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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS2022

Evolution and folding of repeat proteins

Repeat proteins are made with tandem copies of similar amino acid stretches that fold into elongated architectures. These proteins constitute excellent model systems to investigate how evolution relates to structure, folding, and function. Here, we propose a scheme to map evolutionary information at the sequence level to a coarse-grained model for repeat-protein folding and use it to investigate the folding of thousands of repeat proteins. We model the energetics by a combination of an inverse Potts-model scheme with an explicit mechanistic model of duplications and deletions of repeats to calculate the evolutionary parameters of the system at the single-residue level. These parameters are used to inform an Ising-like model that allows for the generation of folding curves, apparent domain emergence, and occupation of intermediate states that are highly compatible with experimental data in specific case studies. We analyzed the folding of thousands of natural Ankyrin repeat proteins and found that a multiplicity of folding mechanisms are possible. Fully cooperative all-or-none transitions are obtained for arrays with enough sequence-similar elements and strong interactions between them, while noncooperative element-by-element intermittent folding arose if the elements are dissimilar and the interactions between them are energetically weak. Additionally, we characterized nucleation-propagation and multidomain folding mechanisms. We show that the global stability and cooperativity of the repeating arrays can be predicted from simple sequence scores.

Ezequiel A. Galpern↗
NASA NTRS1975

Identifying and analyzing methods for reducing the energy consumption of helicopters

The results are presented of a study to identify those helicopter technology areas which would result in the largest energy (or fuel) savings when applied to large tandem (100 passenger) civil helicopters in the 1985 time frame. Baseline aircraft using 1975 technology in the areas of powerplant, rotor efficiency, parasite drag and structure were sized to a very short haul mission of 100 N.M. and a short haul mission of 200 N.M. A systematic parametric analysis was then conducted to assess the impact of technology improvements. Projections of the technology levels that could be obtained in the 1985 time frame were made and the resources estimated to achieve them. Based on these data, the highest payoff (lowest energy) helicopter technologies are identified.

Davis, S. J.↗
NASA NTRS1992

The NASA/Industry Design Analysis Methods for Vibrations (DAMVIBS) Program - A government overview

An overview is presented of government contributions to the program called Design Analysis Methods for Vibrations (DAMV) which attempted to develop finite-element-based analyses of rotorcraft vibrations. NASA initiated the program with a finite-element modeling program for the CH-47D tandem-rotor helicopter. The DAMV program emphasized four areas including: airframe finite-element modeling, difficult components studies, coupled rotor-airframe vibrations, and airframe structural optimization. Key accomplishments of the program include industrywide standards for modeling metal and composite airframes, improved industrial designs for vibrations, and the identification of critical structural contributors to airframe vibratory responses. The program also demonstrated the value of incorporating secondary modeling details to improving correlation, and the findings provide the basis for an improved finite-element-based dynamics design-analysis capability.

Kvaternik, Raymond G.↗
NASA NTRS2017

Development of Structural Energy Storage for Aeronautics Applications

The National Aeronautics and Space Administration (NASA) has identified Multifunctional Structures for High Efficiency Lightweight Load-bearing Storage (M-SHELLS) as critical to development of hybrid gas-electric propulsion for commercial aeronautical transport in the N+3 timeframe. The established goals include reducing emissions by 80 and fuel consumption by 60 from todays state of the art. The advancement will enable technology for NASA Aeronautics Research Mission Directorates (ARMD) Strategic Thrust 3 to pioneer big leaps in efficiency and environmental performance for ultra-efficient commercial transports, as well as Strategic Thrust 4 to pioneer low-carbon propulsion technology in the transition to that scheme. The M-SHELLS concept addresses the hybrid gas-electric highest risk with its primary objective: to save structures energy storage system weight for future commercial hybrid electric propulsion aircraft by melding the load-carrying structure with energy storage in a single material. NASA's multifunctional approach also combines supercapacitor and battery chemistries in a synergistic energy storage arrangement in tandem with supporting good mechanical properties. The arrangement provides an advantageous combination of specific power, energy, and strength.

Santiago-Dejesus, Diana↗
NASA NTRS1978

Terrestrial central station array life-cycle analysis support study

Plant elements evaluated included designs for module, panel and array structures, as well as balance-of-plant systems. Installation and maintenance procedures and the impact of site environment were also evaluated. In terms of the cost of energy produced, the horizontal array configuration was found to be less expensive than the tandem array at latitudes less than 40 deg. Both of these configurations are less expensive than the rack design. However, the costs of energy for all three configurations are within approximately ?10 percent of each other. For flat plate panels, the seasonally adjusted and tracking array configurations are not economically attractive when compared to the three other designs. Balance-of-plant costs are approximately equal to (goal) module costs. The array structures and foundations are the most expensive items in the balance-of-plant costs.

Source record↗
NASA NTRS2007

Ultra-Thin, Triple-Bandgap GaInP/GaAs/GaInAs Monolithic Tandem Solar Cells

The performance of state-of-the-art, series-connected, lattice-matched (LM), triple-junction (TJ), III-V tandem solar cells could be improved substantially (10-12%) by replacing the Ge bottom subcell with a subcell having a bandgap of approx.1 eV. For the last several years, research has been conducted by a number of organizations to develop approx.1-eV, LM GaInAsN to provide such a subcell, but, so far, the approach has proven unsuccessful. Thus, the need for a high-performance, monolithically integrable, 1-eV subcell for TJ tandems has remained. In this paper, we present a new TJ tandem cell design that addresses the above-mentioned problem. Our approach involves inverted epitaxial growth to allow the monolithic integration of a lattice-mismatched (LMM) approx.1- eV GaInAs/GaInP double-heterostructure (DH) bottom subcell with LM GaAs (middle) and GaInP (top) upper subcells. A transparent GaInP compositionally graded layer facilitates the integration of the LM and LMM components. Handle-mounted, ultra-thin device fabrication is a natural consequence of the inverted-structure approach, which results in a number of advantages, including robustness, potential low cost, improved thermal management, incorporation of back-surface reflectors, and possible reclamation/reuse of the parent crystalline substrate for further cost reduction. Our initial work has concerned GaInP/GaAs/GaInAs tandem cells grown on GaAs substrates. In this case, the 1- eV GaInAs experiences 2.2% compressive LMM with respect to the substrate. Specially designed GaInP graded layers are used to produce 1-eV subcells with performance parameters nearly equaling those of LM devices with the same bandgap (e.g., LM, 1-eV GaInAsP grown on InP). Previously, we reported preliminary ultra-thin tandem devices (0.237 cm2) with NREL-confirmed efficiencies of 31.3% (global spectrum, one sun) (1), 29.7% (AM0 spectrum, one sun) (2), and 37.9% (low-AOD direct spectrum, 10.1 suns) (3), all at 25 C. Here, we include recent results of testing similar devices under the concentrated AMO spectrum, and also present the first demonstration of a high-efficiency, ultra-thin GaInP/GaAs/GaInAs tandem cell processed on a flexible kapton handle.

Wanlass, M. W.↗
NASA NTRS1979

Automated Array Assembly, Phase 2

The solar cell module process development activities in the areas of surface preparation are presented. The process step development was carried out on texture etching including the evolution of a conceptual process model for the texturing process; plasma etching; and diffusion studies that focused on doped polymer diffusion sources. Cell processing was carried out to test process steps and a simplified diode solar cell process was developed. Cell processing was also run to fabricate square cells to populate sample minimodules. Module fabrication featured the demonstration of a porcelainized steel glass structure that should exceed the 20 year life goal of the low cost silicon array program. High efficiency cell development was carried out in the development of the tandem junction cell and a modification of the TJC called the front surface field cell. Cell efficiencies in excess of 16 percent at AM1 have been attained with only modest fill factors. The transistor-like model was proposed that fits the cell performance and provides a guideline for future improvements in cell performance.

Carbajal, B. G.↗
NASA NTRS1985

A tandem mirror plasma source for hybrid plume plasma studies

A tandem mirror device to be considered as a hot plasma source for the hybrid plume rocket concept is discussed. The hot plamsa from this device is injected into an exhaust duct, which will interact with an annular hypersonic layer of neutral gas. The device can be used to study the dynamics of the hybrid plume, and to verify the numerical predictions obtained with computer codes. The basic system design is also geared towards low weight and compactness, and high power density at the exhaust. The basic structure of the device consists of four major subsystems: (1) an electric power supply; (2) a low temperature, high density plasma gun, such as a stream gun, an MPD source or gas cell; (3) a power booster in the form of a tandem mirror machine; and (4) an exhaust nozzle arrangement. The configuration of the tandem mirror section is shown.

Yang, T. F.↗
NASA NTRS2004

Simultaneous Multiwavelength Monitoring of 3C66A

The radio-selected BL Lac object 3C66A was the target of an intensive multiwavelength campaign from Sept. 2003 through Feb. 2004. It was monitored by the Whole Earth Blazar Telescope (WEBT) collaboration, in tandem with 20 X-ray monitoring observations by the Rossi X-Ray Timing Explorer (RXTE), VHE gamma-ray observations by STACEE and VERITAS, and long-term monitoring at radio frequencies. In addition. 9 observations using the VLBA are being carried out during the campaign and throughout the year 2004 to follow possible structural changes of the source. 21 pointings with RXTE during the period Sept. 15 - Dec. 27, 2003. All collected data have been fully analyzed, and first results have already been published at the 8th HEAD Meeting in New Orleans, LA, in Sept. 2004, and will also be presented at the 205th AAS Meeting in San Diego, CA, in Jan. 2005. A first Journal paper, to be submitted to the Astrophysical Journal, is currently in preparation, and we plan to have it ready for submission in January 2005. A gradual brightening of the source over the course of the campaign was observed at all optical frequencies, culminating in a very bright flare at the end of January 2004. Optical light curves indicate intraday microvariability on time scales down to about 1.3 hours. No significant color-magnitude correlation for the entire data set was evident, but there is a slight indication of a gradual spectral softening in the optical over the entire duration of multi-day outbursts (in both the rising and decaying phase). The X-ray spectrum is consistent with a power-law with a photon spectral index of approx. 2.1, indicating that the RXTE energy band might be located right at the intersection of the synchrotron and the high-energy emission components. No significant flux or spectral variability at X-ray energies was detected, though there seems to be a trend of very modest brightening in tandem with the optical flux. The first 4 VLBA epochs indicate a rather smooth jet with only very moderate internal structure. After decomposition in Gaussian components, evidence for superluminal motion (11.0+/-4.7/h c) was found in only one out of 6 jet components. The radial radio brightness profile suggests a magnetic field decay infinity/r and, thus, a predominantly perpendicular magnetic field orientation.

Boettcher, M.↗
NASA NTRS1975

Isogrid structures

Test results and related structural instability analyses are presented for a 10-foot-diameter, 37-inch-long cylinder, and a 10-foot-diameter, 40-inch-long, 45-degree conical frustum. Both structures are based upon flanged isogrids and are fabricated in 2024-T851 aluminum. Peak edge load intensities at failure were 1,654 lb/in for the cylinder and 1,457 lb/in at the small diameter of the frustum. General instability cylindrical-monocoque-structure equivalent knockdown factors for both were in good agreement (gamma = 0.48). Design analysis is also derived for estimating critical cylinder instability edge loads from the performance of two tandem isogrid members. Evaluation is made of effective skin contributing to isogrid load-carrying cross-section.

Slysh, P.↗
NASA NTRS1993

Ozone absorption cross section measurements in the Wulf bands

A tandem dual-beam spectrometer has been developed to determine ozone absorption cross sections for 13 selected wavelengths between 750 and 975 nm at room temperature. The increasingly pronounced structure in this region may interfere with atmospheric trace gas transitions that are useful for remote sensing and complicate the measurement of aerosols. Ozone concentrations were determined by absorption at the common HeNe laser transition near 632.8 nm using the absolute cross section reported previously. The overall accuracy of these room temperature measurements is generally better than 2 percent. A synoptic near-IR spectrum scaled to these measurements is employed for comparison with results of previous studies.

Anderson, Stuart M.↗
NASA NTRS2019

Extraction of Dynamic Inflow Models for Coaxial and Tandem Rotors from CFD Simulations

The dynamic inflow coupling with rotor/body dynamics is crucial in the analysis of stability and control law design for helicopters. Over the past several decades, finite-state inflow models for single rotor configurations in hover, forward flight, and maneuver have developed (Ref.1-3). By capturing the interference effects between rotors, the extension of pressure potential finite state inflow model has promising result for coaxial rotor configuration (Ref.4-6). Recently, the focus of the dynamic inflow modeling has shifted to tandem rotor configurations (Ref.7, 8). The development of the dynamic inflow models for tandem rotor configuration still have some limitations due to the lack of knowledge of rotor-to-rotor interference, and rotor-wake interference. Experimental methods, and computational fluid dynamics methods are commonly used to understand the rotor performance and rotor airload variations, and measure or predict inflow velocity distributions at the rotor desk. The inflow distributions are subsequently used to improve the dynamic inflow models. Tandem rotor configurations have been studied experimentally and computationally for several decades (Ref.9-12). Sweet (Ref.10) observed that a tandem rotor with 76-percent-radius overlap required 14% more induced power at hovering condition, relative to an isolated rotor of equivalent disk area. Sweet also found that, above a shaft-to-shaft distance of 1.03 diameter, the performance of the tandem rotor was nearly the same as two isolated rotors. The objective of the present study is to apply computational fluid dynamics simulations of tandem rotors for the extraction of dynamic inflow models. The extended methodology is first validated by comparing the computed induced power against test data. Subsequently inflow distributions and wake structures are analyzed.

Extraction of Dynamic Inflow Models↗
NASA NTRS1998

The effect of track structure on the induction of chromosomal aberrations in murine cells

PURPOSE: To measure chromosome aberrations in C3H 10T1/2 mouse fibroblasts using FISH painting at the first mitosis following exposure to 30 keV/microm hydrogen or neon ions. MATERIALS AND METHODS: Cells in plateau-phase were irradiated with 0.86 MeV protons at the TTT-3 Tandem accelerator in Naples (Italy), or with 400 MeV/n Ne ions at the HIMAC accelerator in Chiba (Japan). Colcemid-blocked cells were harvested at the first mitosis following exposure, and chromosome spreads were hybridized in situ with a fluorescein-labelled composite mouse DNA probe specific for chromosomes 2 and 8. RESULTS: Protons were more efficient than neon ions at the same LET in the induction of chromosome interchanges and breaks. Yields of complex exchanges were similar for both particles at the same dose, but protons produced mostly insertions, while with Ne exposure non-reciprocal exchanges were the most frequent complex-type exchange. CONCLUSIONS: Charged particles with the same LET produce different yields of chromosome aberrations, and some observed differences can be explained based on the available track-structure models.

NASA Center JSC↗
NASA NTRS1983

A fundamental comparison of canard and conventional configurations

This paper examines the relative efficiency of canard, tandem, and aft-tailed aircraft configurations through analysis of an elementary lifting system. Stability and trim requirements are imposed upon the system and its C sub L(max), drag, and structural weight are studied as its geometry varies over a wide range of possible configurations. During the course of the analysis, two general solutions emerge for minimum induced drag as a function of the geometry and the division of lift between the surfaces of such a system - one for fixed span and the other for fixed weight. The conclusion is that the pre-eminence of the conventional aft-tailed configuration has a sound fundamental basis, but that there may be some room for improvement.

Mcgeer, T.↗
NASA NTRSDate not supplied

Aeroservoelastic Control Law Development for the Integrated Adaptive Wing Technology Maturation Wind-Tunnel Test

The NASA Advanced Air Transport Technology (AATT) Project seeks to “explore and develop technologies and concepts for improved energy efficiency and environmental compatibility for fixed wing subsonic transports” [1]. The IAWTM project is a subproject within AATT and is a joint Boeing/NASA effort to, in part, demonstrate the active control systems necessary to employ high-aspect ratio wings for improved aerodynamic efficiency. The aircraft configuration under study for the IAWTM project is a generic jet transport based on the NASA Common Research Model (CRM) whose wing aspect ratio has been increased to 13.5 (as opposed to nominal CRM aspect ratio of 9) and whose development is given in Ref. [2]. A semi-span model of the high-aspect-ratio CRM with 10 trailing edge control surfaces is currently being fabricated and will be delivered to the NASA Langley Transonic Dynamics Tunnel (TDT). There, several tests will be conducted to demonstrate maneuver load alleviation (MLA), gust load alleviation (GLA), active flutter suppression (AFS), and drag reduction, all at transonic conditions. A layout of the wind tunnel model is shown in Fig. 1. The wind-tunnel model is a spar/pod wing design with a relatively rigid fuselage attached to a mounting structure (seen in Fig. 1), which in turn is attached to a load balance behind the tunnel wall. Shims exist that can be attached to force the load to go through the fuselage rather than through the balance so as not to damage the balance in the event of flutter. The spar/pod design is similar to that used in the Boeing truss-braced wing aeroelastic model tested in the TDT in 2013 [3]. There is a central spar running the span of the wing to which the pods are attached that form the aerodynamic shape of the wing. The pods are constructed of ribs for attachment to the spar and skins to create the outer mold line. There are ten active control surfaces that will be used for the test objectives discussed above. Three of these (two outboard ailerons and one inboard aileron) are high-speed electrohydraulic actuators, and the remaining seven are low-speed mini-plane flaps, which have slower servo motors that will be used primarily for drag and maneuver load reductions. Control laws must be developed for each test (MLA, GLA, AFS, and drag reduction) and must be able to work in tandem when two or more control strategies are being tested simultaneously (e.g., when control laws to mitigate maneuver loads and gust loads operate simultaneously). The development of these control laws requires accurate mathematical representations of the aerodynamics, structural dynamics, and control surface dynamics of the system. Taken together, this mathematical representation—which is often in state-space form— is the ASE model. Three low-order ASE models of differing fidelities were developed for the IAWTM test and will be presented here. The differences in fidelity appeared in the aerodynamic modeling—one model assumed purely linear aerodynamics, while the other two models used different techniques to linearize the aerodynamics about a nonlinear mean. Furthermore, simple observer-based full-state feedback controllers for each test (MLA, GLA, AFS, and drag reduction) were designed from these low-order ASE models and implemented in a higher-order, nonlinear computational ASE simulation to assess the effectiveness of each controller. Observers were designed from each of the three lower-order ASE models, and each (linear) observer was then used as an estimate of the nonlinear dynamics of the system. Using the estimated states and the full-state feedback controller, control surface commands were fed back to the higher-order, nonlinear ASE system. The insight gained during this development will be applied to control law development for the physical IAWTM wind-tunnel test.

Josiah M Waite↗
NASA NTRS2002

Progress in the Development of Metamorphic Multi-Junction III-V Space-Solar Cells at Essential Research Incorporated

Theoretical calculations have shown that highest efficiency III-V multi-junction solar cells require alloy structures that cannot be grown on a lattice-matched substrate. Ever since the first demonstration of high efficiency metamorphic single junction 1.1 eV and 1.2 eV InGaAs solar cells by Essential Research Incorporated (ERI), interest has grown in the development of multi-junction cells of this type using graded buffer layer technology. ERI is currently developing a dual-junction 1.6 eV InGaP/1.1 eV InGaAs tandem cell (projected practical air-mass zero (AM0), one-sun efficiency of 28%, and 100-sun efficiency of 37.5%) under a Ballistic Missile Defense Command (BMDO) SBIR Phase II program. A second ongoing research effort at ERI involves the development of a 2.1 eV AlGaInP/1.6 eV InGaAsP/1.2 eV InGaAs triple-junction concentrator tandem cell (projected practical AM0 efficiency of 36.5% under 100 suns) under a SBIR Phase II program funded by the Air Force. We are in the process of optimizing the dual-junction cell performance. In case of the triple-junction cell, we have developed the bottom and the middle cell, and are in the process of developing the layer structures needed for the top cell. A progress report is presented in this paper.

Sinharoy, Samar↗
NASA NTRS1984

Tunable Heterodyne Receiver from 100 Micron to 1,000 Micron for Airborne Observations

Interest in high resolution spectrometers for the submillimeter wavelength range from 100 micron to 1,000 micron is mostly stimulated by molecular spectroscopy in radioastronomy and atmospheric physics, and by plasma diagnostic experiments. Schottky diodes in waveguide mixer technology and InSb-hot electron bolometers are successfully used in the 0.5 to a few millimeter range whereas tandem Fabry-Perot spectrometers combined with photoconductive detectors (Ge:Sb and Ge:Ga) are used for the 100 micron range. Recent research on heterodyne spectrometers, with Schottky diodes in an open structure mixer and a molecular laser as local oscillators, which can be used over the whole wavelength range is summarized.

Roeser, H. P.↗
NASA NTRS2011

Summary of the Tandem Cylinder Solutions from the Benchmark Problems for Airframe Noise Computations-I Workshop

Fifteen submissions in the tandem cylinders category of the First Workshop on Benchmark problems for Airframe Noise Computations are summarized. Although the geometry is relatively simple, the problem involves complex physics. Researchers employed various block-structured, overset, unstructured and embedded Cartesian grid techniques and considerable computational resources to simulate the flow. The solutions are compared against each other and experimental data from 2 facilities. Overall, the simulations captured the gross features of the flow, but resolving all the details which would be necessary to compute the noise remains challenging. In particular, how to best simulate the effects of the experimental transition strip, and the associated high Reynolds number effects, was unclear. Furthermore, capturing the spanwise variation proved difficult.

Lockard, David P.↗