SEARCH · Search NASA

Results for “ATOMIC OXYGEN REACTIVITY”

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.

SourceResearch connectionFrom yearThrough year

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

At least 37 records · Page 2

All sources NASA NTRS DOE OSTI

NASA NTRS1989

Evaluation of atomic oxygen resistant protective coatings for fiberglass-epoxy composites in LEO

Fiberglass-epoxy composite masts are the prime structural members for the Space Station Freedom solar array. At the altitude where Space Station Freedom will operate, atomic oxygen atoms are the most predominant species. Atomic oxygen is highly reactive and has been shown to oxidize organic and some metallic materials. Tests with random and directed atomic oxygen exposure have shown that the epoxy is removed from the composite exposing brittle glass fibers which could be easily removed from the surface where they could contaminate space Station Freedom Systems. Protection or fiber containment systems, inorganic based paints, aluminum braid, and a metal coatinsg, were evaluated for resistance to atomic oxygen, vacuum ultraviolet radiation, thermal cycling, and mechanical flexing. All appeared to protect well against atomic oxygen and provide fiber containment except for the single aluminum braid covering. UV radiation resistance was acceptable and in general, thermal cycling and flexure had little to no effect on the mass loss rate for most coatings.

Rutledge, Sharon K.↗

NASA NTRS1989

Isotope exchange in oxide-containing catalyst

A method of exchanging rare-isotope oxygen for common-isotope oxygen in the top several layers of an oxide-containing catalyst is disclosed. A sample of an oxide-containing catalyst is exposed to a flowing stream of reducing gas in an inert carrier gas at a temperature suitable for the removal of the reactive common-isotope oxygen atoms from the surface layer or layers of the catalyst without damaging the catalyst structure. The reduction temperature must be higher than any at which the catalyst will subsequently operate. Sufficient reducing gas is used to allow removal of all the reactive common-isotope oxygen atoms in the top several layers of the catalyst. The catalyst is then reoxidized with the desired rare-isotope oxygen in sufficient quantity to replace all of the common-isotope oxygen that was removed.

Robert V Hess↗

NASA NTRS1993

Analytical and experimental investigation of the feasibility of accelerated lifetime testing of materials exposed to an atomic oxygen beam

The interaction of atomic particles with surfaces is of both scientific and technological interest. Past work emphasizes the measurement of high-energy sputtering yields. Very little work utilized low-energy beams for which chemical and electronic effects can be important. Even less work has been carried out using well-defined low-energy projectiles. The use of low-energy, reactive projectiles permits one to investigate surface processes that have not been well characterized. As the energy of the projectile decreases, the collisional cascades and spikes, that are common for high-energy projectiles, become less important, and chemical and electronic effects can play a significant role. Aspects of particle-surface interactions are of concern in several areas of technology. For example, the erosion, desorption, and glow of surfaces of spacecraft in orbit are important in the arena of space technology. The materials studied under this contract are of possible use on the exterior portions of the power generation system of Space Station Freedom. Under the original designs, Space Station Freedom's power generation system would generate potential differences on the surface as high as 200 volts. Ions in the plasma that often surround orbiting vehicles would be accelerated by these potentials leading to bombardment and erosion of the exposed surfaces. The major constituent of the atmosphere, approximately 90 percent, in the low earth orbit region is atomic oxygen. Since atomic oxygen is extremely reactive with most materials, chemical effects can arise in addition to the physical sputtering caused by the acceleration of the oxygen ions. Furthermore, the incident oxygen ions can remain embedded in the exposed surfaces, altering the chemical composition of the surfaces. Since the effective binding energy of a chemically altered surface can be quite different from that of the pure substrate, the sputtering yield of a chemically altered surface is usually different also. The low-energy O+ sputtering yield measurements, reported here, will help quantify the erosion rates for materials exposed to the low-earth orbit environment. These measurements are of technological importance in another respect. In most surface analysis techniques, a surface is bombarded with ions, electrons or photons. Information concerning the structure of the surface and near-surface bulk, abundance of impurities and defects, as well as other surface properties are obtained either from the desorbed species or from the scattered projectiles. Because of their low penetration depth, low-energy ions provide an advantage over other techniques because they provide information that is more indicative of conditions on the surface rather than integrated effects arising from deeper in the bulk. A better understanding of the microscopic processes involved in these interactions is not only of basic scientific interest, but will also aid the scientific community by increasing the accuracy and usefulness of these surface analysis techniques.

Albridge, Royal↗

NASA NTRS1972

The composition of the upper atmosphere

Miniature mass spectrometers were developed and were carried on sounding rockets to determine the composition of the upper atmosphere. Techniques have been developed that accurately correct for the velocity and spin of the moving vehicle. Above 120 km N2, O2, and Ar appear to be in diffusive equilibrium. Most He concentration measurements show a more rapid decline with altitude than predicted by diffusive equilibrium. Because of the highly reactive nature of atomic oxygen, measurements of this species by mass spectrometry are low by an unknown factor.

Nier, A. O.↗

NASA NTRS1973

The open-source neutral-mass spectrometer on Atmosphere Explorer-C, -D, and -E.

The open-source mass spectrometer will be used to obtain the number densities of the neutral atmospheric gases in the mass range 1 to 48 amu at the satellite location. The ion source has been designed to allow gas particles to enter the ionizing region with the minimum practicable number of prior collisions with surfaces. This design minimizes the loss of atomic oxygen and other reactive species due to reactions with the walls of the ion source. The principal features of the open-source spectrometer and the laboratory calibration system are discussed.

Nier, A. O.↗

NASA NTRS1992

Atomic oxygen effects on LDEF experiment A0171

Mass and thickness changes measured in thin films, composites, polymers, metals, and paints from LDEF Experiment A0171 are presented. Atomic oxygen accommodation and reactivity numbers along with morphology features are shown for a variety of A0171 materials. The validity of predicting long term erosion rates will be assessed from short term environmental exposures.

Whitaker, Ann F.↗

NASA NTRS1997

Protective Coating Enhances the Durability of Retroreflectors for the International Space Station

Corner cube reflectors (retroreflectors) will be used on the International Space Station to aid in rendezvous and docking. They are designed to reflect light, such as that from a laser, directly back to the source. The resulting bright reflection from the surface can be used for critical alignment purposes. The housing for the reflectors is composed of polyoxymethylene, a polymer known as Delrin (DuPont), which is highly susceptible to erosion by the atomic oxygen environment that surrounds the station. Atomic oxygen is highly chemically reactive and will convert polymers such as Delrin into volatile oxidation products. This could cause the reflectors to detach from the housing or could cause volatile products and other contamination to recondense onto the surface of the reflectors, causing them to darken. The NASA Lewis Research Center is applying their patented fluoropolymer-filled silicon dioxide coating to the surface of the Delrin retroreflector to prevent degradation in performance caused by reactions with atomic oxygen.

Rutledge, Sharon K.↗

NASA NTRS2004

Monte Carlo Technique Used to Model the Degradation of Internal Spacecraft Surfaces by Atomic Oxygen

Atomic oxygen is one of the predominant constituents of Earth's upper atmosphere. It is created by the photodissociation of molecular oxygen (O2) into single O atoms by ultraviolet radiation. It is chemically very reactive because a single O atom readily combines with another O atom or with other atoms or molecules that can form a stable oxide. The effects of atomic oxygen on the external surfaces of spacecraft in low Earth orbit can have dire consequences for spacecraft life, and this is a well-known and much studied problem. Much less information is known about the effects of atomic oxygen on the internal surfaces of spacecraft. This degradation can occur when openings in components of the spacecraft exterior exist that allow the entry of atomic oxygen into regions that may not have direct atomic oxygen attack but rather scattered attack. Openings can exist because of spacecraft venting, microwave cavities, and apertures for Earth viewing, Sun sensors, or star trackers. The effects of atomic oxygen erosion of polymers interior to an aperture on a spacecraft were simulated at the NASA Glenn Research Center by using Monte Carlo computational techniques. A two-dimensional model was used to provide quantitative indications of the attenuation of atomic oxygen flux as a function of the distance into a parallel-walled cavity. The model allows the atomic oxygen arrival direction, the Maxwell Boltzman temperature, and the ram energy to be varied along with the interaction parameters of the degree of recombination upon impact with polymer or nonreactive surfaces, the initial reaction probability, the reaction probability dependence upon energy and angle of attack, degree of specularity of scattering of reactive and nonreactive surfaces, and the degree of thermal accommodation upon impact with reactive and non-reactive surfaces to be varied to allow the model to produce atomic oxygen erosion geometries that replicate actual experimental results from space. The degree of erosion of various interior locations was compared with the erosion that would occur external to the spacecraft. Results of one cavity model indicate that, at depths into a two-dimensional cavity that are equal to 10 cavity widths, the erosion on the walls of the cavity is less than that on the top surface by over 2 orders of magnitude. Wall erosion near the surface of a cavity depends on which wall is receiving direct atomic oxygen attack. However, deep in the cavity little difference is present. Testing of various cavity models such as these gives spacecraft designers an indication of the level of threat to sensitive interior surfaces for different geometries. Even though the Monte Carlo model is two-dimensional, it can be used to provide qualitative information about spacecraft openings that are three-dimensional by offering reasonable insight as to the nature of the attenuation of damage that occurs within a spacecraft in low Earth orbit. As shown, there is more erosion on the side seeing direct atomic oxygen attack until a depth of approximately 5 times the width of the opening, where the erosion is the same on both sides.

Banks, Bruce A.↗

NASA NTRS1980

A molecular beam investigation of the oxidation of CO on Pt/9/111/x/100//

The CO oxidation on Pt/9(111)x(100)/ was studied by molecular beam relaxation spectroscopy (MBRS). The reaction proceeded via the reaction of adsorbed CO and adsorbed oxygen. No evidence for direct reactive collisions between gaseous CO and adsorbed atomic oxygen was seen. The second order rate constant was measured by linearizing the reaction system to be 10 to the -7th exp/-(9700 kcal/mole)RT/ per sq cm s. The relatively low pre-exponential factor was explained by transition state theory on the basis of a high partition function for adsorbed carbon monoxide obtained previously from studies of CO desorption on this surface.

Fair, J. A.↗

NASA NTRS1989

Simulation of the low earth orbital atomic oxygen interaction with materials by means of an oxygen ion beam

Atomic oxygen is the predominant species in low-Earth orbit between the altitudes of 180 and 650 km. These highly reactive atoms are a result of photodissociation of diatomic oxygen molecules from solar photons having a wavelength less than or equal to 2430A. Spacecraft in low-Earth orbit collide with atomic oxygen in the 3P ground state at impact energies of approximately 4.2 to 4.5 eV. As a consequence, organic materials previously used for high altitude geosynchronous spacecraft are severely oxidized in the low-Earth orbital environment. The evaluation of materials durability to atomic oxygen requires ground simulation of this environment to cost effectively screen materials for durability. Directed broad beam oxygen sources are necessary to evaluate potential spacecraft materials performance before and after exposure to the simulated low-Earth orbital environment. This paper presents a description of a low energy, broad oxygen ion beam source used to simulate the low-Earth orbital atomic oxygen environment. The results of materials interaction with this beam and comparison with actual in-space tests of the same meterials will be discussed. Resulting surface morphologies appear to closely replicate those observed in space tests.

Banks, Bruce A.↗

NASA NTRS1977

Planetary atmospheres with mass spectrometers carried on high-speed probes or satellites

Earth satellite-borne mass spectrometers are considered, taking into account the identification of atomic oxygen in the thermosphere with an 'open' source mass spectrometer flown on a sounding rocket, the conventional closed-source instrument, the mass spectrometers on the Atmosphere Explorer satellites, and mass spectrometer electron multiplier output. A description is presented of mass spectrometers and planetary entry probes. Attention is given to an attempt to obtain an atmospheric composition profile with a terrestrial entry probe, the descending trajectory in the early orbits of the Atmosphere Explorer C satellite, and the molecular nitrogen densities for the descending legs of the orbits. It is pointed out that chemical reactions on the surfaces of the mass spectrometer make the measurement of reactive atmospheric species such as atomic oxygen very difficult.

Nier, A. O.↗

NASA NTRS1973

Active cleaning technique device

The objective of this program was to develop a laboratory demonstration model of an active cleaning technique (ACT) device. The principle of this device is based primarily on the technique for removing contaminants from optical surfaces. This active cleaning technique involves exposing contaminated surfaces to a plasma containing atomic oxygen or combinations of other reactive gases. The ACT device laboratory demonstration model incorporates, in addition to plasma cleaning, the means to operate the device as an ion source for sputtering experiments. The overall ACT device includes a plasma generation tube, an ion accelerator, a gas supply system, a RF power supply and a high voltage dc power supply.

Shannon, R. L.↗

NASA NTRS1992

Angularly resolved X-ray photoelectron spectroscopy investigation of PTFE after prolonged space exposure

Monochromatized angularly resolved X-ray photoelectron spectroscopy (ARXPS) was used to study PTFE (Teflon) that had been exposed to an earth orbital environment for approximately six years. The primary interest of the research is on a very reactive component of this environment (atomic oxygen) which, because of the typical orbital velocities of a spacecraft, impinge on exposed surfaces with 5 eV energy. This presentation deals with the method of analysis, the findings as they pertain to a rather complex carbon, oxygen, and fluorine XPS peak analysis, and the character of the valence bands. An improved bias referencing method, based on ARXPS, is also demonstrated for evaluating specimen charging effects. It was found that the polymer molecule tends to resist the atomic oxygen attack by reorienting itself, so that the most electronegative CF3 groups are facing the incoming hyperthermal oxygen atoms. The implications of these findings to ground-based laboratory studies are discussed.

Dalins, I.↗

NASA NTRS1999

Ultraviolet Radiation-induced Alteration of Martian Surface Materials

The nature and origin of martian surface materials cannot be fully characterized without addressing the unusual reactivity of the soil and the effects of exposure to the unique martian environment. Our laboratory experiments show that ultraviolet radiation at the martian surface can result in the oxidation of metal atoms and the creation of reactive oxygen species on grain surfaces. This process is important in understanding the nature and evolution of martian soils. It can explain the reactivity discovered by the Viking Landers and possibly the origin of the ferric component of the soil.

Yen, A. S.↗

NASA NTRS1987

Production of pulsed atomic oxygen beams via laser vaporization methods

Energetic pulsed atomic oxygen beams were generated by laser-driven evaporation of cryogenically frozen ozone/oxygen films and thin films of indium-tin oxide (ITO). Mass and energy characterization of beams from the ozone/oxygen films were carried out by mass spectrometry. The peak flux, found to occur at 10 eV, is estimated from this data to be 3 x 10(20) m(-2) s(-1). Analysis of the time-of-flight data indicates a number of processes contribute to the formation of the atomic oxygen beam. The absence of metastable states such as the 2p(3) 3s(1) (5S) level of atomic oxygen blown off from ITO films is supported by the failure to observe emission at 777.3 nm from the 2p(3) 3p(1) (5P sub J) levels. Reactive scattering experiments with polymer film targets for atomic oxygen bombardment are planned using a universal crossed molecular beam apparatus.

Brinza, David E.↗

NASA NTRS2018

Atomic Oxygen Environments, Effects, and Mitigation

Oxygen atoms↗

NASA NTRS2017

Tutorial on Atomic Oxygen Effects and Contamination

Atomic oxygen is the most predominant specie in low Earth orbit (LEO) and is contained in the upper atmosphere of many other planetary bodies. Formed by photo-dissociation of molecular oxygen, it is highly reactive and energetic enough to break chemical bonds on the surface of many materials and react with them to form either stable or volatile oxides. The extent of the damage for spacecraft depends a lot on how much atomic oxygen arrives at the surface, the energy of the atoms, and the reactivity of the material that is exposed to it. Oxide formation can result in shrinkage, cracking, or erosion which can also result in changes in optical, thermal, or mechanical properties of the materials exposed. The extent of the reaction can be affected by mechanical loading, temperature, and other environmental components such as ultraviolet radiation or charged particles. Atomic oxygen generally causes a surface reaction, but it can scatter under coatings and into crevices causing oxidation much farther into a spacecraft surface or structure than would be expected. Contamination can also affect system performance. Contamination is generally caused by arrival of volatile species that condense on spacecraft surfaces. The volatiles are typically a result of outgassing of materials that are on the spacecraft. Once the volatiles are condensed on a surface, they can then be fixed on the surface by ultraviolet radiation andor atomic oxygen reaction to form stable surface contaminants that can change optical and thermal properties of materials in power systems, thermal systems, and sensors. This tutorial discusses atomic oxygen erosion and contaminate formation, and the effect they have on typical spacecraft materials. Scattering of atomic oxygen, some effects of combined environments and examples of effects of atomic oxygen and contamination on spacecraft systems and components will also be presented.

Earth orbital environments↗

NASA NTRS1988

Materials selection for long life in LEO: A critical evaluation of atomic oxygen testing with thermal atom systems

The use of thermal atom test methods as a materials selection and screening technique for low-Earth orbit (LEO) spacecraft is critically evaluated. The chemistry and physics of thermal atom environments are compared with the LEO environment. The relative reactivities of a number of materials determined to be in thermal atom environments are compared to those observed in LEO and in high quality LEO simulations. Reaction efficiencies measured in a new type of thermal atom apparatus are one-hundredth to one-thousandth those observed in LEO, and many materials showing nearly identical reactivities in LEO show relative reactivities differing by as much as a factor of 8 in thermal atom systems. A simple phenomenological kinetic model for the reaction of oxygen atoms with organic materials can be used to explain the differences in reactivity in different environments. Certain specific thermal test environments can be used as reliable materials screening tools. Using thermal atom methods to predict material lifetime in LEO requires direct calibration of the method against LEO data or high quality simulation data for each material.

Koontz, S. L.↗