Results for “Pressure Core” — Page 55

NASA NTRS2004

Exploration EVA System

In January 2004, the President announced a new Vision for Space Exploration. NASA's Office of Exploration Systems has identified Extravehicular Activity (EVA) as a critical capability for supporting the Vision for Space Exploration. EVA is required for all phases of the Vision, both in-space and planetary. Supporting the human outside the protective environment of the vehicle or habitat and allow ing him/her to perform efficient and effective work requires an integrated EVA "System of systems." The EVA System includes EVA suits, airlocks, tools and mobility aids, and human rovers. At the core of the EVA System is the highly technical EVA suit, which is comprised mainly of a life support system and a pressure/environmental protection garment. The EVA suit, in essence, is a miniature spacecraft, which combines together many different sub-systems such as life support, power, communications, avionics, robotics, pressure systems and thermal systems, into a single autonomous unit. Development of a new EVA suit requires technology advancements similar to those required in the development of a new space vehicle. A majority of the technologies necessary to develop advanced EVA systems are currently at a low Technology Readiness Level of 1-3. This is particularly true for the long-pole technologies of the life support system.

Kearney, Lara↗

NASA NTRS2014

Counter-Rotatable Fan Gas Turbine Engine with Axial Flow Positive Displacement Worm Gas Generator

A counter-rotatable fan turbine engine includes a counter-rotatable fan section, a worm gas generator, and a low pressure turbine to power the counter-rotatable fan section. The low pressure turbine maybe counter-rotatable or have a single direction of rotation in which case it powers the counter-rotatable fan section through a gearbox. The gas generator has inner and outer bodies having offset inner and outer axes extending through first, second, and third sections of a core assembly. At least one of the bodies is rotatable about its axis. The inner and outer bodies have intermeshed inner and outer helical blades wound about the inner and outer axes and extending radially outwardly and inwardly respectively. The helical blades have first, second, and third twist slopes in the first, second, and third sections respectively. A combustor section extends through at least a portion of the second section.

Giffin, Rollin George↗

NASA NTRS2020

Mars 2020 Rover Adaptive Caching Assembly: Caching Martian Samples for Potential Earth Return

The Adaptive Caching Assembly, part of the Sampling and Caching System on the Mars 2020 Rover, consists of multiple stations that together process sample tubes containing collected Martian material, either rock cores or soil samples, and prepares hermetically-sealed sample tubes for caching on the surface of Mars. There are 7 active degrees-of-freedom, as well as a large number of passive mechanisms within the Adaptive Caching Assembly that must operate in extreme Mars conditions (i.e., temperature and pressure). Hardware cleanliness requirements significantly drove design, assembly, and test operations of the Adaptive Caching Assembly, and were found to adversely affect hardware in some cases such that late design changes and revised cleanliness operations had to be implemented. While Adaptive Caching Assembly hardware was designed to accommodate dust, testing in a representative environment is important to validate functionality is not compromised.

Silverman, Milo↗

NASA NTRSDate not supplied

Performance of a Regenerative Fuel Cell System for the Lunar Surface

Regenerative fuel cells (RFCs) are an attractive energy storage solution for lunar missions as a technology capable of providing a higher specific energy (i.e., W∙h/kg) than state-of-the-art packaged Li-ion battery systems. An RFC consists of the (1 & 2) electrochemical stacks (chemical to electrical energy conversion to supply electricity to an external load, i.e. the fuel cell reaction, and electrical to chemical energy conversion of supplied electrical power to dissociate water into hydrogen and oxygen gases, i.e. water electrolysis), (3) fluidic conditioning, (4) reactant storage, (5) avionics, (6) power management and distribution (PMAD), and (7) thermal management. NASA’s Glenn Research Center has designed, assembled, and tested a breadboard RFC sys-tem capable of operating autonomously for multiple simulated lunar day/night cycles in a laboratory environment. The system is comprised of a non-flow through proton exchange membrane (PEM) fuel cell stack and a liquid-anode feed PEM electrolyzer (EZ) stack designed to electrochemically compress the reactants at balanced pressures up to 12.4 MPa (1800 psia). The fluidic conditioning, avionics, PMAD, and thermal management sub-systems are largely comprised of commercial-off-the-shelf components for this system-level development effort. The hardware is controlled by a CubeSat space processor running an operational program based on core flight architecture that can control the RFC hardware autonomously through a state machine with fault monitoring. The testing results highlighted here were completed with the system in an open-loop configuration such that reactants generated through water electrolysis were vented while gas cylinders supplied fuel cell operation. The breadboard operated autonomously, but there were five unplanned transitions to a safe state that required a manual restart after reviewing the data, determining a root cause, and implementing a solution. Four of the transitions were caused by the thermal management subsystem and the fifth was caused by a water management control issue in the EZ sub-system. The RFC system operated for over 550 hours with the final cycle being slightly abbreviated due to reasons unrelated to system performance.

Kerrigan Cain↗

NASA NTRSDate not supplied

Performance of a Regenerative Fuel Cell System for the Lunar Surface

Regenerative fuel cells (RFCs) are an attractive energy storage solution for lunar missions as a technology capable of providing a higher specific energy (i.e., W∙h/kg) than state-of-the-art packaged Li-ion battery systems. An RFC consists of the (1 & 2) electrochemical stacks (chemical to electrical energy conversion to supply electricity to an external load, i.e. the fuel cell reaction, and electrical to chemical energy conversion of supplied electrical power to dissociate water into hydrogen and oxygen gases, i.e. water electrolysis), (3) fluidic conditioning, (4) reactant storage, (5) avionics, (6) power management and distribution (PMAD), and (7) thermal management. NASA’s Glenn Research Center has designed, assembled, and tested a breadboard RFC sys-tem capable of operating autonomously for multiple simulated lunar day/night cycles in a laboratory environment. The system is comprised of a non-flow through proton exchange membrane (PEM) fuel cell stack and a liquid-anode feed PEM electrolyzer (EZ) stack designed to electrochemically compress the reactants at balanced pressures up to 12.4 MPa (1800 psia). The fluidic conditioning, avionics, PMAD, and thermal management sub-systems are largely comprised of commercial-off-the-shelf components for this system-level development effort. The hardware is controlled by a CubeSat space processor running an operational program based on core flight architecture that can control the RFC hardware autonomously through a state machine with fault monitoring. The testing results highlighted here were completed with the system in an open-loop configuration such that reactants generated through water electrolysis were vented while gas cylinders supplied fuel cell operation. The breadboard operated autonomously, but there were five unplanned transitions to a safe state that required a manual restart after reviewing the data, determining a root cause, and implementing a solution. Four of the transitions were caused by the thermal management subsystem and the fifth was caused by a water management control issue in the EZ sub-system. The RFC system operated for over 550 hours with the final cycle being slightly abbreviated due to reasons unrelated to system performance.

Kerrigan Cain↗

NASA NTRS1974

Fundamental and applied research on core engine/combustion noise of aircraft engines

Some results of a study of the importance of geometrical features of the combustor to combustion roughness and resulting noise are presented. Comparison is made among a perforated can flame holder, a plane slotted flame holder and a plane slotted flame holder which introduces two counter swirling streams. The latter is found to permit the most stable, quiet combustion. Crosscorrelations between the time derivative of chamber pressure fluctuations and far field noise are found to be stronger than between the far field noise and the direct chamber pressure signal. Temperature fluctuations in the combustor nozzle are also found to have a reasonably strong crosscorrelation with far field sound.

Plett, E. G.↗

NASA NTRS1986

Shock-induced volatile loss from a carbonaceous chondrite Implications for planetary accretion

Solid recovery impact-induced volatile loss experiments on the Murchison C2M meteorite indicate that for an impact of a given velocity, H2O and total volatiles are driven from the sample in the same proportion as present initially. The primitive surface volatile budget of a planet growing by accretion would have the same bulk elemental composition as the volatiles in the incident planetesimals. Incipient devolatilization of Murchison occurs at an initial shock pressure of about 11 GPa and complete devolatilization occurs at a pressure of about 30 GPa. For the earth, incipient and complete devolatilization of accreting planetesimals would occur when the planet reached approximately 12 percent and 27 percent, respectively, of its present-day radius. Impact-induced devolatilization would profoundly affect the volatile distribution within the accreting planet. Prior to metallic core formation and internal differentiation the growing planet would have a very small core with the same volatile content as the incident material, a volatile depleted mantle, and an extremely volatile rich surface. In the case of the earth, 99.4 wt pct of the total incident volatile material would end up on or near the planetary surface.

Tyburczy, James A.↗

NASA NTRS1993

Particle bed reactor modeling

The topics are presented in viewgraph form and include the following: particle bed reactor (PBR) core cross section; PBR bleed cycle; fuel and moderator flow paths; PBR modeling requirements; characteristics of PBR and nuclear thermal propulsion (NTP) modeling; challenges for PBR and NTP modeling; thermal hydraulic computer codes; capabilities for PBR/reactor application; thermal/hydralic codes; limitations; physical correlations; comparison of predicted friction factor and experimental data; frit pressure drop testing; cold frit mask factor; decay heat flow rate; startup transient simulation; and philosophy of systems modeling.

Sapyta, Joe↗

NASA NTRS1998

Osmium Solubility in Silicate Melts: New Efforts and New Results

In a recent paper, Borisov and Palme reported the first experimental results on the partitioning of Os between metal (Ni-rich OsNi alloys) and silicate melt of anorthite-diopside eutectic composition at 1400 C and 1 atm total pressure and and at function of O2 from 10(exp -8) to 10(exp -12) atm. Experiments were done by equilibrating OsNi metal loops with silicate melt. Metal and glass were analyzed separately by INAA. D(sup 0s) ranged from 10(exp 6) to 10(exp 7), which is inconsistent with core/ mantle equilibrium for HSEs and favors the late veneer hypothesis. Unfortunately, there was practically no function of O2 dependence of Os partitioning, and the scatter of experimental results was quite serious, so the formation of Os nuggets was suspected. This new set of experiments was specifically designed to avoid of at least minimize the nugget problem

Borisov, A.↗

NASA NTRS2009

The Sodium Tail of the Moon

During the few days centered about new Moon, the lunar surface is optically hidden from Earth-based observers. However, the Moon still offers an observable: an extended sodium tail. The lunar sodium tail is the escaping "hot" component of a coma-like exosphere of sodium generated by photon-stimulated desorption, solar wind sputtering and meteoroid impact. Neutral sodium atoms escaping lunar gravity experience solar radiation pressure that drives them into the anti-solar direction forming a comet-like tail. During new Moon time, the geometry of the Sun, Moon and Earth is such that the anti-sunward sodium flux is perturbed by the terrestrial gravitational field resulting in its focusing into a dense core that extends beyond the Earth. An all-sky camera situated at the El Leoncito Observatory (CASLEO) in Argentina has been successfully imaging this tail through a sodium filter at each lunation since April 2006. This paper reports on the results of the brightness of the lunar sodium tail spanning 31 lunations between April 2006 and September 2008. Brightness variability trends are compared with both sporadic and shower meteor activity, solar wind proton energy flux and solar near ultra violet (NUV) patterns for possible correlations. Results suggest minimal variability in the brightness of the observed lunar sodium tail, generally uncorrelated with any single source, yet consistent with a multi-year period of minimal solar activity and non-intense meteoric fluxes.

Matta, M.↗

NASA NTRSDate not supplied

Gateway Integrated Environmental Control and Life Support System (ECLSS) Overview and Status

The Gateway comprised of modules provided by commercial and international partners will be a lunar orbiting platform that is a critical element in the Moon to Mars architecture. Of the 4 modules that comprise the Gateway, the core Environmental Control and Life Support System (ECLSS) is provided by the Habitation and Logistics Outpost (HALO) module provided by NASA, and the International Habitat (I-Hab) provided by the European Space Agency (ESA) with the ECLSS provided by the Japanese Space Agency (JAXA). These modules work together to provide pressure control, air revitalization, and air conditioning capabilities for the Gateway integrated habitable volumes and attached visiting vehicles during open hatch crewed operations. Individually, they maintain the internal atmosphere during the long periods of dormancy between crewed operations to support payload operations and ensure a safe environment when the crew returns. Additionally, NASA bolsters crew survivability by providing government furnished equipment (GFE) to support crew survival in the face of catastrophic hazards (such as fire or a cabin air leak) until the Gateway stack reaches a point in the orbit where crew can safely abort on Orion. This paper explains the key driving requirements, architecture, and development status of the Gateway ECLSS.

Gateway↗

NASA NTRS2003

Vanadium, Cr, Si, and the Mg/Si Ratio of the Earth

Experiments investigating the partitioning of V, Cr, and Si between metal and silicate at various pressures, temperatures, redox state, and composition demonstrate that V and Cr are always more siderophile than Si. The relatively high abundances of V and Cr in the Earth's upper mantle indicate that the high Mg/Si ratio of the Earth's upper mantle cannot be attributed to extraction of Si into the core and must be an intrinsic bulk property of the silicate Earth.

Drake, Michael J.↗

NASA NTRSDate not supplied

A Database of CFD-Based Buffet Forcing Functions for Artemis I Structural Response Evaluation

Time-accurate FUN3D simulations are utilized to estimate buffet-induced unsteady forces experienced by the Space Launch System during the Artemis I (AR01) flight. A set of FUN3D simulations was developed that employed time-accurate mesh translations to simulate the changing velocity and attitude based on the AR01 best estimated trajectory. In these simulations, referred to as accelerating-flow simulations, the freestream Mach number increased from 0.80 to 1.92. Additional time-accurate simulations were obtained at constant freestream Mach number equal to 0.95, 1.18, 1.70, thereby simulating stationary conditions experienced by the flow in a wind-tunnel. On the grounds of favorable comparisons between simulated and flight-measured environments, the FUN3D-based surface pressures were utilized to develop a buffet forcing function (BFF) database. This BFF database was analyzed to characterize the spatial distribution and frequency content of the buffet forces during transonic and supersonic portions of the AR01 flight. The region of interest is located downstream of the forward attachment (FA) hardware between the core stage and the solid rocket boosters where vortex shedding off the FA protuberance produces significant unsteadiness. The analysis reveals that, at transonic and supersonic conditions, buffet forces that are based on constant freestream Mach number data are a good approximation of those based on accelerating-flow simulations.

FUN3D↗

NASA NTRSDate not supplied

A Database of CFD-Based Buffet Forcing Functions for Artemis I Structural Response Evaluation

Time-accurate FUN3D simulations are utilized to estimate buffet-induced unsteady forces experienced by the Space Launch System during the Artemis I (AR01) flight. A set of FUN3D simulations was developed that employed time-accurate mesh translations to simulate the changing velocity and attitude based on the AR01 best estimated trajectory. In these simulations, referred to as accelerating-flow simulations, the freestream Mach number increased from 0.80 to 1.92. Additional time-accurate simulations were obtained at constant freestream Mach number equal to 0.95, 1.18, 1.70, thereby simulating stationary conditions experienced by the flow in a wind-tunnel. On the grounds of favorable comparisons between simulated and flight-measured environments, the FUN3D-based surface pressures were utilized to develop a buffet forcing function (BFF) database. This BFF database was analyzed to characterize the spatial distribution and frequency content of the buffet forces during transonic and supersonic portions of the AR01 flight. The region of interest is located downstream of the forward attachment (FA) hardware between the core stage and the solid rocket boosters where vortex shedding off the FA protuberance produces significant unsteadiness. The analysis reveals that, at transonic and supersonic conditions, buffet forces that are based on constant freestream Mach number data are a good approximation of those based on accelerating-flow simulations.

transonic buffet↗

NASA NTRS1978

Equation of state fits to the lower mantle and outer core

The lower mantle and outer core are subjected to tests for homogeneity and adiabaticity. An earth model is used which is based on the inversion of body waves and Q-corrected normal-mode data. Homogeneous regions are found at radii between 5125 and 4825 km, 4600 and 3850 km, and 3200 and 2200 km. The lower mantle and outer core are inhomogeneous on the whole and are only homogeneous in the above local regions. Finite-strain and atomistic equations of state are fit to the homogeneous regions. The apparent convergence of the finite-strain relations is examined to judge their applicability to a given region. In some cases the observed pressure derivatives of the elastic moduli are used as additional constraints. The effect of minor deviations from adiabaticity on the extrapolations is also considered. An ensemble of zero-pressure values of the density and seismic velocities are found for these regions. The range of extrapolated values from these several approaches provides a measure of uncertainties involved.

Butler, R.↗

NASA NTRS1992

Phase equilibria and trace element partitioning in a magma ocean to 260 kilobars

A magma ocean can solidify in a way that is intermediate between perfect equilibrium and perfect fractional crystallization. In order to model quantitatively any fractional crystallization scenario, it is necessary to understand the geochemical characteristics of the phases that crystallize from a magma ocean, and how they vary with pressure. The crystallizing phase is called the liquidus phase, and their identities were determined by numerous experiments utilizing the multianvil apparatus. For chondritic compositions the liquidus phases are as follows: olivine at 1 atmosphere to 100 kilobars; garnet from 100 to about 260 kilobars; silicate perovskite from 260 kilobars to possibly the core-mantle boundary in the Earth.

Herzberg, Claude↗

NASA NTRS1960

Measurement of Screen-Size Effects on Intensity, Scale, and Spectrum of Turbulence in a Free Subsonic Jet

The results are reported of hot-wire anemometer measurements of the fluctuating longitudinal component of the turbulent velocities in the mean flow downstream of screens in an air jet. These measurements have been analyzed by well-established techniques to give the influence of tile screen mesh size on the turbulent intensity, scale, and the power-spectral-density. The results show a linear dependence of the intensity upon the screen mesh size for locations within the central core of the air jet. The spectral-density curves show that the screens redistribute the turbulent energy from the low frequencies (<1000 cps) to the high frequencies (>1000 cps). The effects of the screens are overwhelmed in the mixing region of the jet flow by the turbulence levels existing there. The large pressure drops occurring across the screens reduce the velocity of the jet as compared to the jet without screens by approximately one-third for the velocity and range of mesh sizes investigated and reported in this report. The turbulence scale is a linear function of distance from the nozzle exit and is somewhat greater than comparable jets without screens.

Howard, Charles D.↗

NASA NTRS1960

Experimental and Theoretical Study of a Rectangular Wing in a Vortical Wake at Low Speed

A systematic study has been made, experimentally and theoretically, of the effects of a vortical wake on the aerodynamic characteristics of a rectangular wing at subsonic speed. The vortex generator and wing were mounted on a reflection plane to avoid body-wing interference. Vortex position, relative to the wing, was varied both in the spanwise direction and normal to the wing. Angle of attack of the wing was varied from -40 to +60. Both chordwise and spanwise pressure distributions were obtained with the wing in uniform and vortical flow fields. Stream surveys were made to determine the flow characteristics in the vortical wake. The vortex-induced lift was calculated by several theoretical methods including strip theory, reverse-flow theory, and reverse-flow theory including a finite vortex core. In addition, the Prandtl lifting-line theory and the Weissinger theory were used to calculate the spanwise distribution of vortex-induced loads. With reverse-flow theory, predictions of the interference lift were generally good, and with Weissinger's theory the agreement between the theoretical spanwise variation of induced load and the experimental variation was good. Results of the stream survey show that the vortex generated by a lifting surface of rectangular plan form tends to trail back streamwise from the tip and does not approach the theoretical location, or centroid of circulation, given by theory. This discrepancy introduced errors in the prediction of vortex interference, especially when the vortex core passed immediately outboard of the wing tip. The wake produced by the vortex generator in these tests was not fully rolled up into a circular vortex, and so lacked symmetry in the vertical direction of the transverse plane. It was found that the direction of circulation affected the induced loads on the wing either when the wing was at angle of attack or when the vortex was some distance away from the plane of the wing.

Smith, Willard G.↗