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At least 1,477 records · Page 82

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NASA NTRS2007

Thermal Conductivity of Polymer Copoly(Ethylene Vinyl Acetate)/Nano-Filler Blends

The development of flexible, thermally conductive fabrics and plastic tubes for the Liquid Cooling and Ventilation Garment (LCVG) are needed to reduce weight and improve the mobility, comfort, and performance of future spacesuits. Such improvements would allow astronauts to operate more efficiently and safely for extended extravehicular activities. As a continuation of our work on the improvement of thermal conductivity (TC) of polymeric materials, nanocomposites were prepared from copoly(ethylene vinyl acetate), trade name Elvax 260 , metallized carbon nanofibers (CNFs), nickel (Ni) nanostrands, boron nitride both alone and as mixtures with aluminum powder. The nanocomposites were prepared by melt mixing at various loading levels and subsequently fabricated into several material forms (i.e., ribbons, tubes, and compression molded plaques) for analysis. Ribbons and tubes were extruded to form samples in which the nanoparticles were aligned in the direction of flow. The degree of dispersion and alignment of the nanoparticles were investigated using high-resolution scanning electron microscopy. Tensile properties of the aligned samples were determined at room temperature. TC measurements were performed using a laser flash (Nanoflash ) technique. The TC of the samples was measured in both the direction of alignment as well as transverse. Tubing of comparable dimensions to that used in the LCVG was extruded from select compositions and the thermal conductivities of the tubes measured.

Ghose, S.↗

NASA NTRS2007

Thermal Conductivity of Ethylene Vinyl Acetate Copolymer/Carbon Nanofiller Blends

To reduce weight and increase the mobility, comfort, and performance of future spacesuits, flexible, thermally conductive fabrics and plastic tubes are needed for the Liquid Cooling and Ventilation Garment. Such improvements would allow astronauts to operate more efficiently and safely for extended extravehicular activities. As an approach to raise the thermal conductivity (TC) of an ethylene vinyl acetate copolymer (Elvax 260), it was compounded with three types of carbon based nanofillers: multi-walled carbon nanotubes (MWCNTs), vapor grown carbon nanofibers (CNFs), and expanded graphite (EG). In addition, other nanofillers including metallized CNFs, nickel nanostrands, boron nitride, and powdered aluminum were also compounded with Elvax 260 in the melt at various loading levels. In an attempt to improve compatibility between Elvax 260 and the nanofillers, MWCNTs and EG were modified by surface coating and through noncovalent and covalent attachment of organic molecules containing alkyl groups. Ribbons of the nanocomposites were extruded to form samples in which the nanofillers were aligned in the direction of flow. Samples were also fabricated by compression molding to yield nanocomposites in which the nanofillers were randomly oriented. Mechanical properties of the aligned samples were determined by tensile testing while the degree of dispersion and alignment of nanoparticles were investigated using high-resolution scanning electron microscopy. TC measurements were performed using a laser flash (Nanoflash ) technique. TC of the samples was measured in the direction of, and perpendicular to, the alignment direction. Additionally, tubing was also extruded from select nanocomposite compositions and the TC and mechanical flexibility measured.

Ghose, S.↗

NASA NTRS1941

Performance Characteristics of an Aircraft Engine with Exhaust Turbine Supercharger, Special Report

The Pratt and Whitney Aircraft company and the Naval Aircraft Factory of the United States Navy cooperated in a laboratory and flight program of tests on an exhaust turbine supercharger. Two series of dynamometer tests of the engine super-charger combination were completed under simulated altitude conditions. One series of hot gas-chamber tests was conducted by the manufacturer of the supercharger. Flight demonstrations of the supercharger installed in a twin-engine flying boat were terminated by failure of the turbine wheels. The analysis of the results indicated that a two-stage supercharger with the first-stage exhaust turbine driven will deliver rated power for a given indicated power to a higher altitude, will operate more efficiently, and will require simpler controls than a similar engine with the first stage of the supercharger driven from the crankshaft through multispeed gears.

Lester, E. M.↗

NASA NTRS2010

System for Hydrogen Sensing

A low-power, wireless gas-sensing system is designed to safeguard the apparatus to which it is attached, as well as associated personnel. It also ensures the efficiency and operational integrity of the hydrogen-powered apparatus. This sensing system can be operated with lower power consumption (less than 30 nanowatts), but still has a fast response. The detecting signal can be wirelessly transmitted to remote locations, or can be posted on the Web. This system can also be operated by harvesting energy.

Lin, Jenshan↗

NASA NTRS2010

Part-Task Simulation of Synthetic and Enhanced Vision Concepts for Lunar Landing

During Apollo, the constraints placed by the design of the Lunar Module (LM) window for crew visibility and landing trajectory were a major problem. Lunar landing trajectories were tailored to provide crew visibility using nearly 70 degrees look-down angle from the canted LM windows. Apollo landings were scheduled only at specific times and locations to provide optimal sunlight on the landing site. The complications of trajectory design and crew visibility are still a problem today. Practical vehicle designs for lunar lander missions using optimal or near-optimal fuel trajectories render the natural vision of the crew from windows inadequate for the approach and landing task. Further, the sun angles for the desirable landing areas in the lunar polar regions create visually powerful, season-long shadow effects. Fortunately, Synthetic and Enhanced Vision (S/EV) technologies, conceived and developed in the aviation domain, may provide solutions to this visibility problem and enable additional benefits for safer, more efficient lunar operations. Piloted simulation evaluations have been conducted to assess the handling qualities of the various lunar landing concepts, including the influence of cockpit displays and the informational data and formats. Evaluation pilots flew various landing scenarios with S/EV displays. For some of the evaluation trials, an eye glasses-mounted, monochrome monocular display, coupled with head tracking, was worn. The head-worn display scene consisted of S/EV fusion concepts. The results of this experiment showed that a head-worn system did not increase the pilot s workload when compared to using just the head-down displays. As expected, the head-worn system did not provide an increase in performance measures. Some pilots commented that the head-worn system provided greater situational awareness compared to just head-down displays.

Arthur, Jarvis J., III↗

NASA NTRS2010

Maglev Facility for Simulating Variable Gravity

An improved magnetic levitation apparatus ("Maglev Facility") has been built for use in experiments in which there are requirements to impose variable gravity (including zero gravity) in order to assess the effects of gravity or the absence thereof on physical and physiological processes. The apparatus is expected to be especially useful for experiments on the effects of gravity on convection, boiling, and heat transfer in fluids and for experiments on mice to gain understanding of bone loss induced in human astronauts by prolonged exposure to reduced gravity in space flight. The maglev principle employed by the apparatus is well established. Diamagnetic cryogenic fluids such as liquid helium have been magnetically levitated for studying their phase transitions and critical behaviors. Biological entities consist mostly of diamagnetic molecules (e.g., water molecules) and thus can be levitated by use of sufficiently strong magnetic fields having sufficiently strong vertical gradients. The heart of the present maglev apparatus is a vertically oriented superconducting solenoid electromagnet (see figure) that generates a static magnetic field of about 16 T with a vertical gradient sufficient for levitation of water in normal Earth gravity. The electromagnet is enclosed in a Dewar flask having a volume of 100 L that contains liquid helium to maintain superconductivity. The Dewar flask features a 66-mm-diameter warm bore, lying within the bore of the magnet, wherein experiments can be performed at room temperature. The warm bore is accessible from its top and bottom ends. The superconducting electromagnet is run in the persistent mode, in which the supercurrent and the magnetic field can be maintained for weeks with little decay, making this apparatus extremely cost and energy efficient to operate. In addition to water, this apparatus can levitate several common fluids: liquid hydrogen, liquid oxygen, methane, ammonia, sodium, and lithium, all of which are useful, variously, as rocket fuels or as working fluids for heat transfer devices. A drop of water 45 mm in diameter and a small laboratory mouse have been levitated in this apparatus.

Liu, Yuanming↗

NASA NTRS2011

Flying Unmanned Aircraft: A Pilot's Perspective

The National Aeronautics and Space Administration (NASA) is pioneering various Unmanned Aircraft System (UAS) technologies and procedures which may enable routine access to the National Airspace System (NAS), with an aim for Next Gen NAS. These tools will aid in the development of technologies and integrated capabilities that will enable high value missions for science, security, and defense, and open the door to low-cost, extreme-duration, stratospheric flight. A century of aviation evolution has resulted in accepted standards and best practices in the design of human-machine interfaces, the displays and controls of which serve to optimize safe and efficient flight operations and situational awareness. The current proliferation of non-standard, aircraft-specific flight crew interfaces in UAS, coupled with the inherent limitations of operating UAS without in-situ sensory input and feedback (aural, visual, and vestibular cues), has increased the risk of mishaps associated with the design of the "cockpit." The examples of current non- or sub- standard design features range from "annoying" and "inefficient", to those that are difficult to manipulate or interpret in a timely manner, as well as to those that are "burdensome" and "unsafe." A concerted effort is required to establish best practices and standards for the human-machine interfaces, for the pilot as well as the air traffic controller. In addition, roles, responsibilities, knowledge, and skill sets are subject to redefining the terms, "pilot" and "air traffic controller", with respect to operating UAS, especially in the Next-Gen NAS. The knowledge, skill sets, training, and qualification standards for UAS operations must be established, and reflect the aircraft-specific human-machine interfaces and control methods. NASA s recent experiences flying its MQ-9 Ikhana in the NAS for extended duration, has enabled both NASA and the FAA to realize the full potential for UAS, as well as understand the implications of current limitations. Ikhana is a Predator-B/Reaper UAS, built by General Atomics, Aeronautical Systems, Inc., and modified for research. Since 2007, the aircraft has been flown seasonally with a wing-mounted pod containing an infrared scanner, utilized to provide real-time wildfire geo-location data to various fire-fighting agencies in the western U.S. The multi-agency effort included an extensive process to obtain flight clearance from the FAA to operate under special provisions, given that UAS in general do not fully comply with current airspace regulations (e.g. sense-and-avoid requirements).

Pestana, Mark E.↗

NASA NTRS2011

Wireless Inductive Power Device Suppresses Blade Vibrations

Vibration in turbomachinery can cause blade failures and leads to the use of heavier, thicker blades that result in lower aerodynamic efficiency and increased noise. Metal and/or composite fatigue in the blades of jet engines has resulted in blade destruction and loss of lives. Techniques for suppressing low-frequency blade vibration, such as gtuned circuit resistive dissipation of vibratory energy, h or simply "passive damping," can require electronics incorporating coils of unwieldy dimensions and adding unwanted weight to the rotor. Other approaches, using vibration-dampening devices or damping material, could add undesirable weight to the blades or hub, making them less efficient. A wireless inductive power device (WIPD) was designed, fabricated, and developed for use in the NASA Glenn's "Dynamic Spin Rig" (DSR) facility. The DSR is used to simulate the functionality of turbomachinery. The relatively small and lightweight device [10 lb (approx.=4.5 kg)] replaces the existing venerable and bulky slip-ring. The goal is the eventual integration of this technology into actual turbomachinery such as jet engines or electric power generators, wherein the device will facilitate the suppression of potentially destructive vibrations in fan blades. This technology obviates slip rings, which require cooling and can prove unreliable or be problematic over time. The WIPD consists of two parts: a remote element, which is positioned on the rotor and provides up to 100 W of electrical power to thin, lightweight piezoelectric patches strategically placed on/in fan blades; and a stationary base unit that wirelessly communicates with the remote unit. The base unit supplies inductive power, and also acts as an input and output corridor for wireless measurement, and active control command to the remote unit. Efficient engine operation necessitates minimal disturbance to the gas flow across the turbine blades in any effort to moderate blade vibration. This innovation makes it possible to moderate vibration on or in turbomachinery blades by providing 100 W of wireless electrical power and actuation control to thin, lightweight vibration-suppressing piezoelectric patches (eight actuation and eight sensor patches in this prototype, for a total of 16 channels) positioned strategically on the surface of, or within, titanium fan blades, or embedded in composite fan blades. This approach moves significantly closer to the ultimate integration of "active" vibration suppression technology into jet engines and other turbomachinery devices such as turbine electrical generators used in the power industry. The novel feature of this device is in its utilization of wireless technology to simultaneously sense and actively control vibration in rotating or stationary turbomachinery blades using piezoelectric patches. In the past, wireless technology was used solely for sensing and diagnostics. This technology, however, will accomplish much more, in terms of simultaneously sensing, suppressing blade vibration, and making it possible for detailed study of vibration impact in turbomachinery blades.

Morrison, Carlos R.↗

NASA NTRS2012

Testing of a Liquid Oxygen/Liquid Methane Reaction Control Thruster in a New Altitude Rocket Engine Test Facility

A relocated rocket engine test facility, the Altitude Combustion Stand (ACS), was activated in 2009 at the NASA Glenn Research Center. This facility has the capability to test with a variety of propellants and up to a thrust level of 2000 lbf (8.9 kN) with precise measurement of propellant conditions, propellant flow rates, thrust and altitude conditions. These measurements enable accurate determination of a thruster and/or nozzle s altitude performance for both technology development and flight qualification purposes. In addition the facility was designed to enable efficient test operations to control costs for technology and advanced development projects. A liquid oxygen-liquid methane technology development test program was conducted in the ACS from the fall of 2009 to the fall of 2010. Three test phases were conducted investigating different operational modes and in addition, the project required the complexity of controlling propellant inlet temperatures over an extremely wide range. Despite the challenges of a unique propellant (liquid methane) and wide operating conditions, the facility performed well and delivered up to 24 hot fire tests in a single test day. The resulting data validated the feasibility of utilizing this propellant combination for future deep space applications.

Meyer, Michael L.↗

NASA NTRS2012

Apparatus and methods for manipulation and optimization of biological systems

The invention provides systems and methods for manipulating, e.g., optimizing and controlling, biological systems, e.g., for eliciting a more desired biological response of biological sample, such as a tissue, organ, and/or a cell. In one aspect, systems and methods of the invention operate by efficiently searching through a large parametric space of stimuli and system parameters to manipulate, control, and optimize the response of biological samples sustained in the system, e.g., a bioreactor. In alternative aspects, systems include a device for sustaining cells or tissue samples, one or more actuators for stimulating the samples via biochemical, electromagnetic, thermal, mechanical, and/or optical stimulation, one or more sensors for measuring a biological response signal of the samples resulting from the stimulation of the sample. In one aspect, the systems and methods of the invention use at least one optimization algorithm to modify the actuator's control inputs for stimulation, responsive to the sensor's output of response signals. The compositions and methods of the invention can be used, e.g., to for systems optimization of any biological manufacturing or experimental system, e.g., bioreactors for proteins, e.g., therapeutic proteins, polypeptides or peptides for vaccines, and the like, small molecules (e.g., antibiotics), polysaccharides, lipids, and the like. Another use of the apparatus and methods includes combination drug therapy, e.g. optimal drug cocktail, directed cell proliferations and differentiations, e.g. in tissue engineering, e.g. neural progenitor cells differentiation, and discovery of key parameters in complex biological systems.

Ho, Chih-Ming↗

NASA NTRS2012

Towards an Improved Pilot-Vehicle Interface for Highly Automated Aircraft: Evaluation of the Haptic Flight Control System

The control automation and interaction paradigm (e.g., manual, autopilot, flight management system) used on virtually all large highly automated aircraft has long been an exemplar of breakdowns in human factors and human-centered design. An alternative paradigm is the Haptic Flight Control System (HFCS) that is part of NASA Langley Research Center s Naturalistic Flight Deck Concept. The HFCS uses only stick and throttle for easily and intuitively controlling the actual flight of the aircraft without losing any of the efficiency and operational benefits of the current paradigm. Initial prototypes of the HFCS are being evaluated and this paper describes one such evaluation. In this evaluation we examined claims regarding improved situation awareness, appropriate workload, graceful degradation, and improved pilot acceptance. Twenty-four instrument-rated pilots were instructed to plan and fly four different flights in a fictitious airspace using a moderate fidelity desktop simulation. Three different flight control paradigms were tested: Manual control, Full Automation control, and a simplified version of the HFCS. Dependent variables included both subjective (questionnaire) and objective (SAGAT) measures of situation awareness, workload (NASA-TLX), secondary task performance, time to recognize automation failures, and pilot preference (questionnaire). The results showed a statistically significant advantage for the HFCS in a number of measures. Results that were not statistically significant still favored the HFCS. The results suggest that the HFCS does offer an attractive and viable alternative to the tactical components of today s FMS/autopilot control system. The paper describes further studies that are planned to continue to evaluate the HFCS.

Schutte, Paul↗

NASA NTRS2012

Particle Filtering for Model-Based Anomaly Detection in Sensor Networks

A novel technique has been developed for anomaly detection of rocket engine test stand (RETS) data. The objective was to develop a system that postprocesses a csv file containing the sensor readings and activities (time-series) from a rocket engine test, and detects any anomalies that might have occurred during the test. The output consists of the names of the sensors that show anomalous behavior, and the start and end time of each anomaly. In order to reduce the involvement of domain experts significantly, several data-driven approaches have been proposed where models are automatically acquired from the data, thus bypassing the cost and effort of building system models. Many supervised learning methods can efficiently learn operational and fault models, given large amounts of both nominal and fault data. However, for domains such as RETS data, the amount of anomalous data that is actually available is relatively small, making most supervised learning methods rather ineffective, and in general met with limited success in anomaly detection. The fundamental problem with existing approaches is that they assume that the data are iid, i.e., independent and identically distributed, which is violated in typical RETS data. None of these techniques naturally exploit the temporal information inherent in time series data from the sensor networks. There are correlations among the sensor readings, not only at the same time, but also across time. However, these approaches have not explicitly identified and exploited such correlations. Given these limitations of model-free methods, there has been renewed interest in model-based methods, specifically graphical methods that explicitly reason temporally. The Gaussian Mixture Model (GMM) in a Linear Dynamic System approach assumes that the multi-dimensional test data is a mixture of multi-variate Gaussians, and fits a given number of Gaussian clusters with the help of the wellknown Expectation Maximization (EM) algorithm. The parameters thus learned are used for calculating the joint distribution of the observations. However, this GMM assumption is essentially an approximation and signals the potential viability of non-parametric density estimators. This is the key idea underlying the new approach.

Solano, Wanda↗

NASA NTRS2014

Apparatus and Methods for Manipulation and Optimization of Biological Systems

The invention provides systems and methods for manipulating biological systems, for example to elicit a more desired biological response from a biological sample, such as a tissue, organ, and/or a cell. In one aspect, the invention operates by efficiently searching through a large parametric space of stimuli and system parameters to manipulate, control, and optimize the response of biological samples sustained in the system. In one aspect, the systems and methods of the invention use at least one optimization algorithm to modify the actuator's control inputs for stimulation, responsive to the sensor's output of response signals. The invention can be used, e.g., to optimize any biological system, e.g., bioreactors for proteins, and the like, small molecules, polysaccharides, lipids, and the like. Another use of the apparatus and methods includes is for the discovery of key parameters in complex biological systems.

Ho, Chih-Ming↗

NASA NTRS2016

Parametric Modeling Investigation of a Radially-Staged Low-Emission Aviation Combustor

Aviation gas-turbine combustion demands high efficiency, wide operability and minimal trace gas emissions. Performance critical design parameters include injector geometry, combustor layout, fuel-air mixing and engine cycle conditions. The present investigation explores these factors and their impact on a radially staged low-emission aviation combustor sized for a next-generation 24,000-lbf-thrust engine. By coupling multi-fidelity computational tools, a design exploration was performed using a parameterized annular combustor sector at projected 100% takeoff power conditions. Design objectives included nitrogen oxide emission indices and overall combustor pressure loss. From the design space, an optimal configuration was selected and simulated at 7.1, 30 and 85% part-power operation, corresponding to landing-takeoff cycle idle, approach and climb segments. All results were obtained by solution of the steady-state Reynolds-averaged Navier-Stokes equations. Species concentrations were solved directly using a reduced 19-step reaction mechanism for Jet-A. Turbulence closure was obtained using a nonlinear K-epsilon model. This research demonstrates revolutionary combustor design exploration enabled by multi-fidelity physics-based simulation.

design analysis↗

NASA NTRS2016

Design and Development Comparison of Rapid Cycle Amine 1.0, 2.0, and 3.0

The development of the Rapid Cycle Amine (RCA) swing-bed technology for carbon dioxide (CO2) removal has been in progress since favorable results were published in 1996. Shortly thereafter, a prototype was designed, developed, and tested successfully and delivered to Johnson Space Center in 1999. An improved prototype (RCA 1.0) was delivered to NASA in 2006 and sized for the extravehicular activity (EVA). The RCA swing-bed technology is a regenerative system which employs two alternating solid-amine sorbent beds to remove CO2 and water. The two-bed design employs a chemisorption process whereby the beds alternate between adsorption and desorption. This process provides for an efficient RCA operation that enables one bed to be in adsorb (uptake) mode, while the other is in the desorb (regeneration) mode. The RCA has progressed through several iterations of technology readiness levels. Test articles have now been designed, developed, and tested for the advanced space suit portable life support system (PLSS) including RCA 1.0, RCA 2.0, and RCA 3.0. The RCA 3.0 was the most recent RCA fabrication and was delivered to NASA-JSC in June 2015. The RCA 1.0 test article was designed with a pneumatically actuated linear motion spool valve. The RCA 2.0 and 3.0 test articles were designed with a valve assembly which allows for switching between uptake and regeneration modes while minimizing gas volume losses to the vacuum source. RCA 2.0 and 3.0 also include an embedded controller design to control RCA operation and provide the capability of interfacing with various sensors and other ventilation loop components. The RCA technology is low power, small, and has fulfilled all test requirements levied upon the technology during development testing thus far. This paper will provide an overview of the design and development of RCA 1.0, 2.0 and 3.0 including detail differences between the design specifications of each. Nomenclature.

Chullen, Cinda↗

NASA NTRS2015

Statistical Engineering in Air Traffic Management Research

NASA is working to develop an integrated set of advanced technologies to enable efficient arrival operations in high-density terminal airspace for the Next Generation Air Transportation System. This integrated arrival solution is being validated and verified in laboratories and transitioned to a field prototype for an operational demonstration at a major U.S. airport. Within NASA, this is a collaborative effort between Ames and Langley Research Centers involving a multi-year iterative experimentation process. Designing and analyzing a series of sequential batch computer simulations and human-in-the-loop experiments across multiple facilities and simulation environments involves a number of statistical challenges. Experiments conducted in separate laboratories typically have different limitations and constraints, and can take different approaches with respect to the fundamental principles of statistical design of experiments. This often makes it difficult to compare results from multiple experiments and incorporate findings into the next experiment in the series. A statistical engineering approach is being employed within this project to support risk-informed decision making and maximize the knowledge gained within the available resources. This presentation describes a statistical engineering case study from NASA, highlights statistical challenges, and discusses areas where existing statistical methodology is adapted and extended.

Wilson, Sara R.↗

NASA NTRS2016

Integrated Turbine Tip Clearance and Gas Turbine Engine Simulation

Gas turbine compressor and turbine blade tip clearance (i.e., the radial distance between the blade tip of an axial compressor or turbine and the containment structure) is a major contributing factor to gas path sealing, and can significantly affect engine efficiency and operational temperature. This paper details the creation of a generic but realistic high pressure turbine tip clearance model that may be used to facilitate active tip clearance control system research. This model uses a first principles approach to approximate thermal and mechanical deformations of the turbine system, taking into account the rotor, shroud, and blade tip components. Validation of the tip clearance model shows that the results are realistic and reflect values found in literature. In addition, this model has been integrated with a gas turbine engine simulation, creating a platform to explore engine performance as tip clearance is adjusted. Results from the integrated model explore the effects of tip clearance on engine operation and highlight advantages of tip clearance management.

aerothermodynamics↗

NASA NTRS2016

Integrated Turbine Tip Clearance and Gas Turbine Engine Simulation

gas path dynamics↗