Outgassing

Room temperature internal friction (Q sup-1) values of the 0.00002-0.00003 range were achieved with lunar rock 70215,85 by thorough outgassing procedures in ultrahigh vacuum. Results are presented on the temperature dependence of Q-1 as measured in the range 25 C to 600 C along with some data on the change in Q-1 with pressure in ultrahigh vacuum. The temperature dependence shows the existence of an internal friction peak at around 200 C followed at high temperatures by an extensive region with flat Q-1 (approximately 0.001); the work at ultrahigh vacuum shows decreases in the internal friction with decreases in ambient pressure even in the range 10 to the -8 to 10 to the -10 power torr.

Many fields including the aerospace industry have shown increased interest in the use of plastics to lower the mass of systems. However, the use of plastics in space can be challenging for a number of reasons. Ultraviolet radiation, atomic oxygen and other phenomena specifically associated with space cause the degradation of polymers. Here we show a path towards creation of space-grade components by combining additive manufacturing (AM) and atomic layer deposition (ALD). Our method produced ALD Al2O3 coated thermoplastic parts, suitable for space applications. The highlight of this work is a significant reduction in outgassing, demonstrated using residual gas analyzer (RGA) sampling. Compared to uncoated parts, the ALD-Al2O3 coating decreased the outgassing of polyether ether ketone (PEEK), acrylonitrile butadiene styrene (ABS), polycarbonate (PC) and nanodiamond-doped polylactide (ND-PLA) by 46%, 49%, 58% and 65% respectively. The manufacturing method used in this work enables the use of topology optimization already in the early concept creation phase. The method is ideally suited for spacecraft applications, where the volume and mass of parts is critical, and could also be adapted for in-space manufacturing.

According to the new proposed model, in addition to the anthropogenic carbon dioxide (CO2) due to land -use change and fossil fuel burning, significant emissions of CO2 are released from the ocean at sites of upwelling currents, which connect the global overturning circulation with the sea surface, as exemplified by the upwelling currents along the Antarctic Circumpolar Current (ACC). Carbon dioxide was sequestered in deep oceanic layers which were disturbed through detonations of the nuclear bomb tests early in the1960s as confirmed by multiple time series of temperature and geochemical records. New features contributed to this article are
• the abrupt and vigorous change of the climate since about 1960, by contrast to the mild and gradual warming since the beginning of the Industrial Era, a period of adaptation after the cold Little Ice Age
• the identification of the temporal coincidence of the initiation of the severe climate change in the 1960s with the bomb tests associated with geochemical anomalies and steady temperature increase,
• the outrageous rate of CO2 emission, five times higher than similar extreme events in the geological past,
• the function of the Southern Ocean both as sink and as source of CO2 with prevailing outgassing currently,
• the heat engine along the boundary of the Antarctica Lithospheric Plate which stimulates upwelling and causes widespread continental warming of the West Antarctic climate, confirmed since 1958.
Therefore, apart from the Greenhouse Effect, we are currently confronted with the Nuclear Bomb Effect, a much more severe likelihood. It is not argued that the Bomb Effect is a proven fact, but only that there are strong indications for it and therefore it is an emergency for the scientific community to accelerate the investigations by absolute priority, which requires significant international support.
The evidence for the climatic change predominantly is based on measurements of the temperature globally and the increase of the carbon dioxide in the atmosphere and the oceans. The relevant data are reconsidered based on the latest results and their current interpretation. Multiple time series are correlated, including the temperature, the greenhouse gases, the isotopic values of the radiocarbon (14C) and the stable isotope 13C. Furthermore, it is suggested that field surveys and modeling applications in the latest couple of years indicate that the Southern Ocean surrounding Antarctica is very likely a source of carbon dioxide from deep oceanic waters in tandem with CO2 intake at the ocean surface from the atmosphere. It is not considered a coincidence that the increase of temperature and the geochemical anomalies start simultaneously with the nuclear bomb spike, approximately in 1960, as highlighted in the following.
The temperature increase is still in the expected range of warming after the cold period of the Little Ice age from 1570 to 1900 AD in the Northern Hemisphere. However, the CO2 increase is beyond any geological record, continues, and will persist so for some time, even after zeroing the fossil fuel burning. The reason is that a proportion of the CO2 in the atmosphere comes from sequestered gases in the ocean which travel southwards along the Global Overturning Circulation to join the Antarctic Circumpolar Current, where they upwell heated by the oceanic ridge of the Antarctic Lithospheric Plate and the elevated relief of the ridge.
It is not argued that the Bomb Effect is a proven fact, but only that there are reliable indications for it and therefore it is an emergency for the scientific community to accelerate the investigations in Antarctica by absolute priority which requires international support and coordination.

The Moon-forming giant impact extensively melts and partially vaporizes the silicate Earth and delivers a substantial mass of metal to Earth's core. The subsequent evolution of the magma ocean and overlying atmosphere has been described by theoretical models but observable constraints on this epoch have proved elusive. Here, we report thermodynamic and climate calculations of the primordial atmosphere during the magma ocean and water ocean epochs respectively and forge new links with observations to gain insight into the behavior of volatiles on the Hadean Earth. As accretion wanes, Earth's magma ocean crystallizes, outgassing the bulk of its volatiles into the primordial atmosphere. The redox state of the magma ocean controls both the chemical composition of the outgassed volatiles and the hydrogen isotopic composition of water oceans that remain after hydrogen escape from the primordial atmosphere. The climate modeling indicates that multi-bar H2-rich atmospheres generate sufficient greenhouse warming and rapid kinetics resulting in ocean-atmosphere H2 O-H2 isotopic equilibration. Whereas water condenses and is mostly retained, molecular hydrogen does not condense and can escape, allowing large quantities (∼10^2 bars) of hydrogen-if present-to be lost from the Earth in this epoch. Because the escaping inventory of H can be comparable to the hydrogen inventory in primordial water oceans, equilibrium deuterium enrichment can be large with a magnitude that depends on the initial atmospheric H2 inventory. With rapid kinetics, the water molecule concentrates deuterium and, to the extent that hydrogen in other forms (e.g., H2) are significant species in the outgassed atmosphere, pronounced D/H enrichments (∼1.5-2x) in the oceans are expected from equilibrium partitioning in this epoch. By contrast, the common view that terrestrial water has a carbonaceous chondritic source requires the oceans to preserve the isotopic composition of that source, undergoing minimal D-enrichment via equilibration with H2 followed by hydrodynamic escape. Such minimal enrichment places upper limits on the amount of primordial atmospheric H2 in contact with Hadean water oceans and implies oxidizing conditions (logfO2>IW+1, H2/H2O<0.3) for outgassing from the magma ocean. Preservation of an approximate carbonaceous chondrite D/H signature in the oceans thus provides evidence that the observed oxidation of silicate Earth occurred before crystallization of the final magma ocean, yielding a new constraint on the timing of this critical event in Earth history. The seawater-carbonaceous chondrite "match" in D/H (to ∼10-20%) further constrains the prior existence of an atmospheric H2 inventory-of any origin-on post-giant-impact Earth to <20 bars, and suggests that the terrestrial mantle supplied the oxidant for the chemical resorption of metals during terrestrial late accretion.

Windows constitute a weak link in the building envelope and hence contribute significantly to the heating energy demand. By evacuating the glazing cavity, heat transfer rates two to five times lower than those of gas-filled conventional glazing units are predicted in theory and have been practically confirmed in a few cases. Of central importance to any practical realization of vacuum glazing is the edge-sealing problem because the technology used defines many secondary and tertiary parameters and strongly influences service life. This work establishes a correlation between the sealing method and its effect on the products service life. A cavity pressure balance model is presented, which takes into account four possible sources to the total pressure increase. Using this model a set of critical parameters is defined and the range of tolerable values for each parameter can be extracted. These findings underline the importance of choosing a sealing process, which is carried out in a high-vacuum environment. A possible source of pressure increase not considered in detail so far is the photofragmentation of long-chain organic adsorbate contaminants on the inner glazing surfaces. It was shown that a surface treatment via UV/ozone cleaning reduces the surface concentration of a model surface contaminant sodium dodecyl sulfate (SDS) by approximately 3 orders of magnitude.

The Magnetospheric Multiscale (MMS) mission is a constellation of 4 observatories designed to investigate the fundamental plasma physics of reconnection in the Earth’s magnetosphere. The various instrument suites measure electric and magnetic fields, energetic particles, and plasma composition. Each spacecraft has undergone extensive environmental testing to prepare it for its minimum 2 year mission. In this paper, we report on the extensive thermal vacuum testing campaign. The testing was performed at the Naval Research Laboratory utilizing the “Big Blue” vacuum chamber. A total of ten thermal vacuum tests were performed, including two chamber certifications, three dry runs, and five tests of the individual MMS observatories. During the test, the observatories were enclosed in a thermal enclosure known as the “hamster cage”. The enclosure allowed for a detailed thermal control of various observatory zone, but at the same time, imposed additional contamination and system performance...

Gravitational-wave laser interferometer detectors use a pair of cylindrical vacuum tubes, placed perpendicular to each other, in which the partial pressure of hydrogen is required to be 10-9mbar to obtain residual gas-phase noise of .10-25Hz-1/2. Because total strain sensitivity decreases
proportionally to arm length, it is advantageous to use longer arm-length interferometers. The vacuum-tube diameters are set by the light-scattering requirements, and also by the possible need for additional optical cavities within the tube. Here, the authors investigate the balance between achievable vacuum and tube diameter for various pumping conditions. For a 5 km arm-length interferometer, they consider whether there is an advantage in reduced tube diameter. They also consider the impact of baffles. They show that the vacuum performance depends critically on the stainless-steel outgassing rate, which is limited by the tube conductance, and requires an outgassing rate .5.10-15 mbar l cm-2 s-1. It is shown that a smaller-diameter tube needs additional pumps,
and that, in general, there is a reduced safety margin for practical design. The vacuum performance depends only weakly on the vacuum-pumping speed for practical pumps and is only weakly degraded by baffles.

Context. Pre-equinox measurements of comet 67P/Churyumov-Gerasimenko with the mass spectrometer ROSINA/DFMS on board the Rosetta spacecraft revealed a strongly heterogeneous coma. The abundances of major and various minor volatile species were found to depend on the latitude and longitude of the nadir point of the spacecraft. The observed time variability of coma species remained consistent for about three months up to equinox. The chemical variability could be generally interpreted in terms of surface temperature and seasonal effects superposed on some kind of chemical heterogeneity of the nucleus. Aims. We compare here pre-equinox (inbound) ROSINA/DFMS measurements from 2014 to measurements taken after the outbound equinox in 2016, both at heliocentric distances larger than 3 AU. For a direct comparison we limit our observations to the southern hemisphere. Methods. We report the similarities and differences in the concentrations and time variability of neutral species under simila...

We present results from the Chandra X-ray Observatory's extensive campaign studying Comet 9P/Tempel 1 (T1) in support of NASA's Deep Impact (DI) mission. T1 was observed for ˜295 ks between 30th June and 24th July 2005, and continuously for ˜64 ks on July 4th during the impact event. X-ray emission qualitatively similar to that observed for the collisionally thin Comet 2P/Encke system [Lisse, C.M., Christian, D.J., Dennerl, K., Wolk, S.J., Bodewits, D., Hoekstra, R., Combi, M.R., Mäkinen, T., Dryer, M., Fry, C.D., Weaver, H., 2005b. Astrophys. J. 635 (2005) 1329-1347] was found, with emission morphology centered on the nucleus and emission lines due to C, N, O, and Ne solar wind minor ions. The comet was relatively faint on July 4th, and the total increase in X-ray flux due to the Deep Impact event was small, ˜20% of the immediate pre-impact value, consistent with estimates that the total coma neutral gas release due to the impact was 5×10 kg ( ˜10 h of normal emission). No obvious prompt X-ray flash due to the impact was seen. Extension of the emission in the direction of outflow of the ejecta was observed, suggesting the presence of continued outgassing of this material. Variable spectral features due to changing solar wind flux densities and charge states were clearly seen. Two peaks, much stronger than the man-made increase due to Deep Impact, were found in the observed X-rays on June 30th and July 8th, 2005, and are coincident with increases in the solar wind flux arriving at the comet. Modeling of the Chandra data using observed gas production rates and ACE solar wind ion fluxes with a CXE mechanism for the emission is consistent, overall, with the temporal and spectral behavior expected for a slow, hot wind typical of low latitude emission from the solar corona interacting with the comet's neutral coma, with intermittent impulsive events due to solar flares and coronal mass ejections.