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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
NASA NTRS1997

Mechanical System Reliability and Cost Integration Using a Sequential Linear Approximation Method

The development of new products is dependent on product designs that incorporate high levels of reliability along with a design that meets predetermined levels of system cost. Additional constraints on the product include explicit and implicit performance requirements. Existing reliability and cost prediction methods result in no direct linkage between variables affecting these two dominant product attributes. A methodology to integrate reliability and cost estimates using a sequential linear approximation method is proposed. The sequential linear approximation method utilizes probability of failure sensitivities determined from probabilistic reliability methods as well a manufacturing cost sensitivities. The application of the sequential linear approximation method to a mechanical system is demonstrated.

Kowal, Michael T.↗
DOE OSTI2024

High-bandwidth Dynamic Load Emulation of Mechanical Systems using Electric Drives

Machine drives are versatile systems that can be programmed to emulate a variety of mechanical loads. In this paper, we walk through the modeling and control framework of a shaft-coupled dual-motor drive system that is programmed to emulate a fictitious mechanical system. We quantitatively evaluate the control performance of such a system and derive a theoretical limit that explains its inaccuracy at high operating frequencies. To overcome this problem, we propose an alternate control structure that achieves the same control objective at high frequencies as well. After suitable adjustments are made to the controller, we validate its performance using simulation results.

machine drives ,load emulation, speed-torque chara↗
NASA NTRS1974

MSFC Skylab structures and mechanical systems mission evaluation

A performance analysis for structural and mechanical major hardware systems and components is presented. Development background testing, modifications, and requirement adjustments are included. Functional narratives are provided for comparison purposes as are predicted design performance criterion. Each item is evaluated on an individual basis: that is, (1) history (requirements, design, manufacture, and test); (2) in-orbit performance (description and analysis); and (3) conclusions and recommendations regarding future space hardware application. Overall, the structural and mechanical performance of the Skylab hardware was outstanding.

Source record↗
NASA NTRS2014

New Method for Characterizing the State of Optical and Opto-Mechanical Systems

James Webb Space Telescope Optical Telescope Element (OTE) is a three mirror anastigmat consisting of a 6.5 m primary mirror (PM), secondary mirror (SM) and a tertiary mirror. The primary mirror is made out of 18 segments. The telescope and instruments will be assembled at Goddard Space Flight Center (GSFC) to make it the Optical Telescope Element-Integrated Science Instrument Module (OTIS). The OTIS will go through environmental testing at GSFC before being transported to Johnson Space Center for testing at cryogenic temperature. The objective of the primary mirror Center of Curvature test (CoC) is to characterize the PM before and after the environmental testing for workmanship. This paper discusses the CoC test including both a surface figure test and a new method for characterizing the state of the primary mirror using high speed dynamics interferometry.

Optical Testing↗
NASA NTRS1992

LDEF mechanical systems

Following LDEF retrieval, a number of studies were made of mechanical hardware and structure flown on the LDEF. The primary objectives are to determine the effects of long term space exposure on (1) mechanisms either used on LDEF or as part of individual experiments; (2) LDEF structural components; and (3) fasteners. Results from examination and testing of LDEF structure, fasteners, LDEF end support beam, environment exposure control canisters, experiment tray clamps, LDEF grapple fixtures, and viscous damper are presented. The most significant finding is the absence of space exposure related cold welding. The instances of seizure or removal difficulties initially attributed to cold welding were shown to have resulted from installation galling damage or improper removal techniques. Widespread difficulties encountered with removal of stainless steel fasteners underscore the need for effective thread lubrication schemes to ensure successful application of proposed orbital replacement units onboard Space Station Freedom.

W Steve Spear↗
NASA NTRS1998

Carbon Nanotube Based Nano-Electro-Mechanical Systems (NEMS)

Carbon nanotubes (CNT) enable nanoelectromechanical systems (NEMS) because of their inherent nanostructure, intrinsic electric conductivity and mechanical resilience. The collaborative work between Stanford (experiment) and NASA Ames (theory and simulation) has made progress in two types of CNT based NEMS for nanoelectronics and sensor applications. The CNT tipped scanning probe microscopy (SPM) is a NEMS in which CNT tips are used for nanoscale probing, imaging and manipulating. It showed great improvement in probing surfaces and biological systems over conventional tips. We have recently applied it to write (lithography) and read (image) uniform SiO2 lines on large Si surface area at speed up to 0.5 mm per s. Preliminary work using approximately 10 nm multiwall nanotube tips produced approximately 10 nm structures and showed that the CNT tips didn't wear down when crashed as conventional tips often do. This presents a solution to the long standing tip-wear problem in SPM nanolithography. We have also explored potential of CNT tips in imaging DNA in water. Preliminary experiment using 10 nm CNT tips reached 5 nm resolution. The 1 nm nanolithography and 1 nm DNA imaging can be expected by using approximately 1 nm CNT tips. In contrast to CNT tipped SPM, we also fabricated CNT devices on silicon wafer in which CNTs connect patterned metallic lines on SiO2/Si by a simple chemical vapor deposition process. Using conventional lithography for silicon wafer, we have been able to obtain CNT based transistors and sensors. Investigations of the CNT NEMS as physical, biological and chemical sensors are in progress and will be discussed.

Han, Jie↗
NASA NTRS2005

Verification of a 2 kWe Closed-Brayton-Cycle Power Conversion System Mechanical Dynamics Model

Vibration test data from an operating 2 kWe closed-Brayton-cycle (CBC) power conversion system (PCS) located at the NASA Glenn Research Center was used for a comparison with a dynamic disturbance model of the same unit. This effort was performed to show that a dynamic disturbance model of a CBC PCS can be developed that can accurately predict the torque and vibration disturbance fields of such class of rotating machinery. The ability to accurately predict these disturbance fields is required before such hardware can be confidently integrated onto a spacecraft mission. Accurate predictions of CBC disturbance fields will be used for spacecraft control/structure interaction analyses and for understanding the vibration disturbances affecting the scientific instrumentation onboard. This paper discusses how test cell data measurements for the 2 kWe CBC PCS were obtained, the development of a dynamic disturbance model used to predict the transient torque and steady state vibration fields of the same unit, and a comparison of the two sets of data.

Ludwiczak, Damian R.↗
NASA NTRS1991

LDEF mechanical systems

Following the Long Duration Exposure Facility (LDEF), the Systems Special Investigation Group (SIG) was involved in a considerable amount of testing of mechanical hardware flown on the LDEF. The primary objectives were to determine the effects of the long term exposure on: (1) mechanisms employed both on the LDEF or as part of individual experiments; (2) structural components; and (3) fasteners. Results of testing the following LDEF hardware are presented: LDEF structure, fasteners, trunnions, end support beam, environment exposure control cannisters, motors, and lubricants. A limited discussion of PI test results is included. The lessons learned are discussed along with the future activities of the System SIG.

Spear, Steve↗
NASA NTRS1996

Derived virtual devices: a secure distributed file system mechanism

This paper presents the design of derived virtual devices (DVDs). DVDs are the mechanism used by the Netstation Project to provide secure shared access to network-attached peripherals distributed in an untrusted network environment. DVDs improve Input/Output efficiency by allowing user processes to perform I/O operations directly from devices without intermediate transfer through the controlling operating system kernel. The security enforced at the device through the DVD mechanism includes resource boundary checking, user authentication, and restricted operations, e.g., read-only access. To illustrate the application of DVDs, we present the interactions between a network-attached disk and a file system designed to exploit the DVD abstraction. We further discuss third-party transfer as a mechanism intended to provide for efficient data transfer in a typical NAP environment. We show how DVDs facilitate third-party transfer, and provide the security required in a more open network environment.

VanMeter, Rodney↗
DOE OSTI2023

Understanding and controlling lithium morphology in solid polymer and gel polymer systems: mechanisms, strategies, and gaps

Lithium metal anode promises the highest theoretical energy density and may enable high energy designs such as lithium–sulfur and lithium–air batteries. However, stable lithium plating and stripping remains a challenge in all electrolyte systems including liquids, polymers, and ceramic electrolytes. In this perspective, we examine literature studies of lithium morphologies in solid polymer and gel polymer systems and compare that with well-studied liquid electrolytes. In solid polymer electrolytes, current density and mechanical properties are both governing parameters for lithium morphology, differing from conventional liquid electrolytes. Stable lithium electrodeposition may be accomplished by a polymer electrolyte with good stiffness operating at significantly lower current densities than its limiting current density, which is defined by the Sand equation. In gel polymer electrolytes, the reported lithium morphology is more similar to that in liquid electrolytes, suggesting similar nucleation and growth mechanisms. Based on experimental evidence and theoretical guidance, current strategies to control lithium morphology in solid polymer and gel polymer electrolytes are summarized. The limitations of these strategies are discussed. In particular, we note the knowledge gap in understanding the solid electrolyte interphase in solid polymer systems and the critical role it can play in regulating lithium morphologies.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Mechanical systems and kinematics

Kinematics is the study of how motion is achieved without reference to the forces that create the motion. This includes the basic structures of all robotic systems, such as links and joints, as well as their mathematical representations. This chapter will provide a brief overview of the types of motion used in additive manufacturing (AM) systems, as well as the mathematical equations that govern them. Rotations are explained using both Euler rotations and quaternions. Combined rotation and translations are shown using homogeneous transform matrices. The robot Jacobian, which relates joint velocities to the end effector translational velocities, is explained with an example calculation. This section will give the reader the basic mathematical foundation in kinematics that is necessary to understand the mechanical underpinnings of path planning for AM systems.

Wang, Peter↗
NASA NTRS1995

Surface Micro-Machining: Progress Towards Micro-Electro Mechanical Systems

Surface micromachining is a technique for building electromechanical systems in silicon. A number of electromechanical systems have been implemented in miniature using the fundamental structural building blocks of tensile and non-tensile springs, differential capacitance sensing cells, and electrostatic drive. The integration of complicated mechanical structures and electrical circuits onto a single chip is expected to improve reliability and testability of systems. Reduction in interconnect wiring, the increased use of automation, and the inherent reliability of integrated circuits will all contribute to increased reliability of systems.

Doscher, James↗
DOE OSTI2022

Integrated Mechanical System Pods (CRADA Final Report)

LBNL provided input to setting the requirements related to indoor air quality and contributed to the development of metrics and test plans to evaluate prototypes of the mechanical pods, which were developed by other members of the project team. The testing of prototypes was conducted by and at Syracuse University, another project partner. LBNL also collaborated with RMI to develop a basic plan for data collection when the pods are deployed for field testing in Phase 2.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
NASA NTRS2011

Carbon-Based Nano-Electro-Mechanical-Systems

We provide an overview of our work where carbon-based nanostructures have been applied to two-dimensional (2D) planar and three-dimensional (3D) vertically-oriented nano-electro-mechanical (NEM) switches. In the first configuration, laterally oriented single-walled nanotubes (SWNTs) synthesized using thermal chemical vapor deposition (CVD) were implemented for forming bridge-type 2D NEMS switches, where switching voltages were on the order of a few volts. In the second configuration, vertically oriented carbon nanofibers (CNFs) synthesized using plasma-enhanced (PE) CVD have been explored for their potential application in 3D NEMS. We have performed nanomechanical measurements on such vertically oriented tubes using nanoindentation to determine the mechanical properties of the CNFs. Electrostatic switching was demonstrated in the CNFs synthesized on refractory metallic nitride substrates, where a nanoprobe was used as the actuating electrode inside a scanning-electron-microscope. The switching voltages were determined to be in the tens of volts range and van der Waals interactions at these length scales appeared significant, suggesting such structures are promising for nonvolatile memory applications. A finite element model was also developed to determine a theoretical pull-in voltage which was compared to experimental results.

Complementary-Metal-Oxide-Semiconductor (CMOS)↗
NASA NTRS1987

Hardware fault insertion and instrumentation system: Mechanization and validation

Automated test capability for extensive low-level hardware fault insertion testing is developed. The test capability is used to calibrate fault detection coverage and associated latency times as relevant to projecting overall system reliability. Described are modifications made to the NASA Ames Reconfigurable Flight Control System (RDFCS) Facility to fully automate the total test loop involving the Draper Laboratories' Fault Injector Unit. The automated capability provided included the application of sequences of simulated low-level hardware faults, the precise measurement of fault latency times, the identification of fault symptoms, and bulk storage of test case results. A PDP-11/60 served as a test coordinator, and a PDP-11/04 as an instrumentation device. The fault injector was controlled by applications test software in the PDP-11/60, rather than by manual commands from a terminal keyboard. The time base was especially developed for this application to use a variety of signal sources in the system simulator.

Benson, J. W.↗