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At least 109 records · Page 6

Evolution of Metastable Phases During Mg Metal Corrosion: An In Situ Cryogenic X-ray Photoelectron Spectroscopy Study

Magnesium and its alloys are potential structural materials candidates for a wide variety of applications due to their high strength-to-weight ratio. However, ductility and poor corrosion resistance under ambient environmental conditions are the bottleneck for industrial deployment. Designing passivation layers and/or corrosion resistant alloys requires fundamental understanding of the corrosion process. The traditional ex-situ spectroscopic measurements of polycrystalline metal surface with ubiquitous surface impurities and grain boundaries only provided an indistinct view of the corrosion process. To clearly distinguish the mechanism and sequence of corrosion process, we employed in-situ cryo-based x-ray photoelectron spectroscopy (XPS) measurements on Mg single crystal surface exposed to aqueous salt solution. Clean Mg (0001) surfaces were exposed to pure D2O and NaCl aqueous solution (5 wt% NaCl+95 wt% D2O). The interfacial reactions were studied using multimodal analysis including XPS, x-ray diffraction (XRD) and scanning electron microscopy (SEM). In contrast to previous studies, our experiments demonstrated the formation of magnesium chloride hydroxide hydrate during aqueous salt corrosion processes. Evidence of metastable ClO* radicals were also found during the initial aqueous salt solution exposure.

Shutthanandan, Vaithiyalingam↗

Subcooling Cryogenic Propellants for Long Duration Space Exploration

The use of cryogenic propellants such as hydrogen and oxygen is crucial for exploration of the solar system because of their superior specific impulse capability. Future missions may require vehicles with the flexibility to remain in orbit or travel in space for months, necessitating long-term storage of these cryogens. One powerful technique for easing the challenge of cryogenic fluid storage is to remove energy from tlie cryogenic propellant by isobaricly subcooling them below their normal boiling point prior to launch. The isobaric subcooling of the cryogenic propellant will be performed by using a cold pressurant to maintain the tank pressure while the cryogen's temperature is simultaneously reduced. After launch, even with the use of the best insulation systems, heat will leak into the cold cryogenic propellant tank. However, the large heat capacity available in highly subcooled cryogenic propellants allows them to absorb the energy that leaks into the tank until the cryogen reaches its operational thermodynamic condition. During this period of heating of the subcooled cryogen there will be no loss of the propellant due to venting for pressure control. This simple technique can extend the operational life of a spacecraft or an orbital cryogenic depot many months with minimal mass penalty. Subcooling technologies for cryogenic propellants would thus provide the Exploration Systems Mission Directorate with an enhanced level of mission flexibility. However, there are a few challenges associated with subcooling cryogenic propellants since compact subcooling ground support equipment has not been demonstrated. This paper explores the beneficial impact of subcooling cryogenic propellants on the launch pad for long-term cryogenic propellant storage in space and proposes a novel method for implementing subcooling of cryogenic propellants for spacecraft such as the Ares V Earth Departure Stage (EDS). Analysis indicates that with a careful strategy to handle the subcooled cryogen it would be possible to store cryogenic propellants in space for many months without venting. A concept for subcooling the cryogenic propellant relatively quickly and inexpensively on the launch pad - the thermodynamic cryogen subcooler (TCS) - will be presented. Important components of the TCS and an associated subcooled cryogen tank (SCT) will be discussed in this paper. Results from a preliminary thermodynamic model of the performance of a TCS for an EDS sized hydrogen tank will also be presented.

Mustafi, Shuvo↗

Hydrophobicity of Cryogenic Fluids for Fuel Transfer in Space Applicaitons

Introduction Hydrophobicity is the tendency of a fluid to repel another material or fluid. Hydrophobiciy can be measured through the wetting angle of the fluid on the surface of the other material. The greater the wetting angle, the more hydrophobic the surface is against the fluid. Hydrophobicity properties can be caused by one of two means, either through physical properties or chemical properties [\citenum{NARBUTT2020121}]. Physical hydrophobicity due to the surface of a solid creating surface roughness/patterning, minimizing the contact area between the fluid and the surface. This can be observed throughout nature, such as the surface of lotus leaves or butterfly wings. This physical property can be induced on a variety of surfaces, namely through laser etching, allowing a surface to be finely lineated to imitate these natural surfaces while controlling quantity, depth, and patterns of the etching on the surface [\citenum{10.1063/1.4905616}]. Physical hydrophobicity is therefore dependent on several variables, including the surface that the fluid is on and properties of the fluid itself, such as density and surface tension, both of which are dependent on temperature and/or pressure. Chemical hydrophobicity [\citenum{MadeiraHydrophobocicicici}] is due to the inherent chemical properties of the materials being used. This is most commonly due to the molecular structures changing the polarity of the materials. Depending on a nonpolar material will repel a polar material, proving to be hydrophobic, conversely if the polarity of the materials is the same (polar – polar, nonpolar – nonpolar), they will attract each other. Cryogenics refers to the behavior of materials at very low temperatures (<\ang{-100} C) [\citenum{ZOHURI20181}]. In space applications many things are inherently cryogenic, therefore this is an important field. There has been little research in how hydrophobicity changes at cryogenic temperatures. Cryogenic fluids are commonly used as fuels for spacecraft, therefore, integrating a hydrophobic surface can increase the transfer rate of the fuel. To test this, several experiments were set up to determine the hydrophobic properties of cryogenic fluids, including nitrogen (LN2), argon (LAr), oxygen (LOx), hydrogen (LH2), and methane (CH4), at cryogenic temperatures. Etched Wafer Testing A silicon wafer cut from a crystal of silicon [100] was used to model the potential hydrophobicity of various cryogenic fluids. Silicon [100] references to the crystallographic orientation of the silicon crystals in the wafer. These wafers were then laser etched to create a surface that is more likely to be hydrophobic. To test the hydrophobicity of the wafers at cryogenic temperatures, the temperatures of the wafers must be reduced to the same temperature as the cryogenic fluid being used to prevent rapid boil-off. To achieve this a double-walled vacuum insulated glass chamber was utilized. The chamber is open, with a double-walled glass that can be placed in a vacuum to remove condensation from the outside to allow easier viewing of the experiment. Furthermore, the silicon wafer's temperature must be lowered to the temperature of LN2, as well as maintain the temperature throughout the experiment. To achieve this a piece of 6061 aluminum was used, creating a stand-off for the wafer and it would allow for the insulation of the temperature of the wafers. The container was then filled with LN2 and once the LN2 stabilized the vaporization and the levels of LN2 dropped under the height of the wafer, the wafer was then allowed to air dry. Once the wafer was dry from the LN2, drops of LN2 were placed on the surface of the wafer for observation. During the first trial, the LN2 that was dropped on the surface displayed nonhydrophobic behaviors, spreading out along the surface, with a minimal wetting angle (too small to be measured). This process was repeated for liquid argon. Further testing with other cryogenic liquids will require different testing apparatuses due to being more volatile. Furthermore, several papers [\citenum{voltvolt7}] have suggested that running a voltage can induce a hydrophobic effect throughout a surface, further testing will include a voltage (constant and oscillating) to determine if voltage influences inducing hydrophobicity at cryogenic temperatures. Chemical Testing Coating the interior walls of the fuel tanks and fuel lines can successfully create a hydrophobic surface. The inherent problem is finding a material that can be used to coat the surface, furthermore, at these temperatures, the coating will remain solid, which could pose issues in maintaining the hydrophobic properties. To test this water (polar) is hydrophobic against oils and fats (nonpolar), therefore the same experiment as the etched wafer testing was conducted to determine if the hydrophobic properties will persist as the nonpolar material remains solid and the polar material remains a fluid. The water remained hydrophobic, allowing testing can expand to the cryogenic fluids. However, another hurdle is faced in finding a chemically opposite material to the cryogenic fluids being tested. As many of the cryogenic fluids being tested are diatomic, they are inherently nonpolar, therefore, the material used for the hydrophobic coating must be polar. Polar greases and lubricants are difficult to come by, however, lithium stearate, appears to be a potential candidate for creating a coated hydrophobic surface for cryogenic fluids at cryogenic temperatures.

Cryogenics↗

Subcooling for Long Duration In-Space Cryogenic Propellant Storage

Cryogenic propellants such as hydrogen and oxygen are crucial for exploration of the solar system because of their superior specific impulse capability. Future missions may require vehicles to remain in space for months, necessitating long-term storage of these cryogens. A Thermodynamic Cryogen Subcooler (TCS) can ease the challenge of cryogenic fluid storage by removing energy from the cryogenic propellant through isobaric subcooling of the cryogen below its normal boiling point prior to launch. The isobaric subcooling of the cryogenic propellant will be performed by using a cold pressurant to maintain the tank pressure while the cryogen's temperature is simultaneously reduced using the TCS. The TCS hardware will be integrated into the launch infrastructure and there will be no significant addition to the launched dry mass. Heat leaks into all cryogenic propellant tanks, despite the use of the best insulation systems. However, the large heat capacity available in the subcooled cryogenic propellants allows the energy that leaks into the tank to be absorbed until the cryogen reaches its operational thermodynamic condition. During this period of heating of the subcooled cryogen there will be minimal loss of the propellant due to venting for pressure control. This simple technique can extend the operational life of a spacecraft or an orbital cryogenic depot for months with minimal mass penalty. In fact isobaric subcooling can more than double the in-space hold time of liquid hydrogen compared to normal boiling point hydrogen. A TCS for cryogenic propellants would thus provide an enhanced level of mission flexibility. Advances in the important components of the TCS will be discussed in this paper.

Mustafi, Shuvo↗

Overview of the Liquid Argon Cryogenics for the Short Baseline Neutrino Program (SBN) at Fermilab

The Short-Baseline Neutrino (SBN) physics program will involve three LAr-TPC detectors located along the Booster Neutrino Beam (BNB) at Fermilab. This new SBN Program will deliver a rich and compelling physics opportunity, including the ability to resolve a class of experimental anomalies in neutrino physics and to perform the most sensitive search to date for sterile neutrinos at the eV mass-scale through both appearance and disappearance oscillation channels. The Program will be composed of an existing and operational detector known as Micro Boone (170 ton LAr mass) plus two new experiments known as the SBN Near Detector (SBND, ~ 260 ton) and the SBN Far Detector (SBN-FD, ~ 600 tons). Fermilab is now building two new facilities to house the experiments and incorporate all cryogenic and process systems to operate these detectors beginning in the 2018-2019 time frame. The SBN cryogenics are a collaborative effort between Fermilab and CERN. The SBN cryogenic systems for both detectors are composed of several sub-systems: External/Infrastructure (or LN2), Proximity (or LAr), and internal cryogenics. For each detector the External/Infrastructure cryogenics includes the equipment used to store and the cryogenic fluids needed for the operation of the Proximity cryogenics, including the LN2 and LAr storage facilities. The Proximity cryogenics consists of all the systems that take the cryogenic fluids from the external/infrastructure cryogenics and deliver them to the internal at the required pressure, temperature, purity and mass flow rate. It includes the condensers, the LAr and GAr purification systems, the LN2 and LAr phase separators, and the interconnecting piping. The Internal cryogenics is comprised of all the cryogenic equipment located within the cryostats themselves, including the GAr and LAr distribution piping and the piping required to cool down the cryostats and the detectors. These cryogenic systems will be engineered, manufactured, commissioned, and qualified by an international engineering team. This contribution presents the performance, the functional requirements and the modes of operation of the SBN cryogenics, and details the current status of the design, present and future needs.

Norris, Barry↗

Cryogenics and the Human Exploration of Mars

Current plans within NASA involve extending the human exploration of space from low earth orbit into the solar system, with the first human exploration of Mars presently planned in 2011. Integral to all hum Mars mission phases is cryogenic fluid management. Cryogenic fluids will be required both as propellant and for In-Situ Resource Utilization (ISRU). Without safe and efficient cryogen storage human Mars missions will not be possible. Effective control and handling of cryogenic fluids is the key to affordable Mars missions, and advancing active thermal control technology is synergistic with all of NASA's exploration initiatives and with existing and future instrument cooling programs, including MTPE and Origins. Present mission scenarios for human exploration require cryogenic propellant storage for up to 1700 days and for up to 60 metric tons. These requirements represent increases of an order of magnitude over previous storage masses and lifetimes. The key cryogenic terminology areas to be addressed in human Mars missions are long-term propellant storage, cryogenic refrigeration, cryogenic liquefaction, and zero gravity fluid management. Long-term storage for the thermal control of cryogenic propellants is best accomplished with a mix of passive and active technologies. Passive technologies such as advanced multilayer insulation (MLI) concepts will be combined with the development of active coolers (cryogenic refrigerators). Candidates for long-life active cooling applications include Reverse Turbo-Brayton, Stirling, and Pulse-Tube coolers. The integration of passive and active technologies will form a hybrid system optimized to minimize the launch mass while preserving the cryogenic propellants. Since cryogenic propellants are the largest mass that Mars missions must launch from earth, even a modest reduction in the percentage of propellant carried results in a significant weight saving. This paper will present a brief overview of cryogenic fluid management technology as it applies to the current human Mars mission scenarios.

Salerno, Louis J.↗

NASA Marshall Space Flight Center In-Space Cryogenic Propulsion Capabilities and Applications to Human Exploration

The current focus on lunar exploration and future human missions to Mars is driving in-space propulsion system requirements toward higher performance cryogenic systems with long-duration storage and operational capabilities. Not only do these systems offer higher performance than storable propellant options, but they also enable the potential for in-situ propellant production. Future Mars transit systems are envisioned to utilize either high-thrust nuclear thermal propulsion (with liquid hydrogen propellant), or hybrid systems with both cryogenic chemical systems (likely LOX/CH4) for high acceleration maneuvers and nuclear electric systems for long duration high Isp maneuvers. Exploration architectures based on either of these options require the use of high-performance cryogenic propellants with long-duration storage capabilities for both in-space transportation as well as planetary descent and ascent functions. Current efforts focusing on lunar exploration also rely on cryogenic propellants (either LOX/LCH4 or LOX/LH2) for lunar transit and descent/ascent transportation functions. In-space cryogenic propulsion systems pose numerous technology challenges with respect to long-duration propellant storage and usage, including advanced insulation, tank stratification and pressure management, cryogenic refrigeration to reduce propellant loss through boil off, low leakage cryogenic valves, low temperature liquid acquisition, and cryogenic propellant transfer. NASA has invested in technology development efforts, demonstrating individual technologies and systems-level operations. NASA Marshal Space Flight Center has also invested in multiple test facilities and modular test rigs that allow ground demonstration of numerous integrated technologies and systems concepts of operations. Additional investments have been made to mature analytical capabilities and design tools. These capabilities, both test/demonstration & engineering design/analysis, are available to support internal efforts and industrial partners in the development of exploration and science mission systems. With this increased interest, it is critical to understand the current state of in-space cryogenic propulsion technology, determine risks to its successful application to human exploration, and prepare the engineering, test, and evaluation capabilities to support the ambitious plans for future systems. This paper provides a survey of recent developments in in-space cryogenic propulsion and cryogenic propellant management technologies, as well as facilities and engineering/analytical capabilities ready to support current and future exploration efforts.

Cryogenic propulsion, cryogenic fluid management, ↗

NASA Marshall Space Flight Center In-Space Cryogenic Propulsion Capabilities and Applications to Human Exploration

The current focus on lunar exploration and future human missions to Mars is driving in-space propulsion system requirements toward higher performance cryogenic systems with long-duration storage and operational capabilities. Not only do these systems offer higher performance than storable propellant options, but they also enable the potential for in-situ propellant production. Future Mars transit systems are envisioned to utilize either high-thrust nuclear thermal propulsion (with liquid hydrogen propellant), or hybrid systems with both cryogenic chemical systems (likely LOX/CH 4 ) for high acceleration manoeuvres and nuclear electric systems for long duration high Isp manoeuvres. Exploration architectures based on either of these options require the use of high-performance cryogenic propellants with long-duration storage capabilities for both in-space transportation as well as planetary descent and ascent functions. Current efforts focusing on lunar exploration also rely on cryogenic propellants (either LOX/LCH 4 or LOX/LH 2 ) for lunar transit and descent/ascent transportation functions. In-space cryogenic propulsion systems pose numerous technology challenges with respect to long-duration propellant storage and usage, including advanced insulation, tank stratification and pressure management, cryogenic refrigeration to reduce propellant loss through boil off, low leakage cryogenic valves, low temperature liquid acquisition, and cryogenic propellant transfer. NASA has invested in technology development efforts, demonstrating individual technologies and systems-level operations. NASA Marshal Space Flight Center has also invested in multiple test facilities and modular test rigs that allow ground demonstration of numerous integrated technologies and systems concepts of operations. Additional investments have been made to mature analytical capabilities and design tools. These capabilities (both test/demonstration & engineering design/analysis) are available to support both internal efforts and industrial partners in the development of exploration and science mission systems. With this increased interest, it is critical to understand the current state of in-space cryogenic propulsion technology, determine risks to its successful application to human exploration, and prepare the engineering, test, and evaluation capabilities to support the ambitious plans for future systems. This paper provides a survey of recent developments in in-space cryogenic propulsion and cryogenic propellant management technologies, as well as facilities and engineering/analytical capabilities ready to support current and future exploration efforts.

Cryogenic propulsion↗

NASA Marshall Space Flight Center In-Space Cryogenic Propulsion Capabilities and Applications to Human Exploration

The current focus on lunar exploration and future human missions to Mars is driving in-space propulsion system requirements toward higher performance cryogenic systems with long-duration storage and operational capabilities. Not only do these systems offer higher performance than storable propellant options, but they also enable the potential for in-situ propellant production. Future Mars transit systems are envisioned to utilize either high-thrust nuclear thermal propulsion (with liquid hydrogen propellant), or hybrid systems with both cryogenic chemical systems (likely LOX/CH4) for high acceleration maneuvers and nuclear electric systems for long duration high Isp maneuvers. Exploration architectures based on either of these options require the use of high-performance cryogenic propellants with long-duration storage capabilities for both in-space transportation as well as planetary descent and ascent functions. Current efforts focusing on lunar exploration also rely on cryogenic propellants (either LOX/LCH4 or LOX/LH2) for lunar transit and descent/ascent transportation functions. In-space cryogenic propulsion systems pose numerous technology challenges with respect to long-duration propellant storage and usage, including advanced insulation, tank stratification and pressure management, cryogenic refrigeration to reduce propellant loss through boil off, low leakage cryogenic valves, low temperature liquid acquisition, and cryogenic propellant transfer. NASA has invested in technology development efforts, demonstrating individual technologies and systems-level operations. NASA Marshal Space Flight Center has also invested in multiple test facilities and modular test rigs that allow ground demonstration of numerous integrated technologies and systems concepts of operations. Additional investments have been made to mature analytical capabilities and design tools. These capabilities, both test/demonstration & engineering design/analysis, are available to support internal efforts and industrial partners in the development of exploration and science mission systems. With this increased interest, it is critical to understand the current state of in-space cryogenic propulsion technology, determine risks to its successful application to human exploration, and prepare the engineering, test, and evaluation capabilities to support the ambitious plans for future systems. This paper provides a survey of recent developments in in-space cryogenic propulsion and cryogenic propellant management technologies, as well as facilities and engineering/analytical capabilities ready to support current and future exploration efforts.

Cryogenic propulsion, cryogenic fluid management, ↗