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At least 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
NASA NTRS1935

The Influence of Tip Shape on the Wing Load Distribution as Determined by Flight Tests

Pressure measurements were made in flight on the right upper wing of an M-3 airplane. The effects of tip plan form, washout, and transverse camber were investigated with eight tip forms in unyawed conditions through the range of positive lift coefficients from zero lift to the stall. The conclusion is that the tip plan form does not influence the span distribution of the coefficients of normal force and moment. It is shown inferentially that temperature, humidity, and the aging of the wood and fabric wing structure used on the M-3 airplane have an appreciable influence on the load distribution.

Rhode, Richard V↗
NASA NTRS1940

Design charts relating to the stalling of tapered wings

An aid in airplane design, charts have been prepared to show the effects of wing taper, thickness ratio, and Reynolds number on the spanwise location of the initial stalling point. Means of improving poor stalling characteristics resulting from certain combinations of the variables have also been considered; additional figures illustrate the influence of camber increase to the wing tips, washout, central sharp leading edges, and wing-tip slots on the stalling characteristics. Data are included from which the drag increases resulting from the use of these means can be computed. The application of the data to a specific problem is illustrated by an example.

Soule, H A↗
NASA NTRS1991

Pulmonary function in microgravity: KC-135 experience

We have commenced a KC-135 program that parallels and proceeds our Spacelab (SLS-1) pulmonary function experiment. Our first task was to elucidate the affect of normal gravitation on the shape of the maximum expiratory flow volume (MEFV) curve. Nine normal subjects performed multiple MEFV maneuvers at 0-G, 1-G, and approximately 1.7-G. The MEFV curves for each subject were filtered, aligned at RV, and ensemble-averaged to produce an average MEFV curve for each state, allowing differences to be studied. Most subjects showed a decrease in the FVC at 0-G, which we attribute to an increased intrathoracic blood volume. In most of these subjects, the mean lung volume associated with a given flow was lower at 0-G, over about the upper half of the vital capacity. This is similar to the change previously reported during heat out immersion and is consistent with the known affect of engorgement of the lung with blood, on elastic recoil. There were also consistent but highly individual changes in the position and magnitude of detailed features of the curve, the individual patterns being similar to those previously reported on transition from the erect to the supine position. This supports the idea that the location and motion of choke points which determine the detailed individual configuration of MEFV curves, can be significantly influenced by gravitational forces, presumably via the effects of change in longitudinal tension on local airway pressure-diameter behavior and wave speed. We have developed a flight mass spectrometer and have commenced a study of single breath gradients in gas exchange, inert gas washouts, and rebreathing cardiac outputs and lung volumes at 0-G, 1-G, and 1.7-G. Comparison of our results with those from SLS-1 should identify the opportunities and limitations of the KC-135 as an accessible microgravity resource.

Guy, Harold J.↗
NASA NTRS1993

Final postflight hardware evaluation report RSRM-28 (STS-53)

The final report for the Clearfield disassembly evaluation and a continuation of the KSC postflight assessment for the RSRM-28 (STS-53) RSRM flight set is presented. All observed hardware conditions were documented on PFOR's and are included in Appendices A through C. Appendices D and E contain the measurements and safety factor data for the nozzle and insulation components. This report, along with the KSC Ten-Day Postflight Hardware Evaluation Report (TWR-64215), represents a summary of the RSRM-28 hardware evaluation. The as-flown hardware configuration is documented in TWR-63638. Disassembly evaluation photograph numbers are logged in TWA-1989. The RSRM-28 flight set disassembly evaluations described were performed at the RSRM Refurbishment Facility in Clearfield, Utah. The final factory joint demate occurred on July 15, 1993. Additional time was required to perform the evaluation of the stiffener rings per special issue 4.1.5.2 because of the washout schedule. The release of this report was after completion of all special issues per program management direction. Detailed evaluations were performed in accordance with the Clearfield PEEP, TWR-50051, Revision A. All observations were compared against limits that are also defined in the PEEP. These limits outline the criteria for categorizing the observations as acceptable, reportable, or critical. Hardware conditions that were unexpected and/or determined to be reportable or critical were evaluated by the applicable team and tracked through the PFAR system.

Starrett, William David, Jr.↗
NASA NTRS1992

Experiments on an unsteady, three-dimensional separation

Unsteady, three-dimensional flow separation occurs in a variety of technical situations including turbomachinery and low-speed aircraft. An experimental program at Stanford in unsteady, three-dimensional, pressure-driven laminar separation has investigated the structure and time-scaling of these flows; of particular interest is the development, washout, and control of flow separation. Results reveal that a two-dimensional, laminar boundary layer passes through several stages on its way to a quasi-steady three-dimensional separation. The quasi-steady state of the separation embodies a complex, unsteady, vortical structure.

Henk, R. W.↗
NASA NTRS1994

Anomalous HNO3/NO(x) ratio of remote tropospheric air: Conversion of nitric acid to formic acid and NO(x)?

The N oxidation ratio, (HNO3)/(NO(x)), in the free troposphere is measured at approx. 1 to 9 (averaging approx. 5), consistently lower than the values of 15-100 which known theory suggests to be reached rapidly. This discrepancy casts doubt on current models' abilities to predict effects of NO sources on remote (NO), and so also (O3) and (OH). HNO3-to-NO(x) recycling processes involving HCHO in solution are appealing explanations for the ratio. Known chemical theory are illustrated using a Lagrangian box model of the mid-troposphere which simulates characteristic episodes form NO(x) input to HNO3 washout. Ratio and budget constraint equations for No(y) can usefully restrict conceivable explanations of missing chemistry of fast nitrogen cycling; most explanations could be called 'fast-cycles' or 're-NO(x)-ification.' These equations also show how current global models may suggest spuriously good N oxidation ratios and errors in OH. Aerosol or cloud droplets reactions with HCHO may produce (a) formic acid (which needs an appropriate source) and NO(x), or alternatively, (b) hydroxymethyl nitrate (or methyl dinitrate), which might supply a large, variable amount of 'missing NO(y) not currently measurable except by NO(y) instruments.

Chatfield, Robert B.↗
NASA NTRS1959

Maximum Mean Lift Coefficient Characteristics at Low Tip Mach Numbers of a Hovering Helicopter Rotor Having an NACA 64(1)A012 Airfoil Section

An investigation has been conducted on the Langley helicopter test tower to determine experimentally the maximum mean lift-coefficient characteristics at low tip Mach number and a limited amount of drag- divergence data at high tip Mach number of a helicopter rotor having an NACA 64(1)AO12 airfoil section and 8 deg of linear washout. Data are presented for blade tip Mach numbers M(t) of 0.29 to 0.74 with corresponding values 6 6 of tip Reynolds number of 2.59 x 10(exp 6) and 6.58 x 10(exp 6). Comparisons are made between the data from the present rotor with results previously obtained from two other rotors: one having NACA 0012 airfoil sections and the other having an NACA 0009 airfoil tip section. At low tip Mach numbers, the maximum mean lift coefficient for the blade having the NACA 64(1)AO12 section was about 0.08 less than that obtained with the blade having the NACA 0009 tip section and 0.21 less than the value obtained with the blade having the NACA 0012 tip section. Blade maximum mean lift coefficient values were not obtained for Mach number values greater than 0.47 because of a blade failure encountered during the tests. The effective mean lift-curve slope required for predicting rotor thrust varied from 5.8 for the tip Mach nuniber range of 0.29 to 0.55 to a value of 6.65 for a tip Mach number of 0.71. The blade pitching-moment coefficients were small and relatively unaffected by changes in thrust coefficient and Mach number. In the instances in which stall was reached, the break in the blade pitching-moment curve was in a stable direction. The efficiency of the rotor decreased with an increase in tip speed. Expressed as figure of merit, at a tip Mach number of 0.29 the maximum value was about 0.74. Similar measurements made on another rotor having an NACA 0012 airfoil and with a rotor having an NACA 0009 tip section, showed a value of 0.75. Synthesized section lift and profile-drag characteristics for the rotor-blade airfoil section are presented as an aid in predicting the high-tip-speed performance of rotors having similar airfoils.

Powell, Robert D., Jr.↗
NASA NTRS1999

Barophysiology and Biophysics

Decompression is an important aspect of extravehicular activity (EVA). Errors can result in decompression sickness (DCS) if the protective measures are too liberal, while valuable on-orbit time is dissipated in prophylactic methodologies that are excessively conservative. Nucleation is an important consideration in many natural events, and its control is very important in many industrial procedures. The amount of Extravehicular Activity (EVA) that will be required during the construction of the International Space Station exceeds all of the other activity combined. The requirements in astronaut time and consumables (breathing oxygen and air) will be considerable. In an attempt to mitigate these requirements, Project ARGO was investigated in 1990 to investigate the effects of gravitational forces on the musculoskeletal system. This work has led to the present plans for the reduction of prebreathe duration. Over the past decade, research has been directed towards an understanding of the biophysical basis of the formation and growth of the decompression gas phase with the goal of improving the efficiency of the EVA process. In the past, we have direct work towards a more complete understanding of gas bubble formation and growth and exercise-enhanced washout during oxygen prebreathe.

Powell, Michael R.↗
NASA NTRS2000

A Multi-Center Controlled Study of the Acute and Chronic Effects of Cooling Therapy for MS

To determine the acute and chronic effects of cooling therapy on patients with MS using objective functional performance measures and self-assessed measures of fatigue. Cooling demyelinated nerves can reduce conduction block, potentially improving symptoms of MS. Significant acute and chronic effects of cooling have not been demonstrated in a multi-center, controlled, blinded study using objective measures of neurologic function. Patients (N=84) with definite MS, mild to moderate disability (EDSS less than 6.0), and self-reported heat sensitivity were enrolled at 5 study sites. Acute effects of cooling were assessed by randomly assigning subjects to high-dose or low-dose cooling for one hour using an active cooling vest and cap (Life Enhancement Technologies, Santa Clara, CA). Settings were individualized to maintain the cooling garments at 55 F for the high-dose treatment and 70 F for the low-dose treatment. Both patients and examining investigators were blinded to treatment assignments. The MSFC and visual acuity/contrast sensitivity were assessed before and 30 minutes after treatment. The following week, subjects had an identical visit with the alternate cooling treatment. Chronic effects of cooling were assessed by randomly assigning the same subjects to unblinded daily home cooling or observation for 4 weeks. All subjects completed the Rochester Fatigue Diary (RFD) twice weekly and subjective measures of strength, cognition, and energy level daily. At the end of the period, subjects completed the Modified Fatigue Impact Scale (MFIS) and underwent another high-dose cooling session with assessment of the MSFC and vision. After a one-week washout period, subjects crossed over to the alternate 4-week treatment. Oral temperatures were reduced with both acute treatments (0.8 +/- .06 F, high and 0.5 +/- .06 F, low). While mean MSFC did not change significantly during individual cooling sessions, post hoc analysis pooling the 3 high-dose cooling sessions revealed an improvement in MSFC scores (acute phase 0.064 +/- 0.020, p = 0.0013; chronic phase 0.044 +/- 0.021, p = 0.0368) from before to after cooling. The change in MSFC scores during the acute cooling sessions was not related to the extent of change in oral temperatures. Both the RFD score and the MFIS indicate a significantly lower fatigue level during the cooling month compared to observation (RFD, 2.53 +/- 0.83,p = 0.0033; MFIS 7.63 +/- 1.56, p = 0.0001).

Luna, Bernadette↗
NASA NTRS1996

Interactions Between Klebanoff Modes and TS Waves

The Harmonic Point Source (HPS) is the simplest possible form of 3D disturbance yet even this case is not fully understood. One of the characteristics of HPS generated Tolmien Schlichting (TS) waves is that the maximum rms amplitude downstream of the source occurs away from the centerline. As the waves fan out in the spanwise direction they can encounter Klebanoff modes (weak streamwise vortices) which may be present as background disturbances within the layer. The vortices originate near the leading edge and they appear to be caused by amplification of almost immeasurably small nonuniformities in the free stream. The vortices can be steady but they often appear as very low frequency background unsteadiness (as observed by Klebanoff). The vortices locally distort the mean flow and therefore (by definition) they are nonlinear phenomena e.g. the growth rate of the TS waves is altered. Kendall (private communication) has demonstrated total suppression of TS waves by deliberately introducing strong vortices generated by a delta wing. For the very weak vortices that are often encountered in experiments, their effect is characterized by a local reduction in the rms TS magnitude. The laminar wake behind a fine wire is used to generate Klebanoff modes and the interactions with HPS generated TS waves are explored in a controlled manner. It is shown that a proportion of the reduction in the observed TS magnitude can be attributed to washout of the phase-averaged signals owing to phase jitter.

Watmuff, Jonathan↗
NASA NTRS1997

Developments in Human Centered Cueing Algorithms for Control of Flight Simulator Motion Systems

The authors conducted further research with cueing algorithms for control of flight simulator motion systems. A variation of the so-called optimal algorithm was formulated using simulated aircraft angular velocity input as a basis. Models of the human vestibular sensation system, i.e. the semicircular canals and otoliths, are incorporated within the algorithm. Comparisons of angular velocity cueing responses showed a significant improvement over a formulation using angular acceleration input. Results also compared favorably with the coordinated adaptive washout algorithm, yielding similar results for angular velocity cues while eliminating false cues and reducing the tilt rate for longitudinal cues. These results were confirmed in piloted tests on the current motion system at NASA-Langley, the Visual Motion Simulator (VMS). Proposed future developments by the authors in cueing algorithms are revealed. The new motion system, the Cockpit Motion Facility (CMF), where the final evaluation of the cueing algorithms will be conducted, is also described.

Houck, Jacob A.↗
NASA NTRS2002

Mode shift of an inhaled aerosol bolus is correlated with flow sequencing in the human lung

We studied the effects on aerosol bolus inhalations of small changes in convective inhomogeneity induced by posture change from upright to supine in nine normal subjects. Vital capacity single-breath nitrogen washout tests were used to determine ventilatory inhomogeneity change between postures. Relative to upright, supine phase III slope was increased 33 +/- 11% (mean +/- SE, P < 0.05) and phase IV height increased 25 +/- 11% (P < 0.05), consistent with an increase in convective inhomogeneity likely due to increases in flow sequencing. Subjects also performed 0.5-microm-particle bolus inhalations to penetration volumes (V(p)) between 150 and 1,200 ml during a standardized inhalation from residual volume to 1 liter above upright functional residual capacity. Mode shift (MS) in supine posture was more mouthward than upright at all V(p), changing by 11.6 ml at V(p) = 150 ml (P < 0.05) and 38.4 ml at V(p) = 1,200 ml (P < 0.05). MS and phase III slope changes correlated positively at deeper V(p). Deposition did not change at any V(p), suggesting that deposition did not cause the MS change. We propose that the MS change results from increased sequencing in supine vs. upright posture.

NASA Discipline Cardiopulmonary↗
NASA NTRS2001

Constraints Pb-210 and Be-7 on Wet Deposition and Transport in a Global Three-Dimensional Chemical Tracer Model Driven by Assimilated Meteorological Fields

The atmospheric distributions of the aerosol tracers Pb-210 and Be-7 are simulated with a global three-dimensional model driven by assimilated meteorological observations for 1991-1996 from the NASA Goddard Earth Observing System (GEOSl). The combination of terrigenic Pb-210 and cosmogenic Be-7 provides a sensitive test of wet deposition and vertical transport in the model. Our simulation of moist transport and removal includes scavenging in wet convective updrafts (40% scavenging efficiency per kilometer of updraft), midlevel entrainment and detrainment, first-order rainout and washout from both convective anvils and large-scale precipitation, and cirrus precipitation. Observations from surface sites in specific years are compared to model results for the corresponding meteorological years, and observations from aircraft missions over the Pacific are compared to model results for the days of the flights. Initial simulation of Be-7 showed that cross-tropopause transport in the GEOSl meteorological fields is too fast by a factor of 3-4. We adjusted the stratospheric Be-7 source to correct the tropospheric simulation. Including this correction, we find that the model gives a good simulation of observed Pb-210 and Be-7 concentrations and deposition fluxes at surface sites worldwide, with no significant global bias and with significant success in reproducing the observed latitudinal and seasonal distributions. We achieve several improvements over previous models; in particular, we reproduce the observed Be-7 minimum in the tropics and show that its simulation is sensitive to rainout from convective anvils. Comparisons with aircraft observations up to 12-km altitude suggest that cirrus precipitation could be important for explaining the low concentrations in the middle and upper troposphere.

Liu, Hong-Yu↗
NASA NTRS2001

The release of alginate lyase from growing Pseudomonas syringae pathovar phaseolicola

Pseudomonas syringae pathovar phaseolicola, which produces alginate during stationary growth phase, displayed elevated extracellular alginate lyase activity during both mid-exponential and late-stationary growth phases of batch growth. Intracellular activity remained below 22% of the total activity during exponential growth, suggesting that alginate lyase has an extracellular function for this organism. Extracellular enzyme activity in continuous cultures, grown in either nutrient broth or glucose-simple salts medium, peaked at 60% of the washout rate, although nutrient broth-grown cultures displayed more than twice the activity per gram of cell mass. These results imply that growth rate, nutritional composition, or both initiate a release of alginate lyase from viable P. syringae pv. phaseolicola, which could modify its entrapping biofilm.

Polysaccharide-Lyases/secretion↗
NASA NTRS2000

Ventilation-perfusion matching in long-term microgravity

We studied the ventilation-perfusion matching pattern in normal gravity (1 G) and short- and long-duration microgravity (microG) using the cardiogenic oscillations in the sulfur hexaflouride (SF(6)) and CO(2) concentration signals during the phase III portion of vital capacity single-breath washout experiments. The signal power of the cardiogenic concentration variations was assessed by spectral analysis, and the phase angle between the oscillations of the two simultaneously expired gases was obtained through cross-correlation. For CO(2), a significant reduction of cardiogenic power was observed in microG, with respect to 1 G, but the reduction was smaller and more variable in the case of SF(6). A shift from an in-phase condition in 1 G to an out-of-phase condition was found for both short- and long-duration microG. We conclude that, although the distribution of ventilation and perfusion becomes more homogeneous in microG, significant inhomogeneities persist and that areas of high perfusion become associated with areas of relatively lower ventilation. In addition, these modifications seem to remain constant during long-term exposure to microG.

Mir Project↗
NASA NTRS2004

Clouds Aerosols Internal Affaires: Increasing Cloud Fraction and Enhancing the Convection

Clouds developing in a polluted environment have more numerous, smaller cloud droplets that can increase the cloud lifetime and liquid water content. Such changes in the cloud droplet properties may suppress low precipitation allowing development of a stronger convection and higher freezing level. Delaying the washout of the cloud water (and aerosol), and the stronger convection will result in higher clouds with longer life time and larger anvils. We show these effects by using large statistics of the new, 1km resolution data from MODIS on the Terra satellite. We isolate the aerosol effects from meteorology by regression and showing that aerosol microphysical effects increases cloud fraction by average of 30 presents for all cloud types and increases convective cloud top pressure by average of 35mb. We analyze the aerosol cloud interaction separately for high pressure trade wind cloud systems and separately for deep convective cloud systems. The resultant aerosol radiative effect on climate for the high pressure cloud system is: -10 to -13 W/sq m at the top of the atmosphere (TOA) and -11 to -14 W/sq m at the surface. For deeper convective clouds the forcing is: -4 to -5 W/sq m at the TOA and -6 to -7 W/sq m at the surface.

Koren, Ilan↗
NASA NTRS1998

Low level CO2 effects on pulmonary function in humans

The purpose of the study was to determine whether chamber exposure to low levels of CO2 results in functional alterations in gas mixing and closing volume in humans. Four healthy volunteer subjects were exposed to 0.7% CO2 and to 1.2% CO2. Spirometry, lung volumes, single breath nitrogen washout, diffusing capacity for carbon monoxide (DLCO) by two methods, and cardiac output were measured in triplicate. Values were obtained over two non-consecutive days during the training period (control) and on days 2 or 3, 4, 6, 10, 13, and 23 of exposure to each CO2 level. Measurements were made during the same time of day. There was one day of testing after exposure, while still in the chamber but off carbon dioxide. The order of testing, up until measurements of DLCO and cardiac output, were randomized to avoid presentation effects. The consistent findings were a reduction in diffusing capacity for carbon monoxide and a fall in cardiac output, occurring to a similar degree with both exposures. For the group as a whole, there was no indication of major effects on spirometry, lung volumes, gas mixing or dead space. We conclude that small changes may occur in the function of distal gas exchanging units; however, these effects were not associated with any adverse health effects. The likelihood of pathophysiologic changes in lung function or structure with 0.7 or 1.2% CO2 exposure for this period of time, is therefore, low.

NASA Discipline Cardiopulmonary↗
NASA NTRS1998

Cardiogenic oscillation phase relationships during single-breath tests performed in microgravity

We studied the phase relationships of the cardiogenic oscillations in the phase III portion of single-breath washouts (SBW) in normal gravity (1 G) and in sustained microgravity (microG). The SBW consisted of a vital capacity inspiration of 5% He-1.25% sulfurhexafluoride-balance O2, preceded at residual volume by a 150-ml Ar bolus. Pairs of gas signals, all of which still showed cardiogenic oscillations, were cross-correlated, and their phase difference was expressed as an angle. Phase relationships between inspired gases (e.g., He) and resident gas (n2) showed no change from 1 G (211 +/- 9 degrees) to microG (163 +/- 7 degrees). Ar bolus and He were unaltered between 1 G (173 +/- 15 degrees) and microG (211 +/- 25 degrees), showing that airway closure in microG remains in regions of high specific ventilation and suggesting that airway closure results from lung regions reaching low regional volume near residual volume. In contrast, CO2 reversed phase with He between 1 G (332 +/- 6 degrees) and microG (263 +/- 27 degrees), strongly suggesting that, in microG, areas of high ventilation are associated with high ventilation-perfusion ratio (VA/Q). This widening of the range of VA/Q in microG may explain previous measurements (G.K. Prisk, A.R. Elliott, H.J.B. Guy, J.M. Kosonen, and J.B. West J. Appl. Physiol. 79: 1290-1298, 1995) of an overall unaltered range of VA/Q in microG, despite more homogeneous distributions of both ventilation and perfusion.

Non-NASA Center↗