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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 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS1984

A comparison of experimental and theoretical results for leakage, pressure distribution, and rotordynamic coefficients for annular gas seals

The importance of seal behavior in rotordynamics is discussed and current annular seal theory is reviewed. A Nelson's analytical-computational method for determining rotordynamic coefficients for this type of compressible-flow seal is outlined. Various means for the experimental identification of the dynamic coefficients are given, and the method employed at the Texas A and M University (TAMU) test facility is explained. The TAMU test apparatus is described, and the test procedures are discussed. Experimental results, including leakage, entrance-loss coefficients, pressure distributions, and rotordynamic coefficients for a smooth and a honeycomb constant-clearance seal are presented and compared to theoretical results from Nelson's analysis. The results for both seals show little sensitivity to the running speed over the test range. Agreement between test results and theory for leakage through the seal is satisfactory. Test results for direct stiffness show a greater sensitivity to fluid pre-rotation than predicted. Results also indicate that the deliberately roughened surface of the honeycomb seal provides improved stability versus the smooth seal.

Nicks, C. O.↗
NASA NTRS1989

Comparison of NAE porous wall and NASA adaptive wall test results using the NAE CAST-10 airfoil model

Wind tunnels can now simulate flows over airfoils at high Reynolds numbers and high subsonic speeds. Methods to correct for (or reduce) test section wall interference at these test conditions must be validated. The National Aeronautics Establishment (NAE) of Canada and NASA have a cooperative agreement to study this area. The NAE designed, built, and tested a CAST-10 airfoil model in its conventional Two-Dimensional High Reynolds Number Facility. The results were corrected using classical correction techniques. NASA then tested the same model in its 0.3-meter Transonic Cryogenic Tunnel with the adaptive wall test section. The adaptive wall test section reduced the wall interference to what was expected to be an acceptable level. The corrected NAE results are compared with the uncorrected NASA results. The NAE results are also compared with NASA results after residual corrections for top and bottom wall interference. Finally, a comparison of both sets of results corrected for interference from all four walls is presented.

Mineck, Raymond E.↗
NASA NTRS1995

Results of the Quasi-Steady Acceleration Environment from the STS-62 Missions

One of the clear benefits of conducting scientific research in space is to take advantage of the reduced acceleration environment. Many accelerometer packages have proven to accurately measure the acceleration environment at frequency levels above one Hz. However, for particular classes of experiments the quality of science returns is a direct function of the extremely low frequency (less than 0.01 Hz), quasi-steady acceleration environment. One class particularly interested in this acceleration regime is the group of crystal growth experimenters. These scientists are primarily interested in knowing the resultant quasi-steady acceleration vector at their respective crystal growth locations. The objective of many of these scientists is to minimize the amount of convective flow acting in a direction perpendicular to the growth axis of the crystal. Convective flow within the crystal can be induced by the direction and magnitude of the quasi-steady acceleration vector. Convective flows acting perpendicular to the growth axis of the crystal can cause nonuniformity within the crystal, thus reducing the quality of the results. The Orbital Acceleration Research Experiment (OARE), an accelerometer package hardmounted to the bottom of the payload bay of the orbiter Columbia (OV-102), has the capability of monitoring and recording the quasi-steady acceleration environment. This paper will describe the components that make up the on-orbit quasi-steady acceleration environment, detail how results from the OARE device were achieved, and compare modelled acceleration results with actual on-orbit OARE results from the STS-62 and STS-65 flights. A summary of the results will be provided along with possible recommendations of how to combine modelled and realtime quasi-steady accelerometer data for future Shuttle flights.

Matisak, Brian↗
NASA NTRS1996

Sonic Boom Ocean Penetration: Noise Metric Comparison and Initial Focusing Results

The purpose of the present research is to determine the impact by sonic boom noise penetration into the ocean. Since the 1994 LaRC High Speed Research Program Sonic Boom Workshop several new results have been obtained. This talk reviews these results, and emphasizes the two most important findings. The first major result is an improved understanding of the noise spectra of the penetrating sonic boom. It was determined that weighted sound exposure levels decrease with deeper ocean depths significantly faster than unweighted sound exposure levels. This is because low frequencies penetrate the ocean deeper than high frequencies. Several noise metrics were used including peak, SEL, C-SEL, A-SEL, and PLdB, and results are given for all. These results are important because they show that the sonic boom noise impact on marine life a few meters below the ocean surface may be significantly lower using weighted sound levels than if one were to measure the impact using unweighted levels. The other major finding is the first estimate of the worst case peak levels produced by a penetrating sonic boom being focused by a sinusoidal ocean surface. The method of analysis chosen was computational, a time domain finite difference algorithm. The method is outlined and then example results are presented. For rounded sonic boom waveforms incident on a sinusoidal ocean surface, it is shown that the percentage increase or decrease in pressure is only occasionally larger than 10%, rarely 25%. These fluctuations indicate, under the assumptions already given, that any increase or decrease in sound level underwater due to focusing or defocusing should be small, less than 3 dB.

Sparrow, Victor W.↗
NASA NTRS2001

Ground Based Experiments in Support of Microgravity Research Results-Vapor Growth of Organic Nonlinear Optical Thin Film

This work is specifically focused on explaining previous results obtained for the crystal growth of an organic material in a reduced gravity environment. On STS-59, in April 1994, two experiments were conducted with N,N-dimethyl-p-(2,2-dicyanovinyl) aniline (DCVA), a promising nonlinear optical (NLO) material. The space experiments were set to reproduce laboratory experiments that yielded small, bulk crystals of DCVA. The results of the flight experiment, however, were surprising. Rather than producing a bulk single crystal, the result was the production of two high quality, single crystalline thin films. This result was even more intriguing when it is considered that thin films are more desirable for NLO applications than are bulk single crystals. Repeated attempts on the ground to reproduce these results were fruitless. A second set of flight experiments was conducted on STS-69 in September 1995. This time eight DCVA experiments were flown, with each of seven experiments containing a slight change from the first reference experiment. The reference experiment was programmed with growth conditions identical to those of the STS-59 mission. The slight variations in each of the other seven were an attempt to understand what particular parameter was responsible for the preference of thin film growth over bulk crystal growth in microgravity. Once again the results were surprising. In all eight cases thin films were grown again, albeit with varying quality. So now we were faced with a phenomenon that not only takes place in microgravity, but also is very robust, resisting all attempts to force the growth of bulk single crystals.

Zugrav, M. Ittu↗
NASA NTRS2001

Cognitive Task Analysis of Business Jet Pilots' Weather Flying Behaviors: Preliminary Results

This report presents preliminary findings from a cognitive task analysis (CTA) of business aviation piloting. Results describe challenging weather-related aviation decisions and the information and cues used to support these decisions. Further, these results demonstrate the role of expertise in business aviation decision-making in weather flying, and how weather information is acquired and assessed for reliability. The challenging weather scenarios and novice errors identified in the results provide the basis for experimental scenarios and dependent measures to be used in future flight simulation evaluations of candidate aviation weather information systems. Finally, we analyzed these preliminary results to recommend design and training interventions to improve business aviation decision-making with weather information. The primary objective of this report is to present these preliminary findings and to document the extended CTA methodology used to elicit and represent expert business aviator decision-making with weather information. These preliminary findings will be augmented with results from additional subjects using this methodology. A summary of the complete results, absent the detailed treatment of methodology provided in this report, will be documented in a separate publication.

Latorella, Kara↗
NASA NTRS2003

Using High-Fidelity Analysis Methods and Experimental Results to Account for the Effects of Imperfections on the Buckling Response of Composite Shell Structures

The results of an experimental and analytical study of the effects of initial imperfections on the buckling response of unstiffened thin-walled compression-loaded graphite-epoxy cylindrical shells are presented. The analytical results include the effects of traditional and nontraditional initial imperfections and uncertainties in the values of selected shell parameters on the buckling loads of the shells. The nonlinear structural analysis results correlate very well with the experimental results. The high-fidelity nonlinear analysis procedure used to generate the analytical results can also be used to form the basis of a new shell design procedure that could reduce the traditional dependence on empirical results in the shell design process. KEYWORDS: high-fidelity nonlinear structural analysis, composite shells, shell stability, initial imperfections

Starnes, James H., Jr.↗
NASA NTRS2014

How HRP Research Results Contribute to Human Space Exploration Risk Mitigation

In addition to the scientific value of publications derived from research, results from Human Research Program (HRP) research also support HRP’s goals of mitigating crew health and performance risks in space flight. Research results are used to build the evidence base characterizing crew health and performance risks, to support risk research plan development, to inform crew health and performance standards, and to provide technologies to programs for meeting those standards and optimizing crew health and performance in space. This talk will describe examples of how research results support these efforts. For example, HRP research results are used to revise or even create new standards for human space flight, which have been established to protect crew health and performance during flight, and prevent negative long-term health consequences due to space flight. These standards are based on the best available clinical and scientific evidence, as well as operational experience from previous space flight missions, and are reviewed as new evidence emerges. Research results are also used to update the HRP evidence base, which is comprised of a set of reports that provide a current record of the state of knowledge from research and operations for each of the defined human health and performance risks for future NASA exploration missions. A discussion of the role of evidence within the HRP architecture will also be presented. The scope of HRP research results extends well beyond publications, as they are used in several capacities to support HRP deliverables and, ultimately, the advancement of human space exploration beyond low-Earth orbit.

Lumpkins, S. B.↗
NASA NTRS2014

How HRP Research Results Contribute to Human Space Exploration Risk Mitigation

In addition to the scientific value of publications derived from research, results from Human Research Program (HRP) research also support HRP's goals of mitigating crew health and performance risks in space flight. Research results are used to build the evidence base characterizing crew health and performance risks, to support risk research plan development, to inform crew health and performance standards, and to provide technologies to programs for meeting those standards and optimizing crew health and performance in space. This talk will describe examples of how research results support these efforts. For example, HRP research results are used to revise or even create new standards for human space flight, which have been established to protect crew health and performance during flight, and prevent negative long-term health consequences due to space flight. These standards are based on the best available clinical and scientific evidence, as well as operational experience from previous space flight missions, and are reviewed as new evidence emerges. Research results are also used to update the HRP evidence base, which is comprised of a set of reports that provide a current record of the state of knowledge from research and operations for each of the defined human health and performance risks for future NASA exploration missions. A discussion of the role of evidence within the HRP architecture will also be presented. The scope of HRP research results extends well beyond publications, as they are used in several capacities to support HRP deliverables and, ultimately, the advancement of human space exploration beyond low-Earth orbit.

Lumpkins, Sarah↗
NASA NTRS2018

A Summary of Results from Two Full-Scale Fokker F28 Fuselage Section Drop Tests

During 2017, two vertical drop tests were conducted on two partial sections removed from a Fokker F28 MK4000 aircraft as a part of a joint NASA / Federal Aviation Administration (FAA) effort to investigate the crashworthiness characteristics of Transport Category Aircraft, as defined by 14 Code of Federal Regulations, Part 25. The first test was a pure vertical drop test of a relatively uniform forward section, which included an underfloor area for luggage. The second test was a canted drop test onto a sloped surface of a portion of the fuselage representing the wingbox stiffened structure. In both tests, accelerometers were installed on the floor, seat track, luggage, and overhead bin to measure responses in the two airframe sections. In addition, ten Anthropomorphic Test Devices (ATDs, a.k.a. crash test dummies) were included in each test to measure the potential of onboard occupant injury. Self-contained data recorders, logging accelerations and rotational rates, were also used on the seat tracks and lower structure for evaluation as potential crash recording devices in future tests. Finally, the starboard side of each section was painted with a stochastic black and white speckle pattern for use in full field photogrammetric imaging techniques. The results collected show notable differences in the Forward and Wingbox Section responses. The Forward Section floor accelerations showed a relatively uniform response of approximately 7 g throughout the impact event. This section exhibited large amounts of subfloor crushing, floor stiffener failures and seat deformation upon impact. These results are contrasted by the Wingbox Section accelerations, which showed large differences when comparing accelerations recorded from either the rear or the front portion of the section reaching peaks of 39 g in some locations. Additionally, the Wingbox Section test induced a forward motion caused from the rotation at impact. With the exception of the lower cavity, there was minimal deformation in the Wingbox Section, and ATD responses were consistently higher than those for the Forward Section. A complete set of results are presented for the airframe, seat, ATD, overhead bin, and subfloor regions for each section. The ATD results are compared to current injury criteria, and determinations will be made on the likelihood of injury. Additional results for cargo-hold stored luggage are presented in an attempt to provide a component-level characterization for better understanding of under-floor loading. Finally, a discussion of the relevance of the results for a proposed airframe level crashworthiness guideline are presented.

Littell, Justin D.↗
NASA NTRSDate not supplied

HERMeS Thruster Magnetic Field Topology Optimization Study: Plasma Plume Results

NASA’s Hall Effect Rocket with Magnetic Shielding (HERMeS) 12.5-kW Technology Demonstration Unit-1 (TDU-1) has been the subject of extensive technology maturation in preparation for flight system development. The magnetic optimization study aims to explore and investigate alternate magnetic field topologies. Four candidate magnetic field topologies that reduce the effectiveness of the shielding along the discharge channel walls with the intent to also reduce the erosion rates along the front pole covers were designed. Three of the four candidate magnetic field topologies (B1, B2, and B4) have been manufactured and were subjected to an extensive test campaign that included laser induced fluorescence (LIF), performance, stability, wear, and plume characterization. In Phase I, LIF measurements along the discharge chamber centerline found that upstream retraction of the thruster’s peak magnetic field does result in an upstream shift of the acceleration zone, but the magnitude of the shift does not correspond one-to-one to the shift in the location of the peak radial magnetic field magnitude. Phase II test segment results found that at a normalized thruster magnetic field setting of 1, the thruster performance and discharge current oscillations were very similar for configurations B0-B2. Also in Phase II abbreviated wear tests found that average inner front pole cover erosion rates for configuration B1 were approximately 65% of those at B0, and the average erosion rates for configuration B2 were approximately 35% of those at B0. This paper reports on the detailed plasma plume mapping results for configurations B0-B4. Faraday probe results indicate that, at 600 V operation, the plume divergence increased slightly for the B4 configuration when compared to B0-B2. Wien filter spectrometer results found that at 600 V, lower multiply-charged species fractions were attained as the thruster transitioned from configurations B0 to B4. Finally, retarding potential analyzer results found that at 600 V operation and at angles above 60,˚ significantly lower high-energy ion content was found for configurations B2 and B4 when compared to B0 and B1.

Electric propulsion,.Hall thruster, laser diagnost↗
NASA NTRSDate not supplied

Large-Drop Ice Accretion Test Results for a Large Scale Swept Wing Model

In-flight icing is an important consideration that affects aircraft design, performance and safety. Newer regulations combined with increasing demand to reduce fuel burn, emissions and noise are driving a need for improvements in icing simulation capability. To that end, this paper presents the results of ice accretion testing conducted in the NASA Icing Research Tunnel on a large swept wing section typical of a modern commercial transport. The model was based upon a section of the Common Research Model wing at the 64% semispan station with a streamwise chord length of 136 in. The test conditions were developed with an icing scaling analysis to generate similar conditions for a small MVD = 25 μm and a large MVD = 110 μm. A series of tests were conducted over a range of total temperature from -23.8 ˚C to -1.4 ˚C with all other conditions held constant. The results for the small MVD cloud conditions were consistent with previous work and showed the changing ice morphology from rime ice at colder temperatures to highly 3D scallop ice in the range of -8.7 ˚C to -3.8 ˚C. The results for the large MVD cloud conditions exhibited some differences in the ice accretion morphology from the small MVD conditions. Scallop-like ice features were observed at total temperature of -3.8˚C. The large MVD ice accretion at lower temperatures tended to be smoother than the corresponding ice accretion for small MVD. The thickness of the main ice shape tended to be larger for the small MVD conditions compared to the corresponding large MVD ice shape while the latter had more ice farther downstream. The measured ice mass was approximately equal between the corresponding small and large MVD ice shapes up to a freezing fraction of 0.6. For higher freezing fraction, the large MVD ice shapes weighed more. Cloud MVD variation from 50 μm to 230 μm while holding the scaling parameters constant resulted in very minor differences in the ice shapes, mostly in the upper and lower surface chordwise extents. Ice volume was computed from 3D scan data and used to calculate a ratio of ice mass to volume. The resulting values were in the range of 240 to 455 Kg/m3. While this is consistent with analogous values previously reported in the literature, more data are needed to determine a specific trend in this ratio as a function of freezing fraction and the corresponding governing physical phenomena. This work has resulted in a significant experimental database of ice accretion for small and large MVD conditions applicable to large-scale swept wings.

Icing↗
NASA NTRSDate not supplied

Large-Drop Ice Accretion Test Results for a Large Scale Swept Wing Section

In-flight icing is an important consideration that affects aircraft design, performance and safety. Newer regulations combined with increasing demand to reduce fuel burn, emissions and noise are driving a need for improvements in icing simulation capability. To that end, this paper presents the results of ice accretion testing conducted in the NASA Icing Research Tunnel on a large swept wing typical of a modern commercial transport. The model was based upon a section of the Common Research Model wing at the 64% semispan station with a streamwise chord length of 136 in. The test conditions were developed with an icing scaling analysis to generate similar conditions for a small MVD = 25 μm and a large MVD = 110 μm. A series of tests were conducted over a range of total temperature from -23.8 ˚C to -1.4 ˚C with all other conditions held constant. The results for the small MVD cloud conditions were consistent with previous work and showed the changing ice morphology from rime ice at colder temperatures to highly 3D scallop ice in the range of -8.7 ˚C to -3.8 ˚C. The results for the large MVD cloud conditions exhibited some differences in the ice accretion morphology. Scallop-like ice features were observed at total temperature of -3.8˚C. The large MVD ice accretion at lower temperatures tended to be smoother than the corresponding ice accretion for small MVD. The thickness of the main ice shape tended to be larger for the small MVD conditions compared to the corresponding large MVD ice shape while the latter had more ice farther downstream. The measured ice mass was approximately equal between the corresponding small and large MVD ice shapes up to a freezing fraction of 0.6. For higher freezing fraction, the large MVD ice shapes weighed more. Cloud MVD variation from 50 μm to 230 μm while holding the scaling parameters constant resulted in very minor differences in the ice shapes, mostly in the upper and lower surface chordwise extents. Ice volume was computed from 3D scan data and used to calculate a ratio of ice mass to volume. The resulting values were in the range of 240 to 455 Kg/m3. While this is consistent with analogous values previously reported in the literature, more data are needed to determine a specific trend in this ratio as a function of freezing fraction and the corresponding governing physical phenomena. This work has resulted in a significant experimental database of ice accretion for small and large MVD conditions applicable to large-scale swept wings.

Icing↗
NASA NTRS1973

Texturing in metals as a result of sliding

Sliding friction experiments were conducted with copper, nickel, iron, and cobalt sliding on themselves in air and argon. The resulting wear surfaces were examined with X-ray analysis to determine if surface texturing had occurred as a result of sliding. Results of the investigation indicate that, for the face-centered-cubic metals copper and nickel, a (111) texture develops with the (111) planes tilted 10 deg in the direction of sliding. The body-centered-cubic metal iron exhibited a (110) texture with the (100) direction oriented in the direction of sliding. It also exhibited a 10 deg tilt in the direction of sliding. The environment influenced the results in that the degree of texture observed in argon was less than that seen in air for iron. No texturing was observed for the close-packed-hexagonal metal cobalt. Recrystallization was observed with copper as a result of sliding.

Wheeler, D. R.↗
NASA NTRS1974

Skylab S192 data evaluation: Comparisons with ERTS-1 results

The author has identified the following significant results. The Skylab S192 data was evaluated by: (1) comparing the classification results using S192 and ERTS-1 data over the Holt County, Nebraska agricultural study area, and (2) investigating the impact of signal-to-noise ratio on classification accuracies using registered S192 and ERTS-1 data. Results indicate: (1) The classification accuracy obtained on S192 data using its best subset of four bands can be expected to be as high as that on ERTS-1 data. (2) When a subset of four S192 bands that are spectrally similar to the ERTS-1 bands was used for classification, an obvious deterioration in the classification accuracy was observed with respect to the ERTS-1 results. (3) The thermal bands 13 and 14 as well as the near IR bands were found to be relatively important in the classification of agricultural data. Although bands 11 and 12 were highly correlated, both were invariably included in the best subsets of the band sizes, four and beyond, according to the divergence criterion. (4) The differentiation of corn from popcorn was difficult on both S192 and ERTS-1 data acquired at an early summer date. (5) The results on both sets of data indicate that it was relatively easy to differentiate grass from any other class.

Chang, C. Y.↗
NASA NTRS1974

First results from the crop identification technology assessment for remote sensing /CITARS/

The CITARS task design, including objectives, analysis methodology and experimental procedures, is described and first results from this effort are presented. The extensive ground truth data set acquired for the CITARS task is described and discussed in some detail. Results of the accuracy tests for the photo interpretative CITARS ground truth are given. Results of the assessment of the ERTS MSS data for cloud cover and electronic quality are presented. Some results of the geometric correction and registration of the time sequential CITARS ERTS data are given. Finally, the field boundary selection problem is addressed and the results of the use of new technology for boundary selection are presented.

Hall, F. G.↗
NASA NTRS1975

Texturing in metals as a result of sliding

Sliding friction experiments were conducted with copper, nickel, iron and cobalt sliding on themselves in air and argon. The resulting wear surfaces were examined by X-ray analysis to determine if surface texturing had occurred as a result of sliding. Results of the investigation indicate that, for the face-centered-cubic metals copper and nickel, a (111) texture develops with the (111) planes tilted 10 deg in the direction of sliding. The body-centered-cubic metal iron exhibited a (110) texture with the (111) direction oriented in the direction of sliding. It also exhibited a 10 deg tilt in the direction of sliding. The environment influenced the results in that the degree of texture observed in argon was less than that seen in air for iron. No texturing was observed for the close-packed-hexagonal metal cobalt. Recrystallization was observed with copper as a result of sliding.

Wheeler, D. R.↗
NASA NTRS1974

MIA computer simulation test results report

Results of the first noise susceptibility computer simulation tests of the complete MIA receiver analytical model are presented. Computer simulation tests were conducted with both Gaussian and pulse noise inputs. The results of the Gaussian noise tests were compared to results predicted previously and were found to be in substantial agreement. The results of the pulse noise tests will be compared to the results of planned analogous tests in the Data Bus Evaluation Laboratory at a later time. The MIA computer model is considered to be fully operational at this time.

Unger, G. E.↗