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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 NTRS1978

A new method for designing shock-free transonic configurations

A new method for the design of shock-free supercritical airfoils, wings, and three-dimensional configurations is described. Results illustrating this procedure in two and three dimensions are given. They include modifications to part of the upper surface of an NACA 64A410 airfoil that will maintain shock-free flow over a range of Mach numbers for a fixed lift coefficient, and the modifications required on part of the upper surface of a swept wing with an NACA 64A410 root section to achieve shock-free flow. While the results are given for inviscid flow, the same procedures can be employed iteratively with a boundary layer calculation in order to achieve shock-free viscous designs. With a shock-free pressure field the boundary layer calculation will be reliable and not complicated by the difficulties of shock-wave boundary-layer interaction.

Sobieczky, H.↗
NASA NTRS1978

A new method for designing shock-free transonic configurations

A method for the design of shock free supercritical airfoils, wings, and three dimensional configurations is described. Results illustrating the procedure in two and three dimensions are given. They include modifications to part of the upper surface of an NACA 64A410 airfoil that will maintain shock free flow over a range of Mach numbers for a fixed lift coefficient, and the modifications required on part of the upper surface of a swept wing with an NACA 64A410 root section to achieve shock free flow. While the results are given for inviscid flow, the same procedures can be employed iteratively with a boundary layer calculation in order to achieve shock free viscous designs. With a shock free pressure field the boundary layer calculation will be reliable and not complicated by the difficulties of shock wave boundary layer interaction.

Sobieczky, H.↗
NASA NTRS1980

Optimal control model predictions of system performance and attention allocation and their experimental validation in a display design study

The influence of different types of predictor displays in a longitudinal vertical takeoff and landing (VTOL) hover task is analyzed in a theoretical study. Several cases with differing amounts of predictive and rate information are compared. The optimal control model of the human operator is used to estimate human and system performance in terms of root-mean-square (rms) values and to compute optimized attention allocation. The only part of the model which is varied to predict these data is the observation matrix. Typical cases are selected for a subsequent experimental validation. The rms values as well as eye-movement data are recorded. The results agree favorably with those of the theoretical study in terms of relative differences. Better matching is achieved by revised model input data.

Johannsen, G.↗
NASA NTRS1985

Methane emissions to the atmosphere through aquatic plants

The movement of methane (CH4) from anaerobic sediments through the leaves, stems, and flowers of aquatic plants and into the atmosphere was found to provide a significant pathway for the emission of CH4 from the aquatic substrates of flooded wetlands. Methane concentrations well above the surrounding ambient air levels were found in the mesophyll of 16 varies of aquatic plants and are attributed to transpiration, diffusion, and pressure-induced flow of gaseous CH4 from the roots when they are embedded in CH4-saturated anaerobic sediments. Methane emissions from the emergent parts of aquatic plants were measured using floating chamber techniques and by enclosing the plants in polyethylene bags of known volume. Concentration changes were monitored in the trapped air using syringes and gas chromatographic techniques. Vertical profiles of dissolved CH4 in sediment pore water surrounding the aquatic plants' rhizomes were obtained using an interstitial sampling technique. Methane emissions from the aquatic plants studied varied from 14.8 mg CH4/d to levels too low to be detectable. Rooted and unrooted freshwater aquatic plants were studied as well as saltwater and brackish water plants. Included in the experiment is detailed set of measurements on CH4 emissions from the common cattail (Typha latifolia). This paper illustrates that aquatic plants play an important gas exchange role in the C cycle between wetlands and the atmosphere.

Sebacher, D. I.↗
NASA NTRS1992

Growth, differentiation and development of Arabidopsis thaliana under microgravity conditions (7-IML-1)

The aim of this set of experiments is to quantify the structural and behavioral changes taking place in germinating seeds of the small plant Arabidopsis thaliana. The protocol to be used will involve germination of the seeds in orbit. Their growth will be followed by fixing and photographing samples of microgravity grown and 1 g control seedlings at intervals over 4 days. The different studies which will then be performed can be classified in relation to the parts of the plants involved. The first study will be an examination of the ultrastructure of the root statocytes, the cells containing gravity sensors, to determine whether their development proceeds normally under microgravity conditions. A second study will examine the differences in root and shoot development and orientation between normal wild type seedlings and those of an agravitropic mutant (aux-1) - one that does not respond normally to gravity. A third set of observations will be made on the structural changes occurring during reserve breakdown and utilization in the cells of the cotyledons, the storage organs of the seed. The fourth part of the work will be an examination of the statocytes present in the shoot and their development in microgravity. The final part of the study will give an answer to the debated question of whether the formation of the hypocotyl hook in seedlings is gravity dependent.

Maher, E. P.↗
NASA NTRS2002

Complex physiological and molecular processes underlying root gravitropism

Gravitropism allows plant organs to guide their growth in relation to the gravity vector. For most roots, this response to gravity allows downward growth into soil where water and nutrients are available for plant growth and development. The primary site for gravity sensing in roots includes the root cap and appears to involve the sedimentation of amyloplasts within the columella cells. This process triggers a signal transduction pathway that promotes both an acidification of the wall around the columella cells, an alkalinization of the columella cytoplasm, and the development of a lateral polarity across the root cap that allows for the establishment of a lateral auxin gradient. This gradient is then transmitted to the elongation zones where it triggers a differential cellular elongation on opposite flanks of the central elongation zone, responsible for part of the gravitropic curvature. Recent findings also suggest the involvement of a secondary site/mechanism of gravity sensing for gravitropism in roots, and the possibility that the early phases of graviresponse, which involve differential elongation on opposite flanks of the distal elongation zone, might be independent of this auxin gradient. This review discusses our current understanding of the molecular and physiological mechanisms underlying these various phases of the gravitropic response in roots.

NASA Discipline Plant Biology↗
NASA NTRS1995

Laser Doppler velocimeter measurements and laser sheet imaging in an annular combustor model

An experimental study was conducted in annular combustor model to provide a better understanding of the flowfield. Combustor model configurations consisting of primary jets only, annular jets only, and a combination of annular and primary jets were investigated. The purpose of this research was to provide a better understanding of combustor flows and to provide a data base for comparison with computational models. The first part of this research used a laser Doppler velocimeter to measure mean velocity and statistically calculate root-mean-square velocity in two coordinate directions. From this data, one Reynolds shear stress component and a two-dimensional turbulent kinetic energy term was determined. Major features of the flowfield included recirculating flow, primary and annular jet interaction, and high turbulence. The most pronounced result from this data was the effect the primary jets had on the flowfield. The primary jets were seen to reduce flow asymmetries, create larger recirculation zones, and higher turbulence levels. The second part of this research used a technique called marker nephelometry to provide mean concentration values in the combustor. Results showed the flow to be very turbulent and unsteady. All configurations investigated were highly sensitive to alignment of the primary and annular jets in the model and inlet conditions. Any imbalance between primary jets or misalignment of the annular jets caused severe flow asymmetries.

Dwenger, Richard Dale↗
NASA NTRS1981

Chromospheric and photospheric evolution of an extremely active solar region in solar cycle 19

a comprehensive investigation was made of phenomena attending the disk passage, July 7 to 21, 1959, of active solar center HAO-59Q. At the photospheric level that comprised an aggregate of groups of sunspots of which one group, Mt. Wilson 14284, showed all the attributes deemed typical of solar regions associated with the production of major flares. A special characteristic of 59Q was its capability to eject dark material. Part of this material remained trapped in the strong magnetic fields above group 14284 where it formed a system of interrelated arches, the legs of which passed through components of the bright chromospheric network of the plage and were rooted in various underlying umbrae. Two apparently diffeent kinds of flare were identified in 59Q; namely, prominence flares (which comprised brightenings within part of the suspended dark prominence) and plage flares (which comprised brightenings within part of the chromospheric network). Prominence flares were of three varieties described as 'impact', 'stationary' and 'moving' prominence flares. Plage flares were accompanied in 3 percent of cases by Type III bursts. These latter radio events indicate the associated passage through the corona of energetic electrons in the approximate energy range 10 to 100 keV. At least 87.5 percent, and probably all, impulsive brightenings in 59Q began directly above minor spots, many of which satellites to major umbrae. Stationary and moving prominence flares were individually triggered at sites beneath which magnetic changes occurred within intervals which included each flare's flash phase.

Mckenna-Lawlor, S. M. P.↗
NASA NTRS2007

Comprehensive Shuttle Foam Debris Reduction Strategies

The Columbia Accident Investigation Board (CAIB) was clear in its assessment of the loss of the Space Shuttle Columbia on February 3, 2003. Foam liberated from the External Tank (ET) impacting the brittle wing leading edge (WLE) of the orbiter causing the vehicle to disintegrate upon re-entry. Naturally, the CAB pointed out numerous issues affecting this exact outcome in hopes of correcting systems of systems failures any one of which might have altered the outcome. However, Discovery s recent return to flight (RTF) illustrates the primacy of erosion of foam and the risk of future undesirable outcomes. It is obvious that the original RTF focused approach to this problem was not equal to a comprehensive foam debris reduction activity consistent with the high national value of the Space Shuttle assets. The root cause is really very simple when looking at the spray-on foam insulation for the entire ET as part of the structure (e.g., actual stresses > materials allowable) rather than as some sort of sizehime limited ablator. This step is paramount to accepting the CAB recommendation of eliminating debris or in meeting any level of requirements due to the fundamental processes ensuring structural materials maintain their integrity. Significant effort has been expended to identify root cause of the foam debris In-Flight Anomaly (FA) of STS-114. Absent verifiable location specific data pre-launch (T-0) and in-flight, only a most probable cause can be identified. Indeed, the literature researched corroborates NASNTM-2004-2 13238 disturbing description of ill defined materials characterization, variable supplier constituents and foam processing irregularities. Also, foam is sensitive to age and the exposed environment making baseline comparisons difficult without event driven data. Conventional engineering processes account for such naturally occurring variability by always maintaining positive margins. Success in a negative margin range is not consistently achieved. Looking at the ET S spray-on foam insulation as part of the structural system (e.g., glass half full mentality) will create an environment where ET debris levels as low as reasonably achievable (ALARA) can be realized. ALARA is a NASA requirements philosophy deployed for the complex, mission altering radiation exposure requirements for life safety of astronauts. In the Shuttle s case, reasonableness is established by exhaustive engineering rigor, allowable debris size/quantity, technology maturity and programmatic constraints. A more robust urethane foam thermal protection system (TPS) will enhance the hctionality of the new Ares I Crew Launch Vehicle (CLV) Upper Stage. This paper will outline the strategy for a comprehensive effort to reduce ET foam debris and outline steps leading to an improved foam TPS. The NASA must remain committed to such an approach no matter what becomes of the next flight s actual debris field lest we fall back into a false sense of security. This commitment along with full implementation of all the other CAB recommendations such as orbiter hardening will significantly improve the Shuttle system, the engineering workforce, future capabilities & alternate policy offramps, national human resource protection, high value national asset protection and increase the level of service to the overall NASA mission.

Semmes, Edmund B.↗
NASA NTRS1976

An analytical method for ride quality of flexible airplanes

A new and easily used state variable method of aircraft ride quality analysis is developed and its use is illustrated by a numerical example using DC-8 airplane equations of motion. The method readily allows any type of stability augmentation system to be included for good handling qualities. As part of the ride quality analysis, a particularly powerful method of specifying and achieving all roots of a desired closed-loop characteristic equation by use of full state variable feedback is described and applied to the DC-8 example.

Swaim, R. L.↗
NASA NTRS1996

Random root movements in weightlessness

The dynamics of root growth was studied in weightlessness. In the absence of the gravitropic reference direction during weightlessness, root movements could be controlled by spontaneous growth processes, without any corrective growth induced by the gravitropic system. If truly random of nature, the bending behavior should follow so-called 'random walk' mathematics during weightlessness. Predictions from this hypothesis were critically tested. In a Spacelab ESA-experiment, denoted RANDOM and carried out during the IML-2 Shuttle flight in July 1994, the growth of garden cress (Lepidium sativum) roots was followed by time lapse photography at 1-h intervals. The growth pattern was recorded for about 20 h. Root growth was significantly smaller in weightlessness as compared to gravity (control) conditions. It was found that the roots performed spontaneous movements in weightlessness. The average direction of deviation of the plants consistently stayed equal to zero, despite these spontaneous movements. The average squared deviation increased linearly with time as predicted theoretically (but only for 8-10 h). Autocorrelation calculations showed that bendings of the roots, as determined from the 1-h photographs, were uncorrelated after about a 2-h interval. It is concluded that random processes play an important role in root growth. Predictions from a random walk hypothesis as to the growth dynamics could explain parts of the growth patterns recorded. This test of the hypothesis required microgravity conditions as provided for in a space experiment.

STS-65 Shuttle Project↗
NASA NTRS1986

Distribution of calmodulin in pea seedlings: immunocytochemical localization in plumules and root apices

Immunofluorescence techniques have been used to study the distribution of calmodulin in several tissues in young etiolated pea (Pisum sativum L.) seedlings. A fairly uniform staining was seen in the nucleoplasm and background cytoplasm of most cell types. Cell walls and nucleoli were not stained. In addition, patterned staining reactions were seen in many cells. In cells of the plumule, punctate staining of the cytoplasm was common, and in part this stain appeared to be associated with the plastids. A very distinctive staining of amyloplasts was seen in the columella of the root cap. Staining associated with cytoskeletal elements could be shown in division stages. By metaphase, staining of the spindle region was quite evident. In epidermal cells of the stem and along the underside of the leaf there was an intense staining of the vacuolar contents. Guard cells lacked this vacuolar stain. Vacuolar staining was sometimes seen in cells of the stele, but the most distinctive pattern in the stele was associated with young conducting cells of the xylem. These staining patterns are consistent with the idea that the interactions of plastids and the cytoskeletal may be one of the Ca(2+)-mediated steps in the response of plants to environmental stimuli. Nuclear functions may also be controlled, at least in part, by Ca2+.

NASA Program Space Biology↗
NASA NTRS2005

Spur Gear Wear Investigated in Support of Space Shuttle Return-To-Flight Efforts

As part of NASA s Return-To-Flight efforts, the Space Operations Program investigated the condition of actuators for the orbiter s rudder speed brake. The actuators control the position of the rudder panels located in the tail of the orbiter, providing both steering control and braking during reentry, approach, and landing. Inspections of flight hardware revealed fretting and wear damage to the critical working surfaces of the actuator gears. To best understand the root cause of the observed damage and to help establish an appropriate reuse and maintenance plan for these safety critical parts, researchers completed a set of gear wear experiments at the NASA Glenn Research Center.

Krantz, Timothy L.↗
NASA NTRS1991

Expression of characteristics of ammonium nutrition as affected by pH of the root medium

To study the effect of root-zone pH on characteristic responses of NH4+ -fed plants, soybeans (Glycine max inverted question markL. inverted question mark Merr. cv. Ransom) were grown in flowing solution culture for 21 d on four sources of N (1.0 mol m-3 NO3-, 0.67 mol m-3 NO3- plus 0.33 mol m-3 NH4+, 0.33 mol m-3 NO3- plus 0.67 mol m-3 NH4+, and 1.0 mol m-3 NH4+) with nutrient solutions maintained at pH 6.0, 5.5, 5.0, and 4.5. Amino acid concentration increased in plants grown with NH4+ as the sole source of N at all pH levels. Total amino acid concentration in the roots of NH4+ -fed plants was 8 to 10 times higher than in NO3(-)-fed plants, with asparagine accounting for more than 70% of the total in the roots of these plants. The concentration of soluble carbohydrates in the leaves of NH4+ -fed plants was greater than that of NO3(-)-fed plants, but was lower in roots of NH4+ -fed plants, regardless of pH. Starch concentration was only slightly affected by N source or root-zone pH. At all levels of pH tested, organic acid concentration in leaves was much lower when NH4+ was the sole N source than when all or part of the N was supplied as NO3-. Plants grown with mixed NO3- plus NH4+ N sources were generally intermediate between NO3(-)- and NH4+ -fed plants. Thus, changes in tissue composition characteristic of NH4+ nutrition when root-zone pH was maintained at 4.5 and growth was reduced, still occurred when pH was maintained at 5.0 or above, where growth was not affected. The changes were slightly greater at pH 4.5 than at higher pH levels.

NASA Discipline Life Support Systems↗
NASA NTRS1995

Kepler Equation solver

Kepler's Equation is solved over the entire range of elliptic motion by a fifth-order refinement of the solution of a cubic equation. This method is not iterative, and requires only four transcendental function evaluations: a square root, a cube root, and two trigonometric functions. The maximum relative error of the algorithm is less than one part in 10(exp 18), exceeding the capability of double-precision computer arithmetic. Roundoff errors in double-precision implementation of the algorithm are addressed, and procedures to avoid them are developed.

Markley, F. Landis↗
NASA NTRS2019

Prognostic Launch Vehicle Probability of Failure Assessment Methodology for Conceptual Systems Predicated on Human Causal Factors

Lessons learned from past failures of launch vehicle developments and operations were used to create a new method to predict the probability of failure of conceptual systems. Existing methods such as Probabilistic Risk Assessments and Human Risk Assessments were considered but found to be too cumbersome for this type of system-wide application for yet-to-be-flown vehicles. The basis for this methodology were historic databases of past failures, where it was determined that various faulty human-interactions were the predominant root causes of failure rather than deficient component reliabilities evaluated through statistical analysis. This methodology contains an expert scoring part which can be used in either a qualitative or a quantitative mode. The method produces two products: a numerical score of the probability of failure or guidance to program management on critical areas in need of increased focus to improve the probability of success. In order to evaluate the effectiveness of this new method, data from a concluded vehicle program (USAF's Titan IV with the Centaur G-Prime upper stage) was used as a test case. Although the theoretical vs. actual probability of failure was found to be in reasonable agreement (4.46% vs. 6.67% respectively) the underlying sub-root cause scoring had significant disparities attributable to significant organizational changes and acquisitions. Recommendations are made for future applications of this method to ongoing launch vehicle development programs.

Craig H Williams↗
NASA NTRS1986

Effects of norflurazon, an inhibitor of carotenogenesis, on abscisic acid and xanthoxin in the caps of gravistimulated maize roots

Maize seeds were germinated in the dark in the presence of the carotenoid synthesis inhibitor norflurazon and the levels of abscisic acid, xanthoxin and total carotenoids were measured in the root cap and in the adjacent 1.5 mm segment. In norflurazon-treated roots abscisic acid levels were markedly reduced, but an increase occurred in the levels of xanthoxin, a compound structurally and physiologically similar to abscisic acid. In the cultivar of maize (Zea mays L. cv. Merit) used for this work, brief illumination of the root is required for gravitropic curving. Following illumination both control and norflurazon-treated roots showed normal gravitropic curvature; however, the rate of curvature was delayed in norflurazon-treated roots. Our data from norflurazon-treated roots are consistent with a role for xanthoxin in maize root gravitropism. The increase in xanthoxin in the presence of an inhibitor of carotenoid synthesis suggests that xanthoxin and abscisic acid originate, at least in part, via different metabolic pathways.

NASA Program Space Biology↗