Search NASA⌕ Search

SEARCH · Search NASA

Results for “Partial Pressure”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 271 records · Page 15
All sourcesNASA NTRSDOE OSTI
NASA NTRS2014

Applying Flammability Limit Probabilities and the Normoxic Upward Limiting Pressure Concept to NASA STD-6001 Test 1

Repeated Test 1 extinction tests near the upward flammability limit are expected to follow a Poisson process trend. This Poisson process trend suggests that rather than define a ULOI and MOC (which requires two limits to be determined), it might be better to define a single upward limit as being where 1/e (where e (approx. equal to 2.7183) is the characteristic time of the normalized Poisson process) of the materials burn, or, rounding, where approximately 1/3 of the samples fail the test (and burn). Recognizing that spacecraft atmospheres will not bound the entire oxygen-pressure parameter space, but actually lie along the normoxic atmosphere control band, we can focus the materials flammability testing along this normoxic band. A Normoxic Upward Limiting Pressure (NULP) is defined that determines the minimum safe total pressure for a material within the constant partial pressure control band. Then, increasing this pressure limit by a factor of safety, we can define the material as being safe to use at the NULP + SF (where SF is on the order of 10 kilopascal, based on existing flammability data). It is recommended that the thickest material to be tested with the current Test 1 igniter should be 3 mm thick (1/8 inches) to avoid the problem of differentiating between an ignition limit and a true flammability limit.

flammability↗
NASA NTRS1978

Water-vapor pressure control in a volume

The variation with time of the partial pressure of water in a volume that has openings to the outside environment and includes vapor sources was evaluated as a function of the purging flow and its vapor content. Experimental tests to estimate the diffusion of ambient humidity through openings and to validate calculated results were included. The purging flows required to produce and maintain a certain humidity in shipping containers, storage rooms, and clean rooms can be estimated with the relationship developed here. These purging flows are necessary to prevent the contamination, degradation, and other effects of water vapor on the systems inside these volumes.

Scialdone, J. J.↗
NASA NTRS2001

Influence of atmospheric oxygen on leaf structure and starch deposition in Arabidopsis thaliana

Plant culture in oxygen concentrations below ambient is known to stimulate vegetative growth, but apart from reports on increased leaf number and weight, little is known about development at subambient oxygen concentrations. Arabidopsis thaliana (L.) Heynh. (cv. Columbia) plants were grown full term in pre-mixed atmospheres with oxygen partial pressures of 2.5, 5.1, 10.1, 16.2, and 21.3 kPa O2, 0.035 kPa CO2 and the balance nitrogen under continuous light. Fully expanded leaves were harvested and processed for light and transmission electron microscopy or for starch quantification. Growth in subambient oxygen concentrations caused changes in leaf anatomy (increased thickness, stomatal density and starch content) that have also been described for plants grown under carbon dioxide enrichment. However, at the lowest oxygen treatment (2.5 kPa), developmental changes occurred that could not be explained by changes in carbon budget caused by suppressed photorespiration, resulting in very thick leaves and a dwarf morphology. This study establishes the leaf parameters that change during growth under low O2, and identifies the lower concentration at which O2 limitation on transport and biosynthetic pathways detrimentally affects leaf development. Grant numbers: NAG5-3756, NAG2-1020, NAG2-1375.

Non-NASA Center↗
NASA NTRS1998

Control of seed development in Arabidopsis thaliana by atmospheric oxygen

Seed development is known to be inhibited completely when plants are grown in oxygen concentrations below 5.1 kPa, but apart from reports of decreased seed weight little is known about embryogenesis at subambient oxygen concentrations above this critical level. Arabidopsis thaliana (L.) Heynh. plants were grown full term under continuous light in premixed atmospheres with oxygen partial pressures of 2.5, 5.1, 10.1, 16.2 and 21.3 kPa O2, 0.035 kPa CO2 and the balance nitrogen. Seeds were harvested for germination tests and microscopy when siliques had yellowed. Seed germination was depressed in O2 treatments below 16.2 kPa, and seeds from plants grown in 2.5 kPa O2 did not germinate at all. Fewer than 25% of the seeds from plants grown in 5.1 kPa oxygen germinated and most of the seedlings appeared abnormal. Light and scanning electron microscopic observation of non-germinated seeds showed that these embryos had stopped growing at different developmental stages depending upon the prevailing oxygen level. Embryos stopped growing at the heart-shaped to linear cotyledon stage in 5.1 kPa O2, at around the curled cotyledon stage in 10.1 kPa O2, and at the premature stage in 16.2 kPa O2. Globular and heart-shaped embryos were observed in sectioned seeds from plants grown in 2.5 kPa O2. Tissue degeneration caused by cell autolysis and changes in cell structure were observed in cotyledons and radicles. Transmission electron microscopy of mature seeds showed that storage substances, such as protein bodies, were reduced in subambient oxygen treatments. The results demonstrate control of embryo development by oxygen in Arabidopsis.

NASA Discipline Plant Biology↗
DOE OSTI2025

Pyrogenic Organic Matter Laboratory Experiment: Aerobic Respiration and Geochemistry from Variably Inundated Stream Sediments (v3)

This dataset supports a broader study examining the effects of variable inundation and pyrogenic organic matter on ecosystem respiration. The dataset provides data generated from a laboratory batch experiment investigating the interaction between variable inundation conditions (wet and dry sediment) and pyrogenic organic matter (burned and unburned treatments). The contents include time series dissolved oxygen, sediment geochemistry data, and field metadata (including qualitative information on instream and river corridor characteristics). This data package was originally published in November 2025. It was updated in April 2026 (v2; new and modified files) and May 2026 (v3; modified files). See the change history section in the readme for more details For details on how to navigate data packages generated by this project, see https://data.ess-dive.lbl.gov/portals/PNNLRiverCorridorSFA/About. In addition to a readme, this data package also includes a file-level metadata (FLMD) file that describes each file and a data dictionary (DD) that describes all column/row headers and variable definitions. This dataset is comprised of (1) file-level metadata; (2) data dictionary; (3) field metadata; (4) international generic sample number (IGSN) mapping file; (5) readme; (6) field protocol; (7) sample name metadata; (8) an environmental context picture for the dry and inundated sampling locations; and (9) a subfolder with sample data from the sediment incubation experiment. The sample data subfolder contains (1) dissolved organic carbon (DOC, measured as non-purgeable organic carbon, NPOC); (2) total nitrogen (TN); (3) gravimetric moisture; (4) partial pressure and production rates of carbon dioxide, methane, and nitrous oxide; (5) field wet sediment mass, dry sediment mass, water mass, and field wet sediment volume in incubation and sediment NPOC/TN vials; (6) methods codes; (7) respiration rates, pH, and temperature from after the incubation, raw time series dissolved oxygen and temperature, and a subfolder containing associated plots and scripts; (8) ions; (9) FTICR-MS methods; and (10) a subfolder of 12 Tesla (12T) FTICR-MS data. This folder contains the CoreMS processed data and three subfolders, one containing the .xml files, one containing the CoreMS output files, and the other containing instructions and scripts for processing the files in CoreMS (https://github.com/EMSL-Computing/CoreMS). All files are .csv, .pdf, .R, .xml, .html, .Rmd, .py, .cal, .json, or .jpg.

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS1976

Theory of low transitions in CO discharge lasers

A self consistent theoretical model which couples the electron and heavy particle finite rate kinetics with the optical and fluid dynamic processes has been employed to identify the various parameters and explain the mechanism responsible for producing low lying transitions in slow flowing CO lasers. It is found that lasing on low lying transitions can be achieved at low temperatures for low pressures (or low flow rates) together with high partial pressures of the He and N2. The role of N2 has been identified as an additive responsible for reducing the electron temperature to a range where the transfer of electrical power to the lower vibrational modes of CO is optimum.

Sidney, B. D.↗
NASA NTRS1977

A high pressure modulated molecular beam mass spectrometric sampling system

The current state of understanding of free-jet high pressure sampling is critically reviewed and modifications of certain theoretical and empirical considerations are presented. A high pressure, free-jet expansion, modulated molecular beam, mass spectrometric sampling apparatus was constructed and this apparatus is described in detail. Experimental studies have demonstrated that the apparatus can be used to sample high temperature systems at pressures up to one atmosphere. Condensible high temperature gaseous species have been routinely sampled and the mass spectrometric detector has provided direct identification of sampled species. System sensitivity is better than one tenth of a part per million. Experimental results obtained with argon and nitrogen beams are presented and compared to theoretical predictions. These results and the respective comparison are taken to indicate acceptable performance of the sampling apparatus. Results are also given for two groups of experiments related to hot corrosion studies. The formation of gaseous sodium sulfate in doped methane-oxygen flames was characterized and the oxidative vaporization of metals was studied in an atmospheric pressure flowing gas system to which gaseous salt partial pressures were added.

Stearns, C. A.↗
NASA NTRS1992

Capacity retention in hydrogen storage alloys

Results of our examination of the properties of several candidate materials for hydrogen storage electrodes and their relation to the decrease in H-storage capacity upon open-circuit storage over time are reported. In some of the alloy samples examined to date, only about 10 percent of the hydrogen capacity was lost upon storage for 20 days, while in others, this number was as high as 30 percent for the same period of time. This loss in capacity is attributed to two separate mechanisms: (1) hydrogen desorbed from the electrode due to pressure differences between the cell and the electrode sample; and (2) chemical and/or electrochemical degradation of the alloy electrode upon exposure to the cell environment. The former process is a direct consequence of the equilibrium dissociation pressure of the hydride alloy phase and the partial pressure of hydrogen in the hydride phase in equilibrium with that in the electrolyte environment, while the latter is related to the stability of the alloy phase in the cell environment. Comparison of the equilibrium gas-phase dissociation pressures of these alloys indicate that reversible loss of hydrogen capacity is higher in alloys with P(eqm) greater than 1 atm than in those with P(eqm) less than 1 atm.

Anani, A.↗
NASA NTRS1999

Preventing Molecular and Particulate Infiltration in a Confined Volume

Contaminants from an instrument's self-generated sources or from sources external to the instrument may degrade its critical surfaces and/or create an environment which limits the instrument's intended performance. Analyses have been carried out on a method to investigate the required purging flow of clean, dry gas to prevent the ingestion of external contaminants into the instrument container volume. The pressure to be maintained and the required flow are examined in terms of their effectiveness in preventing gaseous and particulate contaminant ingestion and abatement of self-generated contaminants in the volume. The required venting area or the existing volume venting area is correlated to the volume to be purged, the allowable pressure differential across the volume, the external contaminant partial pressure, and the sizes of the ambient particulates. The diffusion of external water vapor into the volume while it was being purged was experimentally obtained in terms of an infiltration time constant. That data and the acceptable fraction of the outside pressure into the volume indicate the required flow of purge gas expressed in terms of volume change per unit time. The exclusion of particulates is based on the incoming velocity of the particles and the exit flow speed and density of the purge gas. The purging flow pressures needed to maintain the required flows through the vent passages are indicated. The purge gas must prevent or limit the entrance of the external contaminants to the critical locations of the instrument. It should also prevent self- contamination from surfaces, reduce material outgassing, and sweep out the outgassed products. Systems and facilities that can benefit from purging may be optical equipment, clinical facilities, manufacturing facilities, clean rooms, and other systems requiring clean environments.

Scialdone, John J.↗
NASA NTRS1984

Gas pressure and electron density at the level of the active zone of hollow cathode arc discharges

A model for the longitudinal variations of the partial pressures of electrons, ions, and neutral particles is proposed as a result of an experimental study of pressure variations at the level of the active zone as a function of the various discharge parameters of a hollow cathode arc. The cathode region where the temperature passes through its maximum is called active zone. The proposed model embodies the very important variations which the partial electron and neutral particles pressures undergo at the level of the active zone.

Minoo, M. H.↗
NASA NTRS1975

Theory and experiment of low transitions in CO discharge lasers

A self-consistent model which couples the kinetics of the electrons and heavy particles with the optical and fluid dynamic processes has been employed to identify the various parameters and explain the mechanism responsible for producing low-lying transitions in slow-flowing CO lasers. Both theory and experiment indicate that low-lying transitions can be achieved at low temperatures for low pressures (or low-flow rates) together with high partial pressures of He and N2. The role of N2 has been identified as an additive responsible for reducing the electron temperature to a range where the transfer of electrical power to the lower vibrational modes of CO is optimum.

Sidney, B.↗
NASA NTRS1992

Chemistry of the surface and lower atmosphere of Venus

A comprehensive overview of the chemical interactions between the atmosphere and surface of Venus is presented. Earth-based, earth-orbital, and spacecraft data on the composition of the atmosphere and surface of Venus are presented and applied to quantitative evaluations of the chemical interactions between carbon, hydrogen, sulfur, chlorine, fluorine, and nitrogen-containing gases and possible minerals on the Venus surface. The calculation results are used to predict stable minerals and mineral assemblages on the Venus surface to determine which, if any, atmospheric gases are buffered by mineral assemblages on the surface, and to critically review and assess prior work on atmosphere-surface chemistry on Venus. It is concluded that the CO2 pressure on Venus is comparable to the CO2 equilibrium partial pressure developed by the calcite + wollastonite + quartz assemblage at the mean Venus surface temperature of 740 K.

Fegley, B., Jr.↗
NASA NTRS1971

Low-pressure oxidation of Cb-1Zr alloy.

Resistively heated strip specimens of Cb-1Zr alloy were exposed at 927 C in a vacuum chamber at various levels of total pressure in the 1-microtorr range and at various oxygen partial pressures in the .1-microtorr range. Oxygen reaction rates (sticking probabilities) were found to depend on whether or not the specimens were annealed immediately before the test exposure. It is shown that a normally undetectable oxide film exists on the Cb-1Zr surface as a result of oxidation by ambient air, and this film reduces the sticking probability as compared with a clean metal surface. The alloy is considerably strengthened by addition of oxygen to a level of about 6000 ppm, while still maintaining reasonably good room temperature ductility.

Lyon, T. F.↗
NASA NTRS1977

Membrane has high urea-rejection properties

Membranes are synthesized from ethylene and nitrogen in RF plasma at low power, gas-flow rates, and pressure. Ethylene and nitrogen are used because flow rate and partial pressure of each gas can be independently controlled to produce optimum conditions for synthesizing membrane. Membrane is particularly useful in recycling and purifying water.

Johnson, C. C.↗
NASA NTRS1996

Design of Plant Gas Exchange Experiments in a Variable Pressure Growth Chamber

Sustainable human presence in extreme environments such as lunar and martian bases will require bioregenerative components to human life support systems where plants are used for generation of oxygen, food, and water. Reduced atmospheric pressures will be used to minimize mass and engineering requirements. Few studies have assessed the metabolic and developmental responses of plants to reduced pressure and varied oxygen atmospheres. The first tests of hypobaric pressures on plant gas exchange and biomass production at the Johnson Space Center will be initiated in January 1996 in the Variable Pressure Growth Chamber (VPGC), a large, closed plant growth chamber rated for 10.2 psi. Experiments were designed and protocols detailed for two complete growouts each of lettuce and wheat to generate a general database for human life support requirements and to answer questions about plant growth processes in reduced pressure and varied oxygen environments. The central objective of crop growth studies in the VPGC is to determine the influence of reduced pressure and reduced oxygen on the rates of photosynthesis, dark respiration, evapotranspiration and biomass production of lettuce and wheat. Due to the constraint of one experimental unit, internal controls, called pressure transients, will be used to evaluate rates of CO2 uptake, O2 evolution, and H2O generation. Pressure transients will give interpretive power to the results of repeated growouts at both reduced and ambient pressures. Other experiments involve the generation of response functions to partial pressures of O2 and CO2 and to light intensity. Protocol for determining and calculating rates of gas exchange have been detailed. In order to build these databases and implement the necessary treatment combinations in short time periods, specific requirements for gas injections and removals have been defined. A set of system capability checks will include determination of leakage rates conducted prior to the actual crop growouts. Schedules of experimental events for lettuce and wheat are outlined and include replications in time of diurnal routines, pressure transients, variable pO2, pO2/pCO2 ratio, and light intensity responses.

Corey, Kenneth A.↗
NASA NTRS2002

Electron Field Emission Properties of Textured Platinum Surfaces

During ground tests of electric microthrusters and space tests of electrodynamic tethers the electron emitters must successfully operate at environmental pressures possibly as high as 1x10(exp -4) Pa. High partial pressures of oxygen, nitrogen, and water vapor are expected in such environments. A textured platinum surface was used in this work for field emission cathode assessments because platinum does not form oxide films at low temperatures. Although a reproducible cathode conditioning process did not evolve from this work, some short term tests for periods of 1 to 4 hours showed no degradation of emission current at an electric field of 8 V/mm and background pressures of about 1x10(exp -6) Pa. Increases of background pressure by air flow to about 3x10(exp -4) Pa yield a hostile environment for the textured platinum field emission cathode.

Sovey, James S.↗
NASA NTRS2004

Development of a Portable Unit for Metabolic Analysis

The purpose of this research is to develop, test and calibrate a prototype portable device that will measure human metabolic activity; namely time resolved measurements of gas temperature, pressure and flow-rate, and oxygen and carbon dioxide partial pressure during inhalation and exhalation.

Dietrich, D. L.↗