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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Generalized Quantum Convolution for Multidimensional Data

The convolution operation plays a vital role in a wide range of critical algorithms across various domains, such as digital image processing, convolutional neural networks, and quantum machine learning. In existing implementations, particularly in quantum neural networks, convolution operations are usually approximated by the application of filters with data strides that are equal to the filter window sizes. One challenge with these implementations is preserving the spatial and temporal localities of the input features, specifically for data with higher dimensions. In addition, the deep circuits required to perform quantum convolution with a unity stride, especially for multidimensional data, increase the risk of violating decoherence constraints. In this work, we propose depth-optimized circuits for performing generalized multidimensional quantum convolution operations with unity stride targeting applications that process data with high dimensions, such as hyperspectral imagery and remote sensing. We experimentally evaluate and demonstrate the applicability of the proposed techniques by using real-world, high-resolution, multidimensional image data on a state-of-the-art quantum simulator from IBM Quantum.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2022

First Sagittarius A* Event Horizon Telescope Results. V. Testing Astrophysical Models of the Galactic Center Black Hole

In this paper we provide a first physical interpretation for the Event Horizon Telescope's (EHT) 2017 observations of Sgr A*. Our main approach is to compare resolved EHT data at 230 GHz and unresolved non-EHT observations from radio to X-ray wavelengths to predictions from a library of models based on time-dependent general relativistic magnetohydrodynamics simulations, including aligned, tilted, and stellar-wind-fed simulations; radiative transfer is performed assuming both thermal and nonthermal electron distribution functions. We test the models against 11 constraints drawn from EHT 230 GHz data and observations at 86 GHz, 2.2μm, and in the X-ray. All models fail at least one constraint. Light-curve variability provides a particularly severe constraint, failing nearly all strongly magnetized (magnetically arrested disk (MAD)) models and a large fraction of weakly magnetized models. A number of models fail only the variability constraints. We identify a promising cluster of these models, which are MAD and have inclination i ≤ 30°. They have accretion rate (5.2–9.5) × 10$^{−9}$ M $_{⊙}$ yr$^{−1}$, bolometric luminosity (6.8–9.2) × 10$^{35}$ erg s$^{−1}$, and outflow power (1.3–4.8) × 10$^{38}$ erg s$^{−1}$. We also find that all models with i ≥ 70° fail at least two constraints, as do all models with equal ion and electron temperature; exploratory, nonthermal model sets tend to have higher 2.2μm flux density; and the population of cold electrons is limited by X-ray constraints due to the risk of bremsstrahlung overproduction. Finally, we discuss physical and numerical limitations of the models, highlighting the possible importance of kinetic effects and duration of the simulations.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1987

Design and performance of an arcjet nuclear electric propulsion system for a mid-1990's reference mission

The design and performance of an arcjet nuclear-electric-propulsion spacecraft, suitable for use in the Space Nuclear Power System (SNPS) reference mission, are outlined. The vehicle design was based on a 30-kW ammonia arcjet system operating at an Isp of 1050 s and an efficiency of 45 percent. The arcjet/gimbal system, power-processing unit, and propellant-feed system are described. A 100-kWe SNPS was assumed, and the spacecraft mass was baselined at 5250 kg (excluding the propellant-feed system). A radiation/arcjet efflux diagnostics package was included in the performance analysis. This spacecraft, assuming a Shuttle launch from KSC, can perform a 50-deg inclination change and reach a final orbit of 35,860 km with a 120-d trip time providing a 4-mo active load for the SNPS. Alternatively, a Titan IV launch would provide a mass margin of 120 kg to a 10,000-km, 58-deg final orbit in 74 d. This spacecraft meets the reference-mission constraint of low developmental risk, and is scalable to power levels projected for future space platforms.

Deininger, William D.↗
NASA NTRS1987

Spacecraft and mission design for the SpaceNuclear PowerSystem Reference Mission

The design and performance of a spacecraft employing arcjet nuclear electric propulsion, suitable for use in the Space Nuclear Power System Reference Mission, are outlined. The vehicle design is based on a 92 kW ammonia arcjet system operating at an I(sp) of 1050 s and an efficiency of 45 percent. The arcjet/gimbal system, power processing unit, and propellant feed-system are described. A 100 kW(e) space nuclear power system is assumed and the spacecraft mass is baselined at 5250 kg excluding the propellant, propellent feed system, and integrated chemical boost engine. A radiation/arcjet efflux diagnostics package is included in the performance analysis. Three mission scenarios are described and are capable of demonstrating the full capability of the space nuclear power source. The missions considered include power system deployment to possible SDI platform orbits and a spacecraft storage mission to an orbit of three times geosynchronous (GEO) with return to GEO corresponding to Delta V's between 7400 m/s, and 7900 m/s. This spacecraft meets the Reference Mission constraint of low developmental risk and is scaleable to power levels projected for future space platforms.

Deininger, William D.↗
NASA NTRS2003

Assessing risk from a stakeholder perspective

Planetary exploration missions are subject to a vast array of interpretations of 'success' based on the concerns of multiple stakeholder groups. While project risk management generally focuses on issues of cost/schedule constraints or reliability issues, a broader interpretation of 'risk' as it applies to stakeholders such as sponsors (e.g., NASA), the public at large, the scientific community, the home organization, and the project team itself can provide important insights into the full spectrum of risk that needs to be managed. This paper presents a stakeholder view of risk which is divided into failure, not-a-failure, success, and stunning-success zones. Using the Mars Pathfinder mission as an example, an alternative interpretation of the risks to that mission is presented from the view of key stakeholders. The implications of the stakeholder perspective to project risk management are addressed.

risk management success/failure graph↗
NASA NTRS2014

Asteroid Crewed Segment Mission Lean Development

The next generation of human spaceflight missions presents numerous challenges to designers that must be addressed to produce a feasible concept. The specific challenges of designing an exploration mission utilizing the Space Launch System and the Orion spacecraft to carry astronauts beyond earth orbit to explore an asteroid stored in a distant retrograde orbit around the moon will be addressed. Mission designers must carefully balance competing constraints including cost, schedule, risk, and numerous spacecraft performance metrics including launch mass, nominal landed mass, abort landed mass, mission duration, consumable limits and many others. The Asteroid Redirect Crewed Mission will be described along with results from the concurrent mission design trades that led to its formulation. While the trades presented are specific to this mission, the integrated process is applicable to any potential future mission. The following trades were critical in the mission formulation and will be described in detail: 1) crew size, 2) mission duration, 3) trajectory design, 4) docking vs grapple, 5) extravehicular activity tasks, 6) launch mass and integrated vehicle performance, 7) contingency performance, 8) crew consumables including food, clothing, oxygen, nitrogen and water, and 9) mission risk. The additional Orion functionality required to perform the Asteroid Redirect Crewed Mission and how it is incorporated while minimizing cost, schedule and mass impacts will be identified. Existing investments in the NASA technology portfolio were leveraged to provide the added functionality that will be beneficial to future exploration missions. Mission kits are utilized to augment Orion with the necessary functionality without introducing costly new requirements to the mature Orion spacecraft design effort. The Asteroid Redirect Crewed Mission provides an exciting early mission for the Orion and SLS while providing a stepping stone to even more ambitious missions in the future.

Gard, Joe↗
NASA NTRS2014

Spacecraft Charging Issues for Launch Vehicles

Spacecraft charging is well known threat to successful long term spacecraft operations and instrument reliability in orbits that spend significant time in hot electron environments. In recent years, spacecraft charging has increasingly been recognized as a potentially significant engineering issue for launch vehicles used to deploy spacecraft using (a) low Earth orbit (LEO), high inclination flight trajectories that pass through the auroral zone, (b) geostationary transfer orbits that require exposures to the hot electron environments in the Earths outer radiation belts, and (c) LEO escape trajectories using multiple phasing orbits through the Earths radiation belts while raising apogee towards a final Earth escape geometry. Charging becomes an issue when significant areas of exposed insulating materials or ungrounded conductors are used in the launch vehicle design or the payload is designed for use in a benign charging region beyond the Earths magnetosphere but must survive passage through the strong charging regimes of the Earths radiation belts. This presentation will first outline the charging risks encountered on typical launch trajectories used to deploy spacecraft into Earth orbit and Earth escape trajectories. We then describe the process used by NASAs Launch Services Program to evaluate when surface and internal charging is a potential risk to a NASA mission. Finally, we describe the options for mitigating charging risks including modification of the launch vehicle andor payload design and controlling the risk through operational launch constraints to avoid significant charging environments.

Electrostatics↗
NASA NTRS2014

Spacecraft Charging Issues for Launch Vehicles

Spacecraft charging is well known threat to successful long term spacecraft operations and instrument reliability in orbits that spend significant time in hot electron environments. In recent years, spacecraft charging has increasingly been recognized as a potentially significant engineering issue for launch vehicles used to deploy spacecraft using (a) low Earth orbit (LEO), high inclination flight trajectories that pass through the auroral zone, (b) geostationary transfer orbits that require exposures to the hot electron environments in the Earths outer radiation belts, and (c) LEO escape trajectories using multiple phasing orbits through the Earths radiation belts while raising apogee towards a final Earth escape geometry. Charging becomes an issue when significant areas of exposed insulating materials or ungrounded conductors are used in the launch vehicle design or the payload is designed for use in a benign charging region beyond the Earths magnetosphere but must survive passage through the strong charging regimes of the Earths radiation belts. This presentation will first outline the charging risks encountered on typical launch trajectories used to deploy spacecraft into Earth orbit and Earth escape trajectories. We then describe the process used by NASAs Launch Services Program to evaluate when surface and internal charging is a potential risk to a NASA mission. Finally, we describe the options for mitigating charging risks including modification of the launch vehicle and/or payload design and controlling the risk through operational launch constraints to avoid significant charging environments

electrostatics↗
DOE OSTI2025

The Design of a Multiphase CO2 Turbine Test Facility

As the energy market continues to evolve with increased renewables, such as solar and wind energy, the need to balance energy demand with its availability has become increasingly more challenging. The country’s aggressive decarbonization goals in the upcoming decades will increase renewable energy market penetration, thus exacerbating the disparity between energy demand and renewable resource availability. Long-duration energy storage technologies, such as pumped thermal energy storage (PTES), are potential solutions to this challenge with high potential round-trip efficiency (RTE), no geological or geographical constraints, and low safety risks. The charge mode of a PTES system operates a heat pump cycle, converting input power to thermal energy in hot and cold reservoirs. Fundamentally, heat pumps are commonly used in daily life, but the operating conditions required by high RTE PTES systems are outside the design experience of these systems. The low-pressure side of the cycle for a supercritical CO2 (sCO2) PTES operates just above the vapor-dome and potentially drives the turbine to expand into the dome, resulting in multiphase operation in the rear stages of the turbine. This paper presents the design of the test facility for an advanced multiphase-tolerant sCO2 turbine for the heat pump of a PTES system. Heat rejection and pressure loss estimations for the multiphase sections of the test loop presented unforeseen challenges.

25 ENERGY STORAGE↗
NASA NTRS2009

The Integrated Medical Model: A Risk Assessment and Decision Support Tool for Space Flight Medical Systems

The Integrated Medical Model (IMM) is a decision support tool that is useful to mission planners and medical system designers in assessing risks and designing medical systems for space flight missions. The IMM provides an evidence based approach for optimizing medical resources and minimizing risks within space flight operational constraints. The mathematical relationships among mission and crew profiles, medical condition incidence data, in-flight medical resources, potential crew functional impairments, and clinical end-states are established to determine probable mission outcomes. Stochastic computational methods are used to forecast probability distributions of crew health and medical resource utilization, as well as estimates of medical evacuation and loss of crew life. The IMM has been used in support of the International Space Station (ISS) medical kit redesign, the medical component of the ISS Probabilistic Risk Assessment, and the development of the Constellation Medical Conditions List. The IMM also will be used to refine medical requirements for the Constellation program. The IMM outputs for ISS and Constellation design reference missions will be presented to demonstrate the potential of the IMM in assessing risks, planning missions, and designing medical systems. The implementation of the IMM verification and validation plan will be reviewed. Additional planned capabilities of the IMM, including optimization techniques and the inclusion of a mission timeline, will be discussed. Given the space flight constraints of mass, volume, and crew medical training, the IMM is a valuable risk assessment and decision support tool for medical system design and mission planning.

Kerstman, Eric↗
NASA NTRS2018

Guidelines for Verification Strategies to Minimize RISK Based on Mission Environment, -Application and -Lifetime (MEAL)

There is a trend of compromising verification testing to address the cost and schedule constraints, which poses a high-risk posture for programs/projects. Current and emerging aerospace scientific and/or human exploration programs continue to pose new technological challenges. These technological challenges combined with finite budgets and truncated schedules are forcing designers, scientists, engineers, and managers to push technologies to their physical limits. In addition, budget and schedule pressures challenge how those technologies/missions are verified. A clear understanding of the different verification processes is needed to ensure the proper verification of the technology within the mission (i.e., capabilities, advantages, and limitations). The goal of verification is to prove through test, analysis, inspection, and/or demonstration that a product provides its required function while meeting the performance requirements. It is important that verification yield understanding of representative performance under worst-case conditions so that margins to failure can be evaluated for proposed applications. The capabilities, advantages, and limitations of the testing and inspection performed at each level are different, and the risk incurred by omitting a verification step depends on the level of integration as well as Mission, Environment, Application and Lifetime (MEAL). This paper focuses on verification processes. The goal of the verification process is to ensure the given avionics technology could be safely implemented on the given MEAL consistent with the program/project risk posture.

Gonzalez, Oscar↗
NASA NTRS2002

Risk Management for the International Space Station

The International Space Station (ISS) is an extremely complex system, both technically and programmatically. The Space Station must support a wide range of payloads and missions. It must be launched in numerous launch packages and be safely assembled and operated in the harsh environment of space. It is being designed and manufactured by many organizations, including the prime contractor, Boeing, the NASA institutions, and international partners and their contractors. Finally, the ISS has multiple customers, (e.g., the Administration, Congress, users, public, international partners, etc.) with contrasting needs and constraints. It is the ISS Risk Management Office strategy to proactively and systematically manages risks to help ensure ISS Program success. ISS program follows integrated risk management process (both quantitative and qualitative) and is integrated into ISS project management. The process and tools are simple and seamless and permeate to the lowest levels (at a level where effective management can be realized) and follows the continuous risk management methodology. The risk process assesses continually what could go wrong (risks), determine which risks need to be managed, implement strategies to deal with those risks, and measure effectiveness of the implemented strategies. The process integrates all facets of risk including cost, schedule and technical aspects. Support analysis risk tools like PRA are used to support programatic decisions and assist in analyzing risks.

Sebastian, J.↗
NASA NTRS2021

Designing a Decontamination Solution for the Low-Earth-Orbit, Cryogenic SPHEREx Mission

To address the scientific goals of NASA’s astrophysics division, the JPL and Caltech’s SPHEREx mission conducts the first near-infrared all-sky spectral survey in low-earth-orbit using a passively-cooled, cryogenic telescope. Several unique water contamination issues arise due to the combination of cryogenic operation temperatures and the limited temperature control authority of passive cooling. Because water molecules have adsorption bands within the wavelengths of interest for SPHEREx’s survey, it is imperative that water contamination be controlled and minimized. In this work, a model is developed for the SPHEREx mission to predict the transport and accumulation of outgassed water onto sensitive payload components. The model utilizes the time dependent thermal profiles of the individual payload components, initial water content, and spacecraft geometry to calculate the time dependent water diffusion, transport, and adsorption. This model is subsequently used to predict water contamination risks and design decontamination solutions for each risk. Two major water contamination risks were predicted, water accumulation during cooldown and on cryogenic surfaces during the mission. The first risk occurs during the cooldown of the payload to cryogenic temperatures, predicting water accumulation on optical surfaces in excess of the allowable levels. To mitigate this accumulation, the temperature of the optical surfaces is controlled during cooldown through a combination of heaters and spacecraft pointing. The second risk is that over the course of the mission, is unavoidable water accumulation onto the payload thermal system’s cryogenic surfaces, possibly jeopardizing thermal performance and temperature stability, both of which are required for science success. To decontaminate any water that had collected onto cryogenic thermal system surfaces, a decontamination maneuver was designed. In this decontamination maneuver, cryogenic surfaces of the thermal system are warmed to a temperature where water will desorb by spacecraft pointing while still meeting all avoidance constraints, and thereby avoiding undue risk to the observatory hardware. Through application of the developed analytical model and inclusion of the decontamination maneuver in the mission design, SPHEREx can confidently demonstrate that it is able to decontaminate, at the start of and during the mission as needed to meet its end of life science performance requirements.

Soares, Carolos E.↗
NASA NTRS2010

Managing the Risk for Early Onset Osteoporosis in Long-Duration Astronauts Due to Spaceflight

Early Onset Osteoporosis is probably the most recognized but poorly understood long-term health risk due to spaceflight. Osteoporosis management is primarily prophylactic and clinical interventions rely upon the ability to predict fractures which is currently determined by surrogate measures of bone strength. The RMAT for Early Onset Osteoporosis identified some open issues related to the fact that long-duration astronauts compose a unique group of subjects for which clinical approaches for osteoporosis management do not apply. Long-duration astronauts are healthy, young (25 to 55 years of age), predominantly male, and physical fit relative to the typical osteoporosis patient. Moreover, during prolonged space missions (typically 6-month missions) the skeleton not only adapts to weightlessness, but is influenced by numerous risk factors induced by operational constraints, e.g., inability to maintain preflight weight-bearing and aerobic activities, sub-optimal dietary intake (e.g., high sodium content for food stability, lack of fresh fruit and vegetables), suppression of vitamin D metabolism by uv shielding, and remote medicine care. Moreover, adaptation results in novel changes to astronauts bones that cannot be detected by current medically-useful measures. Consequently, a panel of clinicians (recognized leaders and policy-makers in osteoporosis) was convened to review the dataset of bone measures and bone loss risk factors in long-duration astronauts. Driven by the queries in the RMAT, the panel was charged to determine 1) if an intervention is required to prevent this risk, 2) what type and at what time would intervention be optimal, 3) what is the clinical trigger that would require a medical response from flight surgeons and 4) how should research data be used in the clinical care of astronauts. Hence, the RMAT determined that a bone health policy need to be formulated specific for this unique cohort subjected to a novel skeletal condition

Sibonga, Jean D.↗
DOE OSTI2023

Constraints on OPF Surrogates for Learning Stable Local Volt/Var Controllers

We consider the problem of learning local Volt/Var controllers in distribution grids (DGs). Our approach starts from learning separable surrogates that take both local voltages and reactive powers as arguments and predict the reactive power setpoints that approximate optimal power flow (OPF) solutions. We propose an incremental control algorithm and identify two different sets of slope conditions on the local surrogates such that the network is collectively steered toward desired configurations asymptotically. Our results reveal the trade-offs between each set of conditions, with coupled voltage-power slope constraints allowing an arbitrary shape of surrogate functions but risking limitations on exploiting generation capabilities, and reactive power slope constraints taking full advantage of generation capabilities but constraining the shape of surrogate functions. AC power flow simulations on the IEEE 37-bus feeder illustrate their guaranteed stability properties and respective advantages in two DG scenarios.

asymptotic stability↗
NASA NTRS2014

A Guideline for the Management of Renal Stones in Astronauts

There are no specific guidelines for the management of renal stones in astronauts. Given the increased risk for bone loss, hypercalcuria, and stone formation due to microgravity, a clinical practice guideline is needed. Methods An extensive review of the literature and current aeromedical standards for the management of renal stones was done. The NASA Flight Medicine Clinic's electronic medical record and Longitudinal Survey of Astronaut Health were also reviewed. This information was used to create an algorithm for the management of renal stones in astronauts. Results Guidelines are proposed based on accepted standards of care, with consideration to the environment of spaceflight. In a usual medical setting, asymptomatic, small stones less than 7 mm are often observed over time. Given the constraints of schedule, and the risks to crew health and mission, this approach is too liberal. An upper limit of 3 mm stone diameter was adopted before requiring intervention, because this is the largest size that has a significant chance of spontaneous passage on its own. Other specific guidelines were also created. Discussion The spaceflight environment requires more aggressive treatment than would otherwise be found with the usual practice of medicine. A small stone can become a major problem because it may ultimately require medical evacuation from orbit. Thus renal stones are a significant mission threat and should be managed in a systematic way to mitigate risks to crew health and mission success.

Reyes, David↗
NASA NTRSDate not supplied

IMPACT - Information for the Development of Human Health and Performance Systems

IMPACT is a suite of computational and systems engineering tools. Currently being developed for NASA Exploration Medical Capabilities (ExMC) and could be extended to other Human Research Program (HRP) elements. The purpose is to provide a data-driven means to inform human health and performance risk mitigation during exploration missions considering resource constraints in the medical system. IMPACT enables systematic trade studies to evaluate options. IMPACT uses Probabilistic Risk Assessment (PRA) as a systematic methodology to evaluate risks. IMPACT is currently under development to inform decision-makers the risks involved with trade-options that have likelihoods and consequences backed by scientific research in a medical evidence library. IMPACT supports multi-segment analysis to determine probabilities and risks in different mission segments. There are currently 122 medical conditions and 900 resources in the IMPACT Medical Database. IMPACT modeling is using mission segments and multiple vehicles for the NASA Artemis campaign and could support future complex missions in deep space.

IMPACT PRA↗