O atom etching of graphite in low earth orbit

Ngo, Tue; Snyder, Eric J.; Tong, William M.; Williams, R. Stanley; Anderson, M. S.

doi:10.1016/0039-6028(94)90201-1

Cited by 36 publications

(26 citation statements)

References 13 publications

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“…Incorporation of carbon fiber reinforcement reduced the erosion rate compared to the pure CE, which led to the maximum difference in mass loss between CE and CFCE at the highest AO fluence used. Given the erosion yields of pyrolytic graphite and highly oriented pyrolytic graphite in LEO, 0.4 Â 10 À24 and 1.1 Â 10 À24 cm 3 O-atom À1 , respectively, 49,50 the carbon fibers in CFCE are expected to have a significantly lower erosion yield than the pure CE resin. Indeed, the SEM images show that the carbon fibers become more and more exposed with increasing AO fluence, indicating that the fibers etch at a slower rate than the CE resin.…”

Section: Discussionmentioning

confidence: 99%

Effects of hyperthermal atomic oxygen on a cyanate ester and its carbon fiber-reinforced composite

Wang

Qian

Murray

et al. 2018

High Performance Polymers

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The durability of cyanate ester (CE) to hyperthermal atomic oxygen (AO) attack in low Earth orbit may be enhanced by the addition of carbon fiber to form a carbon fiber-reinforced cyanate ester composite (CFCE). To investigate the durability of CFCE relative to CE, samples were exposed to a pulsed hyperthermal AO beam in two distinct types of experiments. In one type of experiment, samples were exposed to the beam, with pre- and post-characterization of mass (microbalance), surface topography (scanning electron microscopy (SEM)), and surface chemistry (X-ray photoelectron spectroscopy (XPS)). In the second type of experiment, the beam was directed at a sample surface, and volatile products that scattered from the surface were detected in situ with the use of a rotatable mass spectrometer detector. CFCE exhibited less mass loss than pure CE with a given AO fluence, confirming that the incorporation of carbon fiber adds AO resistance to CE. Erosion yields of CE and CFCE were 2.63 ± 0.16 × 10−24 and 1.46 ± 0.08 × 10−24 cm3 O-atom−1, respectively. The reduced reactivity of CFCE in comparison to CE was manifested in less oxidation of the CFCE surface in XPS measurements and reduced CO, CO2, and OH reaction products in beam-surface scattering experiments. The surface topographical images collected by SEM implied different surface deterioration processes for CE and CFCE. A change of surface topography with increasing AO fluence for CE indicated a threshold AO fluence, above which the erosion mechanism changed qualitatively. CFCE showed almost intact carbon fibers after relatively low AO fluences, and while the fibers eventually eroded, they did not erode as rapidly as the CE component of the composite.

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Section: Discussionmentioning

confidence: 99%

Effects of hyperthermal atomic oxygen on a cyanate ester and its carbon fiber-reinforced composite

Wang

Qian

Murray

et al. 2018

High Performance Polymers

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“…An ionizing vacuum gauge will detect neutral gas pressure in the shuttle bay down to 1x10 -7 Torr, to detect any contaminating events like a shuttle water dump. A sacrificial pyrolitic graphite coupon similar to one flown on a previous shuttle mission 15 will be included to record the extent of atomic oxygen damage seen throughout the mission. Also, several contamination witness coupons will be included to keep a record of any non-volatile residue e.g.…”

Section: Environmental Protectionmentioning

confidence: 99%

Field Emission Cathodes used in the FEGI Get-Away-Special Shuttle Mission

Deline

Goldberg

Morris

et al. 2004

40th AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit

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Field emission cathodes are presently being developed as low-power space electric propulsion neutralizers and for spacecraft charge control and electrodynamic tether applications requiring no consumables. These cathodes effect cold electron emission by the application of a relatively high electric field across a small gap from some kind of electron emitting (cathode) surface. Various designs of field emission cathodes are being investigated for charge control on a student-built experiment called Field Emission GetAway Special Investigation (FEGI), including molybdenum, carbon nanotube, boron nitride and diamond surface emission cathodes. This paper presents the current progress of the FEGI experiment with a focus on the emitters that will be flown, and the immediately surrounding electrical, mechanical and environmental support structures. Nomenclature LVTF =

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“…Study of bulk graphite etching in low earth orbit show that one C atom is etched for every eight incident O atoms. 396 Such an etching yield would result in etching out one layer of carbon atoms in 2-3 min in a 400 km altitude orbit. Thus an ultrathin carbon foil directly exposed to the ram oxygen atom flux would not survive more than a few hours in low earth orbit.…”

Section: Ultrathin Foils 1 Foil Fabrication and Characterizationmentioning

confidence: 99%

Energetic neutral atom imaging of space plasmas

Gruntman

1997

Review of Scientific Instruments

172

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Experimental techniques and instrumentation for space plasma imaging in fluxes of energetic neutral atoms ͑ENAs͒ are reviewed. ENAs are born in charge exchange collisions between space plasma energetic ions and background neutral gas. ENAs are ubiquitous in the space environment and their energies are in the range from a few eV up to Ͼ100 keV. Contrary to charged particles, ENAs can travel large distances through space with minimal disturbance, and by recording ENA fluxes as a function of observational direction, one can reconstruct a global image of a planetary magnetosphere or the heliosphere. Plasma ion energy distribution and ion composition can be remotely established by measuring ENA energies and masses. ENA imaging opens a new window on various phenomena in space plasmas with a promise to qualitatively improve our understanding of global magnetospheric and heliospheric processes. At first we review ENA fluxes in space and their properties, and present a brief history of ENA experimental studies and the evolution of experimental approaches. The concepts of ENA imaging and particle identification are considered and followed by comparison with corpuscular diagnostics of fusion plasmas. Basic ENA techniques and instrument components are then described in detail and critically evaluated; performance characteristics, limitations, and requirements to key instrumental elements are discussed. And finally, representative ENA instruments are shown, and promising instrumental approaches are identified.

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O atom etching of graphite in low earth orbit

Cited by 36 publications

References 13 publications

Effects of hyperthermal atomic oxygen on a cyanate ester and its carbon fiber-reinforced composite

Effects of hyperthermal atomic oxygen on a cyanate ester and its carbon fiber-reinforced composite

Field Emission Cathodes used in the FEGI Get-Away-Special Shuttle Mission

Energetic neutral atom imaging of space plasmas

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