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At least 523 records · Page 29
All sourcesNASA NTRSDOE OSTI
NASA NTRS1997

Adventures in Technology = Options in Math and Science

All five school systems on the Virginia Peninsula participate with a total of 21 middle schools in the ATOMS program. More than 20,000 students have participated in the pipeline programs since 1989. The focus has been on creating a diverse pool of academically-prepared students. The number of minority students participating has steadily increased, reaching 49.1 % in 1997. Female participation has remained steady at 55.4%. Female and minority participation will continue to receive high priority. The programs were evaluated by means of student, teacher, and counselor surveys. Questionnaires are distributed immediately after each intervention. The respondents are asked questions concerning the appropriateness of the activity, their interest level and change in opinion after the intervention. More than 90% of all students rate each activity as "Interesting" to "Very Interesting." Almost 70 % of students indicate they intend to take additional higher level mathematics courses in high school after participating in the Site and Campus Visits. Between 70 and 80 % (79.3 % after the Career Awareness Activity, 72.0 % after the Industry Site Visit) of students indicated they have a better understanding of why math and science are important school subjects after participation in each ATOMS activity. Comparisons in scores from the Iowa Test of Basic Skills have been made between the ATOMS students and the remainder of the seventh and eighth grade populations. ATOMS students' math and science achievement scores from the fifth grade were near the district average. After participating in ATOMS, students scored significantly higher than their peers. ATOMS students enrolled at TNCC have been identified and are being tracked further for achievement.

Quanty, Michael↗
NASA NTRS1998

Choosing Meteorological Input for the Global Modeling Initiative Assessment of High Speed Aircraft

The Global Modeling Initiative (GMI) science team is developing a three dimensional chemistry and transport model (CTM) to be used in assessment of the atmospheric effects of aviation. Requirements are that this model be documented, be validated against observations, use a realistic atmospheric circulation, and contain numerical transport and photochemical modules representing atmospheric processes. The model must also retain computational efficiency to be tractable to use for multiple scenarios and sensitivity studies. To meet these requirements, a facility model concept was developed in which the different components of the CTM are evaluated separately. The first use of the GMI model will be to evaluate the impact of the exhaust of supersonic aircraft on the stratosphere. The assessment calculations will depend strongly on the wind and temperature fields used by the CTM. Three meteorological data sets for the stratosphere are available to GMI: the National Center for Atmospheric Research Community Climate Model (CCM2), the Goddard Earth Observing System Data Assimilation System (GEOS DAS), and the Goddard Institute for Space Studies general circulation model (GISS). Objective criteria were established by the GMI team to identify the data set which provides the best representation of the stratosphere. Simulations of gases with simple chemical control were chosen to test various aspects of model transport. The three meteorological data sets were evaluated and graded based on their ability to simulate these aspects of stratospheric measurements. This paper describes the criteria used in grading the meteorological fields. The meteorological data set which has the highest score and therefore was selected for GMI is CCM2. This type of objective model evaluation establishes a physical basis for interpretation of differences between models and observations. Further, the method provides a quantitative basis for defining model errors, for discriminating between different models, and for ready re-evaluation of improved models. These in turn will lead to a higher level of confidence in assessment calculations.

Douglas, A. R.↗
NASA NTRS1997

Science, Engineering, Mathematics and Aerospace Academy

This is an annual report on the Science, Engineering, Mathematics, and Aerospace Academy (SEMAA), which is run as a collaborative effort of NASA Lewis Research Center, and Cuyahgoga Community College. The purpose of SEMA is to increase the percentage of African Americans, and Hispanics in the fields of science and technology. The SEMAA program reaches from kindergarden, to grade 12, involving the family of under-served minorities in the education of the children. The year being reported (i.e., 1996-1997) saw considerable achievement. The program served over 1,939 students, and 120 parents were involved in various seminars. The report goes on to review the program and its implementation for each grade level. It also summarizes the participation, by gender and ethnicity.

Source record↗
NASA NTRS1999

Choosing Meteorological Input for the Global Modeling Initiative Assessment of High Speed Aircraft

The Global Modeling Initiative (GMI) science team is developing a three dimensional chemistry and transport model (CTM) to be used in assessment of the atmospheric effects of aviation. Requirements are that this model be documented be validated against observations, use a realistic atmospheric circulation, and contain numerical transport and photochemical modules representing atmospheric processes. The model must also retain computational efficiency to be tractable to use for multiple scenarios and sensitivity studies. To meet these requirements, a facility model concept was developed in which the different components of the CTM are evaluated separately. The first use of the GMI model will be to evaluate the impact of the exhaust of supersonic aircraft on the stratosphere. The assessment calculations will depend strongly on the wind and temperature fields used by the CTM. Three meteorological data sets for the stratosphere are available to GMI: the National Center for Atmospheric Research Community Climate Model (CCM2), the Goddard Earth Observing System Data Assimilation System (GEOS DAS), and the Goddard Institute for Space Studies general circulation model (GISS). Objective criteria were established by the GMI team to identify the data set which provides the best representation of the stratosphere. Simulations of gases with simple chemical control were chosen to test various aspects of model transport. The three meteorological data sets were evaluated and graded based on their ability to simulate these aspects of stratospheric measurements. This paper describes the criteria used in grading the meteorological fields. The meteorological data set which has the highest score and therefore was selected for GMI is CCM2. This type of objective model evaluation establishes a physical basis for interpretation of differences between models and observations. Further, the method provides a quantitative basis for defining model errors, for discriminating between different models, and for ready re-evaluation of improved models. These in turn will lead to a higher level of confidence in assessment calculations.

Douglass, A. R.↗
NASA NTRS1997

The Kinematics of Treadmill Locomotion in Space

Locomotion on a treadmill in 0 G will probably remain a centerpiece of NASA's exercise countermeasures programme. This form of physical activity has the potential to cause large bone and muscle forces as well as loading during a period of continuous treadmill exercise. A critical concern is the provision of a treadmill which can approximate 1 G performance in space. At this point, no adequate objective measurements of in-flight treadmill kinetics or of the human response to this activity have been made. Interpretation of the results obtained in the present study is limited by the following: (1) bungee tensions were not measured; (2) ground reaction forces were not measured in parallel with the kinematic measurements; and (3) the instrumentation used to film the astronauts could itself have been affected by microgravity. Despite these shortcomings, what is apparent is that exercise during NASA missions STS 7 and STS 8 resulted in leg motions that were similar to those found during 1 G locomotion on an inclined passive treadmill and on an active treadmill at an even steeper grade. In addition, it was apparent that the majority of the loads were transmitted through the forefoot, and one can surmise that this style of running would result in physiologically significant tensions in the calf musculature and resultant ankle compressive loading. Further speculation regarding limb loading is complicated by the fact that varying amounts of force are transmitted through (1) the treadmill handle and (2) bungee cords that act as a tether. New generations of treadmills are being manufactured that could provide I important information for planners of long-duration space missions. If these types of treadmill are flown on future missions, it will be possible to control bungee tensions more precisely, control for grade and speed, and, most importantly, provide data on the rates and magnitudes of limb loading. These data could then be incorporated into biomechanical models of the lower limb to more fully understand mechanisms of load transmission from distal to proximal structures and to optimize in-flight exercise protocols in such a way that muscle and bone loss could be reduced.

Thornton, W. E.↗
NASA NTRS2000

A Compact X-Ray System for Macromolecular Crystallography

We describe the design and performance of a high flux x-ray system for macromolecular crystallography that combines a microfocus x-ray generator (40 gm FWHM spot size at a power level of 46.5Watts) and a 5.5 mm focal distance polycapillary optic. The Cu K(sub alpha) X-ray flux produced by this optimized system is 7.0 times above the X-ray flux previously reported. The X-ray flux from the microfocus system is also 3.2 times higher than that produced by the rotating anode generator equipped with a long focal distance graded multilayer monochromator (Green optic; CMF24-48-Cu6) and 30% less than that produced by the rotating anode generator with the newest design of graded multilayer monochromator (Blue optic; CMF12-38-Cu6). Both rotating anode generators operate at a power level of 5000 Watts, dissipating more than 100 times the power of our microfocus x-ray system. Diffraction data collected from small test crystals are of high quality. For example, 42,540 reflections collected at ambient temperature from a lysozyme crystal yielded R(sub sym) 5.0% for the data extending to 1.7A, and 4.8% for the complete set of data to 1.85A. The amplitudes of the reflections were used to calculate difference electron density maps that revealed positions of structurally important ions and water molecules in the crystal of lysozyme using the phases calculated from the protein model.

Gubarev, Mikhail↗
NASA NTRS2000

NARC Rayon Replacement Program for the Space Shuttle Reusable Solid Rocket Motor Nozzle: Screening Summary

Thiokol Corporation and NASA MSFC are jointly developing a replacement for North American Rayon Corporation (NARC) Aerospace Grade Rayon (1650/720 continuous filament), the precursor for the Carbon Cloth Phenolic (CCP) ablatives used in the Space Shuttle Reusable Solid Rocket Motor (RSRM) Nozzles. NARC discontinued production of Aerospace Grade Rayon in September 1997. NASA maintains a stockpile of NARC Rayon to support RSRM production through the summer of 2005. The program plan for selection and qualification of a replacement for NARC rayon was approved in August 1998. Screening activities began in February 1999. The intent of this paper is to provide a summary of the data generated during the screening phase of the NARC Rayon Replacement Program. Twelve cellulose based fibers (rayon and lyocell) were evaluated. These fibers were supplied by three independent vendors. Many of these fibers were carbonized by two independent carbonizers. Each candidate was tested according to standard acceptance test methods at each step of the manufacturing process. Additional testing was performed with the candidate CCPS, including hot fire tests, Process studies and mechanical and thermal characterization. Six of the twelve fiber candidates tested were dropped at the conclusion of Phase 1. The reasons for the elimination of these candidates included; difficulties in processing the material in the whitegoods, carbon and CCP forms; poor composite mechanical performance; and future availability concerns. The remaining six fibers demonstrated enough promise to merit continued evaluation and optimization of the CCP fabrication process. Note: Certain CCP data falls under the restrictions of US export laws, (ITAR, etc.) and will not be included in this paper.

Cook, R. V.↗
NASA NTRS2000

Development and Testing of Cooled CMCs for High Thermal Flux Applications

Ceramic Matrix Composites (CMCS) offer the potential for significant weight savings and improved performance for a range of propulsion components utilizing refractory materials. This paper describes the fabrication and testing of functionally graded CMCs produced via a low cost process that represents an order of magnitude cost savings over conventionally fabricated CMCS. Test cylinders were fabricated, characterized and evaluated during exposure to high thermal fluxes of up to 10MW/meters squared at the Laser Hardened Materials Evaluation Laboratory (LHMEL). The bulk density of the CMC tubes was approximately 2.2 grams per cubic centimeters. The performance of cryogenically cooled CMCs was compared with uncooled CMCs against similar thermal loads, and fundamental property data collected for this relatively new breed of CMC. Finally, test thrust cells were fabricated from the functionally graded composite and tested using liquid H2 and O2 propellants at NASA Glen.

Patterson , Mark↗
NASA NTRS2000

Statistical Analysis of Risk Factors in the Prebreathe Reduction Protocol

The 165 exposures from four 2-hour protocols were analyzed for correlations or trends between decompression sickness (DCS) or venous gas emboli (VGE), and variables that affect risk in the subject and astronaut populations. The assumption in this global survey is that the distributions of gender, age, body mass index, etc., are equally represented in all four tested procedures. We used Student t-test for comparisons between means and chi-square test between comparisons of proportions with p<0.05 defining a significant level. The type and distribution of the 19 cases of DCS were similar to historical cases. There was no correlation of age, gender, body mass index or fitness level with greater incidence of DCS or VGE. However increased age was associated with more Grade IV VGE in males. The duration and quantity of exercise during prebreathe is inversely related to risk of DCS and VGE. The latency time for VGE was longer (103 min +/- 56 SD, n = 15) when the ergometry was done approximately 15 min into the prebreathe than when done at the start of the prebreathe (53 min +/- 31, n = 13). The order of the ergometry did not influence the overall DCS and VGE incidence. We identified variables other than those of the prebreathe procedures that influence the DCS and VGE outcome. The analysis suggests that males over 40 years have a high incidence of Grade IV VGE.

Gerth, Wayne A.↗
NASA NTRS2000

Design of a 2-Hour Prebreathe Protocol for Space Walks (EVAs) from the International Space Station (ISS)

The majority of extravehicular activities (EVAs) performed from the shuttle use a 10.2 psi staged decompression. The International Space Station (ISS) will operate at 14.7 psi, requiring crews to "campout" in the airlock at 10.2 psi. The constraints associated with campout (crew isolation, oxygen usage, and waste management), provided the rationale to develop a 2-hour prebreathe protocol from 14.7 psi. Previous studies on the affect of microgravity and exercise during prebreathe suggested the feasibility of this approach. Various combinations of adynamia (nonwalking subjects), prebreathe exercise doses, and space suit donning options (10.2 vs. 14.7 psi) were analyzed against timeline and consumable constraints. Prospective decompression sickness (DCS) and venous gas emboli (VGE) accept/reject criteria were defined from statistical analysis of historical DCS data, combined with risk management of DCS under ISS mission circumstances. Maximum operational DCS levels were defined based on protecting for EVA capability with two crew members at 95% confidence, throughout ISS lifetime (within the constraints of NASA DCS disposition policy JPG 1800.3). The accept / reject limits were adjusted for greater safety (including Grade IV VGE criteria) based on analysis of related medical factors. Monte-Carlo simulation was performed to design a closed sequential, multi-center laboratory trial, including the capability of rejecting the primary protocol and testing at least one alternate exercise dose, within the 2-hour prebreathe. The 2-hour protocol incorporates 0, breathing for 5 0 min at 14.7 psi, including 10 min dual cycle ergometry at 75%VO(2max). It requires an additional 30 minO2breathing during depress from 14.7 to 10.2 psi, followed by a 30-60 min suit donning break at 10.2 psi/26.5% O2. It concludes with a 40 min in-suit O2 prebreathe. The protocol would be accepted for operations, if the incidence of DCS was less than 15% and Grade IV VGE less than 20%, both at 95% confidence. The above protocol and accept/reject limits were implemented in a multi-center study.

Gernhardt, M. L.↗
NASA NTRS2000

Evaluating the Effectiveness of the 1998-1999 NASA CONNECT Program

NASA CONNECT is a standards-based, integrated mathematics, science, and technology series of 30-minute instructional distance learning (satellite and television) programs for students in grades 5-8. Each of the five programs in the 1998-1999 NASA CONNECT series included a lesson, an educator guide, a student activity or experiment, and a web-based component. In March 1999, a mail (self-reported) survey (booklet) was sent to a randomly selected sample of 1,000 NASA CONNECT registrants. A total of 401 surveys (351 usable) were received by the established cut-off date. Most survey questions employed a 5-point Likert-type response scale. Survey topics included: (1) instructional technology and teaching, (2) instructional programming and technology in the classroom, (3) the NASA CONNECT program, (4) classroom use of computer technology, and (5) demographics. About 68% of the respondents were female, about 88% identified "classroom teacher" as their present professional duty, about 75% worked in a public school, and about 67% held a master's degree or master's equivalency. Regarding NASA CONNECT, respondents reported that: (1) they used the five programs in the 1998-1999 NASA CONNECT series; (2) the stated objectives for each program were met (4.49); (3) the programs were aligned with the national mathematics, science, and technology standards (4.61); (4) program content was developmentally appropriate for grade level (4.25); and (5) the programs in the 1998-1999 NASA CONNECT series enhanced/enriched the teaching of mathematics, science, and technology (4.45).

Pinelli, Thomas E.↗
NASA NTRS2000

A Compact X-Ray System for Macromolecular Crystallography

We describe the design and performance of a high flux x-ray system for a macromolecular crystallography that combines a microfocus x-ray generator (40 micrometer full width at half maximum spot size at a power level of 46.5 W) and a collimating polycapillary optic. The Cu Ka lpha x-ray flux produced by this optimized system through a 500,um diam orifice is 7.0 times greater than the x-ray flux previously reported by Gubarev et al. [M. Gubarev et al., J. Appl. Crystallogr. 33, 882 (2000)]. The x-ray flux from the microfocus system is also 2.6 times higher than that produced by a rotating anode generator equipped with a graded multilayer monochromator (green optic, Osmic Inc. CMF24-48-Cu6) and 40% less than that produced by a rotating anode generator with the newest design of graded multilayer monochromator (blue optic, Osmic, Inc. CMF12-38-Cu6). Both rotating anode generators operate at a power level of 5000 W, dissipating more than 100 times the power of our microfocus x-ray system. Diffraction data collected from small test crystals are of high quality. For example, 42 540 reflections collected at ambient temperature from a lysozyme crystal yielded R(sub sym)=5.0% for data extending to 1.70 A, and 4.8% for the complete set of data to 1.85 A. The amplitudes of the observed reflections were used to calculate difference electron density maps that revealed positions of structurally important ions and water molecules in the crystal of lysozyme using the phases calculated from the protein model.

Gubarev, Mikhail↗
NASA NTRS2001

Thermo-Elastic Analysis of Internally Cooled Structures Using a Higher Order Theory

This paper presents the results of a study on the thermomechanical behavior of internally cooled silicon nitride structures. Silicon nitride is under consideration for elevated temperature aerospace engine applications. and techniques for lowering the operating temperature of structures composed of this material are under development. Lowering the operating temperature provides a large payoff in terms of fatigue life and may be accomplished through the use of thermal barrier coatings (TBC's) and the novel concept of included cooling channels. Herein, an in-depth study is performed on the behavior of a flame-impinged silicon nitride plate with a TBC and internal channels cooled by forced air. The analysis is performed using the higher order theory for functionally graded materials (HOTFGM), which has been developed through NASA Glenn Research Center funding over the past several years. HOTFGM was chosen over the traditional finite element approach as a prelude to an examination of functionally graded silicon nitride structures for which HOTFGM is ideally suited. To accommodate the analysis requirement% of the internally cooled plate problem, two crucial enhancements were made to the two-dimensional Cartesian-based version of HOTFGM. namely, incorporation of internal boundary capabilities and incorporation of convective boundary conditions. Results indicate the viability and large benefits of cooling the plate via forced air through cooling channels. Furthermore, cooling can positively impact the stress and displacement fields present in the plate, yielding an additional payoff in terms of fatigue life. Finally, a spin-off capability resulted from inclusion of internal boundaries within HOTFGM; the ability to simulate the thermo-elastic response of structures with curved surfaces. This new capability is demonstrated, and through comparison with an analytical solution, shown to be viable and accurate.

Arnold, Steven M.↗
NASA NTRS2000

Echo the Bat and the Pigeon Adventure

A multimedia, CD ROM to teach 2nd graders about remote sensing was created and developed into a web site. Distribution was expanded for Grades K-4 or 5-8. The idea was to have a story introduction, interactive story and a teacher's website. Interactive Multimedia Adventures in Grade School Education using Remote Sensing (I.M.A.G.E.R.S.) was created. The lessons are easy to use, readily available and aligned with national standards. This resource combines hands-on activities with an interactive web site

Butcher, Ginger↗
NASA NTRS2002

Evaluating the Effectiveness of the 1999-2000 NASA CONNECT Program

NASA CONNECT is a standards-based, integrated mathematics, science, and technology series of 30-minute instructional distance learning (satellite and television) programs for students in grades 6-8. Each of the five programs in the 1999-2000 NASA CONNECT series included a lesson, an educator guide, a student activity or experiment, and a web-based component. In March 2000, a mail (self-reported) survey (booklet) was sent to a randomly selected sample of 1,000 NASA CONNECT registrants. A total of 336 surveys (269 usable) were received by the established cut-off date. Most survey questions employed a 5-point Likert-type response scale. Survey topics included (1) instructional technology and teaching, (2) instructional programming and technology in the classroom, (3) the NASA CONNECT program, (4) classroom use of computer technology, and (5) demographics. About 73% of the respondents were female, about 92% identified "classroom teacher" as their present professional duty, about 90% worked in a public school, and about 62% held a master's degree or master's equivalency. Regarding NASA CONNECT, respondents reported that (1) they used the five programs in the 1999-2000 NASA CONNECT series; (2) the stated objectives for each program were met (4.54); (3) the programs were aligned with the national mathematics, science, and technology standards (4.57); (4) program content was developmentally appropriate for grade level (4.17); and (5) the programs in the 1999-2000 NASA CONNECT series enhanced/enriched the teaching of mathematics, science, and technology (4.51).

Pinelli, Thomas E.↗
NASA NTRS1996

A Cross-Industry Analysis of LOFT Debriefings

Line Oriented Simulation (LOS) iss widely used to provide crews opportunities to practice Cockpit Resource Management (CRM) concepts in realistic, challenging simulated flight situations. LOS includes both Line Oriented Flight Training (LOFT), the original "non-jeopardy" form in which the crews are not graded on their performance, and Line Oriented Evaluation (LOE). In LOE, crews are graded, which is required in those airlines that participate in the FAA's Advanced Qualification Program (ALP). How much crews learn in LOS arid take back to the line hinges on the effectiveness of the debriefing that follows the LOS. The simulation itself is a busy, intense experience, and thoughtful discussion afterwards is necessary for the crew to sort out and interpret what happened and why. Instructors are expected to lead briefings in a way that encourages crew members to analyze for themselves their performance in the LOS. Rather than lecturing the crew in the traditional manner on what they did right and wrong, the instructor is expected to facilitate self-discovery and self-critique by the crew. We have recently completed a study in which we observed 36 LOFT briefings at 5 major U.S. airlines. We audiotape recorded the briefings, transcribed the recordings, and coded for more than 70 variables. Our analysis addresses four broad questions: To what extent do instructors attempt to facilitate crew self-analysis? What techniques do instructors use to facilitate and how effective are these techniques? What is the character of crew participation? To what extent do briefings emphasize CRM and crew performance? We discuss the implications of our findings for ALP and LOE.

Dismukes, Key↗
NASA NTRS2002

Development of HVOF Sprayed Erosion/Oxidation Resistant Coatings for Composite Structural Components in Propulsion Systems

Thermally sprayed coatings are being studied and developed as methods of enabling lightweight composites to be used more extensively as structural components in propulsion applications in order to reduce costs and improve efficiency through weight reductions. The primary goal of this work is the development of functionally graded material [FGM] polymer/metal matrix composite coatings to provide improved erosion/oxidation resistance to polyimide-based polymer matrix composite [PMC] substrates. The goal is to grade the coating composition from pure polyimide, similar to the PMC substrate matrix on one side, to 100 % WC-Co on the other. Both step-wise and continuous gradation of the loading of the WC-Co reinforcing phase are being investigated. Details of the coating parameter development will be presented, specifically the high velocity oxy-fuel [HVOF] combustion spraying of pure PMR-11 matrix material and layers of various composition PMR-II/WC-Co blends onto steel and PMR-15 composite substrates. Results of the HVOF process optimization, microstructural characterization, and analysis will be presented. The sprayed coatings were evaluated using standard metallographic techniques - optical and scanning electron microscopy [SEM]. An SEM + electron dispersive spectroscopy [EDS] technique has also been used to confirm retention of the PMR-II component. Results of peel/butt adhesion testing to determine adhesion will also be presented.

Knight, R.↗
NASA NTRS2002

Environmental Barrier Coatings Having a YSZ Top Coat

Environmental barrier coatings (EBCs) with a Si bond coat, a yttria-stabilized zirconia (YSZ) top coat, and various intermediate coats were investigated. EBCs were processed by atmospheric pressure plasma spraying. The EBC durability was determined by thermal cycling tests in water vapor at 1300 C and 1400 C, and in air at 1400 C and 1500 C. EBCs with a mullite (3Al2O3 (dot) 2SiO2) + BSAS (1 - xBaO (dot) xSrO (dot) Al2O3 (dot) 2SiO2) intermediate coat were more durable than EBCs with a mullite intermediate coat, while EBCs with a mullite/BSAS duplex intermediate coat resulted in inferior durability. The improvement with a mullite + BSAS intermediate coat was attributed to enhanced compliance of the intermediate coat due to the addition of a low modulus BSAS second phase. Mullite + BSAS/YSZ and BSAS/YSZ interfaces produced a low melting (less than 1400 C) reaction product, which is expected to degrade the EBC performance by increasing the thermal conductivity. EBCs with a mullite + BSAS / graded mullite + YSZ intermediate coat showed the best durability among the EBCs investigated in this study. This improvement was attributed to diffused CTE (Coefficient of Thermal Expansion) mismatch stress and improved chemical stability due to the compositionally graded mullite+YSZ layer.

Lee, Kang N.↗