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DOE OSTI2021

The preparation and characterization of chemically deuterium incorporated cotton fibers

Preparation of deuterium incorporated cellulose is a vital tool to investigate cellulose internal structure and to expand the application fields of cellulose materials. In this study, cellulosic cotton fibers with anti-rehydration (exchange-resistant) deuterium incorporated in cellulose were prepared by chemical hydrogen–deuterium exchange treatment. The chemical hydrogen–deuterium exchange process, along with exchange time, were characterized by nuclear magnetic resonance hydrogen spectroscopy (1H-NMR). The anti-rehydration deuterium incorporation was determined by Fourier Transform infrared spectroscopy (FTIR) and Stable Isotope Ratio Mass Spectrometer (IRSM). Here, the effect of the deuterium hydroxyl substitution on cotton fiber’s spectral data, microstructure, crystalline information, degree of polymerization, as well as it’s thermogravimetric analysis (charcoalization and combustion) are explored. Analysis of the chemical exchange process indicated that the hydrogen–deuterium exchange occurred preferentially in the amorphous cellulose component over the first several minutes. Deuterium exchange in the anti-rehydration crystalline phase took several hours. Increasing the treatment time, enhanced exchange-resistant deuterium incorporation to as high as about 60% of the cotton fibers’ cellulose hydroxyl groups was achieved. The characterization of FTIR, Fourier transform Raman (FT-Raman), and near-infrared spectra (NIR) all exhibited the deuterium spectral isotope effect on cellulose hydroxl groups. While, apart from the effect of reaction temperature, deuterium incorporation isotope effect did not affect the cellulose microstructure, crystalline index and the degree of polymerization properties. Furthermore, the thermogravimetric analysis of deuterated cotton fibers under N 2 and air atmosphere were both altered due to the thermodynamic isotope effect. These observations revealed the hydrogen–deuterium exchange treatment process and impacts on cellulose fiber properties, which helped us to better understand the cellulose internal structure and may facilitate the potential utilization of deuterated cellulosic materials.

59 BASIC BIOLOGICAL SCIENCES↗

DOE OSTI2021

Bridging Aromatic/Antiaromatic Units: Recent Advances in Aromaticity and Antiaromaticity in Main-group and Transition-Metal Clusters from Bonding and Magnetic Analyses

Synthetic exploration and theoretical characterization of metal clusters are actively developing branches of modern inorganic chemistry. Advances in these areas constantly expand the rich structural diversity of viable species, allowing a detailed study of the fundamental characteristics of bench-stable compounds. In this minireview, we summarize recent achievements in synthesis and computational analyses of main-group and heterometallic clusters containing multiple aromatic/antiaromatic units. These systems range from bare clusters to ligand-decorated aggregates, providing a fundamental understanding of the aromaticity and antiaromaticity concepts in species exhibiting unprecedented shapes and composition. The review gives a comprehensive summary of bonding and magnetic response properties of such systems deciphered from the Adaptive Natural Density Partitioning (AdNDP) approach and induced magnetic field analyses.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2023

Design of enhanced porous organic cage solubility in Type 2 porous liquids

Decreasing cost of technologies for direct air capture of carbon can be achieved through the design of new materials with high CO 2 selectivity that can be incorporated into existing industrial processes. An emerging class of materials for these applications are porous liquids (PLs). PLs are mixtures of porous hosts and solvents with intrinsic porosity due to steric exclusion of solvent from inside the porous host. It is currently unknown how solvent -porous host interactions affect porous host solubility in the bulk solvent. Here, in this study, density functional theory simulations were used to investigate interactions between nine solvents and a CC13 porous organic cage (POC). Calculations identified that solvent molecules were the most stable when placed either inside the CC13 POC or in the pore window compared to interfacial binding sites. Structural changes to the CC13 POC correlated with reported experimental solubilities, including expansion of the CC13 POC with solvent molecule infiltration and expansion or contraction of the pore window. Based on these results, new PL design guidelines should include compositions with (1) high concentrations of POCs with flexible cage structures that can expand when solvated and (2) solvent molecule-POC combinations that contract the pore window during solvent molecule-host binding.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2022

Compressive properties of silicone Bouligand structures

Abstract This article presents an examination of silicone, Bouligand lattices in compression. Appearing frequently in biological organisms and manufacturing design, Bouligand structures comprise layers of parallel strands or fibers oriented in a helical fashion. They can exhibit exceptional fracture resistance when composed of rigid or composite materials. The behavior of elastomeric Bouligand structures, however, is less well understood. Additively manufactured (AM) elastomeric lattices have applications in stress mitigation, medical devices, and soft robotics. This article demonstrates that Bouligand structures are a useful addition to the design space of AM elastomers. By adjusting the layer-rotation parameters, lattice stress can increase by more than 300% without altering the porosity. Additionally, we introduce path length metrics that help explain the observed relationship between layer rotation and compression response. Impact statement Additive manufacturing (AM) continues to push the boundary of manufacturable structures and enhance the ability to robustly design for specific properties and behaviors. The more we understand the design space of a novel AM microstructure, the greater its application range. In this article, we describe the mechanical behavior of helicoidal, elastomeric lattices and introduce path length metrics to help explain their stress response. We show that these structures can exhibit a large range of mechanical behaviors in compression, making them well suited for applications such as stress mitigation and impact absorption. Additionally, the path length metrics could become useful design tools and may be applicable to a larger set of cellular structures. These findings expand our ability to rapidly design materials with highly specific and customizable properties to meet the needs of modern engineering challenges. Graphical abstract

Van Meerbeek, I. M. (ORCID:000000021258132X)↗

NASA NTRS1975

Mount mechanisms for the Saturn 5/Apollo mobile launcher at John F. Kennedy Space Center

A support system was designed to resist hurricane wind loads at the launch pad and to allow the supported structural frame to expand and contract freely under wide ranges of temperature. This system consists of six mount mechanisms devised to meet the previously stated requirements plus a load-carrying capacity for each of 3.2-million kilograms (7-million pounds) downward and 1.6-million kilograms (3.5-million pounds) upward. A similar but lighter system of six mount mechanisms was designed for use in the sheltered environment of the vehicle assembly building. Each requirement and design result is discussed, and each mount mechanism is defined by location and type with references to visual presentations.

Balke, H. A.↗

NASA NTRS1976

Spectroscopic far ultraviolet observations of transition zone instabilities and their possible role in a pre-flare energy build-up

Highly flare-productive newly emerging active regions are characterized by numerous small low-lying loops which frequently show a chaotic pattern. Flare activity in such a region subsides as the chaotic loop structures relax and expand into a bipolar configuration. The transition zone in such an active region is highly unstable, as shown by broadened and shifted nonthermal line profiles of medium-ionized elements like Si III, Si IV, and C IV. These transition-zone instabilities, which occur as isolated events in active regions of low flare productivity, are often observed prior to flares. Transition-zone instabilities can be traced to the footpoints of active loops and seem to be accompanied by heating of the loop. The loops vary in size and show differing degrees of activity, with the brightest and most compact ones seemingly being in a pre-flare state which results in the catastrophic energy release along the loop during a flare.

Brueckner, G. E.↗

NASA NTRS1977

A high-resolution infrared spectrum of IRC +10216

The IR-emitting core and shell of IRC +10216 are investigated using a high-resolution spectrum covering the wavelength interval between 3 and 5 microns. Line identifications made or confirmed include those due to (C-12)(O-16), (C-13)(O-16), (C-12)(O-17), and (C-12)(O-18). A mean heliocentric velocity of about -32 km/s is obtained from the 42 least blended (C-12)O and (C-13)O lines, and the following isotopic abundance ratios are derived by comparing equivalent widths of the observed lines: C-12/C-13, C-12/C-14, O-16/O-17, and O-17/O-18. The structure of the expanding gas shell is examined, an explanation is offered for the lack of P Cygni profiles in the spectrum, and an unsuccessful search for other molecules is briefly discussed. It is concluded that a low C-12/C-13 ratio is not necessarily a signature of a carbon star.

Barnes, T. G.↗

NASA NTRS1979

Development of ultraviolet rigidizable materials

A series of tests was performed to determine an optimum resin to be used as a UV rigidizable matrix in expandable rigidizable space structures. Commercially available resins including several types of polyesters, epoxies, epoxy-acrylics, an acrylic and a urethane were used as well as a polyester, produced by 3M Company's Solar Laboratory facility, which was found the best from the standpoint of physical properties and ability to be 'B' staged. Two other synthesized materials were also tested, but were not found to be superior to the Solar resin. An optimum fabric for use with the preferred resin was not found; however, the 15 ounce fabric from Solar Laboratories has the best combination of physical properties with respect to handling and processing characteristics. Expansion techniques for tubular structures, 'B' staging of the solar resin, and stowage techniques for up to 5 months were developed. A one meter high tetrahedron preprototype structure was prepared to evaluate and demonstrate stowage, deployment, and rigidization techniques.

Salisbury, D. P.↗

NASA NTRS1984

Fully-coupled analysis of jet mixing problems. Part 1. Shock-capturing model, SCIPVIS

A computational model, SCIPVIS, is described which predicts the multiple cell shock structure in imperfectly expanded, turbulent, axisymmetric jets. The model spatially integrates the parabolized Navier-Stokes jet mixing equations using a shock-capturing approach in supersonic flow regions and a pressure-split approximation in subsonic flow regions. The regions are coupled using a viscous-characteristic procedure. Turbulence processes are represented via the solution of compressibility-corrected two-equation turbulence models. The formation of Mach discs in the jet and the interactive analysis of the wake-like mixing process occurring behind Mach discs is handled in a rigorous manner. Calculations are presented exhibiting the fundamental interactive processes occurring in supersonic jets and the model is assessed via comparisons with detailed laboratory data for a variety of under- and overexpanded jets.

Dash, S. M.↗

NASA NTRS1985

Cryogenic refractor design techniques

The Infrared Astronomical Satellite (IRAS) was designed to operate at 2K, and over the spectral range of 8 to 120 micrometers. The focal plane is approximately 2 by 3 inches in size, and contains 62 individual field stop apertures, each with its own field lens, one or more filters and a detector. The design of the lenses involved a number of difficulties and challenges that are not usually encountered in optical design. Operating temperature is assumed during the design phase, which requires reliable information on dN/dT (Index Coefficient) for the materials. The optics and all supporting structures are then expanded to room temperature, which requires expansion coefficient data on the various materials, and meticulous attention to detail. The small size and dense packaging, as well as the high precision required, further contributed to the magnitude of the task.

Darnell, R. J.↗

NASA NTRS1990

Space Station accommodation of the Space Exploration Initiative

It is pointed out that Space Station Freedom (SSF) will support the transportation, research, and development requirements of the Space Exploration Initiative through augmentation of its resources and initial capabilities. These augmentations include providing facilities for lunar and Mars vehicle testing, processing, and servicing; providing laboratories and equipment for such enabling research as microgravity countermeasures development; and providing for the additional crew that will be required to carry out these duties. It is noted that the best way to facilitate these augmentations is to ensure 'design-for-growth' capabilities by incorporating necessary design features in the baseline program. The critical items to be accommodated in the baseline design include provisions for future increased power-generation capability, the ability to add nodes and modules, and the ability to expand the truss structure to accommodate new facilities. The SSF program must also address the effect on nonexploration users (e.g., NASA experimenters, commercial users, university investigators, and international partners of the U.S.) of SSF facilities.

Ahlf, Peter↗

NASA NTRS1992

Theoretical aspects of supersonic jet noise

The topics covered include the following: the three components of supersonic jet noise; shock cell structure of imperfectly expanded jets; large turbulence structures/instability waves; supersonic jet noise theory; generation of turbulent mixing noise; comparisons between predicted peak noise frequency and direction of radiation with measurements; Strouhal number of maximum SPL of hot supersonic jets; near field sound pressure level contours; generation of broadband shock associated noise; calculated and measured far field shock noise spectra; generation of screech tones; and calculated and measured Strouhal number of screech tones.

Tam, Christopher K. W.↗

NASA NTRS1994

An implementation of a tree code on a SIMD, parallel computer

We describe a fast tree algorithm for gravitational N-body simulation on SIMD parallel computers. The tree construction uses fast, parallel sorts. The sorted lists are recursively divided along their x, y and z coordinates. This data structure is a completely balanced tree (i.e., each particle is paired with exactly one other particle) and maintains good spatial locality. An implementation of this tree-building algorithm on a 16k processor Maspar MP-1 performs well and constitutes only a small fraction (approximately 15%) of the entire cycle of finding the accelerations. Each node in the tree is treated as a monopole. The tree search and the summation of accelerations also perform well. During the tree search, node data that is needed from another processor is simply fetched. Roughly 55% of the tree search time is spent in communications between processors. We apply the code to two problems of astrophysical interest. The first is a simulation of the close passage of two gravitationally, interacting, disk galaxies using 65,636 particles. We also simulate the formation of structure in an expanding, model universe using 1,048,576 particles. Our code attains speeds comparable to one head of a Cray Y-MP, so single instruction, multiple data (SIMD) type computers can be used for these simulations. The cost/performance ratio for SIMD machines like the Maspar MP-1 make them an extremely attractive alternative to either vector processors or large multiple instruction, multiple data (MIMD) type parallel computers. With further optimizations (e.g., more careful load balancing), speeds in excess of today's vector processing computers should be possible.

Olson, Kevin M.↗

NASA NTRS2004

Small-scale Interstellar Structure Toward the Open Cluster Chi Persei; Program ID: BO29 (Cycle 2)

The primary objective of this program was to obtain FUSE observations of the interstellar H2 absorption toward six early-type stars in the core of the open star cluster Chi Persei. High resolution optical observations of the interstellar Na I absorption toward these stars and others in the core of Chi Per have revealed a rich variety of small-scale diffuse ISM structure in both the distant Perseus and more local Orion spiral arms. At the 1 arc minute angular scales typically probed by the separations of these stars, this structure corresponds to respective physical length scales of 0.6 and 0.15 pc in the Perseus and Orion arm gas. The principal scientific goal of the FUSE observations was to determine if this small-scale Na I structure toward the core of Chi Per was reflected in the abundance and/or excitation of interstellar H2. In September 2001, we obtained FUSE observations of the Chi Per stars BD +56 563, BD +56 571, BD +56 573, BD +56 574, BD +56 575, and BD +56 578 for this program. The data reveal that the Perseus arm gas exhibits significant small-scale variations in the strength of its molecular hydrogen absorption while the Orion arm H2 absorption is relatively uniform. We presented these results at the January 2003 American Astronomical Society meeting in Seattle, WA (points, Meyer, Lauroesch, Nguyen, and Friedman 2002, Bulletin of the American Astronomical Society, 34,1229). Since Na I is not a dominant ion in H I clouds, the variations detected in the Perseus arm Na I line profiles could be due to spatial differences in either the physical structure or the physical conditions in the gas. Although many of the H2 absorption profiles are too saturated or too weak to be definitive in this regard, it is clear that small-scale variations are present in H2 gas with excitation as high as the J=4 rotational level. In contrast, lower spatial resolution H I 21 cm studies of the Perseus arm gas across the face of the h and Chi Per double cluster have shown smoother, continuous variations on the larger scale. In order to investigate if the global velocity structure of H2 toward h and Chi Per more closely follows the chaotic structure seen in interstellar Na I absorption or the smoother, continuous H I structure, we have expanded our FUSE study with a Cycle 4 program (D902, PI: Points) to survey the H2 absorption toward a number of other stars across the face of the double cluster. We have obtained FUSE spectra of 14 additional h and Chi Per stars through this program and are now combining all of the data into a comprehensive study that will be submitted for publication next year.

Meyer, David M.↗

NASA NTRS2007

Deployable System for Crash-Load Attenuation

An externally deployable honeycomb structure is investigated with respect to crash energy management for light aircraft. The new concept utilizes an expandable honeycomb-like structure to absorb impact energy by crushing. Distinguished by flexible hinges between cell wall junctions that enable effortless deployment, the new energy absorber offers most of the desirable features of an external airbag system without the limitations of poor shear stability, system complexity, and timing sensitivity. Like conventional honeycomb, once expanded, the energy absorber is transformed into a crush efficient and stable cellular structure. Other advantages, afforded by the flexible hinge feature, include a variety of deployment options such as linear, radial, and/or hybrid deployment methods. Radial deployment is utilized when omnidirectional cushioning is required. Linear deployment offers better efficiency, which is preferred when the impact orientation is known in advance. Several energy absorbers utilizing different deployment modes could also be combined to optimize overall performance and/or improve system reliability as outlined in the paper. Results from a series of component and full scale demonstration tests are presented as well as typical deployment techniques and mechanisms. LS-DYNA analytical simulations of selected tests are also presented.

Kellas, Sotiris↗

NASA NTRSDate not supplied

Testing of a Composite Conical-Cylindrical Shell

Launch-vehicle shell structures, which can be comprised of both cylindrical and conical sections, are known to be susceptible to buckling due to their large radius-to-thickness ratios. The advancements in composite manufacturing and numerical methods have enabled designers to consider more nontraditional shapes, such as connecting the conical and cylindrical sections with a toroidal transition to create a single-piece conical-cylindrical shell. This single-piece construction eliminates the need for a heavy interface ring between sections and has the potential to save mass. To better understand the buckling behavior, a composite conical-cylindrical shell was designed, fabricated, and tested. Prior to test, a finite element model that included thickness variations and radial imperfections was created. The test article buckled elastically at 251.8 kN, approximately 8.8% higher than the predicted buckling load of 231.4 kN Continued research in conical-cylindrical structures has the potential to expand the design space for launch-vehicle structures and lead to improved designs and reduced weight.

Buckling↗

NASA NTRSDate not supplied

Test and Analysis of a Composite Conical-Cylindrical Shell

Buckling↗

NASA NTRS2018

Development of an Inflatable Airlock for Deep Space Exploration

An airlock is a required component of a crewed spacecraft to allow for maintenance, repair and exploration outside of a habitable vehicle. Airlock designs in use today are rigid pressure vessels with complex hatches and seals. Inflatable structures technology utilizes high strength fabric materials and internal pressure to create a stiffened pressure vessel that can replace traditional rigid primary structure in a habitable spacecraft. The flexibility of fabric structures allows them to be compactly stowed for launch and expanded in space. Recent developments towards the design of an inflatable airlock structure show feasibility and a significant launch volume savings over a traditional metallic design. This paper provides a detailed summary of historical and current work in inflatable airlock development and provides guidance for the design of a soft goods airlock system. Accommodations for withstanding crew-induced loads, provisions for human interfaces, the design and development of an internal substructure to provide translation aids and restraints, the thermal considerations of a fabric shell, micrometeoroid protection in deep space, and packaging and deployment of an inflatable airlock are all discussed.

Deep Space Exploration↗