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At least 271 records · Page 15

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NASA NTRS2017

Spacecraft Mission Design for the Mitigation of the 2017 PDC Hypothetical Asteroid Threat

This paper presents a detailed mission design analysis results for the 2017 Planetary Defense Conference (PDC) Hypothetical Asteroid Impact Scenario, documented at https:cneos.jpl.nasa.govpdcspdc17. The mission design includes campaigns for both reconnaissance (flyby or rendezvous) of the asteroid (to characterize it and the nature of the threat it poses to Earth) and mitigation of the asteroid, via kinetic impactor deflection, nuclear explosive device (NED) deflection, or NED disruption. Relevant scenario parameters are varied to assess the sensitivity of the design outcome, such as asteroid bulk density, asteroid diameter, momentum enhancement factor, spacecraft launch vehicle, and mitigation system type. Different trajectory types are evaluated in the mission design process from purely ballistic to those involving optimal midcourse maneuvers, planetary gravity assists, and/or low-thrust solar electric propulsion. The trajectory optimization is targeted around peak deflection points that were found through a novel linear numerical technique method. The optimization process includes constrain parameters, such as Earth departure date, launch declination, spacecraft, asteroid relative velocity and solar phase angle, spacecraft dry mass, minimum/maximum spacecraft distances from Sun and Earth, and Earth-spacecraft communications line of sight. Results show that one of the best options for the 2017 PDC deflection is solar electric propelled rendezvous mission with a single spacecraft using NED for the deflection.

Barbee, Brent W.↗

NASA NTRS2017

RFI Mitigation and Testing Employed at GGAO for NASA's Space Geodesy Project (SGP)

Radio Frequency Interference (RFI) Mitigation at Goddard Geophysical and Astronomical Observatory (GGAO) has been addressed in three different ways by NASA's Space Geodesy Project (SGP); masks, blockers, and filters. All of these techniques will be employed at the GGAO, to mitigate the RFI consequences to the Very Long Baseline Interferometer.

Hilliard, Lawrence M.↗

NASA NTRS2017

RFI Mitigation and Testing Employed at GGAO for NASA's Space Geodesy Project (SGP)

Hilliard, L. M.↗

NASA NTRS2015

Plasma Perturbations in High-Speed Probing of Hall Thruster Discharge Chambers: Quantification and Mitigation

An experimental investigation is presented to quantify the effect of high-speed probing on the plasma parameters inside the discharge chamber of a 6-kW Hall thruster. Understanding the nature of these perturbations is of significant interest given the importance of accurate plasma measurements for characterizing thruster operation. An array of diagnostics including a high-speed camera and embedded wall probes is employed to examine in real time the changes in electron temperature and plasma potential induced by inserting a high-speed reciprocating Langmuir probe into the discharge chamber. It is found that the perturbations onset when the scanning probe is downstream of the electron temperature peak, and that along channel centerline, the perturbations are best characterized as a downstream shift of plasma parameters by 15-20% the length of the discharge chamber. A parametric study is performed to investigate techniques to mitigate the observed probe perturbations including varying probe speed, probe location, and operating conditions. It is found that the perturbations largely disappear when the thruster is operated at low power and low discharge voltage. The results of this mitigation study are discussed in the context of recommended methods for generating unperturbed measurements of the discharge chamber plasma.

Jorns, Benjamin A.↗

NASA NTRS2017

Early Action on HFCs Mitigates Future Atmospheric Change

As countries take action to mitigate global warming, both by ratifying the UNFCCC Paris Agreement and enacting the Kigali Amendment to the Montreal Protocol to manage hydrofluorocarbons (HFCs), it is important to consider the relative importance of the pertinent greenhouse gases (GHGs), the distinct structure of their atmospheric impacts, and how the timing of potential GHG regulations would affect future changes in atmospheric temperature and ozone. Chemistry-climate model simulations demonstrate that HFCs could contribute substantially to anthropogenic climate change by the mid-21st century, particularly in the upper troposphere and lower stratosphere i.e., global average warming up to 0.19K at 80hPa. Three HFC mitigation scenarios demonstrate the benefits of taking early action in avoiding future atmospheric change: more than 90 of the climate change impacts of HFCs can be avoided if emissions stop by 2030.

Kigali Amendment↗

NASA NTRS2018

Mitigation of Electrostatic Hazards on Spacecraft

Spacecraft are complex systems operating in challenging environments that require customized testing procedures designed to mitigate the unique hazards of a space launch environment. As an example of those testing procedures, we describe the test methodology and recommendations developed to mitigate electrostatic discharges that could have triggered an explosion of the Space Shuttle during launch, return to launch site, abort after one orbit, or during normal landing.

Calle, C. I.↗

NASA NTRS2018

UAS Autonomous Hazard Mitigation through Assured Compliance with Conformance Criteria

The behavior of a drone depends on the integrity of the data it uses and the reliability of the avionics systems that process that data to affect the operation of the aircraft. Commercial unmanned aircraft systems frequently rely on commercial-off-the-shelf and open source avionics components and data sources whose reliability and integrity are not easily assured. To mitigate failure events for aircraft that do not comply with conventional aviation safety standards, operational limitations are typically prescribed by regulators. Part 107 of the Federal Aviation Regulations serves as a good example of operational limitations that mitigate risk for small unmanned aircraft systems. These limitations, however, restrict growth possibilities for the industry. Any reasonable path toward achieving routine operation of all types of drones will have to address the need for assurance of avionics systems, especially their software. This paper discusses the possibility of strategically using assured systems as a stepping stone to routine operation of drones. A specimen system for assured geofencing, called Safeguard, is described as an example of such a stepping stone.

Dill, Evan, T.↗

NASA NTRS2019

Overexpression of Catalase in Mitochondria Mitigates the Effects of Simulated Microgravity and Social Isolation on Cytokine Expression in Mouse Hippocampus

Space flight missions are becoming longer and more common and evidence points to the physiological toll the missions have on the human body. Aging, sedentary lifestyle, and spaceflight have similar degenerative effects on almost every part of our body; both exposure to the space environment and aging result in cardiovascular deconditioning, bone loss, muscle atrophy, brain changes, and immune response impairment. We hypothesize that exposure to the space environment generates excessive Reactive Oxygen Species (ROS), which results in neuroinflammation and aging-like degenerative symptoms in the brain. We used the hindlimb unloading (HU) model to mimic microgravity with either paired or single housed animals (social isolation). Responses to 30d (30 days) of HU were compared in wildtype or transgenic MCAT (Mitochondrial-targeted CATalase) mice, in which mitochondrial ROS is quenched by over-expression of human catalase. Expression of 4-Hydroxynonenal (4HNE) and Park7 (redox-sensitive chaperone and sensor of oxidative stress) were measured by ELISA (Enzyme-Linked ImmunoSorbent Assay), a protein array quantified from the hippocampal cytokines and 8-hydroxy-2'-deoxyguanosine in serum was measured by ELISA to assess oxidative DNA damage. Preliminary analysis of cage behavior patterns from video collected at the end of the study showed that MCAT HU mice (socially housed) were more active and conducted more exploratory activities compared to NL (Normally Loaded). Our biochemical results showed simulated microgravity and/or social isolation caused changes in levels of cytokines related to immune responses. Two-way ANOVA (Analysis of Variance) revealed significant interaction effects of HU and genotype in expression levels of five cytokines (out of 35) in socially-housed animals. Elevation of these generally pro-inflammatory cytokines by HU in WT (Wild Type) mice was mitigated in MCAT mice, suggesting a role for mitochondrial ROS signaling in inflammatory CNS (Central Nervous System) responses to microgravity. Interestingly, some of these cytokines in the hippocampus displayed strong correlations to the 4HNE levels. We also found substantive cytokine responses to social isolation in the hippocampus; housing and genotype interaction effects were significant (by 2-Factor ANOVA) for 15 cytokines, most of which were mitigated in MCAT mice.Taken together, our results showed that both simulated microgravity and social isolation influenced cytokine levels in the hippocampus and MCAT mice were at least partially protected from these changes. These findings implicate a potentially important role for mitochondrial ROS in CNS responses to the challenges posed by long duration spaceflight.

MCAT↗

NASA NTRS2018

Pre-Flight Training of Autonomic Responses for Mitigating the Effects of Spatial Disorientation During Spaceflight

The National Aeronautics and Space Administration (NASA) has identified a potential risk of spatial disorientation, motion sickness, and degraded performance to astronauts during re-entry and landing of the proposed Orion crew vehicle. The purpose of this study was to determine if a physiological training procedure, Autogenic-Feedback Training Exercise (AFTE), can mitigate these adverse effects. Fourteen men and six women were assigned to two groups (AFTE, no-treatment Control) matched for motion sickness susceptibility and gender. All subjects received a standard rotating chair test to determine motion sickness susceptibility; three training sessions on a manual performance task; and four exposures in the rotating chair (Orion tests) simulating angular accelerations of the crew vehicle during re-entry. AFTE subjects received 2 hours of training before Orion tests 2, 3, and 4. Motion sickness symptoms, task performance, and physiological measures were recorded on all subjects. Results showed that the AFTE group had significantly lower symptom scores when compared to Controls on test 2 (p=.05), test 3 (p=.03), and test 4 (p=.02). Although there were no significant group differences on task performance, trends showed that AFTE subjects were less impaired than Controls. Heart rate change scores (20 revolutions per minute minus baseline) of AFTE subjects indicated significantly less reactivity on Test 4 compared to Test 1 (10.09 versus 16.59, p=.02), while Controls did not change significantly across tests. Results of this study indicate that AFTE may be an effective countermeasure for mitigating spatial dis-orientation and motion sickness in astronauts.

Orion↗

NASA NTRS2019

Incorporation of Functionalized Polyhedral Oligomeric Silsesquioxane Nanomaterials as Reinforcing Agents for Impact Ice Mitigating Coatings

In-flight, aircraft are exposed to a wide range of environments. One commonly exposed environment are clouds containing super-cooled water droplets. These water drop- lets exist in a metastable state below the freezing point of water, in the range of 0 to -20°C. As the vehicle impacts the droplets, latent heat is released and within milliseconds the droplets convert to ice. This process is referred to as impact icing or in-flight icing.1 Impact icing is a major concern for aircraft since it can lead to degraded aerodynamic performance and, if left un- treated, can lead to loss of the vehicle. Active approaches (i.e., pneumatic boots, heated air ducts) typically utilized in mitigating in-flight ice accretion significantly increases vehicle weight and cannot be applied to all aircraft.1-3 A passive approach based on coatings is desired, but durability issues are a concern, especially on the wing leading edge.3 Nanomaterials have been shown to afford significant improvement in coating and composite physical properties at low loading levels.4 In this study, Polyhedral Oligomeric Silsesquioxane (POSS) nanomaterials have been shown to increase coating durability. Also, with wide variety of functionalities present on the arm structure, POSS nanomaterials have been shown to readily alter coating surface chemistry to mitigate impact ice adhesion from -16 to -8°C in a simulated in-flight icing environment.

Beck, Devon M.↗

NASA NTRSDate not supplied

Human placenta-derived stromal cells mitigate select immune responses to simulated weightlessness

Space flight presents unique risks to human health. Microgravity and social isolation are important space flight stressors which have vast impact on multiple systems such as the musculoskeletal, immune and central nervous system (CNS). To explore candidate countermeasures against tissue decrements caused by spaceflight, we performed a pilot study with PLacental-eXpanded stromal (PLX) cells. PLX cells secrete factors that modulate the immune system, but do not trigger host immune responses, enabling treatment in subjects that have intact immune systems. These cells had previous success in treating critical limb ischemia and acute radiation syndrome in murine models. In this study, 4-month-old female mice underwent 30 days of hindlimb unloading (HU) in single housing conditions to simulate long-term weightlessness and isolation. HU and normally ambulating controls were administered with PLX cells or sham-injected with Plasmalyte. We hypothesized that administration of PLX cells will mitigate some of the effects caused by prolonged HU. We found that treatment with PLX cells was well tolerated as indicated by body weights, circulating corticosterone levels and immune organ response to injection of the cells. HU led to the expected decreases in soleus muscle weights and bone loss. We did not observe any protective properties of the PLX cells in the musculoskeletal system but found that the cell treatment partially protected from a subset of HU-induced immune and CNS changes. In the hippocampus, protein levels of 9 of 44 cytokines were downregulated by HU. PLX administration mitigated changes in expression of 8 of these cytokines, including IL-2, IL-6 and MCP-1. To our knowledge, this is the first report on the protective effects of PLX-PAD against HU-induced changes in the cytokine milieu of the CNS. Our findings warrant further studies, which includes testing in actual spaceflight.

Microgravity↗

NASA NTRS2020

Electrified Aircraft Propulsion Systems: Gas Turbine Control Considerations for the Mitigation of Potential Failure Modes and Hazards

This presentation provides a high-level review of the potential failure modes and hazards to which electrified aircraft propulsion (EAP) systems are susceptible, along with potential gas turbine control-based strategies to assist in the mitigation of those failures. To further illustrate the role of gas turbine controls in mitigating EAP failure modes, an example based on a simulated EAP concept aircraft proposed by NASA is given. The effects of failures are discussed, along with turbomachinery control strategies, including reversionary control modes, and control limit logic.

Electrified Aircraft Propulsion↗

NASA NTRS2021

Orbital Debris Mitigation and CubeSats

The 2019 update to the U. S. Government Orbital Debris Mitigation Standard Practices (ODMSP) included CubeSats as a special class of space operations for the first time. This is the first governmental-level policy document that calls for CubeSats to follow quantitative recommendations for orbital debris mitigation. While CubeSats were never exempt from such recommendations, mission designers often “under assess” CubeSats due to their small size and historically low level of stored energy. Qualitative assessments of debris potential are less applicable as miniaturized energy systems (propulsive and electrical) become more available and as the “CubeSat” label is applied to larger payloads. Of particular interest to the long-term evolution of the debris environment is the likelihood of accidental explosion or collision; we must also consider the risk to the human population from reentering spacecraft. We discuss the on-orbit history of CubeSats and present guidance to assist in designing for future compliance with the new standard practices.

Chris L. Ostrom↗

NASA NTRS2009

Mitigation selection and qualification recommendations for Xilinx Virtex, Virtex-II, and Virtex-4 field programmable gate arrays

This work discusses mitigation selection and qualification techniques for Xilinx reconfigurable field programmable gate arrays (FPGAs). The aim of the paper is to provide readers with a better understanding of the engineering/reliability/project cost relationship that occurs when developing a mitigation strategy for static random access memory (SRAM)-based FPGAs.

Allen, Gregory↗

NASA NTRSDate not supplied

Aerosol Physics for the Lunar Environment: Equations for Lunar Dust Control and Mitigation Technologies

Sticky and jagged dust was ubiquitous during the Apollo missions, causing soiling and abrasion problems with seals, coatings and equipment, in addition to eye irritation and breathing discomfort in the cabin. The Artemis Program of NASA aims to place astronauts on the lunar surface by 2024 and establish a sustainable presence in the following decade. Returning to the Moon requires controlling and mitigating the dust which will be inevitably brought inside the cabins. The state-of-the-science for effective collection of aerosols is based on dynamics of airborne particulate matter under terrestrial conditions. However, the governing physics does not apply to extra-vehicular activity in the hard-vacuum lunar condition. For example, the substantial difference in gravity will dictate particle transport both outside and inside the cabin. In this study, we revisited the aerosol physical phenomena that are assumed in the design of Earth-based aerosol instruments and extend the applicability to different scenarios in lunar missions. As shown, long-term lunar habitats, transfer vehicles to lunar orbital platforms, and low pressure cabin atmospheres have different aerosol dynamics. In all cases, the impact of dust control strategies using gravitational, electrical, and thermal techniques for various mitigation and monitoring hardware is explored. The guidelines provided through this study will show how terrestrial aerosol equipment can translate to lunar dust applications.

Nima Afshar-Mohajer↗

NASA NTRSDate not supplied

Orbital Debris Mitigation and CubeSats

The 2019 Update to the United States Government Orbital Debris Mitigation Standard Practices (ODMSP) included CubeSats for the first time as a special class of space operations. This is the first governmental-level policy document that calls for CubeSats to follow quantitative recommendations for orbital debris mitigation. While CubeSats were never exempt from such recommendations, mission designers often under assess CubeSats due to their small size and historically low level of stored energy. Qualitative assessments of debris potential are less applicable as miniaturized energy systems (propulsive and electrical) become more available and as the “CubeSat” label is applied to larger payloads. Of particular interest to the long-term evolution of the debris environment is the likelihood of accidental explosion or collision; we must also consider the risk to the human population from reentering spacecraft. We discuss the on-orbit history of CubeSats and present guidance to assist in designing for future compliance with the new standard practices.

Chris L Ostrom↗

NASA NTRSDate not supplied

Symmetry and Error Mitigation in Quantum Alternating Operator Ansatz

Quantum Alternating Operator Ansatz (QAOA) provides a platform for probing quantum advantage in optimization problems on NISQ hardware. By exploring symmetries in the system and the structure of unitaries in the algorithm, we proposed using problem-specific mixing operators to limit the quantum evolution within a subspace where the target state lives. As an example, in case of equality constraint, we studied the use of XY operators that preserve total Pauli Z. This QAOA variant, in the noiseless case, significantly outperforms the vanilla version of QAOA where the constraints are encoded as penalty in the cost Hamiltonian and the search is in the whole Hilbert space. In presence of noise, although the advantage still holds, error mitigation is needed for QAOA. I will overview our work on the design of QAOA in presence of symmetry, the implementation and compilation of XY-QAOA, its performance and error mitigation techniques in presence of noise.

Zhihui Wang↗

NASA NTRS2021

Fairfax County Urban Development: Identifying Urban Heat Mitigation Strategies for Climate Adaptation Planning in Fairfax County, Virginia

Extreme high temperatures lead to increased instances of cardiovascular disease, pulmonary disease, and even death, as well as increased energy consumption and infrastructure costs. People in urbanized areas experience higher temperatures than rural areas due to diminished vegetation and increased impervious surfaces which absorb and radiate heat. Fairfax County, Virginia has embarked on Resilient Fairfax, a program aimed at addressing climate adaptation and resilience. The DEVELOP team partnered with the Fairfax County Office of Environmental and Energy Coordination (OEEC) to assess the extent of the urban heat island effect on the county and its most vulnerable populations. The team used data from Landsat 8 Operational Land Imager (OLI) and Thermal Infrared Sensor (TIRS), as well as the ECOsystem Spaceborne Thermal Radiometer Experiment on Space Station (ECOSTRESS) for the years 2013 to 2021 and found that the hottest spots were in densely urbanized areas, with temperatures as much as 47°F above that of undeveloped reference areas. The team used the Integrated Valuation of Ecosystem Services and Tradeoffs (InVEST) urban cooling model and determined that areas with higher tree canopy cover had greater heat mitigation capacity. Estimates from the InVEST model showed that a 4.5% increase in canopy cover across the county could result in a temperature reduction of up to 2.4°F in some areas. The results will allow partners to assess heat distribution across Fairfax County and implement effective mitigation strategies, including locating prime locations for cooling centers and increasing canopy cover.

W. Pierce Holloway↗