image. Resulting FMAT (consisting of maximal fuzzy disks) capable of reconstructing exactly original image.

Wang, Lui↗
NASA NTRS2002

Large 0/12 GMT Differences of US Vaisala RS80 Observations

The daily differences between the temperatures and heights taken at 0 GMT and 12 GMT by Vaisala RS80 rawinsondes have been calculated. The observations were obtained during selected months from 1998 - 2002 over North America, Europe and Australia. The daily differences are defined by the formula, Delta T = Delta T(sub 0) - 0.5(T(sub -12) - T(sub +12)) where AT is the 0/12 GMT difference, T(sub 0) is the 0 GMT observation and T(sub -12) and T(sub +12) are the 12 GMT observations taken just prior and after the 0 GMT synoptic time. If T(sub +12) is missing then Delta T = T(sub 0) - T(sub -12). A similar expression is used if T(sub -12) is missing. Monthly averages of the increments at each station that launch RS80 rawinsondes are then calculated. The results show positive systematic differences in the stratosphere with values as high as 5 K and 150 m at 10 hPa over the central United States. The values remain generally positive and gradually decrease as the levels descend into the upper troposphere but are still significant. In addition, the maximum at each level is just westward of 90 W at the highest levels and just eastward in the troposphere with smaller values along both coasts. In Canada as well as in Europe and Australia the differences are much smaller with no systematic patterns similar to those that exist over the contiguous United States. Time-series plots of the temperatures and heights at select stations in the United States show that the observed values taken at 0 GMT are consistently higher than those at 12 GMT. Over Canada the differences become much less apparent and some cases non-existent. The observations were obtained through National Centers for Environmental Prediction (NCEP) but were checked with data from other sources to verify that no modifications were made other than those at the stations. Since the data from outside the the United States exhibit no large systematic differences, the preliminary conclusion is that the large differences are artificial and probably originate from the post-processing software at the observing stations.

Redder, Chris↗
NASA NTRS2010

Global VLBI Observations of Weak Extragalactic Radio Sources: Imaging Candidates to Align the VLBI and Gaia Frames

The space astrometry mission Gaia will construct a dense optical QSO-based celestial reference frame. For consistency between optical and radio positions, it will be important to align the Gaia and VLBI frames (International Celestial Reference Frame) with the highest accuracy. In this respect, it is found that only 10% of the ICRF sources are suitable to establish this link (70 sources), either because most of the ICRF sources are not bright enough at optical wavelengths or because they show extended radio emission which precludes reaching the highest astrometric accuracy. In order to improve the situation, we initiated a multi-step VLBI observational project, dedicated to finding additional suitable radio sources for aligning the two frames. The sample consists of about 450 optically-bright radio sources, typically 20 times weaker than the ICRF sources, which have been selected by cross-correlating optical and radio catalogs. The initial observations, aimed at checking whether these sources are detectable with VLBI, and conducted with the European VLBI Network (EVN) in 2007, showed an excellent 90% detection rate. This paper reports on global VLBI observations carried out in March 2008 to image 105 from the 398 previously detected sources. All sources were successfully imaged, revealing compact VLBI structure for about half of them, which is very promising for the future.

Bourda, Geraldine↗
NASA NTRS1982

On the stability of Schwarzschild's triaxial galaxy model

The numerical model for a triaxial galaxy constructed by Schwartzschild (1979) has been tested by means of fully self-consistent three-dimensional n-body numerical experiments that use a representation of this model to start the integration. The integration, study models, initial load, and correcting potential of the experiment are detailed. Preliminary checks included density values, potential values, and integration in potential of an ideal model. The results showed some particle loss and no significant shape change. The model is rugged and robust, and no growing disturbances with growth rate in excess of 0.5 per crossing time could be detected. Runs were done at 50 percent excess halo and with tube orbits reversed.

Smith, B. F.↗
NASA NTRS2006

SSC Geopositional Assessment of the Advanced Wide Field Sensor

The geopositional accuracy of the standard geocorrected product from the Advanced Wide Field Sensor (AWiFS) was evaluated using digital orthophoto quarter quadrangles and other reference sources of similar accuracy. Images were analyzed from summer 2004 through spring 2005. Forty to fifty check points were collected manually per scene and analyzed to determine overall circular error, estimates of horizontal bias, and other systematic errors. Measured errors were somewhat higher than the specifications for the data, but they were consistent with the analysis of the distributing vendor.

Ross, Kenton↗
NASA NTRS2001

Satellite Retrieval of Atmospheric Water Budget over Gulf of Mexico- Caribbean Basin: Seasonal Variability

This study presents results from a multi-satellite/multi-sensor retrieval system designed to obtain the atmospheric water budget over the open ocean. A combination of hourly-sampled monthly datasets derived from the GOES-8 5 Imager and the DMSP 7-channel passive microwave radiometer (SSM/I) have been acquired for the Gulf of Mexico-Caribbean Sea basin. Whereas the methodology is being tested over this basin, the retrieval system is designed for portability to any open-ocean region. Algorithm modules using the different datasets to retrieve individual geophysical parameters needed in the water budget equation are designed in a manner that takes advantage of the high temporal resolution of the GOES-8 measurements, as well as the physical relationships inherent to the SSM/I passive microwave signals in conjunction with water vapor, cloud liquid water, and rainfall. The methodology consists of retrieving the precipitation, surface evaporation, and vapor-cloud water storage terms in the atmospheric water balance equation from satellite techniques, with the water vapor advection term being obtained as the residue needed for balance. Thus, we have sought to develop a purely satellite-based method for obtaining the full set of terms in the atmospheric water budget equation without requiring in situ sounding information on the wind profile. The algorithm is partly validated by first cross-checking all the algorithm components through multiple-algorithm retrieval intercomparisons. More fundamental validation is obtained by directly comparing water vapor transports into the targeted basin diagnosed from the satellite algorithm to those obtained observationally from a network of land-based upper air stations that nearly uniformly surround the basin. Total columnar atmospheric water budget results will be presented for an extended annual cycle consisting of the months of October-97, January-98, April-98, July-98, October-98, and January-1999. These results are used to emphasize the changing relationship in E-P, as well as in the varying roles of storage and advection in balancing E-P both on daily and monthly time scales and on localized and basin space scales. Results from the algorithm-to-algorithm intercomparisons will also be presented in the context of sensitivity testing to help understand the intrinsic uncertainties in the water budget terms.

Smith, Eric A.↗
NASA NTRS1989

Liquid Rocket Booster (LRB) for the Space Transportation System (STS) systems study. Appendix E: Pressure-fed booster test bed for the liquid rocket booster study

The stress analysis/structural design of the Pressure-Fed Booster Engine Test Bed using the existing F-1 Test Facility Test Stand at Huntsville, Alabama is described. The analysis has been coded and set up for solution on NASTRAN. A separate stress program was established to take the NASTRAN output and perform stress checks on the members. Joint checks and other necessary additional checks were performed by hand. The notes include a brief description of other programs which assist in reproducing and reviewing the NASTRAN results. The redesign of the test stand members and the stress analysis was performed per the A.I.S.C. Code. Loads on the stand consist of the loaded run tanks; wind loads; seismic loads; live loads consisting of snow and ice: live and dead loads of steel; and loaded pressurant bottle. In combining loads, wind loads and seismic loads were each combined with full live loads. Wind and seismic loads were not combined. No one third increase in allowables was taken for the environmental loads except at decks 147 and 214, where the increase was used when considering the stay rods, brackets and stay beams. Wind and seismic loads were considered from each of the four coordinate directions (i.e. N,S,E,W) to give eight basic conditions. The analysis was run with the pressurant tank mounted at level 125. One seismic condition was also run with the tank mounted at levels 169 and 214. No failures were noted with mounting at level 169, but extensive deck failure with mounting at level 214 (the loadsets used are included on the tape, but no detailed results are included in the package). Decking support beams at levels 147 and 214 are not included in the model. The stress program thus does not reduce strut lengths to the length between support beams (the struts are attached to the beams at intersection points) and gives stress ratios larger than one for some of the struts. The affected members were therefore checked by hand.

Source record↗
NASA NTRS1975

Modal test - Measurement and analysis requirements

Data from the Viking Orbiter Modal Test Program are used to illustrate modal test measurement and analysis requirements. The test was performed using a multiple shake dwell technique where data were acquired one channel at a time and recorded on paper tape. Up to ten shakers were used simultaneously, with a complete set of data consisting of 290 strain-gage readings and 125 accelerometer readings. The data analysis provided information sufficient to minimize errors in the data. The list of analyses in order of value is orthogonality, residual mass, frequency sweep, data checks to assure good test data, multilevel trends, global kinetic energy, and global strain energy.

Wada, B. K.↗