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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 397 records · Page 22
All sourcesNASA NTRSDOE OSTI
NASA NTRS2019

Prognostic Launch Vehicle Probability of Failure Assessment Methodology for Conceptual Systems Predicated on Human Causal Factors

Lessons learned from past failures of launch vehicle developments and operations were used to create a new method to predict the probability of failure of conceptual systems. Existing methods such as Probabilistic Risk Assessments and Human Risk Assessments were considered but found to be too cumbersome for this type of system-wide application for yet-to-be-flown vehicles. The basis for this methodology were historic databases of past failures, where it was determined that various faulty human-interactions were the predominant root causes of failure rather than deficient component reliabilities evaluated through statistical analysis. This methodology contains an expert scoring part which can be used in either a qualitative or a quantitative mode. The method produces two products: a numerical score of the probability of failure or guidance to program management on critical areas in need of increased focus to improve the probability of success. In order to evaluate the effectiveness of this new method, data from a concluded vehicle program (USAF's Titan IV with the Centaur G-Prime upper stage) was used as a test case. Although the theoretical vs. actual probability of failure was found to be in reasonable agreement (4.46% vs. 6.67% respectively) the underlying sub-root cause scoring had significant disparities attributable to significant organizational changes and acquisitions. Recommendations are made for future applications of this method to ongoing launch vehicle development programs.

Craig H Williams↗
NASA NTRS2019

International Space Station Spacecraft Charging Hazards: Hazard Identification, Management, and Control Methodologies, with Possible Applications to Human Spaceflight Beyond LEO

In this paper, we present an overview of how the International Space Station (ISS) safety engineering methodology directed to controlling extravehicular activity (EVA) crew electrical shock hazards, caused by ISS spacecraft charging, has evolved over the past 25+ years. Long-term measurements of ISS charging severity and frequency-of-occurrence, combined with detailed probabilistic analysis of EVA electric shock- circuit completion, led to a change in hazard control methodology. The requirement for two-fault tolerant EVA shock hazard control during all EVAs was replaced with a less operationally burdensome and risky EVA shock hazard detection and warning process. The applicability of event probability-based detection-and- warning processes to human spaceflight charging hazard control beyond low-earth orbit (LEO) is also considered.

Koontz, Steve↗
NASA NTRSDate not supplied

RDE Nozzle Computational Design Methodology Development and Application

The Open National Combustion Code (OpenNCC) is used to simulate the aerospike exhaust nozzle region of a rotating detonation engine (RDE).The main objectives of the current study are twofold. The first goal is to validate the proposed computational methodology using the experimental data. The second goal is to demonstrate how the validated prediction tool can be used to optimize the nozzle geometry. To achieve a significant speed-up of computational time, the computational domain in divided into two parts: a combustion region and a throat-nozzle section. In the combustion region, a validated quasi-two-dimensional in-house code is utilized to generate an unsteady RDE flow field solution just upstream of the combustor throat. Subsequently, the unsteady flow data is fed into the three-dimensional throat-nozzle section as the inflow boundary condition. This facilitates the design optimization process since the unsteady inflow can be reused, and a relatively coarse mesh (i.e., larger time-step) can be used to analyze the flow fields around the nozzle. Five nozzle designs were studied and the predicted performance (i.e., thrust)compared. The optimized nozzle was found to produce 3.2% more overall thrust than a baseline nozzle design. Without the nozzle, there is a large low-pressure region at the throat exit, which significantly reduces the overall performance. This methodology is shown to be a promising approach to explore a wide variety of nozzle geometries in a relatively short amount of time.

CFD↗
NASA NTRS2020

Ensemble Methodologies for Astronaut Cancer Risk Assessment in the face of Large Uncertainties

A new approach to NASA space radiation risk modeling has successfully extended the current NASA probabilistic cancer risk model to an ensemble framework able to consider sub-model parameter uncertainty (e.g. uncertainty in a radiation quality parameter) as well as model-form uncertainty associated with differing theoretical or empirical formalisms (e.g. combined dose-rate and radiation quality effects). Ensemble methodologies are already widely used in weather prediction, modeling of infectious disease outbreaks, and certain terrestrial radiation protection applications to better understand how uncertainty may influence risk decision-making. Applying ensemble methodologies to space radiation risk projections offers the potential to efficiently incorporate emerging research results, allow for the incorporation of future (including international) models, improve uncertainty quantification for underlying sub-models developed against sparse experimental data, and reduce the impact of subjective bias on risk projections. Moreover, risk forecasting across an ensemble of multiple predictive models can provide stakeholders additional information on risk acceptance if current health/medical standards cannot be met or the level of knowledge doesn’t permit a specific risk or exposure limit to be developed for future space exploration missions. In this work, ensemble risk projections implementing multiple sub-models of radiation quality, dose and dose-rate effectiveness factors, excess risk, and latency as ensemble members are presented. Initial consensus methods for ensemble model weights and correlations to account for individual model bias are discussed. In these analyses, the ensemble forecast compares well to results from NASA's current operational cancer risk projection model used to assess permissible exposure limits and permissible mission durations for astronauts. However, a large range of projected risk values are obtained at the upper 95th confidence level where models must extrapolate beyond available biological data sets; closer agreement is seen at the median + one sigma due to the inherent similarities in available models. Future work, including the addition of new models and methods for statistical correlation between predictive members are discussed to define alternate ways of thinking about risk and ‘acceptable’ uncertainty with respect to NASA’s current permissible exposure limits.

space radiation↗
NASA NTRS2018

A Systems Architecting Methodology Using Bloom’s Taxonomy to Promote Creative Engineering Synthesis

Architecting complex systems requires high-level cognitive processing and extensive knowledge of the system elements, functions, relationships, and constraints. This paper describes a systems architecting methodology implemented through cognitive psychological creative processes using Bloom’s taxonomy as a framework to generate the expert knowledge required to effectively and systematically synthesize new systems. Systems architecting activities were carried out to identify, develop, and capture factual and conceptual knowledge relevant to the system subject matter and functional elements, as well as to facilitate active processing of the knowledge through remembering, understanding, applying, analyzing, evaluating, and creating. Dual channel and limited capacity principles of learning were incorporated into the format of the systems engineering tools developed to assist with information processing and retention. Meta-cognitive strategies associated with memory and creative idea generation were implemented into the methodology to effectively and efficiently develop system alternatives using the full collection of knowledge. Synthesis of an orbiting sample capture and orientation system architecture to enable spacecraft-based on orbit capture of a Mars sample container for a potential Mars Sample Return campaign was used as a case study.

Adajian, Rama↗
NASA NTRS2021

Robust Control Methodology Via Loop Shaping, Root Locus, and Model Reference Control

The paper describes the development of a robust control methodology that can tolerate large uncertainties in plant dynamics in terms of proportional gain variations as well as frequencies and damping. For this to be accomplished, the methodology starts by designing a feedback controller based on a loop shaping technique. The design is then improved by employing a root locus control design approach. Finally, the response of the feedback system is further improved by augmenting the control design using model reference control. The design approach also takes into consideration the speed of the process actuator for a fast response and for high disturbance rejection. Results from two control design examples covered in the paper show that this control approach can tolerate plant proportional gain uncertainty of approximately ± two orders of magnitude with relatively large variations in plant frequencies and damping.

Control Systems↗
NASA NTRSDate not supplied

Signal and Power Integrity Design Methodology for High-Performance Flight Computing Systems

Computing capabilities of space systems have in-creased onboard performance by orders of magnitude with the use of radiation-tolerant field-programmable gate arrays (FPGA)and processors. The incorporation of signal and power integrity analysis with printed circuit board (PCB) design in reliable computing architectures for space systems has become critical to enable future mission capabilities. Developers launch high-performance processors into a breadth of orbits and missions, running varying applications that create challenges for designing reliable computing hardware. Specifically, for these designs, academic and industry research has focused on component radiation performance, fault mitigation, and reliable architectures. How-ever, other design parameters including electromagnetic interference (EMI), PCB stackup, signal integrity (SI), voltage regulator module (VRM) design, and power distribution network (PDN)are often deprioritized or disregarded as the design matures. Since these characteristics are becoming more significant in high-performance processor designs, this research presents a hardware design and analysis methodology for high-performance, space-computing systems that focuses on a holistic design approach and PDN reliability. While these challenges exist across all space hardware, the reduced PCB dimensions imposed by SmallSats and CubeSats introduce additional hurdles, specifically to VRM and decoupling design. By examining the relationship between the PDN and radiation performance, an analytical relationship is developed that incorporates Total Ionizing Dose and Single-Event Transients to ensure reliability throughout the mission duration. The presented design methodology is applied to the SpaceCube v3.0 Mini, an FPGA-based on-board science data processing system developed at NASA Goddard Space Flight Center.

Advanced avionics↗
NASA NTRS2020

An Efficient Focal Plane Alignment Methodology with Application to the ASTERIA Nanosatellite Space Telescope

The process of aligning an instrument focal plane toprecursor optics such as a telescope can be a difficult and timeconsuming process. The final alignment must achieve sufficientperformance at multiple locations across the field of view. Inthe case of instruments with infinite conjugates, such as a spacetelescope, there are practical challenges in illuminating the system at multiple off-axis field points simultaneously. Iterationduring the alignment process can cause a lengthy search for localminima within the performance cost function.This paper presents a focal plane alignment methodology thatavoids the above difficulties and obtains the desired level ofoptical performance in an efficient manner. The approach isbased on systematically measuring spot size across a set of fieldpoints and defocus positions, and then using a least squaresfit to determine the optimal location for the focal plane. Thisapproach has the additional benefit of revealing the amount offield curvature present in the instrument. It also provides theanalyst with a direct calculation of the shims needed to place thefocal plane at the computed best-fit location.This approach was successfully applied to the Arcsecond SpaceTelescope Enabling Research In Astrophysics (ASTERIA) payload. ASTERIA is a cubesat mission that was deployed intolow-Earth orbit in November 2017 and operated until December2019. In addition to presenting the theoretical basis for themethodology, this paper will present laboratory measurementsobtained during the payload alignment campaign. This approach is applicable to future space-borne optical instrumentsthat require an efficient methodology for focal plane alignmentwith limited cost or schedule resources.

Smith, Matthew W↗
NASA NTRSDate not supplied

A Methodology for Reliability Assessments of Arbitrary Satellite Constellations

The commercial success of small satellite development and multi-satellite missions has led to constellation missions being proposed in every sector of the market. This paradigm shift has the potential to enable more capable and cost-effective space science missions. However, these novel approaches to space missions have outstripped existing policy and analysis methods for assessing the reliability of multi-satellite missions. Mission designers and decisionmakers need new methods and standards for modeling how the reliability of constituent spacecraft elements affect the aggregate reliability of constellations across a wide range of concepts and application-specific requirements. The Space Mission Analysis Branch at NASA’s Langley Research Center has developed a methodology for simulating the on-orbit reliability of arbitrary spacecraft constellations. In this paper, the authors describe the methodology and provides examples of how it can be used to evaluate specific constellation designs. To demonstrate the flexibility of the approach, several different constellation configurations are considered, including both homogenous and heterogenous designs. Next, the authors demonstrate the ability to perform broad parameter sweeps to develop greater insight into the intrinsic reliability trends associated with constellation concepts. Finally, the authors provide tables and novel data graphics which enable decisionmakers to quickly discern the relationships between constellation sizes, topologies, replenishment strategies, and overall constellation reliability.

satellite↗
NASA NTRSDate not supplied

Methodology for Validation of Unsteady Pressure-Sensitive Paint Measurements using Pressure Transducers

Unsteady Pressure-Sensitive Paint (uPSP) technology provides simultaneously high-frequency and high-spatial resolution surface pressure fluctuation measurements. It has demonstrated value in wind tunnel test facilities to evaluate aerospace vehicle unsteady aerodynamics. The calibration of measurements from digital pixel counts into corresponding physical units relies on both lab-based and in-situ calibration steps, and its validation is both challenging and critical to adoption of the technology. We present a rigorous methodology for direct comparison of uPSP-derived surface pressure measurements to reference pressure transducer data based on a model of the camera-based measurement error, a model of the flow field pressure signal, and their propagation through the uPSP data reduction algorithm. The methodology is demonstrated on data collected in a small-scale, subsonic wind tunnel test as well as data collected from a Space Launch System unsteady aerodynamics characterization test at the NASA Ames Research Center Unitary Plan Wind Tunnel Complex.

Pressure-Sensitive Paint↗
NASA NTRSDate not supplied

Comparison of Prediction Modeling Methodologies for Aeroacoustic Characterization of Hovering sUAS Rotors

This work compared artificial neural network and multivariate orthogonal function modeling methodologies for the prediction and characterization of isolated hovering sUAS rotor aerodynamics and aeroacoustics. Design of Experiments was used to create input feature spaces over 9 input features: the number of rotor blades, rotor size, rotor speed, the amount of blade twist, blade taper ratio, tip chord length, collective pitch, airfoil camber, and airfoil thickness. CAMRAD~II and AARON were executed at the points defined by the input feature space to predict aerodynamic and aeroacoustic quantities. These predicted aerodynamic and aeroacoustic data were then used to generate artificial neural networks and polynomial response surface models. The two prediction model methodologies were evaluated over test data previously unseen by the models, which showed good prediction capabilities for both model types, with slightly lower prediction error for the artificial neural networks. A characterization study was performed, which showed that input features correspondent to the spanwise sectional blade lift and drag were the most significant factors to the aerodynamic thrust and power, respectively. It was also shown that the aeroacoustic quantities were highly dependent on variations in rotor speed and size, which affect the Doppler factor for tonal noise and the spanwise Reynolds number for broadband noise.

Christopher S Thurman↗
NASA NTRSDate not supplied

A New ML-Based Adaptive Thinning Methodology to Improve the Impact of AIRS and CrIS Assimilation on Global Tropical Cyclone Forecasts

This work builds on previous research performed by this team to improve the forecast of Tropical Cyclones (TCs) by assimilating AIRS and CrIS radiances into the NASA Global Earth Observing System (GEOS). Past published work demonstrated that the assimilation of radiances with variable density was beneficial to TC forecasting in the GEOS. In the previous setup, a fixed-size moving square named 'TC domain' was activated by the so-called TC-vitals, an international real-time message accessible to all NWP forecasting centers, that documents the existence of a TC, its estimated position, and its size. The information from TC-vitals activated a switch in the GEOS, which allowed to reduce the distance used for thinning AIRS and CrIS data inside a 15 degrees by 15 degrees moving TC domain centered on the storm, so that more data were assimilated in the vicinity of the TC during its lifetime. The methodology produced improved TC analyses and led to better forecasts, particularly related to intensity, without damaging the global forecast skill. In the new version, the adaptive thinning methodology is based on a machine-learning technique. The technique searches for TCs and creates TC masks by using cloud-top temperatures from all geostationary satellites without the need for additional information. It is being trained against the International Best Track Archive for Climate Stewardship (IBTrACS) data base. Once a TC mask is created, a switch identical to the one used in the previous adaptive thinning method is activated, allowing the GEOS to ingest more data in the TC-shaped size-changing domain that follows the storm. As of today, the team has been able to successfully assimilate data inside the ML-detected TC domains. Future work includes an improved capability of reducing false alarm rates (i.e., cloud systems that are erroneously labeled as TCs).

Oreste Reale↗
NASA NTRSDate not supplied

Ares: A Coupling Methodology for Ablation Modeling

To enable modeling of complex and coupled ablation problems, a multi-physics framework is developed. A methodology for modeling shape change in coupled systems is presented. The approach taken to model gas-surface interactions and translate coupled surface phenomena to physically meaningful boundary conditions in the distinct solvers is discussed. Particular emphasis is placed on the nature of coupled boundary conditions pertaining to surface energy and mass balances as well as surface chemistry modeling. The developed methodology is used to simulate a shear test in arc-jet conditions in order to assess the validity of the coupled approach as well as the implementation of the relevant physical processes.

EDL↗
NASA NTRSDate not supplied

Ares: A Coupling Methodology for Ablation Modeling

To enable modeling of complex and coupled ablation problems, a multi-physics framework is developed. A methodology for modeling shape change in coupled systems is presented. The approach taken to model gas-surface interactions and translate coupled surface phenomena to physically meaningful boundary conditions in the distinct solvers is discussed. Particular emphasis is placed on the nature of coupled boundary conditions pertaining to surface energy and mass balances as well as surface chemistry modeling. The developed methodology is used to simulate a shear test in arc-jet conditions in order to assess the validity of the coupled approach as well as the implementation of the relevant physical processes.

EDL↗
NASA NTRSDate not supplied

Uncertainty Quantification Methodology for Sonic Boom Loudness of a Low-Boom Supersonic Concept

This paper presents a comprehensive analysis of uncertainty quantification for sonic boom loudness metrics associated with the X-59 aircraft during its acoustic validation phase. The study focuses on employing advanced methodologies to characterize uncertainties in key sonic boom parameters predicted from a database derived from a computational fluid dynamics (CFD) solver. These methodologies include creating a polynomial chaos expansion (PCE) surrogate model, which is then used to run a Monte Carlo analysis to obtain 95% uncertainty intervals for sonic boom loudness parameters across the full carpet. Atmospheric uncertainties are rigorously considered, leveraging weather models based on historical data near Edwards Air Force Base to simulate potential flight conditions. The findings include preliminary uncertainty results for the full carpet during the validation phase of the Quesst mission. Additionally, a sensitivity study reveals that the primary sources of uncertainty are humidity and cruise weight.

Laura M. White↗
DOE OSTI2024

Protocols and methodologies for acquiring and analyzing critical-current versus longitudinal-strain data in Bi 2 Sr 2 CaCu 2 O 8+x wires

Abstract In the literature on Bi 2 Sr 2 CaCu 2 O 8+ x (Bi-2212) superconducting wires, it is evident that measurement protocols for transport critical-current I c versus longitudinal strain ϵ and definitions of the so-called ‘strain limit’ are generally dissimilar. Yet, values obtained for the ‘strain limit’ are frequently assimilated to being those of the irreversible strain limit ϵ irr , regardless of the I c degradation-criterion used to define it. In effect, ϵ irr should correspond specifically to the I c ( ϵ ) irreversibility onset , where crack formation in Bi-2212 filaments presumably starts. Because I c ( ϵ ) degradation remains progressive over a fairly wide strain range beyond ϵ irr , the different I c degradation-criteria in use do not yield to the same result and, thus, are not equivalent from metrology perspective. Indeed, in studying densified samples of a modern Bi-2212 round wire, we found ϵ irr ≈ 0.4% and ϵ 5% ≈ 0.6% ( ϵ 5% being the strain where I c degrades by 5%). In this paper, we outline and suggest I c ( ϵ )-measurement protocols and data-analysis methodologies in the hope to converge the various approaches taken for studying Bi-2212 strain properties and, thus, remove related result discrepancies. A unified approach would enable more objective data comparisons among laboratories and among different Bi-2212 conductors. It would pave the way for more rigorous studies of effects potentially associated with wire design, powder, heat treatments, and other such parameters on the conductor’s strain properties.

protocols↗
NASA NTRS2001

Analysis of biomaterial using Neural Computing Methodology

This paper describes a novel learning methodology used to analyze bio-materials. The premise of this research is to help pathologists quickly identify anomalous cells in a cost efficient method.

biomaterial neural computing methodology neural ne↗