SEARCH · Search NASA

Results for “electromechanical sensors”

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.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

131 records · Page 8

All sources NASA NTRS DOE OSTI

NASA NTRS1997

Adaptive Full Aperture Wavefront Sensor Study

This grant and the work described was in support of a Seven Segment Demonstrator (SSD) and review of wavefront sensing techniques proposed by the Government and Contractors for the Next Generation Space Telescope (NGST) Program. A team developed the SSD concept. For completeness, some of the information included in this report has also been included in the final report of a follow-on contract (H-27657D) entitled "Construction of Prototype Lightweight Mirrors". The original purpose of this GTRI study was to investigate how various wavefront sensing techniques might be most effectively employed with large (greater than 10 meter) aperture space based telescopes used for commercial and scientific purposes. However, due to changes in the scope of the work performed on this grant and in light of the initial studies completed for the NGST program, only a portion of this report addresses wavefront sensing techniques. The wavefront sensing techniques proposed by the Government and Contractors for the NGST were summarized in proposals and briefing materials developed by three study teams including NASA Goddard Space Flight Center, TRW, and Lockheed-Martin. In this report, GTRI reviews these approaches and makes recommendations concerning the approaches. The objectives of the SSD were to demonstrate functionality and performance of a seven segment prototype array of hexagonal mirrors and supporting electromechanical components which address design issues critical to space optics deployed in large space based telescopes for astronomy and for optics used in spaced based optical communications systems. The SSD was intended to demonstrate technologies which can support the following capabilities: Transportation in dense packaging to existing launcher payload envelopes, then deployable on orbit to form a space telescope with large aperture. Provide very large (greater than 10 meters) primary reflectors of low mass and cost. Demonstrate the capability to form a segmented primary or quaternary mirror into a quasi-continuous surface with individual subapertures phased so that near diffraction limited imaging in the visible wavelength region is achieved. Continuous compensation of optical wavefront due to perturbations caused by imperfections, natural disturbances, and equipment induced vibrations/deflections to provide near diffraction limited imaging performance in the visible wavelength region. Demonstrate the feasibility of fabricating such systems with reduced mass and cost compared to past approaches.

Robinson, William G.↗

DOE OSTI2022

Plasma-Assisted Epitaxy of Piezoelectric Sc x Al 1-x N Films on Sapphire for Use in Harsh-Environment Microwave Acoustic Sensors

The Sc x Al 1-x N wurtzite structure has been shown theoretically and experimentally to exhibit significantly higher piezoelectric coupling compared to pure AlN. In this work, a plasma-assisted epitaxial growth method has been used to synthesize epitaxial (0002) Sc x Al 1-x N films on c-sapphire substrates from x = 0.07 to 0.30 by co-evaporating high-purity Sc and Al sources in the presence of a nitrogen plasma generated by an RF plasma source. Epitaxial Sc x Al 1-x N films with highly oriented (0002) grains and in-plane registry were produced on c-sapphire substrates that were pre-exposed to the nitrogen plasma to form an oxynitride seed layer. Growth of Sc x Al 1-x N films was carried out at 930°C under both metal-rich and N-rich conditions using precisely controlled Sc, Al, and N-plasma fluxes. Metal-rich depositions yielded non-(0002)-oriented Sc x Al 1-x N grains and intermetallic ScAl grains. Nitrogen-rich growth with a Sc/Al flux ratio of 1/3 produced the best (0002) epitaxy as determined by x-ray diffraction analysis. Surface acoustic wave resonator (SAWR) devices were fabricated from 500-nm-thick Sc x Al 1-x N and AlN films to extract their electromechanical coupling coefficients, k 2 . As the Sc concentration in the films increases, the degree of (0002) epitaxy is reduced, yet the value of k 2 increases becasue there is more Sc in the wurzite lattice despite the decreased level of (0002) grain alignment. As a result, the use of a 10-nm-thick Si x N y capping layer on top of the Sc x Al 1-x N films aids in preventing etching during SAWR device photolithography and also helps hinder film oxidation up to 800°C.

36 MATERIALS SCIENCE↗

NASA NTRS2017

Development and Test of Robotically Assisted Extravehicular Activity Gloves

Over the past two years, the High Performance EVA Glove (HPEG) project under NASA's Space Technology Mission Directorate (STMD) funded an effort to develop an electromechanically-assisted space suit glove. The project was a collaboration between the Johnson Space Center's Software, Robotics, and Simulation Division and the Crew and Thermal Systems division. The project sought to combine finger actuator technology developed for Robonaut 2 with the softgoods from the ILC Phase VI EVA glove. The Space Suit RoboGlove (SSRG) uses a system of three linear actuators to pull synthetic tendons attached to the glove's fingers to augment flexion of the user's fingers. To detect the user's inputs, the system utilizes a combination of string potentiometers along the back of the fingers and force sensitive resistors integrated into the fingertips of the glove cover layer. This paper discusses the development process from initial concepts through two major phases of prototypes, and the results of initial human testing. Initial work on the project focused on creating a functioning proof of concept, designing the softgoods integration, and demonstrating augmented grip strength with the actuators. The second year of the project focused on upgrading the actuators, sensors, and software with the overall goal of creating a system that moves with the user's fingers in order to reduce fatigue associated with the operation of a pressurized glove system. This paper also discusses considerations for a flight system based on this prototype development and address where further work is required to mature the technology.

Rogers, Jonathan M.↗

NASA NTRS2002

The Use of Probabilistic Methods to Evaluate the Systems Impact of Component Design Improvements on Large Turbofan Engines

Probabilistic Structural Analysis (PSA) is now commonly used for predicting the distribution of time/cycles to failure of turbine blades and other engine components. These distributions are typically based on fatigue/fracture and creep failure modes of these components. Additionally, reliability analysis is used for taking test data related to particular failure modes and calculating failure rate distributions of electronic and electromechanical components. How can these individual failure time distributions of structural, electronic and electromechanical component failure modes be effectively combined into a top level model for overall system evaluation of component upgrades, changes in maintenance intervals, or line replaceable unit (LRU) redesign? This paper shows an example of how various probabilistic failure predictions for turbine engine components can be evaluated and combined to show their effect on overall engine performance. A generic model of a turbofan engine was modeled using various Probabilistic Risk Assessment (PRA) tools (Quantitative Risk Assessment Software (QRAS) etc.). Hypothetical PSA results for a number of structural components along with mitigation factors that would restrict the failure mode from propagating to a Loss of Mission (LOM) failure were used in the models. The output of this program includes an overall failure distribution for LOM of the system. The rank and contribution to the overall Mission Success (MS) is also given for each failure mode and each subsystem. This application methodology demonstrates the effectiveness of PRA for assessing the performance of large turbine engines. Additionally, the effects of system changes and upgrades, the application of different maintenance intervals, inclusion of new sensor detection of faults and other upgrades were evaluated in determining overall turbine engine reliability.

Packard, Michael H.↗

DOE OSTI2021

Development of a new control rod drive mechanism design for the ISU AGN-201M reactor

The Aerojet General Nucleonics (AGN) model 201-Modified, known as the AGN-201M reactor, plays an essential role in the educational and research activities at Idaho State University (ISU). The ISU AGN-201M's original Control Rod Drive Mechanism (CRDM) has been in operation for more than fifty years with no large-scale redesigns. The CRDM is required to eject the fuel rods within one second during a SCRAM event (also known as a 'reactor trip') and adjust the control rods' insertion speed, and keeps the rod insertion sequence correct. The existing control rod drive mechanisms meet these criteria but experience a few concerns due to aging. Concerns include complex maintenance and costly repairs for old electromechanical components, rod position feedback errors, and the impediment of the plate during a SCRAM due to binding of the lead screws of the existing mechanism. During a binding event, the drive mechanism becomes locked, preventing the control rod's magnetic plate from moving in or out under the reactor's normal and emergency operating conditions. Although, the binding has no effect on the ability of the rod to exit the core during the SCRAM. To counteract the concerns and issues with the current CRDM, a new design has been proposed using newer components and a simplified design. The new design utilizes more advanced electric and mechanical components that are commercially available. The new CRDM system is divided into four main aspects: (1) control rod movement design (motor, lead screw, guide rods), (2) control rod ejection (springs, electromagnet), (3) control rod position and feedback (position transducer, microswitches), and (4) material selection and structural analysis. The new design aims to reduce the overall complexity and probability of failure to improve the reactor's overall reliability. With proper material selection and improved structural design, the new drives are lighter with little to no change in structural integrity. The new control rod drive mechanism eliminates binding scenarios by using a single lead screw and implementing additional guide rods. An advanced linear position sensor and microswitches replace the existing and aging synchro system for accurate rod position feedback resulting in better reactivity control. The new design meets the reactor's operational limits by having an average reactivity insertion of 0.065% Δk/k per second, which corresponds to a total control rod insertion time of 19.23 s, while the control rod's ejection time remains less than one second during a SCRAM event. The new design ensures the reactor's long-term viability for educational and research activities by increasing the reliability and safety of operation for years to come.

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗