Results for “Mass mitigation” — Page 15

NASA NTRS1997

Evolutionary Design of Controlled Structures

Basic physical concepts of structural delay and transmissibility are provided for simple rod and beam structures. Investigations show the sensitivity of these concepts to differing controlled-structures variables, and to rational system modeling effects. An evolutionary controls/structures design method is developed. The basis of the method is an accurate model formulation for dynamic compensator optimization and Genetic Algorithm based updating of sensor/actuator placement and structural attributes. One and three dimensional examples from the literature are used to validate the method. Frequency domain interpretation of these controlled structure systems provide physical insight as to how the objective is optimized and consequently what is important in the objective. Several disturbance rejection type controls-structures systems are optimized for a stellar interferometer spacecraft application. The interferometric designs include closed loop tracking optics. Designs are generated for differing structural aspect ratios, differing disturbance attributes, and differing sensor selections. Physical limitations in achieving performance are given in terms of average system transfer function gains and system phase loss. A spacecraft-like optical interferometry system is investigated experimentally over several different optimized controlled structures configurations. Configurations represent common and not-so-common approaches to mitigating pathlength errors induced by disturbances of two different spectra. Results show that an optimized controlled structure for low frequency broadband disturbances achieves modest performance gains over a mass equivalent regular structure, while an optimized structure for high frequency narrow band disturbances is four times better in terms of root-mean-square pathlength. These results are predictable given the nature of the physical system and the optimization design variables. Fundamental limits on controlled performance are discussed based on the measured and fit average system transfer function gains and system phase loss.

Masters, Brett P.↗

NASA NTRS2001

Unsteady Flow in a Supersonic Turbine with Variable Specific Heats

Modern high-work turbines can be compact, transonic, supersonic, counter-rotating, or use a dense drive gas. The vast majority of modern rocket turbine designs fall into these Categories. These turbines usually have large temperature variations across a given stage, and are characterized by large amounts of flow unsteadiness. The flow unsteadiness can have a major impact on the turbine performance and durability. For example, the Space Transportation Main Engine (STME) fuel turbine, a high work, transonic design, was found to have an unsteady inter-row shock which reduced efficiency by 2 points and increased dynamic loading by 24 percent. The Revolutionary Reusable Technology Turbopump (RRTT), which uses full flow oxygen for its drive gas, was found to shed vortices with such energy as to raise serious blade durability concerns. In both cases, the sources of the problems were uncovered (before turbopump testing) with the application of validated, unsteady computational fluid dynamics (CFD) to the designs. In the case of the RRTT and the Alternate Turbopump Development (ATD) turbines, the unsteady CFD codes have been used not just to identify problems, but to guide designs which mitigate problems due to unsteadiness. Using unsteady flow analyses as a part of the design process has led to turbine designs with higher performance (which affects temperature and mass flow rate) and fewer dynamics problems. One of the many assumptions made during the design and analysis of supersonic turbine stages is that the values of the specific heats are constant. In some analyses the value is based on an average of the expected upstream and downstream temperatures. In stages where the temperature can vary by 300 to 500 K, however, the assumption of constant fluid properties may lead to erroneous performance and durability predictions. In this study the suitability of assuming constant specific heats has been investigated by performing three-dimensional unsteady Navier-Stokes simulations for a supersonic turbine stage.

Dorney, Daniel J.↗

NASA NTRS2009

Design for an 8 Meter Monolithic UV/OIR Space Telescope

ATLAST-8 is an 8-meter monolithic UV/optical/NIR space observatory to be placed in orbit at Sun-Earth L2 by NASA's planned Ares V cargo launch vehicle. The ATLAST-8 will yield fundamental astronomical breakthroughs. The mission concept utilizes two enabling technologies: planned Ares-V launch vehicle (scheduled for 2019) and autonomous rendezvous and docking (AR&D). The unprecedented Ares-V payload and mass capacity enables the use of a massive, monolithic, thin-meniscus primary mirror - similar to a VLT or Subaru. Furthermore, it enables simple robust design rules to mitigate cost, schedule and performance risk. AR&D enables on-orbit servicing, extending mission life and enhancing science return.

Stahl, H. Philip↗

NASA NTRSDate not supplied

Conceptual Thermal Control System Design for a Lunar Surface Habitat

NASA is currently considering a Surface Habitat (SH) to provide 30-60 day habitability for a crew of up to four to explore the Lunar surface at a South Pole location. The SH concept is comprised of an inflatable volume for the habitable space, a metallic airlock and a descent stage with access to a pressurized rover and other surface assets provided through the airlock. A conceptual architecture for the SH Thermal Control System (TCS) is presented with resource estimates. The TCS design employs a dual loop architecture with a water/propylene glycol mix for the internal crew spaces with a freeze tolerant coolant utilized for the external loop. The internal loop is partitioned into low and moderate temperature service with a sublimator available for operational scenarios prior to thermal radiator deployment (or redeployment). Analytical models are utilized to optimize radiator geometry/orientation as well as the TCS internal/external loop architecture. Heritage hardware is utilized for the TCS concept wherever possible and low mass, dust tolerant, deployable/retractable thermal radiators (in partial gravity) present a technology challenge. The TCS must accommodate infrequent eclipse periods lasting up to 100 hours in duration and mitigation strategies to reduce the energy needed to maintain the SH and associated systems above survival temperature limits during this period are explored. Mitigation options include retractable or freezable radiators, other reconfigurable radiator geometries, alternate fluids, re-generable heat exchangers, temperature excursions, thermal energy storage and optimized inflatable optical properties. Finally, TCS sensitivity to SH Electrical Power System (EPS) growth is considered with both operational and dormant impacts quantified.

Thermal Control↗

NASA NTRSDate not supplied

Conceptual Thermal Control System Design for a Lunar Surface Habitat

NASA is currently considering a Surface Habitat (SH) to provide 30-60 day habitability for a crew of up to four to explore the Lunar surface at a South Pole location. The SH concept is comprised of an inflatable volume for the habitable space, a metallic airlock and a descent stage with access to a pressurized rover and other surface assets provided through the airlock. A conceptual architecture for the SH Thermal Control System (TCS) is presented with resource estimates. The TCS design employs a dual loop architecture with a water/propylene glycol mix for the internal crew spaces with a freeze tolerant coolant utilized for the external loop. The internal loop is partitioned into low and moderate temperature service with a sublimator available for operational scenarios prior to thermal radiator deployment (or redeployment). Analytical models are utilized to optimize radiator geometry/orientation as well as the TCS internal/external loop architecture. Heritage hardware is utilized for the TCS concept wherever possible and low mass, dust tolerant, deployable/retractable thermal radiators (in partial gravity) present a technology challenge. The TCS must accommodate infrequent eclipse periods lasting up to 100 hours in duration and mitigation strategies to reduce the energy needed to maintain the SH and associated systems above survival temperature limits during this period are explored. Mitigation options include retractable or freezable radiators, other reconfigurable radiator geometries, alternate fluids, re-generable heat exchangers, temperature excursions, thermal energy storage and optimized inflatable optical properties. Finally, TCS sensitivity to SH Electrical Power System (EPS) growth is considered with both operational and dormant impacts quantified.

Thermal Control↗

DOE OSTI2026

Validating a Dynamic PWR Safety and Security Model?

Nuclear power plants (NPPs) are assessed for safety and security using separate models that cannot capture how an attacker's decisions and a plant's response unfold together in real time, leaving regulators and operators without a complete picture of true plant vulnerability. Traditional probabilistic risk assessment (PRA) methods treat adversarial events as fixed initiators with predetermined outcomes, and are structurally incapable of representing the time-dependent interplay between physical security events, safety system response, and operator mitigative actions. At Idaho National Laboratory (INL), I contributed to the development and validation of Modeling and Analysis for Safety and Security using the Dynamic EMRALD Framework (MASS-DEF). Where static PRA relies on event-tree logic that cannot evolve mid-scenario, MASS-DEF couples a time-dependent dynamic PRA tool EMRALD (Event Modeling Risk Assessment using Linked Diagrams) with attack simulation software, allowing attacker behavior, plant system states, and operator actions to interact across time. My work focused on validating a general Pressurized Water Reactor (PWR) model. I traced model logic against PWR plant to identified errors in logic and confirm accuracy. I then built and tested attack scenarios against a general PWR model to verify that the model produced expected outcomes across all logical pathways. I also contributed a section to a related technical paper applying the same EMRALD platform to radiation dose modeling. Results show that MASS-DEF can quantitatively demonstrate that many plants exceed their regulatory security thresholds. This demonstrated margin provides a technically defensible basis for reducing the number of guards without compromising regulatory compliance. Physical security costs represent roughly 10% of annual operating budgets, making such reductions directly meaningful to INL's mission of sustaining existing commercial NPPs. This internship strengthened my understanding of nuclear systems, probabilistic modeling, and technical writing, and has solidified my pursuit of a career at a national laboratory.

98 - NUCLEAR DISARMAMENT, SAFEGUARDS, AND PHYSICAL↗

NASA NTRS2009

Management of Service Projects in Support of Space Flight Research

Goal:To provide human health and performance countermeasures, knowledge, technologies, and tools to enable safe, reliable, and productive human space exploration . [HRP-47051] Specific Objectives: 1) Develop capabilities, necessary countermeasures, and technologies in support of human space exploration, focusing on mitigating the highest risks to human health and performance. 2) Define and improve human spaceflight medical, environmental, and human factors standards. 3) Develop technologies that serve to reduce medical and environmental risks, to reduce human systems resource requirements (mass, volume, power, data, etc.) and to ensure effective human-system integration across exploration systems. 4) Ensure maintenance of Agency core competencies necessary to enable risk reduction in the following areas: A. Space medicine B. Physiological and behavioral effects of long duration spaceflight on the human body C. Space environmental effects, including radiation, on human health and performance D. Space "human factors" [HRP-47051]. Service projects can form integral parts of research-based project-focused programs to provide specialized functions. Traditional/classic project management methodologies and agile approaches are not mutually exclusive paradigms. Agile strategies can be combined with traditional methods and applied in the management of service projects functioning in changing environments. Creative collaborations afford a mechanism for mitigation of constrained resource limitations.

Love, J.↗

DOE OSTI2020

Stabilized Co-Free Li-Rich Oxide Cathode Particles with An Artificial Surface Prereconstruction

Li-rich metal oxide (LXMO) cathodes have attracted intense interest for rechargeable batteries because of their high capacity above 250 mAh g –1 . However, the side effects of hybrid anion and cation redox (HACR) reactions, such as oxygen release and phase collapse that result from global oxygen migration (GOM), have prohibited the commercialization of LXMO. GOM not only destabilizes the oxygen sublattice in cycling, aggravating the well-known voltage fading, but also intensifies electrolyte decomposition and Mn dissolution, causing severe full-cell performance degradation. In this study, an artificial surface prereconstruction (ASR) for Li 1.2 Mn 0.6 Ni 0.2 O 2 particles with a molten-molybdate leaching is conducted, which creates a crystal-dense anion-redox-free LiMn 1.5 Ni 0.5 O 4 shell that completely encloses the LXMO lattice (ASR-LXMO). Differential electrochemical mass spectroscopy and soft X-ray absorption spectroscopy analyses demonstrate that GOM is shut down in cycling, which not only stabilizes HACR in ASR-LXMO, but also mitigates the electrolyte decomposition and Mn dissolution. ASR-LXMO displays greatly stabilized cycling performance as it retains 237.4 mAh g –1 with an average discharge voltage of 3.30 V after 200 cycles. More crucially, while the pristine LXMO cycling cannot survive 90 cycles in a pouch full-cell matched with a commercial graphite anode and lean (2 g A –1 h –1 ) electrolyte, ASR-LXMO shows high capacity retention of 76% after 125 cycles in full-cell cycling.

25 ENERGY STORAGE↗

DOE OSTI2022

Mitigation of rapid capacity decay in silicon-LiNi 0.6 Mn 0.2 Co 0.2 O 2 full batteries

Silicon (Si)-based materials have been considered as the most promising anode materials for high-energy-density lithium-ion batteries because of their higher storage capacity and similar operating voltage, as compared to the commercial graphite (Gr) anode. But the use of Si anodes including silicon-graphite (Si-Gr) blended anodes often leads to rapid capacity decay in Si-Gr/LiNixMnyCo z O 2 (x+y+z=1) full cells, which has been attributed to surface instability of the Si component. In addition to stabilizing the surface, this work investigates the potential of the Si-Gr blended anodes in a full-cell configuration and its impact on the capacity contribution from active components. Using dQ/dV plots of the full cells, a powerful but simple-to-implement differential potential approach is developed to decouple the capacity contribution and degradation from the graphite and silicon components. Data collected from three-electrode cells confirm the results from the differential potential approach, which suggests a voltage slippage to a higher voltage at the blended anode side. Additionally, the voltage slippage causes a reduced utilization of the Gr component and exacerbates side reactions between the Si-Gr anode and carbonate electrolytes. Furthermore, based on these failure mechanisms, we adopted a mitigation strategy to tune the open circuit voltage of the prelithiated anode while stabilizing the surface. As a result, the full cells with the modified Si-Gr anodes (mass loading, 2.5 mAh/cm 2 ) offer a highly reversible full-cell energy density of 390 Wh/kg (based on the mass of both anode and cathode materials in a full cell) with a cycling CE of 99.9% over 200 cycles.

25 ENERGY STORAGE↗

DOE OSTI2022

TDCOSMO. IX. Systematic comparison between lens modelling software programs: time delay prediction for WGD 2038-4008

The importance of alternative methods for measuring the Hubble constant, such as time-delay cosmography, is highlighted by the recent Hubble tension. It is paramount to thoroughly investigate and rule out systematic biases in all measurement methods before we can accept new physics as the source of this tension. In this study, we perform a check for systematic biases in the lens modelling procedure of time-delay cosmography by comparing independent and blind time-delay predictions of the system WGD 2038-4008 from two teams using two different software programs: GLEE and LENSTRONOMY. The predicted time delays from the two teams incorporate the stellar kinematics of the deflector and the external convergence from line-of-sight structures. The un-blinded time-delay predictions from the two teams agree within 1.2σ, implying that once the time delay is measured the inferred Hubble constant will also be mutually consistent. However, there is a ~4σ discrepancy between the power-law model slope and external shear, which is a significant discrepancy at the level of lens models before the stellar kinematics and the external convergence are incorporated. We identify the difference in the reconstructed point spread function (PSF) to be the source of this discrepancy. When the same reconstructed PSF was used by both teams, we achieved excellent agreement, within ~0.6σ<, indicating that potential systematics stemming from source reconstruction algorithms and investigator choices are well under control. We recommend that future studies supersample the PSF as needed and marginalize over multiple algorithms or realizations for the PSF reconstruction to mitigate the systematics associated with the PSF. A future study will measure the time delays of the system WGD 2038-4008 and infer the Hubble constant based on our mass models.

79 ASTRONOMY AND ASTROPHYSICS↗

NASA NTRS2008

Trajectory Model of Lunar Dust Particles

The goal of this work was to predict the trajectories of blowing lunar regolith (soil) particles when a spacecraft lands on or launches from the Moon. The blown regolith is known to travel at very high velocity and to damage any hardware located nearby on the Moon. It is important to understand the trajectories so we can develop technologies to mitigate the blast effects for the launch and landing zones at a lunar outpost. A mathematical model was implemented in software to predict the trajectory of a single spherical mass acted on by the gas jet from the nozzle of a lunar lander.

Source record↗

NASA NTRS2014

The Atmospheres of Directly Imaged Planets: Where Has All the Methane Gone?

Methane and ammonia both first appear at lower effective temperatures in brown dwarf atmospheres than equilibrium chemistry models would suggest. This has traditionally been understood as a consequence of vertical mixing timescales being shorter than chemical equilibration timescales in brown dwarf photospheres. Indeed the eddy diffusivity, a variable accounting for the vigor of vertical mixing, has become a standard part of the description of brown dwarf atmosphere models, along with Teff and log g. While some models have suggested that methane is less favored at lower gravity, the almost complete absence of methane in the atmospheres of directly imaged planets, such as those orbiting HR 8799, even at effective temperatures where methane is readily apparent in brown dwarf spectra, has been puzzling. To better understand the paucity of methane in low gravity atmospheres we have revisited the problem of methane chemistry and mixing. We employed a 1-D atmospheric chemistry code augmented with an updated and complete network of the chemical reactions that link CO to CH4. We find the methane abundance at altitudes at or above the effective photosphere is a strong function of surface gravity because higher g shifts the p-T structure to higher pressures (i.e., a given optical depth is proportional to p/g, a relation mitigated somewhat by pressure broadening). Thus quenching in more massive brown dwarfs occurs at a lower temperature and higher pressure, both favoring CH4. We predict that in the lowest mass young giant planets, methane will appear very late, at effective temperatures as low as 600 K rather than the 1200 K seen among field brown dwarfs. This methane deficiency has important implications for the interpretation of spectra as well as methane-based planetary companion searches, such as the NICI survey. The GPI and SPHERE surveys will test these ideas and probe atmospheric chemistry and composition in an entire new range of parameter space. A caveat is that these calculations presume that the C to O ratio is comfortably less than one; the behavior is quite different if C and O are equally abundant, and of course CH4 is always present if C exceeds O.

young giant planets↗

NASA NTRS2017

Temperature and Snowfall in Western Queen Maud Land Increasing Faster than Climate Model Projections

East Antarctic Ice Sheet (EAIS) mass balance is largely driven by snowfall. Recently, increased snowfall in Queen Maud Land led to years of EAIS mass gain. It is difficult to determine whether these years of enhanced snowfall are anomalous or part of a longer-term trend, reducing our ability to assess the mitigating impact of snowfall on sea level rise. We determine that the recent snowfall increases in western Queen Maud Land (QML) are part of a long-term trend (+5.2 +/- 3.7% decade(exp -1)) and are unprecedented over the past two millennia. Warming between 1998 and 2016 is significant and rapid (+1.1 +/- 0.7 C decade(exp -1)). Using these observations, we determine that the current accumulation and temperature increases in QML from an ensemble of global climate simulations are too low, which suggests that projections of the QML contribution to sea level rise are potentially overestimated with a reduced mitigating impact of enhanced snowfall in a warming world.

WAIS↗

NASA NTRSDate not supplied

Thermal Control System Architecture and Technology Challenges for a Lunar Surface Habitat

NASA’s current plans for exploration of the Lunar South Pole region include a Surface Habitat (SH) to provide up to 60-day habitability for a crew of four. The SH concept is comprised of several elements including an inflatable volume for the habitable space and a metallic airlock for access to a pressurized rover and other surface assets. A conceptual architecture for the SH Thermal Control System (TCS) is presented. A TCS dual loop design is utilized with a water/propylene glycol mix for the internal crew spaces and an external loop with low temperature coolant. The internal loop is partitioned into low and moderate temperature service with a sublimator available for operational scenarios prior to thermal radiator deployment (or redeployment). Waste heat is rejected through thermal radiators contained in the external loop. Optimization of the thermal radiator geometry/orientation as well as the TCS internal/external loop architecture is accomplished via analytical models of the system. Low mass, dust tolerant, deployable/retractable thermal radiators (in partial gravity) and thermal control surfaces, along with accommodating infrequent eclipse periods lasting up to 100 hours, present the major technology challenges. Mitigation strategies to reduce the energy needed to maintain the SH and associated systems above survival temperature limits during the eclipse period are considered in the paper. Options include retractable radiators, re-generable heat exchangers, temperature excursions, thermal energy storage and optimized inflatable optical properties. TCS sensitivity to potential SH Electrical Power System (EPS) growth is also a consideration for both operational and dormant mission phases.

Thermal Control System↗

NASA NTRSDate not supplied

Thermal Control System Architecture and Technology Challenges for a Lunar Surface Habitat

NASA’s current plans for exploration of the Lunar South Pole region include a Surface Habitat (SH) to provide up to 60-day habitability for a crew of four. The SH concept is comprised of several elements including an inflatable volume for the habitable space and a metallic airlock for access to a pressurized rover and other surface assets. A conceptual architecture for the SH Thermal Control System (TCS) is presented. A TCS dual loop design is utilized with a water/propylene glycol mix for the internal crew spaces and an external loop with low temperature coolant. The internal loop is partitioned into low and moderate temperature service with a sublimator available for operational scenarios prior to thermal radiator deployment (or redeployment). Waste heat is rejected through thermal radiators contained in the external loop. Optimization of the thermal radiator geometry/orientation as well as the TCS internal/external loop architecture is accomplished via analytical models of the system. Low mass, dust tolerant, deployable/retractable thermal radiators (in partial gravity) and thermal control surfaces, along with accommodating infrequent eclipse periods lasting up to 100 hours, present the major technology challenges. Mitigation strategies to reduce the energy needed to maintain the SH and associated systems above survival temperature limits during the eclipse period are considered in the paper. Options include retractable radiators, re-generable heat exchangers, temperature excursions, thermal energy storage and optimized inflatable optical properties. TCS sensitivity to potential SH Electrical Power System (EPS) growth is also a consideration for both operational and dormant mission phases.

Thermal Control System↗

NASA NTRS2014

Space Radiation and the Challenges Towards Effective Shielding Solutions

The hazards of space radiation and their effective mitigation strategies continue to pose special science and technology challenges to NASA. It is widely accepted now that shielding space vehicles and structures will have to rely on new and innovative materials since aluminum, like all high Z materials, are poor shields against the particulate and highly ionizing nature of space radiation. Shielding solutions, motivated and constrained by power and mass limitations, couple this realization with "multifunctionality," both in design concept as well as in material function and composition. Materials endowed with effective shielding properties as well as with some degree of multi‐functionality may be the kernel of the so‐called "radiation‐smart" structures and designs. This talk will present some of the challenges and potential mitigation ideas towards the realization of such structures and designs.

Barghouty, Abdulnasser↗

DOE OSTI2023

Comparison of different noble gas injections by massive gas injection on plasma disruption mitigation on Experimental Advanced Superconducting Tokamak

Massive gas injection (MGI) is a traditional plasma disruption mitigation method. This method directly injected massive gas into the pre-disruption plasma and had been developed on the Experimental Advanced Superconducting Tokamak (EAST). Different noble gas injection experiments, including He, Ne, and Ar, were performed to compare the mitigation effect of plasma disruption by evaluating the key parameters such as flight time, pre-thermal quench (pre-TQ), and current quench (CQ). The flight time was shorter for low atomic number ( Z ) gas, and the decrease in flight time by increasing the amount of gas was insignificant. However, both pre-TQ and CQ durations decreased considerably with the increase in gas injection amount. The effect of atomic mass on pre-TQ and CQ durations showed the opposite trend. The observed trend could help in controlling CQ duration in a reasonable area. Moreover, the analysis of radiation distribution with different impurity injections indicated that low Z impurity could reduce the asymmetry of radiation, which is valuable in mitigating plasma disruption. These results provided essential data support for plasma disruption mitigation on EAST and future fusion devices.

Physics↗

DOE OSTI2020

Thermodynamic Origin of Reaction Non-Uniformity in Battery Porous Electrodes and Its Mitigation

The development of non-uniform reaction current distribution within porous electrodes is a ubiquitous phenomenon during battery charging/discharging and frequently controls the rate performance of battery cells. Reaction inhomogeneity in porous electrodes is usually attributed to the kinetic limitation of mass transport within the electrolyte and/or solid electrode phase. In this work, however, we reveal that it is also strongly influenced by the intrinsic thermodynamic behavior of electrode materials, specifically the dependence of the equilibrium potential on the state of charge: the electrode reaction becomes increasingly non-uniform when the slope of the equilibrium potential curve is reduced. We employ numerical simulations and equivalent circuit model to elucidate such a correlation and show that the degree of reaction inhomogeneity and the resultant discharge capacity can be predicted by a dimensionless reaction uniformity number. For electrode materials that have equilibrium potentials insensitive to the state of charge and exhibit significant reaction non-uniformity, we demonstrate several approaches to spatially homogenizing the reaction current inside porous electrodes, including matching the electronic and ionic resistances, introducing graded electronic conductivity and reducing the surface reaction kinetics.

25 ENERGY STORAGE↗