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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 991 records · Page 55

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NASA NTRS1995

The Capabilities of Space Stations

Over the past two years the U.S. space station program has evolved to a three-phased international program, with the first phase consisting of the use of the U.S. Space Shuttle and the upgrading and use of the Russian Mir Space Station, and the second and third phases consisting of the assembly and use of the new International Space Station. Projected capabilities for research, and plans for utilization, have also evolved and it has been difficult for those not directly involved in the design and engineering of these space stations to learn and understand their technical details. The Committee on the Space Station of the National Research Council, with the concurrence of NASA, undertook to write this short report in order to provide concise and objective information on space stations and platforms -- with emphasis on the Mir Space Station and International Space Station -- and to supply a summary of the capabilities of previous, existing, and planned space stations. In keeping with the committee charter and with the task statement for this report, the committee has summarized the research capabilities of five major space platforms: the International Space Station, the Mir Space Station, the Space Shuttle (with a Spacelab or Spacehab module in its cargo bay), the Space Station Freedom (which was redesigned to become the International Space Station in 1993 and 1994), and Skylab. By providing the summary, together with brief descriptions of the platforms, the committee hopes to assist interested readers, including scientists and engineers, government officials, and the general public, in evaluating the utility of each system to meet perceived user needs.

Source record↗

NASA NTRS2003

Optical Tweezers Array and Nimble Tweezers Probe Generated by Spatial- Light Modulator

An optical tweezers is being developed at the NASA Glenn Research Center as a visiblelight interface between ubiquitous laser technologies and the interrogation, visualization, manufacture, control, and energization of nanostructures such as silicon carbide (SiC) nanotubes. The tweezers uses one or more focused laser beams to hold micrometer-sized particles called tools (sometimes called tips in atomic-force-microscope terminology). A strongly focused laser beam has an associated light-pressure gradient that is strong enough to pull small particles to the focus, in spite of the oppositely directed scattering force; "optical tweezers" is the common term for this effect. The objective is to use the tools to create carefully shaped secondary traps to hold and assemble nanostructures that may contain from tens to hundreds of atoms. The interaction between a tool and the nanostructures is to be monitored optically as is done with scanning probe microscopes. One of the initial efforts has been to create, shape, and control multiple tweezers beams. To this end, a programmable spatial-light modulator (SLM) has been used to modify the phase of a laser beam at up to 480 by 480 points. One program creates multiple, independently controllable tweezer beams whose shapes can be tailored by making the SLM an adaptive mirror in an interferometer (ref. 1). The beams leave the SLM at different angles, and an optical Fourier transform maps these beams to different positions in the focal plane of a microscope objective. The following figure shows two arrays of multiple beams created in this manner. The patterns displayed above the beam array control the intensity-to-phase transformation required in programming the SLM. Three of the seven beams displayed can be used as independently controllable beams.

Decker, Arthur J.↗

NASA NTRS1993

Caul and method for bonding and curing intricate composite structures

The invention disclosed here is a method for forming and curing an intricate structure of criss-crossing composite stringers and frames that are bonded to a skin panel. A structure constructed in accordance with the invention would be well-suited for use as a portion of an aircraft fuselage, a boat hull, or the like. The method is preferably practiced by applying uncured composite stringers to an uncured composite sheet panel. This is followed by placing cured frames crosswise over the stringers. The frames have openings at the locations where they intersect with the stringers which enables the frames to come into direct contact with the skin along most of their length. During the forming and curing process, the stringers are covered with a plurality of cauls, and the entire assembly of skin panel, stringers, frames and cauls is subjected to a vacuum bagging and curing process. The cauls serve to maintain both part shape and to control the flow of resin within the stringers as they are cured. Further, they probably eliminate the need for intermediate protective materials between the vacuum bag and the stringers.

Willden, Kurtis S.↗

NASA NTRS2018

The Influence of Dihedral Angle Error Stability on Beam Deviation for Hollow Retro-Reflectors

Retro-reflectors consist of three reflective optical surfaces, which are oriented to reflect the input beam by 180 ◦. For retro-reflector components, it is common to specify an angular beam deviation tolerance, or rather the deviation from the exact 180 def return direction. Precision-aligned retro-reflectors provide 180 deg beam deviation with tolerances on the order of an arcsecond. It is well known that the performance of the retro-reflector depends on the ability to precisely orient the reflective surfaces at mutually perpendicular angles. Precision assembly is therefore critical to ensure highly accurate beam deviation. The dihedral angle errors, and hence the reflected beam deviation, can be measured for the retro-reflector after fabrication, typically by using interferometric techniques. Yet, what is not commonly reported for a fabricated retro-reflector is the stability of the angular beam deviation. For instance, thermo-mechanical effects of the components will contribute to variations in the return beam direction. While the actual stability is design-specific one can develop a mathematical representation for the expected change in the reflected beam direction as a function of the variation in the dihedral angle errors. Presented here is a mathematical formulation for a hollow retro-reflector's beam deviation as a function of the dihedral angle error stability.

Swank, Aaron J.↗

DOE OSTI2023

rRNA methylation by Spb1 regulates the GTPase activity of Nog2 during 60S ribosomal subunit assembly

Biogenesis of the large ribosomal (60S) subunit involves the assembly of three rRNAs and 46 proteins, a process requiring approximately 70 ribosome biogenesis factors (RBFs) that bind and release the pre-60S at specific steps along the assembly pathway. The methyltransferase Spb1 and the K-loop GTPase Nog2 are essential RBFs that engage the rRNA A-loop during sequential steps in 60S maturation. Spb1 methylates the A-loop nucleotide G2922 and a catalytically deficient mutant strain ( spb 1 D52A ) has a severe 60S biogenesis defect. However, the assembly function of this modification is currently unknown. Here, we present cryo-EM reconstructions that reveal that unmethylated G2922 leads to the premature activation of Nog2 GTPase activity and capture a Nog2-GDP-AlF 4 - transition state structure that implicates the direct involvement of unmodified G2922 in Nog2 GTPase activation. Genetic suppressors and in vivo imaging indicate that premature GTP hydrolysis prevents the efficient binding of Nog2 to early nucleoplasmic 60S intermediates. We propose that G2922 methylation levels regulate Nog2 recruitment to the pre-60S near the nucleolar/nucleoplasmic phase boundary, forming a kinetic checkpoint to regulate 60S production. Our approach and findings provide a template to study the GTPase cycles and regulatory factor interactions of the other K-loop GTPases involved in ribosome assembly.

59 BASIC BIOLOGICAL SCIENCES↗

NASA NTRS2017

Examination of the Structural Response of the Orion European Service Module to Reverberant and Direct Field Acoustic Testing

The NASA Orion Multi-Purpose Crew Vehicle (MPCV), comprised of the Service Module, the Crew Module, and the Launch Abort System, is the next generation human spacecraft designed and built for deep space exploration. Orion will launch on NASAs new heavy-lift rocket, the Space Launch System. The European Space Agency (ESA) is responsible for providing the propulsion sub-assembly of the Service Module to NASA, called the European Service Module (ESM). The ESM is being designed and built by Airbus Safran Launchers for ESA. Traditionally, NASA has utilized reverberant acoustic testing for qualification of spaceflight hardware. The ESM Structural Test Article (E-STA) was tested at the NASA Plum Brook Stations (PBS) Reverberant Acoustic Test Facility in April-May 2016. However, Orion is evaluating an alternative acoustic test method, using direct field acoustic excitation, for the MPCVs Service Module and Crew Module. Lockheed Martin is responsible for the Orion proof-of-concept direct field acoustic test program. The E-STA was exposed to direct field acoustic testing at NASA PBS in February 2017. This paper compares the dynamic response of the E-STA structure and its components to both the reverberant and direct field acoustic test excitations. Advantages and disadvantages of direct field acoustic test excitation method are discussed.

Acoustics↗

NASA NTRS2017

Examination of the Structural Response of the Orion European Service Module to Reverberant and Direct Field Acoustic Testing

Acoustics↗

NASA NTRS2006

Pointing Reference Scheme for Free-Space Optical Communications Systems

A scheme is proposed for referencing the propagation direction of the transmit laser signal in pointing a free-space optical communications terminal. This recently developed scheme enables the use of low-cost, commercial silicon-based sensors for tracking the direction of the transmit laser, regardless of the transmit wavelength. Compared with previous methods, the scheme offers some advantages of less mechanical and optical complexity and avoids expensive and exotic sensor technologies. In free-space optical communications, the transmit beam must be accurately pointed toward the receiver in order to maintain the communication link. The current approaches to achieve this function call for part of the transmit beam to be split off and projected onto an optical sensor used to infer the pointed direction. This requires that the optical sensor be sensitive to the wavelength of the transmit laser. If a different transmit wavelength is desired, for example to obtain a source capable of higher data rates, this can become quite impractical because of the unavailability or inefficiency of sensors at these wavelengths. The innovation proposed here decouples this requirement by allowing any transmit wavelength to be used with any sensor. We have applied this idea to a particular system that transmits at the standard telecommunication wavelength of 1,550 nm and uses a silicon-based sensor, sensitive from 0.5 to 1.0 micrometers, to determine the pointing direction. The scheme shown in the figure involves integrating a low-power 980-nm reference or boresight laser beam coupled to the 1,550-nm transmit beam via a wavelength-division-multiplexed fiber coupler. Both of these signals propagate through the optical fiber where they achieve an extremely high level of co-alignment before they are launched into the telescope. The telescope uses a dichroic beam splitter to reflect the 980- nm beam onto the silicon image sensor (a quad detector, charge-coupled device, or active-pixel-sensor array) while the 1,550- nm signal beam is transmitted through the optical assembly toward the remotely located receiver. Since the 980-nm reference signal originates from the same single-mode fiber-coupled source as the transmit signal, its position on the sensor is used to accurately determine the propagation direction of the transmit signal. The optics are considerably simpler in the proposed scheme due to the use of a single aperture for transmitting and receiving. Moreover, the issue of mechanical misalignment does not arise because the reference signal and transmitted laser beams are inherently co-aligned. The beam quality of the 980-nm reference signal used for tracking is required to be circularly symmetric and stable at the tracking-plane sensor array in order to minimize error in the centroiding algorithm of the pointing system. However, since the transmit signal is delivered through a fiber that supports a single mode at 1,550 nm, propagation of higher order 980-nm modes is possible. Preliminary analysis shows that the overall mode profile is dominated by the fundamental mode, giving a near symmetric profile. The instability of the mode was also measured and found to be negligible in comparison to the other error contributions in the centroid position on the sensor array.

Wright, Malcolm↗

NASA NTRS1997

A Novel Silicon Micromachined Integrated MCM Thermal Management System

"Micromachining" is a chemical means of etching three-dimensional structures, typically in single- crystalline silicon. These techniques are leading toward what is coming to be referred to as MEMS (Micro Electro Mechanical Systems), where in addition to the ordinary two-dimensional (planar) microelectronics, it is possible to build three-dimensional n-ticromotors, electrically- actuated raicrovalves, hydraulic systems and much more on the same microchip. These techniques become possible because of differential etching rates of various crystallographic planes and materials used for semiconductor n-ticrofabfication. The University of Cincinnati group in collaboration with Karl Baker at NASA Lewis were the first to form micro heat pipes in silicon by the above techniques. Current work now in progress using MEMS technology is now directed towards the development of the next generation in MCM (Multi Chip Module) packaging. Here we propose to develop a complete electronic thermal management system which will allow densifica6on in chip stacking by perhaps two orders of magnitude. Furthermore the proposed technique will allow ordinary conu-nercial integrated chips to be utilized. Basically, the new technique involves etching square holes into a silicon substrate and then inserting and bonding commercially available integrated chips into these holes. For example, over a 100 1/4 in. by 1 /4 in. integrated chips can be placed on a 4 in. by 4 in. silicon substrate to form a Multi-Chip Module (MCM). Placing these MCM's in-line within an integrated rack then allows for three-diniensional stacking. Increased miniaturization of microelectronic circuits will lead to very high local heat fluxes. A high performance thermal management system will be specifically designed to remove the generated energy. More specifically, a compact heat exchanger with milli / microchannels will be developed and tested to remove the heat through the back side of this MCM assembly for moderate and high heat flux applications, respectively. The high heat load application of particular interest in mind is the motor controller developed by Martin Marietta for Nasa to control the thruster's directional actuators on space vechicles. Work is also proposed to develop highly advanced and improved porous wick structures for use in advanced heat loops. The porous wick will be micromachined from silicon using MEMS technology, thus permitting far superior control of pore size and pore distribution (over wicks made from sintered n-ietals), which in turn is expected to led to significantly improved heat loop performance.

Kazmierczak, M. J.↗

DOE OSTI2022

Durable High-Power Membrane Electrode Assemblies with Low Pt Loading

Recent progress in developing and implementing Pt-alloy cathode catalysts and thin (10-15 micron) low resistance membranes has enabled high performance state of art (SOA) membrane electrode assembly (MEA) with low Pt loading. However, these high performing MEAs do not meet durability requirements, especially at peak power, because of complex degradation mechanisms that are sensitive to the materials, MEA design, and fuel cell operating strategy. Specifically, power degradation of the cathode occurs via Pt and Co dissolution as well as deterioration of O 2 transport properties. Additionally, thin membranes are subject to failure due to manufacturing defects in the adjacent gas diffusion media and electrodes and the formation of membrane-attacking radical species caused by high gas crossover. In this project led by General Motors LLC (GM), the objective was to enhance the durability of SOA MEA through optimization of operating conditions, instead of new materials development. Along with our project partners, we have mapped the impact of operating conditions on the durability of SOA MEA. Output of the project include a low Pt loading SOA MEA that exceeds Department of Energy (DOE) 2020 target of >1 W/cm 2 at rated power and pathway to achieve >5000 h of durability. Durability studies in the project provide a detailed understanding of failure modes and operating condition sensitivity on cathode and membrane failure, critical for defining operating conditions and hybridization strategies that can guide system controls to maximize low-Pt MEA life. The project also generated and validated degradation models that will provide future research direction, critical for guiding future cycles of automotive MEA development.

08 HYDROGEN↗

DOE OSTI2026

A Low Loss, Fast Ramp HTS Solenoid Prototype for Compact Spherical Tokamaks

To explore AC loss characteristics of commercial Bi-2212 conductors made in the USA, a small ohmic heating (OH) prototype coil is being developed for compact tokamaks using high performance Bi-2212 wires newly manufactured by Bruker EST. Here, the goal is to build and test Bi-2212 prototype coils for fast ramp central solenoid (CS) operation of spherical tokamaks (ST). For a ST pilot plant, one of the key challenges is the tight space available for CS in a center column where in-board legs of the toroidal field (TF) and OH coils are assembled into a cryostat with a few millimeters clearance. A high current density Rutherford cable consisting of 17 legacy Bi-2212 wires, a contribution of the US Magnet Development Program (MDP), was fabricated at the Lawrence Berkeley National Laboratory (LBNL) for the development of fast ramp CS magnets in the ST Advanced Reactor (STAR) designed by PPPL. Characterization of the new and legacy HTS wires is presented, along with the coil design wound directly with new wire, and a Rutherford cable-wound solenoid using the legacy wire. A comparison of AC losses is made based on expected performance for a fast ramp ST operation. The HTS cable and cabled coil fabrication issues such as the heat treatment, coil mandrel design, assembly and 2212 quench characteristics are discussed, along with a test plan for CS design validation.

Zhai, Yuhu [Princeton Plasma Physics Laboratory (P↗

DOE OSTI2020

Supramolecular Tuning Enables Selective Oxygen Reduction Catalyzed by Cobalt Porphyrins for Direct Electrosynthesis of Hydrogen Peroxide

Abstract We report a supramolecular strategy for promoting the selective reduction of O 2 for direct electrosynthesis of H 2 O 2 . We utilized cobalt tetraphenylporphyrin (Co‐TPP), an oxygen reduction reaction (ORR) catalyst with highly variable product selectivity, as a building block to assemble the permanently porous supramolecular cage Co‐PB‐1(6) bearing six Co‐TPP subunits connected through twenty‐four imine bonds. Reduction of these imine linkers to amines yields the more flexible cage Co‐rPB‐1(6). Both Co‐PB‐1(6) and Co‐rPB‐1(6) cages produce 90–100 % H 2 O 2 from electrochemical ORR catalysis in neutral pH water, whereas the Co‐TPP monomer gives a 50 % mixture of H 2 O 2 and H 2 O. Bimolecular pathways have been implicated in facilitating H 2 O formation, therefore, we attribute this high H 2 O 2 selectivity to site isolation of the discrete molecular units in each supramolecule. The ability to control reaction selectivity in supramolecular structures beyond traditional host–guest interactions offers new opportunities for designing such architectures for a broader range of catalytic applications.

Smith, Peter T.↗

DOE OSTI2020

Supramolecular Tuning Enables Selective Oxygen Reduction Catalyzed by Cobalt Porphyrins for Direct Electrosynthesis of Hydrogen Peroxide

Smith, Peter T.↗

DOE OSTI2025

Leveraging operator learning to accelerate convergence of the preconditioned conjugate gradient method

We propose a new deflation strategy to accelerate the convergence of the preconditioned conjugate gradient (PCG) method for solving parametric large-scale linear systems of equations. Unlike traditional deflation techniques that rely on eigenvector approximations or recycled Krylov subspaces, we generate the deflation subspaces using operator learning, specifically the Deep Operator Network (DeepONet). To this aim, we introduce two complementary approaches for assembling the deflation operators. The first approach approximates near-null space vectors of the discrete PDE operator using the basis functions learned by the DeepONet. The second approach directly leverages solutions predicted by the DeepONet. To further enhance convergence, we also propose several strategies for prescribing the sparsity pattern of the deflation operator. Here, a comprehensive set of numerical experiments encompassing steady-state, time-dependent, scalar, and vector-valued problems posed on both structured and unstructured geometries is presented and demonstrates the effectiveness of the proposed DeepONet-based deflated PCG method, as well as its generalization across a wide range of model parameters and problem resolutions.

Deflation↗

DOE OSTI2019

Direct visualization of degradation microcompartments at the ER membrane

To promote the biochemical reactions of life, cells can compartmentalize molecular interaction partners together within separated non–membrane-bound regions. It is unknown whether this strategy is used to facilitate protein degradation at specific locations within the cell. Leveraging in situ cryo-electron tomography to image the native molecular landscape of the unicellular alga Chlamydomonas reinhardtii , we discovered that the cytosolic protein degradation machinery is concentrated within ∼200-nm foci that contact specialized patches of endoplasmic reticulum (ER) membrane away from the ER–Golgi interface. These non–membrane-bound microcompartments exclude ribosomes and consist of a core of densely clustered 26S proteasomes surrounded by a loose cloud of Cdc48. Active proteasomes in the microcompartments directly engage with putative substrate at the ER membrane, a function canonically assigned to Cdc48. Live-cell fluorescence microscopy revealed that the proteasome clusters are dynamic, with frequent assembly and fusion events. We propose that the microcompartments perform ER-associated degradation, colocalizing the degradation machinery at specific ER hot spots to enable efficient protein quality control.

Science & Technology - Other Topics↗

NASA NTRS1975

A new arc heater shroud test technique for thermo-structural testing of full-scale, nose-tip skirt materials

An arc heater shroud test technique was developed for thermostructural testing of full-scale, missile nose tip-skirt assemblies. Reentry trajectory simulation is provided by changing the arc heater operation in a prescribed manner through manual and automatic controls. Excellent test repeatability allows screening of materials by direct comparison of test results. Continuous recordings of model surface temperature, pressure, heat flux, and model internal temperatures are made at several locations during the test.

Williams, R. R.↗

NASA NTRS1982

Matching Dissimilar Graphical Scales

Projection of one drawing on another with projected image adjusted to have same scale as other drawing permits quick comparisons of such features as relative sizes of parts and clearance or interferences in assemblies. Technique uses standard overhead projector and transparency of one drawing to project an enlarged image, the scale of which matches scale of second drawings. Image may be traced directly onto copy of second drawing.

French, R. H.↗

NASA NTRS1982

Non-contacting power transfer device

A transformer for coupling AC electrical energy from a stationary element to a rotating element without the use of sliding contacts is described. The transformer is of the rotary type and includes a ferrite core and two primary windings which are stationary with respect to a seconary winding which rotates within an annular cavity adjacent an axial bore in the core. The core is comprised of two cup type core halves. Electrical connection to the secondary winding is made through a split bobbin assembly which couples to a coaxial shaft assembly located in the axial bore. The electrical coupling to the coaxial shaft assembly is made through a continuous transverse channel connecting the axial bore with the annular cavity. The transverse channel forms a single air gap; however, it is not open directly to free space but is shielded by the magnetic permeable material of the core halves.

Studer, P. A.↗