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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 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS2019

Validation of Proposed Go-Around Criteria Under Various Environmental Conditions

This paper evaluates the effects of environmental conditions on touchdown performance under varying approach states and validates proposed go-around criteria developed using data from a previously conducted study under these various environmental conditions. An experiment was conducted using Boeing 737-800 and Airbus A330-200 Level D full-flight simulators in which 24 pilots flew multiple approaches under different approach conditions and environmental variables. Pilots were instructed to always land the aircraft, even from conditions considered to be an unstable approach. Various touchdown performance metrics were analyzed. In addition, pilots’ perceptions of risk under the various unstable approach conditions and resulting landings were assessed. The results of the study revealed that wind speed/direction and visibility had a stronger effect on touchdown performance than the approach parameters. Specifically, wind had a highly significant effect on longitudinal and lateral touchdown point, as well as a significant effect on sink-rate at touchdown. Wind and visibility, along with localizer deviation, also had a strong effect on pilots’ perception of risk and workload ratings. Furthermore, the study confirmed that touchdown performance was similar among the runs with a 300-foot and 500-foot starting gate, as was found in the previously conducted experiment. These results support the previous finding that lowering the go-around decision gate to 300-foot might be acceptable, but suggest that certain environmental conditions might warrant altered thresholds of the proposed go-around criteria at this gate. Finally, the findings of this experiment highlight the importance of environmental factors in the assessment of risk of unwanted outcomes on approach and landing.

Transport Aircraft↗
NASA NTRS1993

The importance of environmental conditions in reflectance spectroscopy of laboratory analogs for Mars surface materials

Reflectance spectra are presented here for a variety of particulate, ferric-containing analogs to Martian soil (Fe(3+)-doped smectites and palagonites) to facilitate interpretation of remotely acquired spectra. The analog spectra were measured under differing environmental conditions to evaluate the influence of exposure history on water content and absorption features due to H2O in these samples. Each of these materials contains structural OH bonded to metal cations, adsorbed H2O, and bound H2O (either in a glass, structural site, or bound to a cation). Previous experiments involving a variety of Mars analogs have shown that the 3 micron H2O band in spectra of palagonites is more resistant to drying than the 3 micron H2O band in spectra of montmorillonites. Other experiments have shown that spectra of ferrihydrite and montmorillonites doped with ferric sulfate also contain sufficient bound H2O to retain a strong 3 micron band under dry conditions. Once the effects of the environment on bound water in clays, oxides, and salts are better understood, the hydration bands measured via reflectance spectroscopy can be used to gain information about the chemical composition and moisture content of real soil systems. Such information would be especially useful in interpreting observations of Mars where subtle spatial variations in the strengths of metal-OH and H2O absorptions have been observed in telescopic and ISM spectra. We measured bidirectional reflectance spectra of several Mars soil analogs under controlled environmental conditions to assess the effects of moisture content on the metal-OH and H2O absorptions. The samples analyzed include chemically altered montmorillonites, ferrihydrite. and palagonites from Hawaii and Iceland. Procedures for preparation of the cation-exchanged montmorillonites, ferric-salt doped montmorillonites, and ferric oxyhydroxides are described in detail elsewhere.

Bishop, J.↗
NASA NTRS2005

Environmental Conditions for Space Flight Hardware: A Survey

Interest in generalization of the physical environment experienced by NASA hardware from the natural Earth environment (on the launch pad), man-made environment on Earth (storage acceptance an d qualification testing), the launch environment, and the space environment, is ed to find commonality among our hardware in an effort to reduce cost and complexity. NASA is entering a period of increase in its number of planetary missions and it is important to understand how our qualification requirements will evolve with and track these new environments. Environmental conditions are described for NASA projects in several ways for the different periods of the mission life cycle. At the beginning, the mission manager defines survivability requirements based on the mission length, orbit, launch date, launch vehicle, and other factors . such as the use of reactor engines. Margins are then applied to these values (temperature extremes, vibration extremes, radiation tolerances, etc,) and a new set of conditions is generalized for design requirements. Mission assurance documents will then assign an additional margin for reliability, and a third set of values is provided for during testing. A fourth set of environmental condition values may evolve intermittently from heritage hardware that has been tested to a level beyond the actual mission requirement. These various sets of environment figures can make it quite confusing and difficult to capture common hardware environmental requirements. Environmental requirement information can be found in a wide variety of places. The most obvious is with the individual projects. We can easily get answers to questions about temperature extremes being used and radiation tolerance goals, but it is more difficult to map the answers to the process that created these requirements: for design, for qualification, and for actual environment with no margin applied. Not everyone assigned to a NASA project may have that kind of insight, as many have only the environmental requirement numbers needed to do their jobs but do not necessarily have a programmatic-level understanding of how all of the environmental requirements fit together.

Plante, Jeannette↗
NASA NTRS1991

A correlational analysis of the effects of changing environmental conditions on the NR atomic hydrogen maser

An extensive statistical analysis has been undertaken to determine if a correlation exists between changes in an NR atomic hydrogen muser's frequency offset and changes in environmental conditions. Data have been acquired over the past 20 months by recording the frequency offset of three NR atomic hydrogen masers along with the relative and absolute humidity, barometric pressure, and ambient temperature of the laboratory in which the masers are maintained. Correlational analyses have been performed comparing barometric pressure, humidity, and temperature with maser frequency offset as functions of time for periods ranging from 5.5 to 17 days. Semi partial correlation coefficients as large as -0.9 have been fond between barometric pressure and maser frequency offset for data covering periods as long as a week. Maser frequency offset and barometric pressure were consistently found to change simultaneously. The correlation between humidity and frequency offset is less predictable, and the resulting semi partial correlation coefficients were usually small when compared with those derived from the relationship between pressure and frequency offset. The time delay between changes in humidity and correlated changes in maser frequency offset was found to vary extensively with no predictable pattern. Analysis of temperature data indicates that, in the most current design, temperature does not significant(y affect maser frequency offset in the laboratory environment. Thus, the results of the analyses disclose a significant statistical correlation between changes in maser frequency offset and changes in barometric pressure. The statistics also reveal some correlation between humidity and frequency offset, bat for reasons to be discussed, the effects of humidity should be considered secondary to the effects of changing barometric pressure.

R. A. Dragonette↗
NASA NTRS2014

Compact Multi-Gas Monitor for Life Support Systems Control in Space: Evaluation Under Realistic Environmental Conditions

Advanced space life support systems require lightweight, low-power, durable sensors for monitoring critical gas components. A luminescence-based optical flow-through cell to monitor carbon dioxide, oxygen, and humidity has been developed and was demonstrated using bench top instrumentation under environmental conditions relevant to portable life support systems, including initially pure oxygen atmosphere, pressure range from 3.5 to 14.7 psi, temperature range from 50 F to 150 F, and humidity from dry to 100% RH and under liquid water saturation. This paper presents the first compact readout unit for these optical sensors, designed for the volume, power, and weight restrictions of a spacesuit portable Life support system and the analytical characterization of the optical sensors interrogated by the novel optoelectronic system. Trace gas contaminants in a space suit, originating from hardware and material off-gassing and crew member metabolism, are from many chemical families. The result is a gas mix much more complex than the pure oxygen fed into the spacesuit, which may interfere with gas sensor readings. The paper also presents an evaluation of optical sensor performance when exposed to the most significant trace gases reported to be found in spacesuits. The studies were conducted with the spacecraft maximum allowable concentrations for those trace gases and the calculated 8-hr. concentrations resulting from having no trace contaminant control system in the ventilation loop. Finally, a profile of temperature, pressure, humidity, and gas composition for a typical EVA mission has been defined, and the performance of sensors operated repeatedly under simulated EVA mission conditions has been studied.

Delgado, Jesus↗
NASA NTRS2014

Compact Multi-Gas Monitor for Life Support Systems Control in Space: Evaluation Under Realistic Environmental Conditions

Advanced space life support systems require lightweight, low-power, durable sensors for monitoring critical gas components. A luminescence-based optical flow-through cell to monitor carbon dioxide, oxygen, and humidity has been developed and was demonstrated using bench-top instrumentation under environmental conditions relevant to portable life support systems, including initially pure oxygen atmosphere, temperature range from 50 F to 150 F, and humidity from dry to 100% RH and under conditions of water condensation. This paper presents the most recent progress in the development of this sensor technology. Trace gas contaminants in a space suit, originating from hardware and material off-gassing and crew member metabolism, are from many chemical families. The result is a gas mix much more complex than the pure oxygen fed into the space suit, and this complexity may interfere with gas sensor readings. This paper presents an evaluation of optical sensor performance when exposed to the most significant trace gases reported to be found in space suits. A study of the calibration stability of the sensors is also presented. For that purpose, a profile of temperature, pressure, humidity, and gas composition for the duration of an EVA has been defined, and the performance of sensors operated repeatedly under those conditions has been studied. Finally, this paper presents the first compact readout unit for these optical sensors, designed for the volume, power, and weight restrictions of a PLSS.

Alonso, Jesus Delgado↗
NASA NTRS1990

The effect of changing environmental conditions on microwave signatures of forest ecosystems - Preliminary results of the March 1988 Alaskan aircraft SAR experiment

In preparation for the ESA ERS-1 mission, a series of multitemporal, multifrequency, multipolarization aircraft SAR data sets were acquired near Fairbanks in March 1988. P-, L-, and C-band data were acquired with the NASA/JPL Airborne SAR on five different days over a period of two weeks. The airborne data were augmented with intensive ground calibration data as well as detailed simultaneous in situ measurements of the geometric, dielectric, and moisture properties of the snow and forest canopy. During the time period over which the SAR data were collected, the environmental conditions changed significantly; temperatures ranged from unseasonably warm (1 to 9 C) to well below freezing (-8 to -15 C), and the moisture content of the snow and trees changed from a liquid to a frozen state. The SAR data clearly indicate the radar return is sensitive to these changing environmental factors, and preliminary analysis of the L-band SAR data shows a 0.4 to 5.8 dB increase (depending on polarization and canopy type) in the radar cross section of the forest stands under the warm conditions relative to the cold. These SAR observations are consistent with predictions from a theoretical scattering model.

Way, Jobea↗
NASA NTRS1985

Design of test specimens and procedures for generating material properties of Douglas fir/epoxy laminated wood composite material: With the generation of baseline data at two environmental conditions

In support of the design of wind turbine generator airfoils/blades utilizing Douglas Fir/West System Epoxy laminated composite material, a program was undertaken to define pertinent material properties utilizing small scale test specimens. Task 1 was the development of suitable monotonic tension, compression, short beam shear and full reversed cyclic specimen designs and the companion grips and testing procedures. Task 2 was the generation of the material properties at two environmental conditions utilizing the specimens and procedures developed in Task 1. The monotonic specimens and procedures generated results which compare favorably with other investigators while the cyclic results appear somewhat conservative. Adding moisture and heat or scarf joints degraded the monotonic performance but had a more nebulus effect with cyclic loading.

Johnson, Paul E.↗
NASA NTRS2001

Crops Models for Varying Environmental Conditions

New variable environment Modified Energy Cascade (MEC) crop models were developed for all the Advanced Life Support (ALS) candidate crops and implemented in SIMULINK. The MEC models are based on the Volk, Bugbee, and Wheeler Energy Cascade (EC) model and are derived from more recent Top-Level Energy Cascade (TLEC) models. The MEC models simulate crop plant responses to day-to-day changes in photosynthetic photon flux, photoperiod, carbon dioxide level, temperature, and relative humidity. The original EC model allows changes in light energy but uses a less accurate linear approximation. The simulation outputs of the new MEC models for constant nominal environmental conditions are very similar to those of earlier EC models that use parameters produced by the TLEC models. There are a few differences. The new MEC models allow setting the time for seed emergence, have realistic exponential canopy growth, and have corrected harvest dates for potato and tomato. The new MEC models indicate that the maximum edible biomass per meter squared per day is produced at the maximum allowed carbon dioxide level, the nominal temperatures, and the maximum light input. Reducing the carbon dioxide level from the maximum to the minimum allowed in the model reduces crop production significantly. Increasing temperature decreases production more than it decreases the time to harvest, so productivity in edible biomass per meter squared per day is greater at nominal than maximum temperatures, The productivity in edible biomass per meter squared per day is greatest at the maximum light energy input allowed in the model, but the edible biomass produced per light energy input unit is lower than at nominal light levels. Reducing light levels increases light and power use efficiency. The MEC models suggest we can adjust the light energy day-to- day to accommodate power shortages or Lise excess power while monitoring and controlling edible biomass production.

Jones, Harry↗
NASA NTRS1999

Dependence of Cumulus Anvil Radiative Properties on Environmental Conditions in the Tropical West Pacific

Areally extensive, optically thick anvil clouds associated with mesoscale convective clusters dominate the shortwave cloud forcing in the tropics and provide longwave forcing comparable to that of thin cirrus. Changes in the cover and optical thickness of tropical anvils as climate warms can regulate the sign of cloud feedback. As a prelude to the study of MMCR data from the ARM TWP sites, we analyze ISCCP-derived radiative characteristics of anvils observed in the tropical west Pacific during the TOGA-COARE IOP. Anvils with radius greater than 100 km were identified and tracked from inception to decay using the Machado-Rossow algorithm. Corresponding environmental conditions just prior to the start of the convectove event were diagnosed using the Lin-Johnson objective analysis product. Small clusters (100-200 km radius) are observed to have a broad range of optical thicknesses (10-50), while intermediate optical thickness clusters are observed to range in size from 100 km to almost 1000 km. Large-size clusters appear to be favored by strong pre-storm large scale upward motion throughout the troposphere, moist low-to-midlevel relative humidities, environments with slightly higher CAPE than those for smaller clusters, and strong front-to-rear flow. Optically thick anvils are favored in situations of strong low-level moisture convergence and strong upper-level shear.

Ye, B.↗
NASA NTRS2015

The Dependence of Cirrus Gamma Size Distributions Expressed as Volumes in N(sub 0)-Lambda-Mu Phase Space and Bulk Cloud Properties on Environmental Conditions: Results from the Small Ice Particles in Cirrus Experiment (SPARTICUS)

The variability of cirrus ice microphysical properties is investigated using observations obtained during the Small Particles in Cirrus (SPARTICUS) campaign. An existing approach that represents a size distribution (SD) as a single gamma function using an ellipsoid of equally realizable solutions in (N(sub 0), lambda, mu) phase space is modified to automatically identify multiple modes in SDs and characterize each mode by such an ellipsoid. The modified approach is applied to ice crystals with maximum dimension D greater than15 micrometers collected by the 2-D stereo and 2-D precipitation probes on the Stratton Park Engineering Company Learjet. The dependencies of N(sub 0), mu, and lambda from each mode, total number concentration, bulk extinction, ice water content (IWC), and mass median maximum dimension D(sub mm) as a function of temperature T and cirrus type are then analyzed. The changes in the observed codependencies between N(sub 0), mu, and lambda, bulk extinction, IWC, and D(sub mm) with environmental conditions indicate that particles were larger at higher T during SPARTICUS. At most two modes were observed in any SD during SPARTICUS, with the average boundary between them at 115 micrometers, similar to past studies not using probes with shatter mitigating tips and artifact removal algorithms. The bimodality of the SDs increased with T. This and the differences in N(sub 0), mu, and lambda between the modes suggest that particles with smaller D nucleated more recently than particles with larger D, which grew via vapor deposition and aggregation. Because smaller crystals, whose concentrations are uncertain, make marginal contributions to higher order moments, the use of higher moments for evaluating model fields is suggested.

Ellipsoids↗