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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 1,405 records · Page 78
All sourcesNASA NTRSDOE OSTI
NASA NTRS2004

Integrated Modeling Activities for the James Webb Space Telescope: Structural-Thermal-Optical Analysis

The James Web Space Telescope (JWST) is a large, infrared-optimized space telescope scheduled for launch in 2011. This is a continuation of a series of papers on modeling activities for JWST. The structural-thermal-optical, often referred to as STOP, analysis process is used to predict the effect of thermal distortion on optical performance. The benchmark STOP analysis for JWST assesses the effect of an observatory slew on wavefront error. Temperatures predicted using geometric and thermal math models are mapped to a structural finite element model in order to predict thermally induced deformations. Motions and deformations at optical surfaces are then input to optical models, and optical performance is predicted using either an optical ray trace or a linear optical analysis tool. In addition to baseline performance predictions, a process for performing sensitivity studies to assess modeling uncertainties is described.

Johnston, John D.↗
NASA NTRS1979

Fabrication methods for construction from lunar materials

Cost-driving parameters of space industrialization are discussed, specifically cost of transportation from earth to low earth orbit and productivity of labor in space. A design procedure for a space manufacturing facility (SMF) is outlined, and the design of a reference SMF is described. This SMF receives lunar materials and converts them to components of space structures such as solar power satellites. The effect of machine reliability is discussed. The SMF appears versatile and productive, and the space environment has some beneficial characteristics which may simplify manufacturing processes. Technology demonstration programs are needed, but prototypes of SMF equipment can be small devices.

Miller, R. H.↗
NASA NTRS1990

Control-Structure-Interaction (CSI) technologies and trends to future NASA missions

Control-structure-interaction (CSI) issues which are relevant for future NASA missions are reviewed. This goal was achieved by: (1) reviewing large space structures (LSS) technologies to provide a background and survey of the current state of the art (SOA); (2) analytically studying a focus mission to identify opportunities where CSI technology may be applied to enhance or enable future NASA spacecraft; and (3) expanding a portion of the focus mission, the large antenna, to provide in-depth trade studies, scaling laws, and methodologies which may be applied to other NASA missions. Several sections are presented. Section 1 defines CSI issues and presents an overview of the relevant modeling and control issues for LLS. Section 2 presents the results of the three phases of the CSI study. Section 2.1 gives the results of a CSI study conducted with the Geostationary Platform (Geoplat) as the focus mission. Section 2.2 contains an overview of the CSI control design methodology available in the technical community. Included is a survey of the CSI ground-based experiments which were conducted to verify theoretical performance predictions. Section 2.3 presents and demonstrates a new CSI scaling law methodology for assessing potential CSI with large antenna systems.

Source record↗
NASA NTRS1985

Thermally induced stresses and deformations in layered composite tubes

The thermally induced stresses and deformations in layered, orthotropic tubes are studied. The motivation for studying tubes is their likely application for use in space structures. Tubes are a strong candidate for this application because of their high structural efficiency, as measured by stiffness per unit weight, and their relative ease of fabrication. Also, tubes have no free edges to deteriorate or delaminate. An anticipated thermal condition for tubes in space is a circumferential temperature gradient. This type of gradient will introduce dimensional changes into the structure and may cause stresses large enough to cause damage to the material. There are potentially large differences in temperatures at different circumferential locations on the tube. Because of this, the effects of temperature dependent material properties on the stresses and deformations may be important. The study is composed of three parts: experiments to determine the functional form of the circumferential gradient and to measure tube deflections; an elasticity solution to compute the stresses and deformations; and an approximate approach to determine the effects of temperature dependent material properties.

Cooper, D. E.↗
NASA NTRS2005

A Method for Assessing the Accuracy of a Photogrammetry System for Precision Deployable Structures

The measurement techniques used to validate analytical models of large deployable structures are an integral Part of the technology development process and must be precise and accurate. Photogrammetry and videogrammetry are viable, accurate, and unobtrusive methods for measuring such large Structures. Photogrammetry uses Software to determine the three-dimensional position of a target using camera images. Videogrammetry is based on the same principle, except a series of timed images are analyzed. This work addresses the accuracy of a digital photogrammetry system used for measurement of large, deployable space structures at JPL. First, photogrammetry tests are performed on a precision space truss test article, and the images are processed using Photomodeler software. The accuracy of the Photomodeler results is determined through, comparison with measurements of the test article taken by an external testing group using the VSTARS photogrammetry system. These two measurements are then compared with Australis photogrammetry software that simulates a measurement test to predict its accuracy. The software is then used to study how particular factors, such as camera resolution and placement, affect the system accuracy to help design the setup for the videogrammetry system that will offer the highest level of accuracy for measurement of deploying structures.

Moore, Ashley↗
DOE OSTI2023

Self-supervised learning of spatiotemporal thermal signatures in additive manufacturing using reduced order physics models and transformers

Microstructure control via additive manufacturing has enormous potential as manufacturers, materials scientists, and designers alike seek to exploit novel fabrication technologies to improve component performance. Recent works have demonstrated the feasibility of producing materials with controlled microstructures across various length scales. However, the experimental approach towards exploring the process-structure space can be laborious and costly. This is particularly true if also considering scan pattern optimization which is well suited for processes such as powder bed fusion electron beam melting. In this work we propose an approach for encoding additive manufacturing layer-wise thermal response signatures using self-supervised representation learning. Thermal simulations from a reduced order model are utilized to estimate the spatiotemporal response during printing. A machine learning framework, using video-transformers, is utilized to efficiently distill spatiotemporal patterns into a compact latent space representation. This latent state representation encodes the relevant physics which is then utilized to establish a data-driven process-structure model for an additively manufactured Ni-based superalloy. In conclusion, the proposed methodology could potentially be used towards in-situ process monitoring, scan pattern experimental design, and component qualification.

97 MATHEMATICS AND COMPUTING↗
NASA NTRS1987

Flexible structure control laboratory development and technology demonstration

An experimental structure is described which was constructed to demonstrate and validate recent emerging technologies in the active control and identification of large flexible space structures. The configuration consists of a large, 20 foot diameter antenna-like flexible structure in the horizontal plane with a gimballed central hub, a flexible feed-boom assembly hanging from the hub, and 12 flexible ribs radiating outward. Fourteen electrodynamic force actuators mounted to the hub and to the individual ribs provide the means to excite the structure and exert control forces. Thirty permanently mounted sensors, including optical encoders and analog induction devices provide measurements of structural response at widely distributed points. An experimental remote optical sensor provides sixteen additional sensing channels. A computer samples the sensors, computes the control updates and sends commands to the actuators in real time, while simultaneously displaying selected outputs on a graphics terminal and saving them in memory. Several control experiments were conducted thus far and are documented. These include implementation of distributed parameter system control, model reference adaptive control, and static shape control. These experiments have demonstrated the successful implementation of state-of-the-art control approaches using actual hardware.

Vivian, H. C.↗
NASA NTRSDate not supplied

Spacecraft Observatory Benchmark Problem for Optical Disturbance Rejection

Since mid-1980s NASA has launched several first-generation interplanetary observatory missions. A salient feature of these missions has been the mounting of the optical payload on top of a large flexible space structure. This imposes challenging control-structure interaction problems (CSI) that have been studied over several decades. The Dec. 2021 launch of the James Webb Telescope marks the latest example of such a mission. One way to encourage development of novel control methods is to provide a benchmark problem for researchers. By the mid-2000s, there were a few well-known benchmark problems developed by the control community with a focus on CSI applications. However, in the past 15 years, the control challenges in optical observation missions have shifted from CSI to line-of-sight (LOS) precision pointing. This is because popular designs of the second-generation (Gen II) space earth missions have eliminated the large structure interface by mounting the optical payload directly on top of a rigid bus platform. The focus now is to achieve accurate pointing with maximum rejection of the surrounding disturbances. The NASA Safety and Engineering Center (NESC) has tasked T he Aerospace Corporation to develop a Benchmark Problem to study the challenging control issues that Gen II observatory missions encounter. This software tool is to be released as a public domain platform aimed at government, academic, and industry researchers. The focus of this benchmark problem is for researchers to design a set of innovative payload control laws with the maximum Optical Disturbance Rejection (ODR) capability to meet a set of pre-defined μrad-level of LOS jitter requirements. This paper describes the development of the benchmark problem. Aerospace/NASA will provide an integrated LOS plant model and disturbance/command profiles for users to run their design and simulation with as well as a user’s guide describing the required interfaces. The Aerospace Corp is also working to develop a hardware fast steering mirror testbed for users to demonstrate their innovative design in real hardware, if so desired.

Spacecraft Observatory Benchmark Problem↗
NASA NTRS1988

Identification and characterization of structural nonlinearities in the Space Shuttle Main Engine

Structural nonlinearities should be considered in the analysis and modeling of mechanical systems for accuracy in predicting dynamic behavior. Moreover, checks for nonlinearity should address the type and class of nonlinearity in the structure and identify the probable cause. A series of experimental modal survey tests were carried out to determine and characterize the structural nonlinearities of the Space Shuttle Main Engine main injector. Different excitation regimes at various amplitudes were utilized to induce vibration and strain, and acceleration measurements were taken at judiciously selected locations. The test results indicated that both stiffness and damping nonlinearities were present.

Panossian, H. V.↗
DOE OSTI2019

Atomically imaged crystal structure and normal-state properties of superconducting C a 10 P t 4 A s 8 ( ( F e 1 – x P t x ) 2 A s 2 ) 5

Superconducting Ca 10 Pt 4 As 8 (Fe 2 As 2 ) 5 is rare because optimal superconducting transition temperature is achieved without chemical doping or pressure. Furthermore, the unclear crystal structure limits our ability to understand the structure-property relationship. Using atomically resolved scanning transmission electron microscopy and electron diffraction, we directly determine the structure of this superconductor: it forms a monoclinic structure (space group P 2 1 /n) with lattice parameters a = b = 8.76Å, c = 20.18Å, and γ = 90.5°. Compared with previously reported structures derived from diffraction experiments, the c-lattice constant is doubled due to alternating stacking of Pt 4 As 8 layers, which induces a high density of stacking faults. With the establishment of the crystal structure, stacking faults, and chemical composition, the distinctive normal-state electrical and thermal transport properties of our superconducting Ca 10 Pt 4 As 8 ((Fe 1–x Pt x ) 2 As 2 ) 5 (x ~ 0.05) single crystals can be explained.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2021

Transport barriers to self-propelled particles in fluid flows

Here, we present theory and experiments demonstrating the existence of invariant manifolds that impede the motion of microswimmers in two-dimensional fluid flows. One-way barriers are apparent in a hyperbolic fluid flow that block the swimming of both smooth-swimming and run-and-tumble Bacillus subtilis bacteria. We identify key phase-space structures, called swimming invariant manifolds (SwIMs), that serve as separatrices between different regions of long-time swimmer behavior. When projected into xy space, the edges of the SwIMs act as one-way barriers, consistent with the experiments.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
NASA NTRS1979

Manned remote work station - Safety and rescue considerations

It is noted that due to restrictions of payload and volume limitations of current and projected launch systems, space construction of ultralarge space structures is essential. The present paper discusses the concepts of a key piece of construction equipment needed to support assembly of such large structures. Attention is given to the manned remote work station (MRWS), a universal crew cabin to be used as a construction cherry picker, space crane turret, work station on a construction base rail system, or a free flyer. Concepts and safety and rescue requirements for this spacecraft are delineated for early applications in support of Shuttle operations, as well as applications in support of a mid to late 1980's space construction base. Finally, applications in support of constructing and maintaining a solar power satellite system are covered.

Nathan, C. A.↗
NASA NTRS1985

Thermal analysis of the ACCESS space truss

This paper introduces the Assembly Concept for the Construction of Erectable Space Structure (ACCESS) experiment and describes the thermal requirements in detail. The experiment, an erectable truss beam to be flown and assembled aboard the Space Shuttle, was thermally modeled using the TRASYS and SINDA computer codes. Results from the thermal analysis are presented. Development tests dictate the application of a metallized film insulation on the aluminum beam struts to control transient orbital temperature extremes.

Foss, R. A.↗
NASA NTRS1990

Effects of cure temperature, electron radiation, and thermal cycling on P75/930 composites

Graphite/epoxy composites are candidates for future space structures due to high stiffness and dimensional stability requirements of these structures. Typical graphite/epoxy composites are brittle and have high residual stresses which often result in microcracking during the thermal cycling typical of the space environment. Composite materials used in geosynchronous orbit applications will also be exposed to high levels of radiation. The purpose of the present study was to determine the effects of cure temperature and radiation exposure on the shear strength and thermal cycling-induced microcrack density of a high modulus, 275 F cure epoxy, P75/930. The results from the P75/930 are compared to previously reported data on P75/934 and T300/934 where 934 is a standard 350 F cure epoxy. The results of this study reveal that P75/930 is significantly degraded by total doses of electron radiation greater than 10(exp 8) rads and by thermally cycling between -250 F and 150 F. The P75/930 did not have improved microcrack resistance over the P75/934, and the 930 resin system appears to be more sensitive to electron radiation-induced degradation than the 934 resin system.

Funk, Joan G.↗
NASA NTRS1992

Dynamics and control of high precision magnetically levitated vibration isolation systems

Vibration control of flexible structures has received a great deal of interest in recent years. Several authors have investigated this topic in the areas of robot manipulators, space structures, and flexible rotors. Key issues associated with the dynamics and control of vibration isolation systems are addressed. Among other important issues to consider in the control of such systems, the location and number of actuators and sensors are essential to effectively control and suppress vibration. We first address the selection of proper actuator and sensor locations leading to a controllable and observable system. The Rayleigh-Ritz modal analysis method is used to develop a lumped-parameter model of a flexible vibration isolation table top. This model is then used to investigate the system's controllability and observability including the coupling effects introduced by the magnetic bearing. This analysis results in necessary and sufficient conditions for proper selection of actuator and sensor locations. These locations are also important for both controller system's complexity and stability of point of views. A favorable pole-zero plot of the open loop transfer functions is presented. Necessary and sufficient conditions for reducing the controller complexity are derived. The results are illustrated by examples using approximate mode shape functions.

Youcef-Toumi, K.↗
NASA NTRS1981

Advanced science and applications space platform

Requirements for and descriptions of the mission equipment, subsystems, configuration, utilities, and interfaces for an Advanced Science and Applications Space Platform (ASASP) are developed using large space structure technology. Structural requirements and attitude control system concepts are emphasized. To support the development of ASASP requirements, a mission was described that would satisfy the requirements of a representative set of payloads requiring large separation distances selected from the Science and Applications Space Platform data base. Platform subsystems are defined which support the payload requirements and a physical platform concept is developed. Structural system requirements which include utilities accommodation, interface requirements, and platform strength and stiffness requirements are developed. An attitude control system concept is also described. The resultant ASASP is analyzed and technological developments deemed necessary in the area of large space systems are recommended.

White, J.↗
NASA NTRS1978

Automated space fabrication of structural elements

A description is presented of an automated space fabrication technique for basic structural elements, taking into account as representative the design loads and requirements of the solar power satellite structure. Roll forming for continuous cap and brace members is applicable for all proposed metallic materials. Spot-welding, electron beam welding, ultrasonic welding, laser welding, cold welding, and various mechanical fastening techniques are applicable for the automated fabrication process. Termination of the formed cap and brace members can be accomplished by sawing, shearing, punching, and laser cutting. The most cost effective materials were found to be the aluminum alloys. Selected for further study were AL20224T3 and AL2219-T62. In the area of fiber composites, thermoplastic matrix materials with graphite fibers were selected for future studies.

Engler, E. E.↗
NASA NTRS1981

Antenna systems requirements definition study

A plan to use a 55m wrap rib antenna in a second generation land mobile satellite service application as a specific mission to define a large space structure technology system and its interfaces is described. The system design aims to examine the launch phase of the mission including interface with the space transportation system and the orbital transfer vehicle, and the deployment from the spacecraft of the boom, antennas, and solar panels. Methods for determining the effect of system configuration on the interfaces and of the space environment and operational events on the system and its subsystem interfaces are discussed.

Golden, C. T.↗