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At least 487 records · Page 27

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NASA NTRS2016

Relationships Between Vestibular Measures as Potential Predictors for Spaceflight Sensorimotor Adaptation

Introduction: During space exploration missions astronauts are exposed to a series of novel sensorimotor environments, requiring sensorimotor adaptation. Until adaptation is complete, sensorimotor decrements occur, affecting critical tasks such as piloted landing or docking. Of particularly interest are locomotion tasks such as emergency vehicle egress or extra-vehicular activity. While nearly all astronauts eventually adapt sufficiently, it appears there are substantial individual differences in how quickly and effectively this adaptation occurs. These individual differences in capacity for sensorimotor adaptation are poorly understood. Broadly, we aim to identify measures that may serve as pre-flight predictors of and individual's adaptation capacity to spaceflight-induced sensorimotor changes. As a first step, since spaceflight is thought to involve a reinterpretation of graviceptor cues (e.g. otolith cues from the vestibular system) we investigate the relationships between various measures of vestibular function in humans. Methods: In a set of 15 ground-based control subjects, we quantified individual differences in vestibular function using three measures: 1) ocular vestibular evoked myogenic potential (oVEMP), 2) computerized dynamic posturography and 3) vestibular perceptual thresholds. oVEMP responses are elicited using a mechanical stimuli approach. Computerized dynamic posturography was used to quantify Sensory Organization Tests (SOTs), including SOT5M which involved performing pitching head movements while balancing on a sway-reference support surface with eyes closed. We implemented a vestibular perceptual threshold task using the tilt capabilities of the Tilt-Translation Sled (TTS) at JSC. On each trial, the subject was passively roll-tilted left ear down or right ear down in the dark and verbally provided a forced-choice response regarding which direction they felt tilted. The motion profile was a single-cycle sinusoid of angular acceleration with a duration of 5 seconds (frequency of 0.2 Hz), which was selected as it requires sensory integration of otolith and semicircular canal cues. Stimuli direction was randomized and magnitude was determined using an adaptive sampling procedure. One hundred trials were provided and each subject's responses were fit with a psychometric curve to estimate the subject's threshold. Results: Roll tilt perceptual thresholds at 0.2 Hz ranged from 0.5 degrees to 1.82 degrees across the 15 subjects (geometric mean of 1.04 degrees), consistent with previous studies. The inter-individual variability in thresholds may be able to help explain individual differences observed in sensorimotor adaptation to spaceflight. Analysis is ongoing for the oVEMPS and computerized dynamic posturography to identify relationships between the various vestibular measures. Discussion: Predicting individual differences in sensorimotor adaptation is critical both for the development of personalized countermeasures and mission planning. Here we aim to develop a basis of vestibular tests and parameters which may serve as predictors of individual differences in sensorimotor adaptability through studying the relationship between these measures.

Clark, T. K.↗

NASA NTRS1998

Mechanical Behavior and Analytical Modeling of Melt-Infiltrated SiC/SiC Woven Composite

The desirable properties in ceramic matrix composites (CMCs), such as high temperature strength, corrosion resistance, high toughness, low density, or good creep resistance have led to increased use of CMCs in high-speed engine structural components and structures that operate in extreme temperature and hostile aero-thermo-chemical environments. Ceramic matrix composites have been chosen for turbine material in the design of 21st century civil propulsion systems to achieve high fuel economy, improved reliability, extended life, and reduced cost. Most commercial CMCs are manufactured using a chemical vapor infiltration (CVI) process. However, a lower cost fabrication known as melt-infiltration process is also providing CMCs marked for use in hot sections of high-speed civil transports. Limited samples of a SiC/SiC melt-infiltrated woven composites are being investigated at room and elevated temperature below and above matrix cracking. These samples show graceful failure and toughness at room temperature with a reduction in strength and modulus at elevated temperatures. A generic finite element model is also being developed to predict monotonic and cyclic loading behavior of the woven composite. Use of the initial test data from the woven composite is being used for the development of the analytical model. This model is the first of a iterative process leading towards the development the model's capability to predict behavior at room and elevated temperature for monotonic and cyclic loading. The purpose of this paper is to report on the material and mechanical findings of the SiC/SiC melt-infiltrated woven composite and progress on the development of the finite element model.

Lang, J.↗

NASA NTRS2011

Enterprise Reference Library

Introduction: Johnson Space Center (JSC) offers two extensive libraries that contain journals, research literature and electronic resources. Searching capabilities are available to those individuals residing onsite or through a librarian s search. Many individuals have rich collections of references, but no mechanisms to share reference libraries across researchers, projects, or directorates exist. Likewise, information regarding which references are provided to which individuals is not available, resulting in duplicate requests, redundant labor costs and associated copying fees. In addition, this tends to limit collaboration between colleagues and promotes the establishment of individual, unshared silos of information The Integrated Medical Model (IMM) team has utilized a centralized reference management tool during the development, test, and operational phases of this project. The Enterprise Reference Library project expands the capabilities developed for IMM to address the above issues and enhance collaboration across JSC. Method: After significant market analysis for a multi-user reference management tool, no available commercial tool was found to meet this need, so a software program was built around a commercial tool, Reference Manager 12 by The Thomson Corporation. A use case approach guided the requirements development phase. The premise of the design is that individuals use their own reference management software and export to SharePoint when their library is incorporated into the Enterprise Reference Library. This results in a searchable user-specific library application. An accompanying share folder will warehouse the electronic full-text articles, which allows the global user community to access full -text articles. Discussion: An enterprise reference library solution can provide a multidisciplinary collection of full text articles. This approach improves efficiency in obtaining and storing reference material while greatly reducing labor, purchasing and duplication costs. Most importantly, increasing collaboration across research groups provides unprecedented access to information relevant to NASA s mission. Conclusion: This project is an expansion and cost-effective leveraging of the existing JSC centralized library. Adding key word and author search capabilities and an alert function for notifications about new articles, based on users profiles, represent examples of future enhancements.

Bickham, Grandin↗

DOE OSTI2026

An adaptive model-free robotic force control strategy for hydrodynamic real-time hybrid simulation of floating offshore wind turbines

Real-time hybrid simulation (RTHS) - a cyber-physical testing approach - promises to enhance the simulation fidelity of the model-scale experiments used to prototype floating offshore wind turbines (FOWTs). In hydrodynamic RTHS (hydro-RTHS), actuators emulate aerodynamic forces on model-scale FOWT specimens subjected to physical waves in a hydrodynamic laboratory. Robotic arms are promising candidates for actuation in hydro-RTHS due to their compact multi-degree-of-freedom (DOF) capabilities. Unlike classical RTHS for seismic applications, which typically relies on displacement control, hydro-RTHS requires 6-DOF force control on newly designed floating prototypes in a model-scale setting, which presents significant challenges, including modeling uncertainties, directional asymmetry, configuration drift, bandwidth limitations, and time-varying delays. To mitigate these constraints without extensive pre-test calibration, this study proposes an adaptive model-free robotic force control strategy that combines task-space explicit force control with a secondary joint-space pose-keeping task. The Adaptive Feedforward Compensator (AFC) is integrated into the force control loop to compensate for time-varying delay. Experimental testing was conducted using a Franka Emika Panda robotic arm with a 1:50 scale FOWT specimen under operational wind and wave conditions. Results demonstrate stable and consistent 6-DOF force tracking. Effective delay compensation was observed, with low-frequency delay reductions ranging from 71.4% to 91.8% and improvements in low-frequency surge force tracking of 25.0% to 52.1%. This study enhances robotic actuation performance in hydro-RTHS and introduces a force control strategy that supports reliable robotic operation in uncertain floating environments. Future work will explore disturbance-observer mechanisms to further enhance wave rejection capabilities under extreme wind and wave conditions.

17 WIND ENERGY↗

NASA NTRS2014

Simulating the Impact Response of Composite Airframe Components

In 2010, NASA Langley Research Center obtained residual hardware from the US Army's Survivable Affordable Repairable Airframe Program (SARAP). The hardware consisted of a composite fuselage section that was representative of the center section of a Black Hawk helicopter. The section was fabricated by Sikorsky Aircraft Corporation and designated the Test Validation Article (TVA). The TVA was subjected to a vertical drop test in 2008 to evaluate a tilting roof concept to limit the intrusion of overhead mass items, such as the rotor transmission, into the fuselage cabin. As a result of the 2008 test, damage to the hardware was limited primarily to the roof. Consequently, when the post-test article was obtained in 2010, the roof area was removed and the remaining structure was cut into six different types of test specimens including: (1) tension and compression coupons for material property characterization, (2) I-beam sections, (3) T-sections, (4) cruciform sections, (5) a large subfloor section, and (6) a forward framed fuselage section. In 2011, NASA and Sikorsky entered into a cooperative research agreement to study the impact responses of composite airframe structures and to evaluate the capabilities of the explicit transient dynamic finite element code, LS-DYNA®, to simulate these responses including damage initiation and progressive failure. Finite element models of the composite specimens were developed and impact simulations were performed. The properties of the composite material were represented using both a progressive in-plane damage model (Mat 54) and a continuum damage mechanics model (Mat 58) in LS-DYNA. This paper provides test-analysis comparisons of time history responses and the location and type of damage for representative I-beam, T-section, and cruciform section components.

Jackson, Karen E.↗

DOE OSTI2025

A compact electromagnetic neutron nutator for precise neutron spin manipulation

A superconducting electromagnetic nutator (EMN) capable of generating a magnetic field vector along an arbitrary direction on a 2D plane has been designed. Its performance in precisely manipulating the neutron polarization vector has been tested at the HB2-D polarized development beamline at the High Flux Isotope Reactor. Unlike mechanical nutators that require physical handling or motor-driven actuation to rotate the magnetic field, the magnitude and orientation of the magnetic field produced by the EMN can be controlled electromagnetically. Further, the compact design (~15 mm depth, not including cryogenic housing) of this device ensures ease of coupling within existing superconducting neutron spin manipulation devices, such as magnetic Wollaston prisms (MWP), resonant radio frequency (RF) flippers, spherical neutron polarimetry (SNP) devices, etc.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

NASA NTRS1979

Design alternatives for the Shuttle Infrared Telescope Facility

The paper discusses the Shuttle Infrared Telescope Facility (SIRTF), a versatile astronomical telescope that can accomodate photometric, spectroscopic, and polarimetric measurements. It is expected to be 100 to 1000 times more sensitive than any existing infrared telescope; detailed designs of cooled IR telescopes were made for the Infrared Astronomical Satellite and the Small Helium Cooled Infrared Telescope for Spacelab 2. Rocket tests verified the capability of using superfluid helium as a cryogen in zero gravity. Constraints on funds for Shuttle payloads require an evolutionary approach to the development of the full potential of SIRTF, necessitating consideration of design alternatives involving the optical configuration, the cryogen, the mechanical structure, and size of SIRTF.

Witteborn, F. C.↗

NASA NTRS1983

Low-cost single-crystal turbine blades, volume 1

The exothermic casting process was successfully developed into a low cost nonproprietary method for producing single crystal (SC) castings. Casting yields were lower than expected, on the order of 20 percent, but it is felt that the casting yield could be significantly improved with minor modifications to the process. Single crystal Mar-M 247 and two derivative SC alloys were developed. NASAIR 100 and SC Alloy 3 were fully characterized through mechanical property testing. SC Mar-M 247 shows no significant improvement in strength over directionally solidified (DS) Mar-M 247, but the derivative alloys, NASAIR 100 and Alloy 3, show significant tensile and fatigue improvements. The 1000 hr/238 MPa (20 ksi) stress rupture capability compared to DS Mar-M 247 was improved over 28 C. Firtree testing, holography, and strain gauge rig testing were used to evaluate the effects of the anisotropic characteristics of single crystal materials. In general, the single crystal material behaved similarly to DS Mar-M 247. Two complete engine sets of SC HP turbine blades were cast using the exothermic casting process and fully machined.

Strangman, T. E.↗

NASA NTRS1990

Intelligent Robotic Systems Study (IRSS), phase 2

Under the Intelligent Robotics System Study (IRSS) contract, a generalized robotic control architecture was developed for use with the ProtoFlight Manipulator Arm (PFMA). The controller built for the PFMA provides localized position based force control, teleoperation and advanced path recording and playback capabilities. Various hand controllers can be used with the system in conjunction with a synthetic time delay capability to provide a realistic test bed for typical satellite servicing tasks. The configuration of the IRSS system is illustrated and discussed. The PFMA has six computer controllable degrees of freedom (DOF) plus a seventh manually indexable DOF, making the manipulator a pseudo 7 DOF mechanism. Because the PFMA was not developed to operate in a gravity field, but rather in space, it is counter balanced at the shoulder, elbow and wrist and a spring counterbalance has been added near the wrist to provide additional support. Built with long slender intra-joint linkages, the PFMA has a workspace nearly 2 meters deep and possesses sufficient dexterity to perform numerous satellite servicing tasks. The manipulator is arranged in a shoulder-yaw, pitch, elbow-pitch, and wrist-pitch, yaw, roll configuration, with an indexable shoulder roll joint. Digital control of the PFMA is implemented using a variety of single board computers developed by Heurikon Corporation and other manufacturers. The IRSS controller is designed to be a multi-rate, multi-tasking system. Independent joint servos run at a 134 Hz rate and position based impedance control functions at 67 Hz. Autonomous path generation and hand controller inputs are processed at a 33 Hz.

Source record↗

NASA NTRS1990

Examples of finite element mesh generation using SDRC IDEAS

IDEAS (Integrated Design Engineering Analysis Software) offers a comprehensive package for mechanical design engineers. Due to its multifaceted capabilities, however, it can be manipulated to serve the needs of electrical engineers, also. IDEAS can be used to perform the following tasks: system modeling, system assembly, kinematics, finite element pre/post processing, finite element solution, system dynamics, drafting, test data analysis, and project relational database.

Zapp, John↗

NASA NTRS1994

EM-ANIMATE: A Computer Program for Displaying and Animating Electromagnetic Near-Field and Surface-Current Solutions: Video Supplement to NASA Technical Memorandum 4539

In this video, several examples of electromagnetic field and surface-current animation sequences are shown to demonstrate the visualization capabilities of the EM-ANIMATE computer program. These examples show the animation of total and scattered electric near fields from test bodies of a flat plate, a corner reflector, and a sphere. These test cases show the electric-field behavior caused by different scattering mechanisms through the animation of electromagnetic data from the EM-ANIMATE routine.

Hom, Kam W.↗

NASA NTRS1999

Mars Observer Propulsion and Pyrotechnics Corrective Actions Test Program Status-1999

An extensive propulsion and pyrotechnic test program has been in progress at the NASA White Sands Test Facility since 1995. This program created the capabilities to: accurately measure and characterize pyrovalve combustion product blow-by into propellant systems; characterize valve operation using a Velocity Interferometer System for Any Reflector (VISAR); and evaluate hydrazine and monomethylhydrazine thermal decomposition initiated by blow-by. These capabilities were further utilized and refined this year. Low blow-by pyrovalves manufactured by Conax Florida Corporation continued to be evaluated as a potential corrective measure for blow-by induced propellant explosions. Development and testing of various advanced pyrovalves and investigation of explosion mechanisms also continued. Current and near-term testing includes: evaluation of 3/8 in. Conax pyrovalves and other commercially available valves; development and testing of advanced pyrovalve subcomponent technologies including a zero blow-by pyrovalve ram, composite overwrapped ram cylinder, and a zero particulate generating poppet; investigation of non-destructive evaluation techniques to evaluate pyrovalve ram seals; and testing and modeling of pyrotechnically induced explosive hydrazine decomposition. Evaluation of 3/8 in. Conax valves will include operational margin testing to be accomplished at NASA Langley Research Center. The test program also seeks to compile and format significant amounts of data from this and other pyrovalve test programs to generate a pyrovalve applications handbook. The handbook will facilitate formation of standards that ensure safe spacecraft applications. Current data and future plans are discussed, and community interaction is encouraged.

Saulsberry, Regor↗

NASA NTRS2019

ASPIRE Aerodynamic Models and Flight Performance

The Advanced Supersonic Parachute Inflation Research Experiments (ASPIRE) project waslaunched to develop the capability for testing supersonic parachutes at Mars-relevant conditions.Three initial parachute tests, targeted as a risk-reduction activity for NASA's upcomingMars2020 mission, successfully tested two candidate parachute designs and provided valuabledata on parachute inflation, forces, and aerodynamic behavior. Design of the flight tests dependedon flight mechanics simulations which in turn required aerodynamic models for the payload, andthe parachute. Computational Fluid Dynamics (CFD) was used to generate these models preflightand are compared against the flight data after the tests. For the payload, the reconstructedaerodynamic behavior is close to the pre-flight predictions, but the uncertainties in thereconstructed data are high due to the low dynamic pressures and accelerations during the flightperiod of comparison. For the parachute, the predicted time to inflation agrees well with the preflightmodel; the peak aerodynamic force and the steady state drag on the parachute are withinthe bounds of the pre-flight models, even as the models over-predict the parachute drag atsupersonic Mach numbers. Notably, the flight data does not show the transonic drag decreasepredicted by the pre-flight model. The ASPIRE flight tests provide previously unavailablevaluable data on the performance of a large full-scale parachute behind a slender leading bodyat Mars-relevant Mach number, dynamic pressure and parachute loads. This data is used topropose a new model for the parachute drag behind slender bodies to aid future experiments.

Muppidi, Suman↗

NASA NTRSDate not supplied

Material Response Modeling of Ablative Thermal Protection Systems using PATO

Developing thermal protection systems (TPS) for future space vehicles involves an extensive design and test cycle. A key component of the cycle is determining margins for a safe design that rely on confidence in the performance of the TPS. Predicting the complicated multiphysics phenomena that occur during atmospheric entry requires high-fidelity modeling tools. To this end, the Porous-material Analysis Toolbox based on OpenFOAM (PATO) has been developed. PATO is an open-source software for computing material response of reactive porous materials submitted to high-temperature environments. Recent applications of PATO include computation of the full heatshield 3D material response from the Mars Science Laboratory atmospheric entry and ablation during arc jet testing. Current efforts are underway to loosely couple PATO with other discipline specialized codes including hypersonic computational fluid dynamics (CFD) to assess the effects of pyrolysis-gas blowing into the boundary layer and computational solid mechanics to address modeling of mechanical erosion. Surface phenomena modeling capabilities to address the effects of silicone-based coatings applied to the TPS during flight preparation are also being added.

Thermal Protection Systems↗

NASA NTRSDate not supplied

Material Response Modeling of Ablative Thermal Protection Systems using PATO

Thermal Protection Systems↗

NASA NTRS2020

Sealing Station Mechanisms for the Mars 2020 Rover Sample Caching Subsystem

The Sealing Station is composed of two mechanisms: the Gripper Mechanism, for orientation and support of the Sample Tube during the Hermetic Seal activation activity, as well as ejecting Sample Tubes out of the Rover, and the Ram Mechanism, which produces and applies a high force for seal activation. The Ram Mechanism is a compact high force linear actuator that uses a planetary roller screw (PRS) as the output linear stage, tapered roller bearings (TRB) to support the PRS at the high loads, a set of spur gears supported by cylinder roller bearings, and a brushless motor with a planetary gearhead and magnetic detent brake. This paper describes the role of these mechanisms in the Mars 2020 Rover mission as a part of the Sample Caching Subsystem (SCS) and Adaptive Caching Assembly (ACA) and their interactions with the Hermetic Seal and Sample Tube hardware. We report on development testing performed with the PRS that show it has capability of supporting cross-moment loads, something manufacturers of these components do not rate. Also discussed is the interaction of the passive holding torque from magnetic detent brakes and hardstop preload, setting of a very light preload in the TRB, and the complex linear dyno test equipment used, and how that testing could have been improved.

Grimes-York, Jesse↗

NASA NTRS2022

RVLT Concept Vehicle Powertrain Arrangement Study and Candidate Powertrain System Test Arrangements

This work was motivated by the vision of the NASA’s Revolutionary Vertical Lift Technology (RVLT) Project and project goals to support the Urban Air Mobility mission. A RVLT concept vehicle, namely the side-by-side helicopter with hybrid electric propulsion, was selected to conduct a powertrain study. The specific objectives of this work were to explore powertrain designs for the RVLT side by side hybrid electric concept vehicle to assess powertrain configurations, and in the process identify general trends for design tradeoffs, technology barriers, and research needs. A notional powertrain for the vehicle was created, and this led to identifying some mechanical components for development and testing. Three powertrain component concepts designs were created, namely a pericyclic drive mast gearbox, a control clutch, and an overrunning cutch. The design approach and evolution are documented. A universal combining gearbox was conceived and designed that would extend the capability of a NASA test facility for testing and demonstration of technologies for urban air mobility vehicle powertrains. Candidate powertrain test arrangements as enabled by the proposed universal combining gearbox are explained and depicted.

gears↗

NASA NTRS2026

PROTECT: Production and Reuse of Thermally Efficient Ceramic Thermal Protection Systems

PROTECT (Production and Reuse Of Thermally Efficient Ceramic TPS) is a NASA Early Career Initiative focused on developing the next generation of reusable ceramic thermal protection systems (TPS). This project addresses key challenges in TPS design, including temperature capability, thermal stability, and refurbishment time, by integrating novel material development with predictive modeling. Leveraging enhanced capabilities in NASA’s Porous Microstructure Analysis (PuMA) software, PROTECT introduces new modeling tools to predict the thermal and mechanical behavior of fibrous ceramic materials. These tools enable accurate prediction of performance metrics such as thermal conductivity and structural integrity, reducing reliance on costly physical testing. Preliminary advances in these areas will be presented. To support model validation, PROTECT is building a comprehensive database of raw material properties using advanced characterization techniques, including micro computed tomography (CT) scanning in collaboration with the University of Illinois Urbana-Champaign (UIUC). The presentation will detail the sampling workflows and analysis methods used to generate this detailed microstructural data and how it is used to develop improved models in PuMA. This multi-center collaboration, spanning NASA (JSC, ARC, KSC, GRC), Oak Ridge National Laboratory, UIUC, and SpaceX, is developing tailored TPS solutions for LEO, lunar, and Martian missions. By bridging heritage systems with the demands of modern spaceflight, PROTECT contributes to the advancement of reusable TPS technologies for future exploration missions.

Propulsion, Refractory, and Coating Materials↗