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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 271 records · Page 15

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NASA NTRS1975

Conceptual design of reduced energy transports

This paper reports the results of a conceptual design study of new, near-term fuel-conservative aircraft. A parametric study was made to determine the effects of cruise Mach number and fuel cost on the 'optimum' configuration characteristics and on economic performance. Supercritical wing technology and advanced engine cycles were assumed. For each design, the wing geometry was optimized to give maximum return on investment at a particular fuel cost. Based on the results of the parametric study, a reduced energy configuration was selected. Compared with existing transport designs, the reduced energy design has a higher aspect ratio wing with lower sweep, and cruises at a lower Mach number. It yields about 30% more seat-miles/gal than current wide-body aircraft. At the higher fuel costs anticipated in the future, the reduced energy design has about the same economic performance as existing designs.

Ardema, M. D.↗

NASA NTRSDate not supplied

Computational investigation on the combined effect of pore attributes on strain concentrators in metal additively manufactured materials

Metal additive manufacturing provides a pathway for creating highly optimized components. However, porosity continues to be a prevalent issue for fatigue performance despite best efforts in optimizing process parameters and postprocessing techniques. This work uses finite element analysis to conduct a parametric study to link various pore attributes (i.e., aspect ratio, orientation, and location) to strain concentration factors (SCF) under elastic/plastic deformation during uniaxial loading. Keyhole and lack-of-fusion pores are idealized by prolate and oblate ellipsoids, respectively. Each simulation of the parametric study assumes a single isolated pore in a Ti-6Al-4V material, modeled with J2-plasticity. A reduced-order model is developed to relate pore attributes to SCF, and then used to quantify the variability in SCF for a given experimentally characterized probability distribution of pore attributes. This reduced-order model can be used in a production environment to provide a first-order evaluation to rapidly screen sub-optimally performing components.

Additive Manufacturing↗

NASA NTRS1974

Feasibility Study of a Satellite Solar Power Station

A feasibility study of a satellite solar power station (SSPS) was conducted to: (1) explore how an SSPS could be flown and controlled in orbit; (2) determine the techniques needed to avoid radio frequency interference (RFI); and (3) determine the key environmental, technological, and economic issues involved. Structural and dynamic analyses of the SSPS structure were performed, and deflections and internal member loads were determined. Desirable material characteristics were assessed and technology developments identified. Flight control performance of the SSPS baseline design was evaluated and parametric sizing studies were performed. The study of RFI avoidance techniques covered (1) optimization of the microwave transmission system; (2) device design and expected RFI; and (3) SSPS RFI effects. The identification of key issues involved (1) microwave generation, transmissions, and rectification and solar energy conversion; (2) environmental-ecological impact and biological effects; and (3) economic issues, i.e., costs and benefits associated with the SSPS. The feasibility of the SSPS based on the parameters of the study was established.

Glaser, P. E.↗

NASA NTRS1987

Parametric study of laser photovoltaic energy converters

Photovoltaic converters are of interest for converting laser power to electrical power in a space-based laser power system. This paper describes a model for photovoltaic laser converters and the application of this model to a neodymium laser silicon photovoltaic converter system. A parametric study which defines the sensitivity of the photovoltaic parameters is described. An optimized silicon photovoltaic converter has an efficiency greater than 50 percent for 1000 W/sq cm of neodymium laser radiation.

Walker, G. H.↗

NASA NTRS1988

Composite panel development at JPL

Parametric computer studies can be use in a cost effective manner to determine optimized composite mirror panel designs. An InterDisciplinary computer Model (IDM) was created to aid in the development of high precision reflector panels for LDR. The materials properties, thermal responses, structural geometries, and radio/optical precision are synergistically analyzed for specific panel designs. Promising panels designs are fabricated and tested so that comparison with panel test results can be used to verify performance prediction models and accommodate design refinement. The iterative approach of computer design and model refinement with performance testing and materials optimization has shown good results for LDR panels.

Mcelroy, Paul↗

NASA NTRS2009

Using Covariance Analysis to Assess Pointing Performance

A Pointing Covariance Analysis Tool (PCAT) has been developed for evaluating the expected performance of the pointing control system for NASA s Space Interferometry Mission (SIM). The SIM pointing control system is very complex, consisting of multiple feedback and feedforward loops, and operating with multiple latencies and data rates. The SIM pointing problem is particularly challenging due to the effects of thermomechanical drifts in concert with the long camera exposures needed to image dim stars. Other pointing error sources include sensor noises, mechanical vibrations, and errors in the feedforward signals. PCAT models the effects of finite camera exposures and all other error sources using linear system elements. This allows the pointing analysis to be performed using linear covariance analysis. PCAT propagates the error covariance using a Lyapunov equation associated with time-varying discrete and continuous-time system matrices. Unlike Monte Carlo analysis, which could involve thousands of computational runs for a single assessment, the PCAT analysis performs the same assessment in a single run. This capability facilitates the analysis of parametric studies, design trades, and "what-if" scenarios for quickly evaluating and optimizing the control system architecture and design.

Bayard, David↗

NASA NTRS2019

Space Launch System and Missions to Near Rectilinear Halo Orbits

The first major evolution of NASA’s Space Launch System (SLS) will begin its flights starting in the mid-2020’s. This new configuration, called Block 1B, replaces the Interim Cryogenic Propulsion Stage with a larger Exploration Upper Stage (EUS). The additional capability provided by the new upper stage will allow SLS to send heavier payloads into deep space. One destination of interest to the SLS program is called a Near Rectilinear Halo Orbit (NRHO). This is a type of lunar orbit with multiple advantages for deep space exploration. These benefits include Earth/lunar access, low station-keeping requirements, and high communication potential with Earth. Therefore, it is a leading candidate for the proposed Lunar Orbital Platform-Gateway (LOP-G). This paper will provide a detailed assessment of the SLS Block 1B requirements and capabilities for sending payloads to an NRHO. Analysts at Marshall Space Flight Center are producing a multi-year mission availability scan for the SLS Block 1B configuration to a predefined NRHO orbit. The analysis produces an optimized trajectory for each day of the scan window. A maximized payload and minimized propellant requirement are determined for each day. All maneuvers from launch to the end of the Trans-Lunar-Injection (TLI) are being modeled as finite burns. Injections into an NRHO are being modeled as impulsive maneuvers. The payload element is arbitrary, but includes sufficient mass to represent a large habitat or propulsion module. The resulting parameters of payload capability, delta-v requirements, and launch windows length vary over the course of the scan. Many launch days in the scan are eliminated in post-processing as they violate mission constraints such as payload mass and propellant usage to insert into an NRHO. Based off previous one-year scan results for the SLS Block 1B Design Analysis Cycle 2 (DAC-2), it is expected that there will be one to three days per week where the payload is able to insert into an NRHO within SLS constraints objectives. This scan provides results for longer than one-year, allowing analysts to better understand the launch availability and energy requirements of SLS Block 1B over time. The in-space mission design and scans utilize Copernicus, an n-body trajectory optimization tool originally developed out of the University of Texas at Austin with further development at Johnson Space Center in Houston, TX. To seed the in-space trajectory, Copernicus uses a plugin to call a database of SLS ascent trajectories optimized in the Program to Simulate Optimized Trajectories II (POST2). The ascent trajectories are developed using a framework that parametrizes payload mass and LEO inclination, and targets a 100 nmi (nautical mile) altitude circular parking orbit. Though this analysis is specific to the SLS program, it will provide a summary of mission design benefits and constraints associated with generic NRHO access, and may be applied to other programs or concepts that will utilize this orbit.

Statham, T. L.↗

NASA NTRS2019

Operational Stability Limits in Rotating Detonation Engine Numerical Simulations

An instability is described which arises in computational fluid dynamic (CFD) simulations of semi-idealized rotating detonation engines (RDE) configured with a throat at the exit. Its existence is verified by examining output from two independently developed CFD codes simulating the same configuration and producing solutions that agree well. The instability is shown to be thermo-acoustic in that a spatial integral of the product of pressure and heat release fluctuations develops a regular oscillation which grows in time. The instability can become severe enough to cause detonation failure. Its onset is shown to be closely linked to the size of the exit throat and the size of the inlet restriction; both parameters that strongly influence RDE performance. It is shown that the instability places a cap on ideal RDEperformance, but that an optimized exhaust throat and inlet restriction combination still yields substantial pressure gain. Other parametric sensitivities are also examined in terms ofinstability growth. These include axial length, inlet manifold pressure, and air-fuel ratio.

Paxson, Daniel E.↗

NASA NTRS2023

Multiphysics Modeling of Electrode Dissolution under Hydrodynamic Conditions in Low Conductivity Water

Efficient plug-flow electrochemical reactors are characterized by their ability to effectively convert species with significant ionic strength and/or with the assistance of a well-behaved electrolyte. Because of the classic electroconductivity requirement, electrochemical reactors are not particularly attractive options for applications with low-conductivity conditions, especially for low-pressure feeds. However, these reactors can still find application in dedicated processes such as ultra-clean water conditioning and biological-coupled separation systems. Consequently, a multi-physics model was developed using COMSOL Multiphysics to characterize different reactor-design conditions based on the Tertiary Current Distribution which accounts for the effects of expected variations in electrolyte composition and ionic strength on the electrochemical process, as well as solution resistance and electrode kinetics. The modelling framework presented here employs single-phase laminar fluid flow, the Nernst-Planck equation, the water-based electroneutrality condition, and concentration-dependent overpotentials. This investigation particularly explores the electrolysis process of “anodic dissolution,” in which elemental species dissociate from the solid matrix of the electrode and enter the liquid phase of the electrolyte as soluble ions. The reactor configuration of interest has a rectangular parallel-electrode design and is operated galvanostatically. A series of parametric studies are carried out to inspect the response of the system when hydrodynamic, kinetic, and geometric conditions are changed. The parametric sweep resulted in variable effluent concentrations and system voltage, which reveal underlaying optimization patterns for electrode dissolution in low conductivity water.

Multiphysics↗

NASA NTRSDate not supplied

Optimized Entanglement Distribution Among Quantum Memories

We evaluate entanglement distribution performance when an optimized quantum memory encoding method is used for two sources, the standard spontaneous parametric down conversion source and the zero added loss multiplexing source. Physical non-idealities are considered.

Entanglement distribution↗

NASA NTRS2004

On the Use of CAD and Cartesian Methods for Aerodynamic Optimization

The objective for this paper is to present the development of an optimization capability for Curt3D, a Cartesian inviscid-flow analysis package. We present the construction of a new optimization framework and we focus on the following issues: 1) Component-based geometry parameterization approach using parametric-CAD models and CAPRI. A novel geometry server is introduced that addresses the issue of parallel efficiency while only sparingly consuming CAD resources; 2) The use of genetic and gradient-based algorithms for three-dimensional aerodynamic design problems. The influence of noise on the optimization methods is studied. Our goal is to create a responsive and automated framework that efficiently identifies design modifications that result in substantial performance improvements. In addition, we examine the architectural issues associated with the deployment of a CAD-based approach in a heterogeneous parallel computing environment that contains both CAD workstations and dedicated compute engines. We demonstrate the effectiveness of the framework for a design problem that features topology changes and complex geometry.

Nemec, M.↗

NASA NTRSDate not supplied

A Parametric Battery Model for the Conceptual Design of Electric Aircraft

Electric aircraft conceptual designs usually have an assumed specific power and specific energy for the aircraft’s energy storage system that dictates the total capacity and the peak power available. The specific energy and power are inherently linked to the state-of-charge and discharge rate from which they were derived; therefore, they will not directly correspond to the diverse circumstances encountered in various aircraft missions and flight segments. These parameters turn the battery system into a black box, disregard potential electrical restrictions, and disallow the aircraft and battery to be optimized as a system. Peering into this box, this study highlights the importance of incorporating a parametric battery model into the conceptual design workflow by splitting high-level terms such as power into voltage and current and investigating their variability during the discharge process. Through the modeling of these more detailed parameters, this methodology shows the feasibility of using low states-of-charge for contingency operations, including the end of the reserve mission, expanding the amount of usable capacity for electric aircraft. Stark differences in aircraft capabilities can arise between varying fidelity battery models due to late-mission, high-power flight operations. This parametric battery model effectively captures these differences by evaluating the limitations that arise within the individual battery cells and the aircraft powertrain. This paper shows that the unusable charge of a battery is set by the balked landing power requirement and can realistically range from 5% to 44% based on assumptions. This sets the analog to unusable fuel capacity in aircraft with liquid fuel systems. Needing only aircraft- and mission-level inputs and only seconds of run time, this model is a prime fit for the fast, accurate exploration of the electric aircraft conceptual design space.

Battery↗

NASA NTRS2010

N plus 2 Supersonic Concept Development and Systems Integration

Supersonic airplanes for two generations into the future (N+2, 2020-2025 EIS) were designed: the 100 passenger 765-072B, and the 30 passenger 765-076E. Both achieve a trans-Atlantic range of about 4000nm. The larger 765-072B meets fuel burn and emissions goals forecast for the 2025 time-frame, and the smaller 765-076E improves the boom and confidence in utilization that accompanies lower seat count. The boom level of both airplanes was reduced until balanced with performance. The final configuration product is two "realistic", non-proprietary future airplane designs, described in sufficient detail for subsequent multi-disciplinary design and optimization, with emphasis on the smaller 765-076E because of its lower boom characteristics. In addition IGES CAD files of the OML lofts of the two example configurations, a non-proprietary parametric engine model, and a first-cycle Finite Element Model are also provided for use in future multi-disciplinary analysis, optimization, and technology evaluation studies.

Wedge, Harry R.↗

NASA NTRS1984

On the design of contractions and settling chambers for optimal turbulence manipulations in wind tunnels

The sensitivity of a moderate axisymmetric contraction of turbulence to upstream conditions is parametrically investigated in terms of turbulence intensities and integral length scales. Semi-empirical correlations are derived to characterize the development of turbulence intensities and integral length scales downstream of typical wind-tunnel turbulence manipulators. A new approach is described, permitting wind-tunnel designers to select the characteristic mesh of the turbulence manipulators, a well as the distance from them to the contraction, in order to obtain certain required turbulence characteristics in the test section at the exit of the contraction. The design charts strongly suggest that it may not be possible to achieve small scales and low intensities simultaneously, when using a contraction ratio of nine or larger. The results also confirm that the rapid distortion theory is only valid, with a proper viscous dissipation correction, up to the 'critical point' of a contraction. At that point, the scales of the various components of the velocity are equal and intercomponent transfer from the lateral to the streamwise velocities commences.

Nagib, H. M.↗

NASA NTRS1996

Optimally Scaled H(sub infinity) Full Information Control Synthesis with Real Uncertainty

This paper presents an algorithm to synthesize optimal controllers for the scaled H(sub infinity). full information problem with real and complex uncertainty. The control problem is reduced to a linear matrix inequality which can be solved via a finite dimensional convex optimization. This technique is compared with the optimal scaled H(sub infinity). full information with only complex uncertainty and D - K iteration control design to synthesize controllers for a missile autopilot. Directly including real parametric uncertainty into the control design results in improved robust performance of the missile autopilot. The controller synthesized via D - K iteration achieves results similar to the optimal designs.

Balas, Gary J.↗

NASA NTRS2024

Piezoelectric impedance-based high-accuracy damage identification using sparsity conscious multi-objective optimization inverse analysis

Two elements are essential in structural health monitoring utilizing dynamic responses: response measurement with high-frequency contents, i.e., small characteristic wavelengths, that can adequately reflect damage features, and effective inverse identification analysis that is however oftentimes under-determined. The advancement of smart structure integration has led to active interrogation through frequency-sweeping piezoelectric impedance measurement at high frequency range. In this research we develop a multi-objective optimization formulation for the identification of damage location and severity utilizing piezoelectric impedance. While one optimization objective is to match the response measurement with finite element model prediction in the damage parametric space, the other is the number of locations of damage, i.e., the sparsity of damage index as the solution vector, since damage usually occurs within a small number of locations. This multi-objective formulation fits well the under-determined nature of damage identification, as it naturally provides multiple solutions as basis for further elucidation. The challenge remaining is how to find a small solution set that can include the actual damage scenario. Here we develop a novel inverse identification framework utilizing the intelligent swarm optimizer which possesses flexibility for enhancement. We first embed a sparsity enforcement process into the population generation of the optimizer, which yields a solution repository intrinsically possessing sparsity. We then apply reinforcement learning so the agents can adaptively opt for local strategies with the aim of enriching the searching patterns to diversify the solutions. Through the incorporation of a Q-table, searching toward more promising directions will be rewarded. Our case analyses employing experimental data indicate that this sparsity-conscious multi-objective particle swarm optimization technique can lead to a small solution set which generally encompasses the true damage scenario. This effectively solves the structural damage identification problem with piezoelectric impedance measurement.

Yang Zhang↗

NASA NTRS1976

Analytical and experimental studies of an optimum multisegment phased liner noise suppression concept

Results are presented from detailed analytical studies made to define methods for obtaining improved multisegment lining performance by taking advantage of relative placement of each lining segment. Properly phased liner segments reflect and spatially redistribute the incident acoustic energy and thus provide additional attenuation. A mathematical model was developed for rectangular ducts with uniform mean flow. Segmented acoustic fields were represented by duct eigenfunction expansions, and mode-matching was used to ensure continuity of the total field. Parametric studies were performed to identify attenuation mechanisms and define preliminary liner configurations. An optimization procedure was used to determine optimum liner impedance values for a given total lining length, Mach number, and incident modal distribution. Optimal segmented liners are presented and it is shown that, provided the sound source is well-defined and flow environment is known, conventional infinite duct optimum attenuation rates can be improved. To confirm these results, an experimental program was conducted in a laboratory test facility. The measured data are presented in the form of analytical-experimental correlations. Excellent agreement between theory and experiment verifies and substantiates the analytical prediction techniques. The results indicate that phased liners may be of immediate benefit in the development of improved aircraft exhaust duct noise suppressors.

Sawdy, D. T.↗

NASA NTRS1992

Membrane triangles with corner drilling freedoms. III - Implementation and performance evaluation

This paper completes a three-part series on the formulation of 3-node, 9-dof membrane triangles with corner drilling freedoms based on parametrized variational principles. The first four sections cover element implementation details including determination of optimal parameters and treatment of distributed loads. Then three elements of this type, labeled ALL, FF and EFF-ANDES, are tested on standard plane stress problems. ALL represents numerically integrated versions of Allman's 1988 triangle; FF is based on the free formulation triangle presented by Bergan and Felippa in 1985; and EFF-ANDES represent two different formulations of the optimal triangle derived in Parts I and II. The numerical studies indicate that the ALL, FF and EFF-ANDES elements are comparable in accuracy for elements of unitary aspect ratios. The ALL elements are found to stiffen rapidly in inplane bending for high aspect ratios, whereas the FF and EFF elements maintain accuracy. The EFF and ANDES implementations have a moderate edge in formation speed over the FF.

Felippa, Carlos A.↗