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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 NTRS1991

Experimental and computational studies of hovering rotor flows

HELIX-I, an essentially standard full-potential CFD helicopter rotor code, is unique in its use of the Clebisch kinematical flow description to specify a freely convecting wake and its capacity for predicting hover performance. A study is presently performed to assess the method's sensitivity to grids and solution-starting techniques. The effects of these parameters on thrust, power, load distribution, and wake geometry are ascertained and compared with an extensive rotor data base. The use of a fairly accurate starting solution yields no obvious advantage over the use of a novel starting method which employs a succession of diminishing artificial flows.

Nsi Mba, M.↗
NASA NTRS1991

Approach to developing reliable space reactor power systems

During Phase II, the Engineering Development Phase, the SP-100 Project has defined and is pursuing a new approach to developing reliable power systems. The approach to developing such a system during the early technology phase is described along with some preliminary examples to help explain the approach. Developing reliable components to meet space reactor power system requirements is based on a top-down systems approach which includes a point design based on a detailed technical specification of a 100-kW power system. The SP-100 system requirements implicitly recognize the challenge of achieving a high system reliability for a ten-year lifetime, while at the same time using technologies that require very significant development efforts. A low-cost method for assessing reliability, based on an understanding of fundamental failure mechanisms and design margins for specific failure mechanisms, is being developed as part of the SP-100 Program.

Mondt, Jack F.↗
NASA NTRS1992

Findings of a review of spacecraft fire safety needs

Discussions from a workshop to guide UCLA and NASA investigators on the state of knowledge and perceived needs in spacecraft fire safety and its risk management are reviewed, for an introduction to an analytical and experimental project in this field. The report summarizes the workshop discussions and includes the visual aids used in the presentations. Probabilistic Safety Assessment (PSA) methods, which are currently not used, would be of great value to the designs and operation of future human-crew spacecraft. Key points in the discussions were the importance of understanding and testing smoldering as a likely fire scenario in space and the need for smoke damage modeling, since many fire-risk models ignore this mechanism and consider only heat damage.

Apostolakis, G. E.↗
NASA NTRS1993

Ceramic matrix composites properties/microstresses with complete and partial interphase bond

A multilevel substructuring technique which includes a unique fiber substructuring concept is used for the analysis of continuous fiber reinforced ceramic matrix composites. This technique has four levels of substructuring--from laminate to ply, to supply, and then to fiber. A stand-alone computer code CEMCAN (Ceramic Matrix Composites Analyzer), incorporating this technique and specifically for the simulation of ceramic matrix composites behavior, is currently under development at NASA Lewis Research Center in Cleveland, Ohio. The thermal and mechanical properties, along with the microstresses, for a SiC/RBSN (silicon carbide fiber and reaction bonded silicon nitride matrix) composite at different fiber volume ratios and varying degrees of interfacial bond around the fiber circumference are computed. Values predicted by CEMCAN computer code are shown to bound the experimentally measured values. Results also show that transverse tensile strength test can be a sensitive test method to assess interfacial conditions.

Mital, Subodh K.↗
NASA NTRS1993

Solar coronal observations and formation of the He II 304 A line

Although a large body of recent work supports the formation of the He II 304 A resonance line by collisional excitation in the quiet sun, the formation mechanism is less clear in strong coronal active regions and flares. The 1989 May 5 flight of the Goddard Solar Extreme Ultraviolet Rocket Telescope and Spectrograph (SERTS-3) provided a data set that is well suited to addressing this question. This paper develops a method of assessment of the line formation mechanism that is based on simple non-LTE theory and is applied to these data. The results support the conclusion of other authors that the 304 A line is formed by collisional excitation in the quiet sun, but that photoionization-recombination (p-r) may play a significant role in coronal active regions, and that p-r is important, and may even be predominant, in many flares.

Jordan, S. D.↗
NASA NTRS1993

Earth imaging results from Galileo's second encounter

The recent flyby of the Galileo spacecraft en route to Jupiter contributes a unique perspective to our view of our home planet. Imaging activities conducted during the second Earth encounter provide an important opportunity to assess new methods and approaches on familiar territory. These include unique multispectral observations, low light-level imaging (searches for aurorae, lightning and artificial lights on the nightside) and experiments with multiple exposure times to extend the effective radiometric resolution and dynamic range of the camera system. Galileo imaging data has the potential to make important contributions to terrestrial remote sensing. This is because the particular set of filters included in the Solid State Imaging system are not presently incorporated in any currently operating Earth-orbiting sensor system. The visible/near-infrared bandpasses of the SSI filters are well suited to remote sensing of geological, glaciological, botanical, and meteorological phenomena. Data from this and the previous Earth encounter may provide an extremely valuable reference point in time for comparison with similar data expected from EOS or other systems in the future, contributing directly to our knowledge of global change. The highest resolution imaging (0.2 km/pixel) during the December, 1992 encounter occurred over the central Andes; a five filter mosaic of visible and near infrared bands displays the remarkable spectral heterogeneity of this geologically diverse region. As Galileo departed the Earth, cooperative imaging with the Near Infrared Mapping Spectrometer (NIMS) instrument targeted Antarctica, Australia, and Indonesia at 1.0 to 2.5 km/pixel resolutions in the early morning local times near the terminator. The Antarctic data are of particular interest, potentially allowing ice grain size mapping using the 889 and 968 nm filters and providing an important means of calibrating the technique for application to the Galilean satellites. As the spacecraft receded further, regional scale imaging provided data which, along with data from the previous encounter, will enable the production of global multispectral mosaics of Earth in each of the SSI filters.

Greenberg, R.↗
NASA NTRS1993

Multigrid schemes for viscous hypersonic flows

Several multigrid schemes are considered for the numerical computation of viscous hypersonic flows. For each scheme, the basic solution algorithm employs upwind spatial discretization with explicit multistage time stepping. Two-level versions of the various multigrid algorithms are applied to the two-dimensional advection equation, and Fourier analysis is used to determine their damping properties. The capabilities of the multigrid methods are assessed by solving two different hypersonic flow problems. Some new multigrid schemes, based on semicoarsening strategies, are shown to be quite effective in relieving the stiffness caused by the high-aspect-ratio cells required to resolve high Reynolds number flows. These schemes exhibit good convergence rates for Reynolds numbers up to 200 x 10(exp 6).

Swanson, R. C.↗
NASA NTRS1992

Psychological training of NASA astronauts for extended missions

The success of operational teams working in remote and hostile environments rests in large part on adequate preparation of those teams prior to emplacement in field settings. Psychological training, directed at the maintenance of crew health and performance becomes increasingly important as space missions grow in duration and complexity. Methods: Topics to be discussed include: the conceptual framework of psychological training; needs analysis; content and delivery options; methods of assessing training efficacy; use of testbeds and analogies and the relationship of training to crew selection and real-time support activities. Results and Conclusions: This paper will discuss the psychological training approach being developed at the NASA/JSC Behavior and Performance Laboratory. This approach will be compared and contrasted with those underway in the U.S. Department of Defense and in other space agencies.

Holland, A. W.↗
NASA NTRS1994

Technology Benefit Estimator (T/BEST): User's Manual

The Technology Benefit Estimator (T/BEST) system is a formal method to assess advanced technologies and quantify the benefit contributions for prioritization. T/BEST may be used to provide guidelines to identify and prioritize high payoff research areas, help manage research and limited resources, show the link between advanced concepts and the bottom line, i.e., accrued benefit and value, and to communicate credibly the benefits of research. The T/BEST software computer program is specifically designed to estimating benefits, and benefit sensitivities, of introducing new technologies into existing propulsion systems. Key engine cycle, structural, fluid, mission and cost analysis modules are used to provide a framework for interfacing with advanced technologies. An open-ended, modular approach is used to allow for modification and addition of both key and advanced technology modules. T/BEST has a hierarchical framework that yields varying levels of benefit estimation accuracy that are dependent on the degree of input detail available. This hierarchical feature permits rapid estimation of technology benefits even when the technology is at the conceptual stage. As knowledge of the technology details increases the accuracy of the benefit analysis increases. Included in T/BEST's framework are correlations developed from a statistical data base that is relied upon if there is insufficient information given in a particular area, e.g., fuel capacity or aircraft landing weight. Statistical predictions are not required if these data are specified in the mission requirements. The engine cycle, structural fluid, cost, noise, and emissions analyses interact with the default or user material and component libraries to yield estimates of specific global benefits: range, speed, thrust, capacity, component life, noise, emissions, specific fuel consumption, component and engine weights, pre-certification test, mission performance engine cost, direct operating cost, life cycle cost, manufacturing cost, development cost, risk, and development time. Currently, T/BEST operates on stand-alone or networked workstations, and uses a UNIX shell or script to control the operation of interfaced FORTRAN based analyses. T/BEST's interface structure works equally well with non-FORTRAN or mixed software analysis. This interface structure is designed to maintain the integrity of the expert's analyses by interfacing with expert's existing input and output files. Parameter input and output data (e.g., number of blades, hub diameters, etc.) are passed via T/BEST's neutral file, while copious data (e.g., finite element models, profiles, etc.) are passed via file pointers that point to the expert's analyses output files. In order to make the communications between the T/BEST's neutral file and attached analyses codes simple, only two software commands, PUT and GET, are required. This simplicity permits easy access to all input and output variables contained within the neutral file. Both public domain and proprietary analyses codes may be attached with a minimal amount of effort, while maintaining full data and analysis integrity, and security. T/BESt's sotware framework, status, beginner-to-expert operation, interface architecture, analysis module addition, and key analysis modules are discussed. Representative examples of T/BEST benefit analyses are shown.

Generazio, Edward R.↗
NASA NTRS1994

Fiber-matrix interphase characterization in composites using ultrasonic velocity data

A nondestructive method is introduced to determine the effective elastic of fiber-matrix interphases from measured composite moduli. The composite moduli are obtained by measuring the angular dependences of ultrasonic longitudinal and transverse phase velocities in planes along and perpendicular to the fibers. Three independent interphase effective moduli are found using micromechanical multiphase models which were applied after averaging composite transverse moduli to account for the composite orthotropy. Sensitivity analysis shows that errors in the calculated interphasial moduli are approximately ten times those in the composite moduli. Experiments are performed on Si3N4 ceramic and Ti-24Al-11Nb intermetallic matrix composites reinforced with carbon coated silicon carbide fibers. The experimental interphasial moduli for the intermetallic composites agree with literature data after accounting for the interphase microstructure. The interphasial moduli for ceramic composites are lower than those for the intermetallic composite due to imperfect mechanical contact between the interphase and the porous matrix. The use of the method to assess the interphase degradation is demonstrated for interphasial oxidation damage. The analysis helps to determine the morphology of the damaged interphase.

Chu, Y. C.↗
NASA NTRS1995

Buckling Analysis of Debonded Sandwich Panel Under Compression

A sandwich panel with initial through-the-width debonds is analyzed to study the buckling of its faceskin when subject to an in-plane compressive load. The debonded faceskin is modeled as a beam on a Winkler elastic foundation in which the springs of the elastic foundation represent the sandwich foam. The Rayleigh-Ritz and finite-difference methods are used to predict the critical buckling load for various debond lengths and stiffnesses of the sandwich foam. The accuracy of the methods is assessed with a plane-strain finite-element analysis. Results indicate that the elastic foundation approach underpredicts buckling loads for sandwich panels with isotropic foam cores.

Sleight, David W.↗
NASA NTRS1996

Semiautomated Motility Assay For Determining Toxicity

Improved method of assessing toxicities of various substances based on observation of effects of those substances on motilities of manageably small number of cells of protozoan species Tetrahema pyriformis. Provides repeatable, standardized tests with minimal handling by technicians and with minimal exposure of technicians to chemicals. Rapid and economical alternative to Draize test.

Noever, David A.↗
NASA NTRS1995

T/BEST: Technology Benefit Estimator Select Features and Applications

A Technology Benefit Estimator (T/BEST) system has been developed to provide a formal method to assess advanced aerospace technologies and quantify the benefit contributions for prioritization. An open-ended, modular approach is used to allow for upgrade and insertion of advanced technology modules. T/BEST's software framework, beginner-to-expert operation, interface architecture, and key analysis modules are discussed. In this paper, selected features and applications of T/BEST are demonstrated. Sample cases pertaining to structural analysis of titanium and composite blades are presented. The performance of hot and cold composite fan blades is also discussed. The cost required to manufacture titanium and composite fan blades is estimated.

Generazio, Edward R.↗
NASA NTRS1995

Spacecraft Cabin Air Quality Control and Its Application to Tight Buildings

Air quality is an important consideration not only for the external environment, but also for the indoor environment. Most people spend a majority of their lives indoors and the air that they breathe is important to their physical and emotional well being. Since most modern building designs have focused on energy efficiency, less fresh air is brought from the outside. As a result, pollutants from building materials, furniture, cleaning, and cooking have no place to go. To make matters worse, most ventilation systems do not include any means for removing pollutants from the recycled air. Unfortunately, pollution at even a small level can result in eye, throat, and lung irritation in addition to chronic headaches, nausea, and fatigue. A spacecraft cabin, which represents the worst case in tight building design, requires special consideration of air quality since any effects pollutants may have on a crewmember can potentially place a mission or other crewmembers at risk. A detailed approach has been developed by the National Aeronautics and Space Administration (NASA) to minimize cabin atmosphere pollution and provide the crew with an environment which is as free of pollutants as possible. This approach is a combination of passive and active contamination control concepts involving the evaluation and selection of materials to be used onboard the spacecraft, the establishment of air quality standards to ensure crew health, and the use of active control means onboard the spacecraft to further ensure an acceptable atmosphere. This approach has allowed NASA to prevent illness by providing crewmembers with a cabin atmosphere which contains pollutant concentrations up to 100 times lower than those specified for terrestrial indoor environments. Standard building construction, however, does not take into account the potentially harmful effects of materials used in the construction process on the health of future occupants and relies primarily on remedial rather than preventive techniques when addressing contamination. This approach results in a building that theoretically has low operating costs, but may actually have high costs associated with lost work days, increased medical claims, decreased productivity, and problem remediation. A similar approach to NASA's may be adopted by the building construction community which can tap the extensive database of material offgassing properties that has been collected to support the space program. Many materials used by NASA are commercially available and are frequently used in building construction. In addition, computer models which have been developed for assessing various methods of active contamination control can be applied to building ventilation system design and the analysis of their economics. Through using NASA' s experience, the expense associated with the current remedial approach can be avoided.

Perry, J. L.↗
NASA NTRS1995

Integrated Logistics Support Analysis of the International Space Station Alpha: An Overview of the Maintenance Time Dependent Parameter Prediction Methods Enhancement

The objective of this publication is to introduce the enhancement methods for the overall reliability and maintainability methods of assessment on the International Space Station. It is essential that the process to predict the values of the maintenance time dependent variable parameters such as mean time between failure (MTBF) over time do not in themselves generate uncontrolled deviation in the results of the ILS analysis such as life cycle costs, spares calculation, etc. Furthermore, the very acute problems of micrometeorite, Cosmic rays, flares, atomic oxygen, ionization effects, orbital plumes and all the other factors that differentiate maintainable space operations from non-maintainable space operations and/or ground operations must be accounted for. Therefore, these parameters need be subjected to a special and complex process. Since reliability and maintainability strongly depend on the operating conditions that are encountered during the entire life of the International Space Station, it is important that such conditions are accurately identified at the beginning of the logistics support requirements process. Environmental conditions which exert a strong influence on International Space Station will be discussed in this report. Concurrent (combined) space environments may be more detrimental to the reliability and maintainability of the International Space Station than the effects of a single environment. In characterizing the logistics support requirements process, the developed design/test criteria must consider both the single and/or combined environments in anticipation of providing hardware capability to withstand the hazards of the International Space Station profile. The effects of the combined environments (typical) in a matrix relationship on the International Space Station will be shown. The combinations of the environments where the total effect is more damaging than the cumulative effects of the environments acting singly, may include a combination such as temperature, humidity, altitude, shock, and vibration while an item is being transported. The item's acceptance to its end-of-life sequence must be examined for these effects.

Sepehry-Fard, F.↗
NASA NTRS1997

Handbook of Analytical Methods for Textile Composites

The purpose of this handbook is to introduce models and computer codes for predicting the properties of textile composites. The handbook includes several models for predicting the stress-strain response all the way to ultimate failure; methods for assessing work of fracture and notch sensitivity; and design rules for avoiding certain critical mechanisms of failure, such as delamination, by proper textile design. The following textiles received some treatment: 2D woven, braided, and knitted/stitched laminates and 3D interlock weaves, and braids.

Cox, Brian N.↗
NASA NTRS1999

Establishing a Distance Learning Plan for International Space Station (ISS) Interactive Video Education Events (IVEE)

Educational outreach is an integral part of the International Space Station (ISS) mandate. In a few scant years, the International Space Station has already established a tradition of successful, general outreach activities. However, as the number of outreach events increased and began to reach school classrooms, those events came under greater scrutiny by the education community. Some of the ISS electronic field trips, while informative and helpful, did not meet the generally accepted criteria for education events, especially within the context of the classroom. To make classroom outreach events more acceptable to educators, the ISS outreach program must differentiate between communication events (meant to disseminate information to the general public) and education events (designed to facilitate student learning). In contrast to communication events, education events: are directed toward a relatively homogeneous audience who are gathered together for the purpose of learning, have specific performance objectives which the students are expected to master, include a method of assessing student performance, and include a series of structured activities that will help the students to master the desired skill(s). The core of the ISS education events is an interactive videoconference between students and ISS representatives. This interactive videoconference is to be preceded by and followed by classroom activities which help the students aftain the specified learning objectives. Using the interactive videoconference as the centerpiece of the education event lends a special excitement and allows students to ask questions about what they are learning and about the International Space Station and NASA. Whenever possible, the ISS outreach education events should be congruent with national guidelines for student achievement. ISS outreach staff should recognize that there are a number of different groups that will review the events, and that each group has different criteria for acceptance. For example, school administrators are more likely to be concerned about an event meeting national standards and the cost of the event. In contrast, a teacher's acceptance of an education event may be directly related to the amount of extra work the event imposes upon that teacher. ISS education events must be marketed differently to the different groups of educators, and must never increase the workload of the average teacher.

Wallington, Clint↗
NASA NTRS1999

Understanding Skill in EVA Mass Handling: An Integrated Methodology for Evaluating Space Suit Mobility and Stability - Volume 4

The empirical investigation of extravehicular activity (EVA) mass handling conducted on NASA's Precision Air-Bearing Floor led to a Phase I SBIR from JSC. The purpose of the SBIR was to design an innovative system for evaluating space suit mobility and stability in conditions that simulate EVA on the surface of the Moon or Mars. The approach we used to satisfy the Phase I objectives was based on a structured methodology for the development of human-systems technology. Accordingly the project was broken down into a number of tasks and subtasks. In sequence, the major tasks were: 1) Identify missions and tasks that will involve EVA and resulting mobility requirements in the near and long term; 2) Assess possible methods for evaluating mobility of space suits during field-based EVA tests; 3) Identify requirements for behavioral evaluation by interacting with NASA stakeholders;.4) Identify necessary and sufficient technology for implementation of a mobility evaluation system; and 5) Prioritize and select technology solutions. The work conducted in these tasks is described in this final volume of the series on EVA mass handling. While prior volumes in the series focus on novel data-analytic techniques, this volume addresses technology that is necessary for minimally intrusive data collection and near-real-time data analysis and display.

McDonald, P. Vernon↗