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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 181 records · Page 10
All sourcesNASA NTRSDOE OSTI
NASA NTRS2003

Analysis of Photothermal Characterization of Layered Materials: Design of Optimal Experiments

In this paper numerical calculations are presented for the steady-periodic temperature in layered materials and functionally-graded materials to simulate photothermal methods for the measurement of thermal properties. No laboratory experiments were performed. The temperature is found from a new Green s function formulation which is particularly well-suited to machine calculation. The simulation method is verified by comparison with literature data for a layered material. The method is applied to a class of two-component functionally-graded materials and results for temperature and sensitivity coefficients are presented. An optimality criterion, based on the sensitivity coefficients, is used for choosing what experimental conditions will be needed for photothermal measurements to determine the spatial distribution of thermal properties. This method for optimal experiment design is completely general and may be applied to any photothermal technique and to any functionally-graded material.

Cole, Kevin D.↗
NASA NTRS2009

Investigating Liquid CO2 as a Coolant for a MTSA Heat Exchanger Design

Metabolic heat regenerated Temperature Swing Adsorption (MTSA) technology is being developed for thermal and carbon dioxide (CO 2) control for a future Portable Life Support System (PLSS), as well as water recycling. CO 2 removal and rejection is accomplished by driving a sorbent through a temperature swing of approximately 210 K to 280 K . The sorbent is cooled to these sub-freezing temperatures by a Sublimating Heat Exchanger (SHX) with liquid coolant expanded to sublimation temperatures. Water is the baseline coolant available on the moon, and if used, provides a competitive solution to the current baseline PLSS schematic. Liquid CO2 (LCO2) is another non-cryogenic coolant readily available from Martian resources which can be produced and stored using relatively low power and minimal infrastructure. LCO 2 expands from high pressure liquid (~5800 kPa) to Mars ambient (0.8 kPa) to produce a gas / solid mixture at temperatures as low as 156 K. Analysis and experimental work are presented to investigate factors that drive the design of a heat exchanger to effectively use this sink. Emphasis is given to enabling efficient use of the CO 2 cooling potential and mitigation of heat exchanger clogging due to solid formation. Minimizing mass and size as well as coolant delivery are also considered. The analysis and experimental work is specifically performed in an MTSA-like application to enable higher fidelity modeling for future optimization of a SHX design. In doing so, the work also demonstrates principles and concepts so that the design can be further optimized later in integrated applications (including Lunar application where water might be a choice of coolant).

Paul, Heather L.↗
NASA NTRS1973

Determination and evaluation of performance limit criteria of fast-response electrohydraulic servosystems

Limit criteria for determining the dynamic performance capabilities of high performance, fast-response (greater than 100 Hz) electrohydraulic servosystems are presented. A detailed analysis of the maximum load locus of these systems is used as a basis for the derivation of improved limit criteria. These criteria predict the maximum performance limits caused by system nonlinearities and physical limitations. The criteria are applied to experimental data to verify their validity. Design criteria which assist in the selection of system components for optimal performance are also discussed.

Zeller, J. R.↗
NASA NTRS1989

An empirical study of the performance of APMOVPE AM0 InP homojunction solar cells as a function of emitter thickness and doping, and base doping

Their excellent radiation resistance and conversion efficiencies greater than 20 percent, measured under global conditions, make InP shallow-homojunction solar cells very attractive for space or terrestrial application. In addition, modeling studies show that, for optimized design, efficiencies of these devices should exceed 20 percent even under AM0 conditions. However, a systematic experimental investigation of the influence of the various cell design parameters on cell performance has not as yet been made. For the n+/p/p+ structures investigated in the previous modeling study, the design parameters include the impurity concentrations and thicknesses of the emitter and base layers. In the work reported here, researchers discuss an experimental investigation of the effects on cell performance of varying the impurity concentrations of the emitter and base and thickness of the emitter.

Wanlass, M. W.↗
NASA NTRS1994

Full-scale testing and analysis of fuselage structure

This paper presents recent results from a program in the Boeing Commercial Airplane Group to study the behavior of cracks in fuselage structures. The goal of this program is to improve methods for analyzing crack growth and residual strength in pressurized fuselages, thus improving new airplane designs and optimizing the required structural inspections for current models. The program consists of full-scale experimental testing of pressurized fuselage panels in both wide-body and narrow-body fixtures and finite element analyses to predict the results. The finite element analyses are geometrically nonlinear with material and fastener nonlinearity included on a case-by-case basis. The analysis results are compared with the strain gage, crack growth, and residual strength data from the experimental program. Most of the studies reported in this paper concern the behavior of single or multiple cracks in the lap joints of narrow-body airplanes (such as 727 and 737 commercial jets). The phenomenon where the crack trajectory is curved creating a 'flap' and resulting in a controlled decompression is discussed.

Miller, M.↗
NASA NTRS2002

The Focal Surface of EUSO Telescope

The Extreme Universe Space Observatory (EUSO) is a science mission under conceptual design for the detection of extremely high energy cosmic rays and neutrinos by the observation of time-resolved images of atmospheric fluorescence photons generated along the extensive air shower, in the near ultraviolet wavelength region. A refractive telescope with double-sided double Fresnel lens will be employed to achieve a large field of view of 60 degrees. The energy and arrival direction of the primary particles will be determined by observing the time evolution of the airshower. The focal surface of the EUSO telescope will be segmented to a few hundred thousand pixels to resolve the entire field of view with the angular resolution of the order of 0.1 degree. The time evolution will be observed with the time resolution of 0.8 microsecond. A large scale array of multianode photomultiplier (MAPMT) is being studied as the EUSO focal surface. The MAPMT array is capable of detecting near ultraviolet photons at single photoelectron level. In this contribution, we will report the present status of the focal surface design including the optimization of anode segmentation and the minimization of the dead area and discuss overall experimental performance in detecting extensive airshowers.

Shimizu, H. M.↗
NASA NTRS2011

Frame-Transfer Gating Raman Spectroscopy for Time-Resolved Multiscalar Combustion Diagnostics

Accurate experimental measurement of spatially and temporally resolved variations in chemical composition (species concentrations) and temperature in turbulent flames is vital for characterizing the complex phenomena occurring in most practical combustion systems. These diagnostic measurements are called multiscalar because they are capable of acquiring multiple scalar quantities simultaneously. Multiscalar diagnostics also play a critical role in the area of computational code validation. In order to improve the design of combustion devices, computational codes for modeling turbulent combustion are often used to speed up and optimize the development process. The experimental validation of these codes is a critical step in accepting their predictions for engine performance in the absence of cost-prohibitive testing. One of the most critical aspects of setting up a time-resolved stimulated Raman scattering (SRS) diagnostic system is the temporal optical gating scheme. A short optical gate is necessary in order for weak SRS signals to be detected with a good signal- to-noise ratio (SNR) in the presence of strong background optical emissions. This time-synchronized optical gating is a classical problem even to other spectroscopic techniques such as laser-induced fluorescence (LIF) or laser-induced breakdown spectroscopy (LIBS). Traditionally, experimenters have had basically two options for gating: (1) an electronic means of gating using an image intensifier before the charge-coupled-device (CCD), or (2) a mechanical optical shutter (a rotary chopper/mechanical shutter combination). A new diagnostic technology has been developed at the NASA Glenn Research Center that utilizes a frame-transfer CCD sensor, in conjunction with a pulsed laser and multiplex optical fiber collection, to realize time-resolved Raman spectroscopy of turbulent flames that is free from optical background noise (interference). The technology permits not only shorter temporal optical gating (down to <1 s, in principle), but also higher optical throughput, thus resulting in a substantial increase in measurement SNR.

Nguyen, Quang-Viet↗
NASA NTRS2006

An Axenic Plant Culture System for Optimal Growth in Long-Term Studies: Design and Maintenance

The symbiotic co-evolution of plants and microbes leads to difficulties in understanding which of the two components is responsible for a given environmental response. Plant-microbe studies greatly benefit from the ability to grow plants in axenic (sterile) culture. Several studies have used axenic plant culture systems, but experimental procedures are often poorly documented, the plant growth environment is not optimal, and axenic conditions are not rigorously verified. We developed a unique axenic system using inert components that promotes plant health and can be kept sterile for at least 70 d. Crested wheatgrass (Agropyron cristatum cv. DII) plants were grown in sand within flow-through glass columns that were positively pressured with filtered air. Plant health was optimized by regulating temperature, light level, CO2 concentration, humidity, and nutrients. The design incorporates several novel aspects, such as pretreatment of the sand with Fe, graduated sand layers to optimize the air-water balance of the root zone, and modification of a laminar flow hood to serve as a plant growth chamber. Adaptations of several sterile techniques were necessary for maintenance of axenic conditions. Axenic conditions were verified by plating and staining leachates as well as rhizoplane stain. This system was designed to study nutrient and water stress effects on root exudates, but is useful for assessing a broad range of plant-microbe-environment interactions. Based on total organic C analysis, 74% of exudates was recovered in the leachate, 6% was recovered in the bulk sand, and 17% was recovered in the rhizosphere sand. Carbon in the leachate after 70 d reached 255 micro-g/d. Fumaric, malic, malonic, oxalic, and succinic acids were measured as components of the root exudates.

Henry, Amelia↗
NASA NTRS1991

Multi-element airfoil optimization for maximum lift at high Reynolds numbers

An experimental study has been performed to assess the maximum lift capability of a supercritical multielement airfoil representative of an advanced transport aircraft wing. The airfoil model was designed with a leading-edge slat and single or two-segment trailing-edge flaps. Optimization work was performed at various slat/flap deflections as well as gap/overhang positions. Landing configurations and the attainment of maximum lift coefficients of 4.5 with single-element flaps and 5.0 with two-segment flaps was emphasized. Test results showed a relatively linear variation of the optimum gap/overhang positioning of the slat versus slat deflection, considerable differences in optimum rigging between single and double segment flaps, and large Reynolds number effects on multielement airfoil optimization.

Valarezo, Walter O.↗
NASA NTRS1972

Outer planet Grand Tour missions photometry/polarimetry experiment critical components study

Work performed during this effort was limited to two primary areas of technical concern: optical design optimization, and sensor selection. An optical system concept was established, and various system components were evaluated through experimental test sequences. Photodetectors were investigated for the applicability in meeting OPGT requirements as constrained by the photometry/polarimetry team directives. The most promising (gallium arsenide PMT) was further experimentally tested to ascertain its behavior with respect to anticipated environmental conditions. Results of testing and summary of the preceding tradeoff study effort are presented.

Pellicori, S. F.↗
NASA NTRS1981

Classical and modern control design of a speed-hold system for a STOL airplane

A speed-hold system for an experimental short takeoff and landing jet airplane has been designed using both classical root-locus and modern optimal control synthesis techniques. The purpose of the speed-hold system is to maintain airspeed during final approach in the presence of wind shears, gusts, engine failures, and pilot control inputs. Designs were based on using airspeed as a single measurement and two symmetrically deployed upper surface blown flaps as a single control. An optimal control law feeding back all the states and the integral of airspeed through constant gains provided superior performance in terms of speed tracking and control surface activity. However, when a constant-gain Kalman filter was inserted to estimate the states using only the measurement of airspeed, the performance of the optimal control law was reduced to the same as that of a much simpler classical proportional-path plus integral-path control law. To improve the performance of the optimal control law, additional measurements would be required.

Blight, J. D.↗
NASA NTRS1985

Evaluation of results of cell electrophoresis experiments on space shuttle STS-3 including pre-flight and post-flight laboratory experiments

The objectives of the red blood cell experiments were to provide a visual check on the electrophoretic process and especially electroosmotic flow in space as well as to provide test separations of non-degradable standard particles for comparison with the separations of the three viable cell types studied on the Apollo-Soyuz Test Project. Determination of the maximum concentrations of cells that can be separated in column electrophore was a significant goal. Two of the eight columns were available for red cell experiments, so two concentrations of human and rabbit RBC mixtures were used. The objectives of another experiment were to evaluate the reproducibility of microgravity electrophoretic separation of living kidney cells, to separate cells with highly viability despite two freeze-thaw cycles, and to optimize the physical conditions of cell separation. Owing to the uncertain heterogeneity of the starting material, the experimental design does not assess resolution in microgravity, but improved separability was sought in comparison to density-gradient electrophoresis or continuous-flow electrophoresis. Efforts were made to increase cell yield and cell viability and to assess reproducibility directly.

Todd, P. W.↗
NASA NTRS1991

Approaches for optimizing the first electronic hyperpolarizability of conjugated organic molecules

Conjugated organic molecules with electron-donating and -accepting moieties can exhibit large electronic second-order nonlinearities, or first hyperpolarizabilities, beta. The present two-state, four-orbital independent-electron analysis of beta leads to the prediction that its absolute value will be maximized at a combination of donor and acceptor strengths for a given conjugated bridge. Molecular design strategies for beta optimization are proposed which give attention to the energetic manipulations of the bridge states. Experimental results have been obtained which support the validity of this approach.

Marder, S. R.↗
NASA NTRS1992

Analysis and design technology for high-speed aircraft structures

Recent high-speed aircraft structures research activities at NASA Langley Research Center are described. The following topics are covered: the development of analytical and numerical solutions to global and local thermal and structural problems, experimental verification of analysis methods, identification of failure mechanisms, and the incorporation of analysis methods into design and optimization strategies. The paper describes recent NASA Langley advances in analysis and design methods, structural and thermal concepts, and test methods.

Starnes, James H., Jr.↗
NASA NTRS1992

Effect of operating conditions on gearbox noise

Low contact ratio spur gears were tested in the NASA gear noise rig to study the noise radiated from the top of the gearbox. The measured sound power from the gearbox top was obtained from a near field acoustic intensity scan taken at 63 nodes just above the surface. The sound power was measured at a matrix of 45 operating speeds and torque levels. Results are presented in the form of a spectral speed map and as a plot of sound power versus torque (at constant speed) and as sound power versus speed (at constant torque). Because of the presence of vibration modes, operating speed was found to have more impact on noise generation than torque level. A NASA gear dynamics code was used to compute the gear tooth dynamic overload at the same 45 operating conditions used for the experiment. Similar trends were found between the analytical results for dynamic tooth overload and experimental results for sound power. Dynamic analysis may be used to design high quality gears with profile relief optimized for minimum dynamic load and noise.

Oswald, Fred B.↗
NASA NTRS2004

A practical six-degree of freedom solar sail dynamics model for optimizing solar sail trajectories with torque constraints

Controlled flight of a solar sail-propelled spacecraft ('sailcraft') is a six-degree-of-freedom dynamics problem. Current state-of-the-art tools that simulate and optimize the trajectories flown by sailcraft do not treat the full kinetic (i.e. force and torque-constrained) motion, instead treating a discrete history of commanded sail attitudes, and either neglecting the sail attitude motion over an integration timestep, or treating the attitude evolution kinematically with a spline or similar treatment. The present paper discusses an aspect of developing a next generation sailcraf trajectory designing optimization tool JPL, for NASA's Solar Sail Spaceflight Simulation Software (SS). The aspect discussed in an experimental approach to modeling full six-degree-of-freedom kinetic motion of a solar sail in a trajectory propagator. Early results from implementing this approach in a new trajectory propagation tool are given.

six-degree-of-freedom↗
NASA NTRS2024

AC and DC Fault Management for Megawatt Electrified Aircraft Electrical Powertrains - Task 2: Power Quality Filtering Using Nanocrystalline Soft Magnetic Inductor

The NASA RTAPS program on AC and DC Fault Management for Megawatt Electrified Power Train is a multi-year joint project with Pratt & Whitney (P&W), Collins Aerospace (CA), and RTX Technology Research Center (RTRC). This research program focuses on the high-voltage distribution issues that present a significant technological obstacle in the adoption of Electrified Aviation Propulsion (EAP) systems. One challenge to the adoption of high-voltage distribution systems with power electronic converters is the need for filter elements to limit the generation and propagation of noise, protect the cable systems from premature aging and prevent against excessive heating within subcomponents due to high-frequency induced currents. While increased distribution voltages aide in reducing the cable mass for a fixed power system, the associated mass with the filtering elements for power electronic converter can grow with increasing distribution voltages – thereby mitigating any benefit associated with increasing the distribution system voltage. To enable high-voltage distribution systems with high system specific power densities, new magnetic materials must be developed. Therefore, the second task of the NASA RTAPS program is associated with the design and application of advanced soft magnetic components for Megawatt class electric propulsion systems, specifically the motor drive system. This report covers the collaborative work between NASA Glenn Research Center (GRC), RTRC, P&W and CA in the development of three types of magnetic components over the span of the three-year program. These critical magnetic components are the DC side EMI filter, which limits the propagation of harmful electromagnetic noise to the rise of the distribution system, and the AC side damping with the dv/dt filter, which limits the fast rise time of the power electronic converter output voltage to limit the degradation on the cable/motor insulation systems. Each of these components are investigated from component level design and are optimized at the system level with a combined modelling and testing effort. In the final experimental evaluation of the NASA developed soft magnetic material with a dv/dt filter, a commercial-off-the-shelf (COTS) magnetic core and the GRC magnetic core are optimized and loaded at 320Arms to evaluate their difference in performance. After a run time of 30 minutes in a MW-class motor driver at RTRC, the NASA GRC cores were found to not only offer a lower temperature rise of nearly 25°𝐶, but also a reduction in measured core loss of 25% (12.75W to 9.5W).

Elecrified Aircraft Propulsion↗
NASA NTRS1976

Design of optimum acoustic treatment for rectangular ducts with flow

A design optimization technique for acoustic treatment in rectangular ducts with uniform mean flow is presented. The technique is based on the acoustic wave solution in terms of series of characteristic duct modes. The analysis allows multiple axial treatment sections along the length of the duct and requires a known modal characterization of the sound source. Conditions of acoustic pressure and acoustic velocity continuity are used to match modal solutions at planes of impedance discontinuity in the duct. Experimental techniques for obtaining this modal characterization are presented. Using duct modes measured at the source plane, the optimization technique is exercised to design an optimized single element liner in a case without mean flow, and optimized single and dual element liners in cases with mean flow. The validity of the program for predicting noise suppression is demonstrated by comparing analytical predictions with measured data for several (non-optimum) cases. Application to treatment design in turbomachinery exhaust ducts is considered.

Motsinger, R. E.↗