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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 NTRS2007

Thermal Modeling of the Mars Reconnaissance Orbiter's Solar Panel and Instruments during Aerobraking

The Mars Reconnaissance Orbiter (MRO) launched on August 12, 2005 and started aerobraking at Mars in March 2006. During the spacecraft s design phase, thermal models of the solar panels and instruments were developed to determine which components would be the most limiting thermally during aerobraking. Having determined the most limiting components, thermal limits in terms of heat rate were established. Advanced thermal modeling techniques were developed utilizing Thermal Desktop and Patran Thermal. Heat transfer coefficients were calculated using a Direct Simulation Monte Carlo technique. Analysis established that the solar panels were the most limiting components during the aerobraking phase of the mission.

Dec, John A.↗
NASA NTRS2018

Mitigation of Polystyrene Microsphere Surface Contamination for Wind Tunnel Applications

Polystyrene latex (PSL) microspheres have been utilized as seed material for flow visualization in wind tunnels. However, PSL microspheres have been observed to strongly adhere to wind tunnel and model surfaces. Surface contamination on the cleaning screens that remove vorticity and provide laminar flow in the test section, is particularly problematic. Agglomeration of particles on these screens cause constriction of the airflow through the screen resulting in inconsistent airflow properties in the test section. The adhesion mechanism of PSL microspheres to wind tunnel screens and 316 stainless steel flat plates, were evaluated in a contamination apparatus where small sections of screen material were exposed to PSL-seeded airflow. Using a design of experiments (DOE) methodology airflow seeding parameters were changed to evaluate how these modifications affected the degree of surface contamination. The solution composition, comprised of ethanol and water, was determined to be the most significant factor in particle adhesion. Utilizing image analysis software, data were collected from the contaminated surfaces and incorporated to generate predictive particle contamination models. A relationship was identified between the solvent evaporation rate, and the morphology and magnitude of PSL contaminants on the test surfaces. This analysis can be extended to other solvent mixtures to provide insight into simultaneously improving wind tunnel testing capabilities while diminishing facility contamination.

Wohl, Christopher J.↗
NASA NTRS1993

Lightweight linear alternators with and without capacitive tuning

Permanent magnet excited linear alternators rated tens of kW and coupled to free-piston Stirling engines are presently viewed as promising candidates for long term generation of electric power in both space and terrestrial applications. Series capacitive cancellation of the internal inductive reactance of such alternators was considered a viable way to both increase power extraction and to suppress unstable modes of the thermodynamic oscillation. Idealized toroidal and cylindrical alternator geometries are used for a comparative study of the issues of specific mass and capacitive tuning, subject to stability criteria. The analysis shows that the stator mass of an alternator designed to be capacitively tuned is always greater than the minimum achievable stator mass of an alternator designed with no capacitors, assuming equal utilization of materials ratings and the same frequency and power to a resistive load. This conclusion is not substantially altered when the usually lesser masses of the magnets and of any capacitors are added. Within the reported stability requirements and under circumstances of normal materials ratings, this study finds no clear advantage to capacitive tuning. Comparative plots of the various constituent masses are presented versus the internal power factor taken as a design degree of freedom. The explicit formulas developed for stator core, coil, capacitor, and magnet masses and for the degree of magnet utilization provide useful estimates of scaling effects.

Niedra, Janis M.↗
NASA NTRS1972

Millimeter wave propagation measurements using the ATS 5 satellite

The ATS 5 millimeter wave propagation experiment determines long- and short-term attenuation statistics of operational millimeter wavelength earthspace links as functions of defined meteorological conditions. A preliminary analysis of results with 15 GHz downlink and 32 GHz uplink frequency bands indicates that both frequency bands exhibit an excellent potential for utilization in reliable high data rate earth-space communications systems.

Ippolito, L. J.↗
NASA NTRS1975

Thermal acoustic oscillations, volume 2

A number of thermal acoustic oscillation phenomena and their effects on cryogenic systems were studied. The conditions which cause or suppress oscillations, the frequency, amplitude and intensity of oscillations when they exist, and the heat loss they induce are discussed. Methods of numerical analysis utilizing the digital computer were developed for use in cryogenic systems design. In addition, an experimental verification program was conducted to study oscillation wave characteristics and boiloff rate. The data were then reduced and compared with the analytical predictions.

Spradley, L. W.↗
NASA NTRS1983

The workload book: Assessment of operator workload to engineering systems

The structure and initial work performed toward the creation of a handbook for workload analysis directed at the operational community of engineers and human factors psychologists are described. The goal, when complete, will be to make accessible to such individuals the results of theoretically-based research that are of practical interest and utility in the analysis and prediction of operator workload in advanced and existing systems. In addition, the results of laboratory study focused on the development of a subjective rating technique for workload that is based on psychophysical scaling techniques are described.

Gopher, D.↗
NASA NTRS1988

Proposed modifications to ice accretion/icing scaling theory

The difficulty of conducting full-scale icing tests has long been appreciated. Testing in an icing wind tunnel has been undertaken for decades. While aircraft size and speeds have increased, tunnel facilities have not, thus making subscale geometric tests a necessity. Scaling laws governing these tests are almost exclusively based on analysis performed over 30 years ago and have not been rigorously validated. The following work reviews past scaling analyses and suggests revision to these analyses based on recent experimental observation. It is also suggested, based on the analysis contained herein, that current ice accretion predictive technologies, such as LEWICE when utilized in the glaze ice accretion regime, may need upgrading to more accurately estimate the rate of ice build-up on aerodynamic surfaces.

Bilanin, Alan J.↗
NASA NTRS2008

Rescue Shuttle Flight Re-Entry: Controlling Astronaut Thermal Exposure

A rescue mission for the STS-125 Hubble Telescope Repair Mission requires reentry from space with 11 crew members aboard, exceeding past cabin thermal load experience and risking crew thermal stress potentially causing cognitive performance and physiological decrements. The space shuttle crew cabin air revitalization system (ARS) was designed to support a nominal crew complement of 4 to 7 crew and 10 persons in emergencies, all in a shirt-sleeve environment. Subsequent to the addition of full pressure suits with individual cooling units, the ARS cannot maintain a stable temperature in the crew cabin during reentry thermal loads. Bulk cabin thermal models, used for rescue mission planning and analysis of crew cabin air, were unable to accurately represent crew workstation values of air flow, carbon dioxide, and heat content for the middeck. Crew temperature models suggested significantly elevated core temperatures. Planning for an STS-400 potential rescue of seven stranded crew utilized computational fluid dynamics (CFD) models to demonstrate inhomogeneous cabin thermal properties and improve analysis compared to bulk models. In the absence of monitoring of crew temperature, heart rate, metabolic rate and incomplete engineering data on the performance of the integrated cooling garment/cooling unit (ICG/CU) at cabin temperatures above 75 degrees F, related systems & models were reevaluated and tests conducted with humans in the loop. Changes to the cabin ventilation, ICU placement, crew reentry suit-donning procedures, Orbiter Program wave-off policy and post-landing power down and crew extraction were adopted. A second CFD and core temperature model incorporated the proposed changes and confirmed satisfactory cabin temperature, improved air distribution, and estimated core temperatures within safe limits. CONCLUSIONS: These changes in equipment, in-flight and post-landing procedures, and policy were implemented for the STS-400 rescue shuttle & will be implemented in any future rescue flights from the International Space Station of stranded shuttle crews.

Gillis, David B.↗
NASA NTRS1979

The ground processing simulator - A tool for mission model analysis and planning from a launch site perspective

The Ground Processing Simulator (GPS) is a computer-assisted planning tool designed and developed for Space Shuttle launch site application. Utilizing two programming languages, General Purpose Simulation System and FORTRAN, GPS provides the capability to analyze proposed Shuttle mission models via computer simulation. NASA-developed mission models which specify Shuttle launch rates, mission durations, cargo elements, and designated launch site are tested for feasibility by the simulator. GPS produces facility utilization schedules (including the identification of conflicts), launch data options, cargo element requirement dates, ground support equipment inventory requirements, and other data necessary to assess both the programmatic and launch site resources required to support proposed mission models. The purpose of this computer-assisted analysis is to determine methods which will permit the launching of the maximum number of cargoes per year on schedule, and in the sequence desired, with the minimum expenditure of resources.

Ralph, J. A.↗
NASA NTRS1978

Computer-aided analysis and design of the shape rolling process for producing turbine engine airfoils

Mild steel (AISI 1018) was selected as model cold rolling material and Ti-6A1-4V and Inconel 718 were selected as typical hot rolling and cold rolling alloys, respectively. The flow stress and workability of these alloys were characterized and friction factor at the roll/workpiece interface was determined at their respective working conditions by conducting ring tests. Computer-aided mathematical models for predicting metal flow and stresses, and for simulating the shape rolling process were developed. These models utilized the upper bound and the slab methods of analysis, and were capable of predicting the lateral spread, roll separating force, roll torque, and local stresses, strains and strain rates. This computer-aided design system was also capable of simulating the actual rolling process, and thereby designing the roll pass schedule in rolling of an airfoil or a similar shape.

Lahoti, G. D.↗
NASA NTRS1981

A time Fourier analysis of zonal averaged ozone heating rates

A time-Fourier analysis is presented for the yearly variation of the zonal averaged ozone heating rates in the middle atmosphere based on a model study. The ozone heating rates are determined by utilizing two-dimensional ozone distributions, the altitude and latitude, and by including the effect of the curved earth's atmosphere. In addition, assumptions are introduced to the yearly variations of the ozone distributions due to the lack of sufficient existing ozone data. Among other results, it is shown that the first harmonic component indicates that the heating rates are completely out of phase between the northern and southern hemispheres. The second Fourier component shows a symmetric pattern with respect to the equator, as well as five distinct local extreme values of the ozone heating rate. The third harmonic component shows a pattern close to that of the first component except in the regions above 70 deg between 45-95 km in both hemispheres.

Wang, P.-H.↗
NASA NTRS1986

Sublaminate analysis of interlaminar fracture in composites

A simple analysis method based upon a transverse shear deformation theory and a sublaminate approach is utilized to analyze a mixed-mode edge delamination specimen. The analysis provides closed form expressions for the interlaminar shear stresses ahead of the crack, the total energy release rate, and the energy release rate components. The parameters controlling the behavior are identified. The effect of specimen stacking sequence and delamination interface on the strain energy release rate components is investigated. Results are compared with a finite element simulation for reference. The simple nature of the method makes it suitable for preliminary design analyses which require a large number of configurations to be evaluated quickly and economically.

Armanios, E. A.↗
NASA NTRS1990

High power density dc/dc converter: Selection of converter topology

The work involved in the identification and selection of a suitable converter topology is described. Three new dc/dc converter topologies are proposed: Phase-Shifted Single Active Bridge DC/DC Converter; Single Phase Dual Active Bridges DC/DC Converter; and Three Phase Dual Active Bridges DC/DC Converter (Topology C). The salient features of these topologies are: (1) All are minimal in structure, i.e., each consists of an input and output bridge, input and output filter and a transformer, all components essential for a high power dc/dc conversion process; (2) All devices of both the bridges can operate under near zero-voltage conditions, making possible a reduction of device switching losses and hence, an increase in switching frequency; (3) All circuits operate at a constant frequency, thus simplifying the task of the magnetic and filter elements; (4) Since, the leakage inductance of the transformer is used as the main current transfer element, problems associated with the diode reverse recovery are eliminated. Also, this mode of operation allows easy paralleling of multiple modules for extending the power capacity of the system; (5) All circuits are least sensitive to parasitic impedances, infact the parasitics are efficently utilized; and (6) The soft switching transitions, result in low electromagnetic interference. A detailed analysis of each topology was carried out. Based on the analysis, the various device and component ratings for each topology operating at an optimum point, and under the given specifications, are tabulated and discussed.

Divan, Deepakraj M.↗
NASA NTRS1990

Modification of the background flow by roll vortices

Use of observed wind profiles, such as those obtained from ascent or descent aircraft soundings, for the identification of the expected roll modes is hindered by the fact that these modes are able to modify the wind profiles. When such modified wind profiles are utilized to estimate the critical values of the dynamic and thermodynamic forcing rates, large errors in the preferred orientation angles and aspect ratios of the rolls may result. Nonlinear analysis of a 14 coefficient spectral model of roll circulations shows that the primary modification of the background wind is the addition of a linear component. When the linear profile having the correct amount of shear is subtracted from the observed cross-roll winds, then the pre-roll wind profile can be estimated. A preliminary test of this hypothesis is given for a case in which cloud streets were observed during FIRE.

Shirer, Hampton N.↗
NASA NTRS1993

The 1992-1993 advanced design program. Part 1: The Mars methane engine project. Part 2: The Mars oxygen processor new furnace

Three constituents of the Martian atmosphere, methane, carbon dioxide, and oxygen, can be used for internal combustion in engines utilized for future space exploration on Mars. These three gases, considered as the test case in this research, will be examined to determine required flow rates needed for combustion and optimization of engine performance. Results of the test case are examined in relation to a base case of methane and air for comparative purposes. Testing of exhaust temperatures, cylinder pressure, and exhaust gas analysis were performed for the base case and test case. Also described is a study utilizing a zirconia cell to convert carbon dioxide into usable oxygen to help support future Mars missions.

Lauer, Stephen↗
NASA NTRS1999

Numerical Analysis of the Trailblazer Inlet Flowfield for Hypersonic Mach Numbers

A study of the Trailblazer vehicle inlet was conducted using the Global Air Sampling Program (GASP) code for flight Mach numbers ranging from 4-12. Both perfect gas and finite rate chemical analysis were performed with the intention of making detailed comparisons between the two results. Inlet performance was assessed using total pressure recovery and kinetic energy efficiency. These assessments were based upon a one-dimensional stream-thrust-average of the axisymmetric flowfield. Flow visualization utilized to examine the detailed shock structures internal to this mixed-compression inlet. Kinetic energy efficiency appeared to be the least sensitive to differences between the perfect gas and finite rate chemistry results. Total pressure recovery appeared to be the most sensitive discriminator between the perfect gas and finite rate chemistry results for flight Mach numbers above Mach 6. Adiabatic wall temperature was consistently overpredicted by the perfect gas model for flight Mach numbers above Mach 4. The predicted shock structures were noticeably different for Mach numbers from 6-12. At Mach 4, the perfect gas and finite rate chemistry models collapse to the same result.

Steffen, C. J., Jr.↗
NASA NTRS1990

Analysis of coolant flow and heat transfer in the SSME HPOTP Number 4 bearing assembly

The PHOENICS code has been applied to simulate the flow of liquid oxygen through the number 4 ball bearing assembly of the Space Shuttle Main Engine High-Pressure Oxidizer Turbopump. The Body-Fitted Coordinate system capability of PHOENICS was utilized to create a geometrically accurate model. Effects accounted for by the model include the rotation rate of the calculation domain, viscous heating in the liquid oxygen and two-phase effects due to LOX boiling. A separation program was used to account for conduction within a ball bearing element which was coupled with the PHOENICS flow and heat transfer analysis. Solutions have been obtained for the velocity and temperature fields within the LOX coolant and the temperature within the ball element. The predicted ball temperatures indicate that the coolant is boiling in the region near the ball surface.

Owens, S. F.↗
NASA NTRS2014

Investigation of HZETRN 2010 as a Tool for Single Event Effect Qualification of Avionics Systems

NASA's future missions are focused on deep space for human exploration that do not provide a simple emergency return to Earth. In addition, the deep space environment contains a constant background Galactic Cosmic Ray (GCR) radiation exposure, as well as periodic Solar Particle Events (SPEs) that can produce intense amounts of radiation in a short amount of time. Given these conditions, it is important that the avionics systems for deep space human missions are not susceptible to Single Event Effects (SEE) that can occur from radiation interactions with electronic components. The typical process to minimizing SEE effects is through using heritage hardware and extensive testing programs that are very costly. Previous work by Koontz, et al. [1] utilized an analysis-based method for investigating electronic component susceptibility. In their paper, FLUKA, a Monte Carlo transport code, was used to calculate SEE and single event upset (SEU) rates. This code was then validated against in-flight data. In addition, CREME-96, a deterministic code, was also compared with FLUKA and in-flight data. However, FLUKA has a long run-time (on the order of days), and CREME-96 has not been updated in several years. This paper will investigate the use of HZETRN 2010, a deterministic transport code developed at NASA Langley Research Center, as another tool that can be used to analyze SEE and SEU rates. The benefits to using HZETRN over FLUKA and CREME-96 are that it has a very fast run time (on the order of minutes) and has been shown to be of similar accuracy as other deterministic and Monte Carlo codes when considering dose [2, 3, 4]. The 2010 version of HZETRN has updated its treatment of secondary neutrons and thus has improved its accuracy over previous versions. In this paper, the Linear Energy Transfer (LET) spectra are of interest rather than the total ionizing dose. Therefore, the LET spectra output from HZETRN 2010 will be compared with the FLUKA and in-flight data to validate HZETRN 2010 as a computational tool for SEE qualification by analysis. Furthermore, extrapolation of these data to interplanetary environments at 1 AU will be investigated to determine whether HZETRN 2010 can be used successfully and confidently for deep space mission analyses.

Rojdev, Kristina↗