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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 163 records · Page 9
All sourcesNASA NTRSDOE OSTI
NASA NTRS1992

Multidisciplinary optimization of aeroservoelastic systems using reduced-size models

Efficient analytical and computational tools for simultaneous optimal design of the structural and control components of aeroservoelastic systems are presented. The optimization objective is to achieve aircraft performance requirements and sufficient flutter and control stability margins with a minimal weight penalty and without violating the design constraints. Analytical sensitivity derivatives facilitate an efficient optimization process which allows a relatively large number of design variables. Standard finite element and unsteady aerodynamic routines are used to construct a modal data base. Minimum State aerodynamic approximations and dynamic residualization methods are used to construct a high accuracy, low order aeroservoelastic model. Sensitivity derivatives of flutter dynamic pressure, control stability margins and control effectiveness with respect to structural and control design variables are presented. The performance requirements are utilized by equality constraints which affect the sensitivity derivatives. A gradient-based optimization algorithm is used to minimize an overall cost function. A realistic numerical example of a composite wing with four controls is used to demonstrate the modeling technique, the optimization process, and their accuracy and efficiency.

Karpel, Mordechay↗
NASA NTRS1989

Residual mode filters and adaptive control in large space structures

One of the most difficult problems in controlling large systems and structures is compensating for the destructive interaction which can occur between the reduced-order model (ROM) of the plant, which is used by the controller, and the unmodeled dynamics of the plant, often called the residual modes. The problem is more significant in the case of large space structures because their naturally light damping and high performance requirements lead to more frequent, destructive residual mode interaction (RMI). Using the design/compensation technique of residual mode filters (RMF's), effective compensation of RMI can be accomplished in a straightforward manner when using linear controllers. The use of RMF's has been shown to be effective for a variety of large structures, including a space-based laser and infinite dimensional systems. However, the dynamics of space structures is often uncertain and may even change over time due to on-orbit erosion from space debris and corrosive chemicals in the upper atmosphere. In this case, adaptive control can be extremely beneficial in meeting the performance requirements of the structure. Adaptive control for large structures is also based on ROM's and so destructive RMI may occur. Unfortunately, adaptive control is inherently nonlinear, and therefore the known results of RMF's cannot be applied. The purpose is to present the results of new research showing the effects of RMI when using adaptive control and the work which will hopefully lead to RMF compensation of this problem.

Davidson, Roger A.↗
DOE OSTI2023

Co-Extrusion of Dissimilar Aluminum Alloys via Shear-Assisted Processing and Extrusion

Bimetallic tubes are used when a component requires more than one performance requirement, for instance, strength/creep resistance and oxidation/corrosion resistance. Shear-assisted processing and extrusion (ShAPE) can be used to fabricate extrudates that are comparable or superior in performance relative to conventionally manufactured extrudates. For the first time, ShAPE has been successfully employed in producing bimetallic Al tubing consisting of 6061 and 7075 Al alloys. Both light and electron microscopy techniques were used to investigate the integrity of the tubes, especially the interface between the core and cladding of the bimetallic tubes. Void-free bimetallic tubes were produced using ShAPE. Quantification of tube integrity was carried out with tensile testing under as-extruded and post-aged conditions. All the bimetallic tubes in the as-extruded samples exhibited uniform elongation above 5% with good tensile strength. Key insights such as material flow during bimetallic tube extrusion were obtained from the characterization of remnant billet and simulation results from a smoothed particle hydrodynamics model.

36 MATERIALS SCIENCE↗
NASA NTRS1994

A volatile organic analyzer for Space Station: Description and evaluation of a gas chromatography/ ion mobility

A Volatile Organic Analyzer (VOA) is being developed as an essential component of the Space Station's Environmental Health System (EHS) air quality monitoring strategy to provide warning to the crew and ground personnel if volatile organic compounds exceed established exposure limits. The short duration of most Shuttle flights and the relative simplicity of the contaminant removal mechanism have lessened the concern about crew exposure to air contaminants on the Shuttle. However, the longer missions associated with the Space Station, the complex air revitalization system and the proposed number of experiments have led to a desire for real-time monitoring of the contaminants in the Space Station atmosphere. Achieving the performance requirements established for the VOA within the Space Station resource (e.g., power, weight) allocations led to a novel approach that joined a gas chromatograph (GC) to an ion mobility spectrometer (IMS). The authors of this paper will discuss the rational for selecting the GC/IMS technology as opposed to the more established gas chromatography/mass spectrometry (GC/MS) for the foundation of the VOA. The data presented from preliminary evaluations will demonstrate the versatile capability of the GC/IMS to analyze the major contaminants expected in the Space Station atmosphere. The favorable GC/IMS characteristics illustrated in this paper included excellent sensitivity, dual-mode operation for selective detection, and mobility drift times to distinguish co-eluting GC peaks. Preliminary studies have shown that the GC/IMS technology can meet surpass the performance requirements of the Space Station VOA.

Limero, Thomas F.↗
DOE OSTI2023

Important Factors for the Reliable and Reproducible Preparation of Non-aqueous Electrolyte Solutions for Lithium Batteries

Electrolyte solutions play a crucial role in rechargeable lithium batteries. Driven by an ever-increasing demand for better batteries, more and more stringent performance requirements are being asked of electrolytes. This demand to achieve electrolytes beyond the state-of-the-art has driven an increasing number of publications over the past decade. Nevertheless, a detailed description of electrolyte preparation is frequently missing when reporting new electrolytes for batteries, creating a barrier for others to reproduce important findings. In addition, false or misleading information in a paper may result from unintentional inaccuracies during the electrolyte preparation process. This article highlights important factors for the reliable and reproducible preparation of non-aqueous electrolyte solutions for lithium batteries, with the aim of encouraging researchers to follow more rigorous reporting standards.

Cao, Xia↗
DOE OSTI2020

Towards Off-policy Evaluation as a Prerequisite for Real-world Reinforcement Learning in Building Control

We present an initial study of off-policy evaluation (OPE), a problem prerequisite to real-world reinforcement learning (RL), in the context of building control. OPE is the problem of estimating a policy's performance without running it on the actual system, using historical data from the existing controller. It enables the control engineers to ensure a new, pretrained policy satisfies the performance requirements and safety constraints of a real-world system, prior to interacting with it. While many methods have been developed for OPE, no study has evaluated which ones are suitable for building operational data, which are generated by deterministic policies and have limited coverage of the state-action space. After reviewing existing works and their assumptions, we adopted the approximate model (AM) method. Furthermore, we used bootstrapping to quantify uncertainty and correct for bias. In a simulation study, we evaluated the proposed approach on 10 policies pretrained with imitation learning. On average, the AM method estimated the energy and comfort costs with 1.84% and 14.1% error, respectively.

Chen, B↗
DOE OSTI2026

Elevating SolTrace's Capabilities for the Next Generation of Concentrating Solar Analysis

SolTrace is an open-source Monte Carlo ray tracing software developed at NREL. SolTrace can characterize concentrating solar thermal (CST) collector optical performance and is CST technology agnostic. Shown in Fig. 1, SolTrace is a foundational tool in NREL's CST system and component modeling suite. SolTrace's generic surface elements can flexibly model novel collector and receiver designs to predict spatial and temporal flux distributions - critical to understand for CST component design, performance prediction, and system integration. Since its initial development, SolTrace has over 1,650 references on Google Scholar, over 9,800 downloads since 2017, and has served the CST research and development community as a benchmark of 3rd party verification. SolTrace provides users with many options for defining surface shape and boundaries. However, SolTrace provides limited documentation which can result in a steep learning curve for new users. Additionally, SolTrace lacks the computational performance required to evaluate optical performance of a CST system over the course of a year and/or iteratively over design parameters in a timely manner. To address this, we are working towards a new release of SolTrace that enables increased computational throughput by implementing ray tracing acceleration structures and enabling GPU parallelization. Additionally, we are working to improve SolTrace's usability, accessibility, and maintainability by (1) automating solar position time-dependent simulation processes, (2) creating general CST collector templates of grouped elements, (3) updating the user interface to better visualize model inputs and outputs, and (4) creating a user support network through forums, "how to" videos, and documentation.

14 SOLAR ENERGY↗
NASA NTRS1973

Volume accumulator design analysis computer codes

The computer codes, VANEP and VANES, were written and used to aid in the design and performance calculation of the volume accumulator units (VAU) for the 5-kwe reactor thermoelectric system. VANEP computes the VAU design which meets the primary coolant loop VAU volume and pressure performance requirements. VANES computes the performance of the VAU design, determined from the VANEP code, at the conditions of the secondary coolant loop. The codes can also compute the performance characteristics of the VAU's under conditions of possible modes of failure which still permit continued system operation.

Whitaker, W. D.↗
NASA NTRS1973

Development of Emergency Intravehicular Spacesuit (EIS) assembly

A program was undertaken to develop and test two prototype pressure suits to operate at pressures up to 413 mm Hg (8.0 PSIG). The units were designated Emergency Intravehicular Spacesuits (EIS). Performance requirements, design evolution, testing performed, problems encountered, and final EIS configuration are reported.

Source record↗
NASA NTRS1978

A portable L-band voice transceiver for satellite communication

A portable L-band voice transceiver was developed as a feasibility model and can provide a half-duplex voice link to another terminal via the L-band transponder on the Applications Technology Satellite, ATS-6. The narrow band FM transceiver utilizes commercial subsystems including a UHF transceiver, provides an RF output power of 20 watts, weights less than 25 lbs., is housed in a plastic briefcase, can be powered by an automobile electrical system, and has been successfully operated with ATS-6 on numerous occasions. Design considerations and operation of the transceiver are described, along with alignment and testing procedures, packaging and cost considerations, subsystem performance requirements and overall transceiver performance characteristics.

Maruschak, J.↗
NASA NTRS1979

Formulation of advanced consumables management models: Environmental control and electrical power system performance models requirements

Software design specifications for developing environmental control and life support system (ECLSS) and electrical power system (EPS) programs into interactive computer programs are presented. Specifications for the ECLSS program are at the detail design level with respect to modification of an existing batch mode program. The FORTRAN environmental analysis routines (FEAR) are the subject batch mode program. The characteristics of the FEAR program are included for use in modifying batch mode programs to form interactive programs. The EPS program specifications are at the preliminary design level. Emphasis is on top-down structuring in the development of an interactive program.

Daly, J. K.↗
NASA NTRS1981

Verification of the Space Shuttle entry GN&C system

The certification procedures for the initial Shuttle flight are discussed. Particular attention is paid to the entry guidance, navigation, and control (GNC) verification, comprising tests, analysis, demonstration, inspection, and simulation. Flow diagrams for the verification and operational flight sequences are provided, along with a block diagram of the GNC circuitry interfaces. The development of the test matrix software for the GNC is outlined, noting the constant interplay between software verification and spacecraft reconfiguration to meet simulated performance requirements. Comparison of GNC performance predictions with actual entry flight data showed a good match in all performance areas except for sideslip excursions, bank overshoots, an area of transonic buffet, and an increased lift/drag ratio in the preflare to landing flight phase.

Van Hoften, J. D. A.↗
NASA NTRS1993

Strength capabilities and load requirements while performing torquing tasks in zero gravity

A generic examination of the loads produced by individuals performing maximal efforts with a torquing tool in zero gravity, to determine operator strength when performing torquing tasks; quantify the loads placed on foot restraints while performing these tasks; and examine effects of orientation and direction of tool rotation on strength effectiveness was conducted. The experiment was conducted aboard NASA's KC-135 reduced-gravity aircraft, using two force plates attached to a test stand, one with a foot restraint. Subjects used a wrench to apply maximum torques to various fittings, in different positions, in clockwise and counterclockwise directions. It was seen that these subjects could produce approximately 400 to 750 N of force, depending on the orientation of the tool and the direction of effort. The most force could be produced when pushing the tool upwards. A force effectiveness ratio (FER) defined as an indication of how much of the subjects' total effort actually went into performing the desired task. Values of FER ranged from 0.55 to 0.90, with the greatest FER occurring with UP and DOWN efforts, and the lowest with AWAY and LEFT efforts. Designers can use these results to set specifications for craft structures; tools can be developed based on the known strength of the tool users; and tasks can be developed to not exceed the crewmembers' capabilities.

Poliner, Jeffrey↗
NASA NTRS1994

Fault tolerant computer control for a Maglev transportation system

Magnetically levitated (Maglev) vehicles operating on dedicated guideways at speeds of 500 km/hr are an emerging transportation alternative to short-haul air and high-speed rail. They have the potential to offer a service significantly more dependable than air and with less operating cost than both air and high-speed rail. Maglev transportation derives these benefits by using magnetic forces to suspend a vehicle 8 to 200 mm above the guideway. Magnetic forces are also used for propulsion and guidance. The combination of high speed, short headways, stringent ride quality requirements, and a distributed offboard propulsion system necessitates high levels of automation for the Maglev control and operation. Very high levels of safety and availability will be required for the Maglev control system. This paper describes the mission scenario, functional requirements, and dependability and performance requirements of the Maglev command, control, and communications system. A distributed hierarchical architecture consisting of vehicle on-board computers, wayside zone computers, a central computer facility, and communication links between these entities was synthesized to meet the functional and dependability requirements on the maglev. Two variations of the basic architecture are described: the Smart Vehicle Architecture (SVA) and the Zone Control Architecture (ZCA). Preliminary dependability modeling results are also presented.

Lala, Jaynarayan H.↗
NASA NTRS1995

Evolution of the INMARSAT aeronautical system: Service, system, and business considerations

A market-driven approach was adopted to develop enhancements to the Inmarsat-Aeronautical system, to address the requirements of potential new market segments. An evolutionary approach and well differentiated product/service portfolio was required, to minimize system upgrade costs and market penetration, respectively. The evolved system definition serves to minimize equipment cost/size/mass for short/medium range aircraft, by reducing the antenna gain requirement and relaxing the performance requirements for non safety-related communications. A validation program involving simulation, laboratory tests, over-satellite tests and flight trials is being conducted to confirm the system definition. Extensive market research has been conducted to determine user requirements and to quantify market demand for future Inmarsat Aero-1 AES, using sophisticated computer assisted survey techniques.

Sengupta, Jay R.↗