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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 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
NASA NTRSDate not supplied

Investigating the Adhesion Force of Lunar Regolith Particulates on Air Plasma Sprayed Alumina Coatings

Ceramic materials, often used to protect components due to their high strength, and wear resistance, have added benefits of being lightweight and providing multifunctional properties. They are, therefore, significant to provide durability and support during long-duration missions to the moon’s surface for rovers, landers, robotic systems, habitats, and many other components. Materials such as aluminum oxide with high mechanical strength and hardness can help to improve the durability of structures used in space exploration. Devices used for space exploration require the use of materials with the ability to withstand exposure to extreme environments. Lunar regolith is a constituent with the ability to adhere electrostatically and damage the components used to perform these missions due to adhesion of lunar dust projectiles that can cause delamination on surfaces, which may not be physically visible. The particulates of lunar dust are classified as corrosive material, leading to the degradation of structures. Aluminum oxide presents excellent resistance to different types of wear due to its high strength and hardness. Air plasma sprayed (APS) aluminum oxide coatings have demonstrated the potential to protect the surface to which they are applied. However, the parameters of roughness and porosity of the coatings need to be considered to establish if they can protect the components from extreme environments. Considering the electrostatic forces that the components are exposed to, the adhesion between the lunar regolith and the surface of the components needs to be investigated. In this work, the adhesion forces of lunar dust simulants with an average size of 30 𝜇m are investigated considering the roughness of the surface of the APS aluminum oxide. The centrifugal technique utilized here offers the advantage of establishing the adhesion force between particles with different shapes on smooth or rough surfaces. The simulants were deposited on the surface of APS aluminum oxide using an aerosolization technique to achieve a monolayer coating in three different locations across the specimen to determine the increments in adhesion force at the centrifuge. The roughness of the APS aluminum oxide was determined to be 2.257 𝜇m. The specimen was tested under an incremental centrifugal speed from 100 rpm to 3000 rpm for 20 seconds. Low magnification microscopy images were collected to cover a larger surface area of the test coating. The adhesion force was measured considering the distance from the centrifugal axis and the rotational speed. Due to the coating roughness, and the distance from the centrifugal axis, the results demonstrated a larger adhesion force in locations closer to the centrifugal axis. Smaller particles were entrapped within the roughness of the coating, and a stronger adhesion force was measured. In order to continue designing wear-resistant coating for structural protection in space missions, press-on experiments using a centrifuge will be performed. Future experiments will allow us to determine the design parameters for APS aluminum oxide coating to protect the structures from harsh space environments.

Perla Latorre-Suarez↗
NASA NTRS1979

Biocompatibility of surgical implants

Method of selecting biocompatible materials for surgical implants uses fracture mechanic relationships and surface energies of candidate materials in presence of blood plasma. Technique has been used to characterize 190 materials by parameters that reflect their biocompatibility.

Kaelble, D. H.↗
NASA NTRS1997

A Comparison of Atomic Oxygen Degradation in Low Earth Orbit and in a Plasma Etcher

In low Earth orbit (LEO) significant degradation of certain materials occurs from exposure to atomic oxygen (AO). Orbital opportunities to study this degradation for specific materials are limited and expensive. While plasma etchers are commonly used in ground-based studies because of their low cost and convenience, the environment produced in an etcher chamber differs greatly from the LEO environment. Because of the differences in environment, the validity of using etcher data has remained an open question. In this paper, degradation data for 22 materials from the orbital experiment Evaluation of Oxygen Interaction with Materials (EOIM-3) are compared with data from EOIM-3 control specimens exposed in a typical plasma etcher. This comparison indicates that, when carefully considered, plasma etcher results can produce order-of-magnitude estimates of orbital degradation. This allows the etcher to be used to screen unacceptable materials from further, more expensive tests.

Townsend, Jacqueline A.↗
NASA NTRSDate not supplied

Development of Langmuir and Spatially Resolved OES Diagnostics for Arc Jet Shock and Boundary Layer Measurements Relevant to Atmospheric Re-Entry Environments

The second-generation miniature Arc Jet Research Chamber (mARC) ground testing facility at NASA Ames requires physical characterization of its supersonic plasma flow to verify numerical models and material sample testing. Two types of plasma diagnostics will be utilized: Langmuir probes and optical emission spectroscopy (OES). Several single and triple Langmuir probes have been constructed and will be inserted parallel to the flow via a sweep arm to measure post-shock electron temperature and number density along radial profiles at different axial distances. Due to the high heat flux (200-3000 W/cm2) sweep durations are necessarily short (< 0.1 s). Measuring these properties near the probe surface provide characterization of the post-shock environment. This is an important metric for validating coupled CFD-material codes, and will provide insight into longstanding thermocouple anomalies attributed to charging of heatshield surfaces. An OES system has also been assembled to obtain spatially resolved density and temperature for various flow species. The system consists of a convex lens that forms an image of the plasma onto a 16-channel linear fiber array, which will simultaneously capture the spectra from sixteen different locations. The light emission from the plasma is then focused by a spherical mirror into a spectrometer and recorded with a camera. These measurements non-intrusively provide a new spatially resolved flow characterization capability. This will initially be used to resolve issues with shock radiation interference in pyrometer measurements of material surface temperature. The design of each diagnostic and any initial results will be discussed.

Ethan Main-Loam Leong↗
NASA NTRS2010

Adaptable Holders for Arc-Jet Screening Candidate Thermal Protection System Repair Materials

Reusable holders have been devised for evaluating high-temperature, plasma-resistant re-entry materials, especially fabrics. Typical material samples tested support thermal-protection-system damage repair requiring evaluation prior to re-entry into terrestrial atmosphere. These tests allow evaluation of each material to withstand the most severe predicted re-entry conditions.

Riccio, Joe↗
NASA NTRS1992

Experimental breakdown of selected anodized aluminum samples in dilute plasmas

Anodized aluminum samples representative of Space Station Freedom structural material were tested for electrical breakdown under space plasma conditions. In space, this potential arises across the insulating anodized coating when the spacecraft structure is driven to a negative bias relative to the external plasma potential due to plasma-surface interaction phenomena. For anodized materials used in the tests, it was found that breakdown voltage varied from 100 to 2000 volts depending on the sample. The current in the arcs depended on the sample, the capacitor, and the voltage. The level of the arc currents varied from 60 to 1000 amperes. The plasma number density varied from 3 x 10 exp 6 to 10 exp 3 ions per cc. The time between arcs increased as the number density was lowered. Corona testing of anodized samples revealed that samples with higher corona inception voltage had higher arcing inception voltages. From this it is concluded that corona testing may provide a method of screening the samples.

Grier, Norman T.↗
NASA NTRS1986

Oxidation-resistant reflective surfaces for solar dynamic power generation in near Earth orbit

Reflective surfaces for space station power generation systems are required to withstand the atomic oxygen-dominated environment of near Earth orbit. Thin films of platinum and rhodium, which are corrosion resistant reflective metals, have been deposited by ion beam sputter deposition onto various substrate materials. Solar reflectances were then measured as a function of time of exposure to a RF-generated air plasma. Similarly, various protective coating materials, including MgF2, SiO2, Al2O3, and Si3N4, were deposited onto silver-coated substrates and then exposed to the plasma. Analysis of the films both before and after exposure by both ESCA and Auger spectroscopy was also performed. The results indicate that Pt and Rh do not suffer any loss in reflectance over the duration of the tests. Also, each of the coating materials survived the plasma environment. The ESCA and Auger analyses are discussed as well.

Gulino, D. A.↗
NASA NTRS1989

Plasma torch testing for thermostructural evaluation of rocket motor nozzle materials

This paper presents data from the thermostructural testing of tape-wrapped carbon phenolic. This work has been performed with the use of a plasma torch and loading device in an effort to study the anomalous erosion characteristicfs of that seen in the Space Shuttle Solid Rocket Motor Nozzle STS-8A. Testing is conducted in an effort to determine conditions or parameters involved in this mode of failure.

Prince, Andrew S.↗
NASA NTRS1989

The deceleration of infalling plasma in magnetized neutron star atmospheres - Nonisothermal atmospheres

This paper examines the deceleration of accreting material in the strongly magnetized plasma atmosphere of an X-ray pulsar, for accretion rates less than 0.1 times the Eddington flux. The previous work on accretion, flow deceleration is extended to nonisothermal atmospheres. A rough model of radiative processes in neutron star atmospheres bombarded by accreting material is used to calculate the atmosphere's temperature and density profiles. The atmospheric structure and the accretion flow stopping depth are computed iteratively. For cases where the infall velocity is close to the free-fall velocity, a simple prescription for an equivalent single temperature, T(iso), is given. It is found that the plasma deceleration is close to stopping in a homogeneous, isothermal atmosphere at T(iso). Exceptions to this result occur for small infall velocities.

Miller, Guy↗
NASA NTRS1981

Evidence for the acceleration of ionospheric O/+/ in the magnetosheath of Venus

Plasma spectra from 12 orbits of the Pioneer-Venus Orbiter are reported which suggest the presence of ionospheric material in the magnetosheath plasma near and sunward of the terminator plane. Each spectrum shows a high E/q peak, consistent with O(+) moving at a speed lower than or comparable to that of the ambient magnetosheath plasma. It is pointed out that even though the data set is limited, the most intense heavy-ion fluxes clearly occur at altitudes less than a few thousand km. With the identification of the energetic component at O(+), the data reveal a trend for the speed of O(+) near the planet to be lower than the local magnetosheath speed, whereas the two speeds are comparable at altitudes above a few thousand km. These data, in combination with related observations that indicate O(+) moving at ambient speed in the distant wake, suggest that ionospheric material is swept up by the magnetosheath, accelerated to ambient speed within a few thousand km, and carried back through the wake region.

Mihalov, J. D.↗
NASA NTRS2017

CMAS Interactions with Advanced Environmental Barrier Coatings Deposited via Plasma Spray- Physical Vapor Deposition

Materials for advanced turbine engines are expected to have temperature capabilities in the range of 1370-1500C. At these temperatures the ingestion of sand and dust particulate can result in the formation of corrosive glass deposits referred to as CMAS. The presence of this glass can both thermomechanically and thermochemically significantly degrade protective coatings on metallic and ceramic components. Plasma Spray- Physical Vapor Deposition (PS-PVD) was used to deposit advanced environmental barrier coating (EBC) systems for investigation on their interaction with CMAS compositions. Coatings were exposed to CMAS and furnace tested in air from 1 to 50 hours at temperatures ranging from 1200-1500C. Coating composition and crystal structure were tracked with X-ray diffraction and microstructure with electron microscopy.

Coatings↗
NASA NTRS1986

Xe isotopic fractionation in a cathodeless glow discharge

Results are reported on the isotopic composition of Xe processed in cathodeless glow discharges in rarefied air at pressures of 20-40 microns Hg, in the presence of activated charcoal and in empty pyrex containers. Residual gas phase Xe and trapped Xe were found to be fractionated, with the trapped Xe fractionated up to 1 percent per amu. A model is presented for the fractionating process in which Xe ions are simultaneously implanted and sputtered from substrate material, with a mass dependence favoring retention of the heavy isotopes in the substrate. Results of the investigation show that plasma synthesis of carbonaceous material is unnecessary for producing Xe fractionations, and that the fractionations observed in previous synthesis experiments are probably due to implantation of ions into the synthesized material.

Bernatowicz, T. J.↗
NASA NTRS1999

Electrical Breakdown of Anodized Structures in a Low Earth Orbital Environmental

A comprehensive set of investigations involving arcing on a negatively biased anodized aluminum plate immersed in a low density argon plasma at low pressures (P(sub O), 7.5 x 10(exp -5) Torr) have been performed. These arcing experiments were designed to simulate electrical breakdown of anodized coatings in a Low Earth Orbital (LEO) environment. When electrical breakdown of an anodized layer occurs, an arc strikes, and there is a sudden flux of electrons accelerated into the ambient plasma. This event is directly followed by ejection of a quasi-neutral plasma cloud consisting of ejected material blown out of the anodized layer. Statistical analysis of plasma cloud expansion velocities have yielded a mean propagation velocity, v = (19.4 +/- 3.5) km/s. As the plasma cloud expands into the ambient plasma, energy in the form of electrical noise is generated. The radiated electromagnetic noise is detected by means of an insulated antenna immersed in the ambient plasma. The purpose of the investigations is (1) to observe and record the electromagnetic radiation spectrum resulting from the arcing process. (2) Make estimates of the travel time of the quasi-neutral plasma cloud based on fluctuations to several Langmuir probes mounted in the ambient plasma. (3) To study induced arcing between two anodized aluminum structures in close proximity.

Galofaro, J. T.↗
NASA NTRS1985

Plasma Production by Meteoroid Impact

Material ejected from the surfaces of satellites in the outer solar system plays an important role in the magnetospheres of the outer planets, and may dominate the mass loading, as in the vicinity of the Jovian satellite Io. At least four potential ejection mechanisms can be identified - intrinsic geologic activity, thermal sublimation, sputtering, and micrometeoroid impact vaporization. On all the icy satellites, except possibly Enceladus, sputtering and impact vaporization are the only two potentially important sources of magnetospheric plasma. Sputtering was shown to be an important mass source at both Jupiter and Saturn. The impact mechanism as a plasma source is assessed.

Haff, P. K.↗
NASA NTRS2015

Techniques for Measuring Surface Potentials in Space

Materials exposed to the space plasma environment charge to a net potential relative to the ambient plasma. The charging process is due to differential currents to the material surface that results in a net surface charge density. While this process is termed "spacecraft surface charging" when applied to aerospace hardware, it also applies to the surfaces of astronomical objects in direct contact with the space plasma environment including a number of planetary bodies, asteroids, and dust particles. The ability to measure surface potentials is important to many techniques used in conducting fundamental heliospheric science, spacecraft engineering operations, and space technology development activities. This presentation provides a survey of current technologies used to measure surface potentials of spacecraft and planetary bodies with examples of their application to space science and technology programs.

Minow, Joseph I.↗