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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 163 records · Page 9
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NASA NTRS1974

Assembly and analysis of fragmentation data for liquid propellant vessels

Fragmentation data was assembled and analyzed for exploding liquid propellant vessels. These data were to be retrieved from reports of tests and accidents, including measurements or estimates of blast yield, etc. A significant amount of data was retrieved from a series of tests conducted for measurement of blast and fireball effects of liquid propellant explosions (Project PYRO), a few well-documented accident reports, and a series of tests to determine auto-ignition properties of mixing liquid propellants. The data were reduced and fitted to various statistical functions. Comparisons were made with methods of prediction for blast yield, initial fragment velocities, and fragment range. Reasonably good correlation was achieved. Methods presented in the report allow prediction of fragment patterns, given type and quantity of propellant, type of accident, and time of propellant mixing.

Baker, W. E.↗
NASA NTRSDate not supplied

X-Ray Imagery as the Record of All Data of Interest in Hypervelocity Impact Fragment Studies

Laboratory study of hypervelocity spacecraft fragmentation has traditionally involved the collection and analysis of fragments that were caught in deceleration material surrounding the impact. This process has typically involved the disintegration of the catchment material either through chemical dissolution, or through physical excavation to recover the fragments. Due to the scale of the three impact tests—the Satellite Orbital Debris Characterization Impact Test (SOCIT), the DebriSat satellite impact test, and the DebrisLV launch vehicle impact test—the latter two using more than 12 cubic meters of polyurethane foam to capture the fragments, hese projects have used x-ray imagery to precisely locate and thus, to more efficiently extract fragments in the soft-catch material. Three years into the DebriSat fragment extraction process, a side study was initiated to explore what additional information could be discerned from the x-rays, with significant results. This study was instrumental to a rapid replacement and retooling as the project was forced to replace the x-ray system around which the extraction process had been based. The revised process continues to map the debris for extraction. The project has, in parallel, systematically addressed the limits/tolerances of what x-rays can reveal about size, shape, density, mass, velocity, energy, and deformation/damage of the fragment during the deceleration in the catchment material while replicating the original extraction mapping function. All of these features have been optimized or have sufficient understanding to characterize the basic factors that will define a complete data set extracted solely from x-ray imagery. It is an ideal time to develop such a process, with extracted fragments providing “ground truth” against image-only data, and abundant available imagery of the same fragments under both the prior and replacement x-ray technologies, which have several fundamentally different characteristics. This paper addresses the types and quality of hypervelocity fragmentation data that can be and has been extracted from x-rays. It further addresses the question of whether and under what circumstances future hypervelocity experiments can use x-ray methods to largely—or to completely—avoid the extraction process in recording all appropriate results. Lastly, this paper addresses lessons learned and how future efforts can be further optimized.

John B. Bacon↗
DOE OSTI2026

The Kinetic Consequences of Water on Catalytic Methane Pyrolysis

Hydrogen production from biomass and natural gas has emerged as a prominent research area in response to the growing demand for energy from alternative sources that minimize CO 2 emissions. In this study, we investigate the impact of water, which is present in and generated from biomass-derived streams, on carbon nanotube (CNT) growth and hydrogen production during methane decomposition using Ni–Mo/MgO as a catalyst. We reveal here that the role of water on CNT growth is highly complex; its effect depends on the stage of growth at which the water is incorporated. When water is introduced at the beginning of methane decomposition ( t = 0 h), methane conversion rates are negatively impacted. We hypothesize that water inhibits the significant phase changes the Ni–Mo/MgO catalyst undergoes during catalyst carburization. In contrast, the incorporation of a small percentage of water after a stabilization period ( t = 3 h) results in methane conversion rate enhancements that scale with the introduced water partial pressure as water selectively reacts with amorphous carbon deposits that lead to catalyst deactivation, thus prolonging the lifetime of some of the most active sites. Moreover, water incorporation after stabilization significantly reduces the apparent activation energy. Density Functional Theory (DFT) calculations reveal that water preferentially interacts with carbon fragments on the catalyst surface to remove carbon deposits with a barrier lower than that required for methane activation, further supporting its role in cleaning active sites on the catalyst surface. Characterization of the resulting carbon nanotubes reveals the formation of more graphitic materials produced in the presence of water, highlighting the impact of water on nanotube properties. These results provide clarity toward the many ways in which water, or cofeeding of biomass-derived materials, may impact catalytic methane pyrolysis rates.

carbon nanotubes↗
NASA NTRS1992

Production of H-3 at large momentum in alpha-(C-12) collisions at 2A GeV

Calculations of the longitudinal and transverse momentum distributions for H-3 production at large momentum in alpha-(C-12) collisions near 2A GeV are compared to experiment. Triton exchange and final-state interactions are shown to represent large corrections to the impulse approximation for proton knockout. A method for calculating interference effects for inelastic fragmentation is discussed. Good agreement with experiment using a phenomenological overlap function for (H-3)-p is found successful in describing H-3 production in pion-induced reactions. Comparisons to momentum distributions obtained through (p, 2p) and (e, ep) reactions on He-4 are made.

Cucinotta, Francis A.↗
NASA NTRS2019

Decomposition of Electron Ionization Mass Spectra for Space Application Using a Monte-Carlo approach

Rationale: Quadrupole mass spectrometers equipped with an electron ionization (EI) sources have been widely used in space exploration to investigate the composition of planetary surfaces and atmospheres. However, the complexity of the samples and the minimal calibration for the fragmentation of molecules in the ionization chambers have prevented the deconvolution of the majority of the mass spectra obtained at different targets, thus limiting the determination of the exact composition of the samples analyzed. We propose a Monte‐Carlo approach to solve this issue mathematically. Methods: We decomposed simulated mass spectra of mixtures acquired with unit resolving power mass spectrometers and EI sources into the sum of the single components fragmentation patterns weighted by their relative concentration using interior‐point least‐square fitting. To fit compounds with poorly known fragmentation patterns, we used a Monte‐Carlo method to vary the intensity of individual fragment ions. We then decomposed the spectrum thousands of times to obtain a statistical distribution. Results: By performing the deconvolution on a mixture of seven different molecules with interfering fragmentation patterns (H2O, O2, CH4, Ar, N2, C2H4, and C2H6) we show that this approach retrieves the mixing ratio of the individual components more accurately than regular mass spectra decomposition methods that rely on fragmentation patterns from general databases. It also provides the probability density function for each species's mixing ratio. Conclusions: By removing the solution degeneracy in the decomposition of mass spectra, the method described herein could significantly increase the scientific retrieval from archived space flight mass spectrometry data, where calibration of the ionization source is no longer an option.

Thomas Gautier↗
NASA NTRS2017

Fragmentation Increases Impact of Wind Disturbance on Forest Structure and Carbon Stocks in a Western Amazonian Landscape

Tropical second-growth forests could help mitigate climate change, but the degree to which their carbon potential is achieved will depend on exposure to disturbance. Wind disturbance is common in tropical forests, shaping structure, composition, and function, and influencing successional trajectories. However, little is known about the impacts of extreme winds in fragmented landscapes, though second-growth forests are often located in mosaics of forest, pasture, cropland, and other land cover types. Though indirect evidence suggests that fragmentation increases risk of wind damage, few studies have found such impacts following severe storms. In this study, we ask whether fragmentation and forest type (old vs. second growth) were associated with variation in wind damage after a severe convective storm in a fragmented production landscape in western Amazonia. We applied linear spectral unmixing to Landsat 8 imagery from before and after the storm, and combined it with field observations of damage to map wind effects on forest structure and biomass (Figure 4, 5). We also used Landsat 8 imagery to map land cover with the goals of identifying old- and second-growth forest and characterizing fragmentation. We used these data to assess variation in wind disturbance across 95,596 hectares of forest, distributed over 6,110 patches. We find that fragmentation is significantly associated with wind damage, with damage severity higher at forest edges and in edgier, more isolated patches (Figure 7). Damage was more severe in old-growth than in second-growth forests, but this effect was weaker than that of fragmentation (Figure 8). These results illustrate the importance of considering spatial configuration and landscape context in planning tropical forest restoration and predicting carbon sequestration in second-growth forests. Future research should address the mechanisms behind these results, to minimize wind damage risk in second-growth forests so their carbon potential can be maximally achieved.

Schwartz, Naomi B.↗
DOE OSTI2025

Convergent Protocols for Computing Protein–Ligand Interaction Energies Using Fragment-Based Quantum Chemistry

Fragment-based quantum chemistry methods offer a way to sidestep the steep nonlinear scaling of electronic structure calculations so that large molecular systems can be investigated using high-level methods. Here, we use fragmentation to compute protein–ligand interaction energies in systems with several thousand atoms, using a new software platform for managing fragment-based calculations that implements a screened many-body expansion. Convergence tests using a minimal-basis semiempirical method (HF-3c) indicate that two-body calculations, with single-residue fragments and simple hydrogen caps, are sufficient to reproduce interaction energies obtained using conventional supramolecular electronic structure calculations, to within 1 kcal/mol at about 1% of the computational cost. We also demonstrate that the HF-3c results are illustrative of trends obtained with density functional theory in basis sets up to augmented quadruple-ζ quality. Strategic deployment of fragmentation facilitates the use of converged biomolecular model systems alongside high-quality electronic structure methods and basis sets, bringing ab initio quantum chemistry to systems of hitherto unimaginable size. This will be useful for generation of high-quality training data for machine learning applications.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS2004

The Conservation of Structure and Mechanism of Catalytic Action in a Family of Thiamin Pyrophosphate (TPP)-dependent Enzymes

Thiamin pyrophosphate (TPP)-dependent enzymes are a divergent family of TPP and metal ion binding proteins that perform a wide range of functions with the common decarboxylation steps of a -(O=)C-C(OH)- fragment of alpha-ketoacids and alpha- hydroxyaldehydes. To determine how structure and catalytic action are conserved in the context of large sequence differences existing within this family of enzymes, we have carried out an analysis of TPP-dependent enzymes of known structures. The common structure of TPP-dependent enzymes is formed at the interface of four alpha/beta domains from at least two subunits, which provide for two metal and TPP-binding sites. Residues around these catalytic sites are conserved for functional purpose, while those further away from TPP are conserved for structural reasons. Together they provide a network of contacts required for flip-flop catalytic action within TPP-dependent enzymes. Thus our analysis defines a TPP-action motif that is proposed for annotating TPP-dependent enzymes for advancing functional proteomics.

Dominiak, P.↗
NASA NTRS1998

C2 Fragmentation Energy of C60 Revisited: Theory Disagrees with Most Experiments

Following our earlier work on the subject, we have carried out density functional theory (DFT) and second-order Moller-Plesset perturbation theory (MP2) calculations of the dissociation energy of the reaction C60 yields C58 + C2 using polarized basis sets and geometries optimized with DFT methods. The present theoretical results support an electronic fragmentation energy D(sub e) around 10-11 eV in disagreement with most experimental results that place the dissociation energy D(sub o) (including zero point energy) around 7-8 eV. The plausible errors remaining in the theoretical calculations are unlikely to account for this big difference (2-4 eV).

Boese, A. Daniel↗
NASA NTRS1996

Study of Analytic Statistical Model for Decay of Light and Medium Mass Nuclei in Nuclear Fragmentation

The angular momentum independent statistical decay model is often applied using a Monte-Carlo simulation to describe the decay of prefragment nuclei in heavy ion reactions. This paper presents an analytical approach to the decay problem of nuclei with mass number less than 60, which is important for galactic cosmic ray (GCR) studies. This decay problem of nuclei with mass number less than 60 incorporates well-known levels of the lightest nuclei (A less than 11) to improve convergence and accuracy. A sensitivity study of the model level density function is used to determine the impact on mass and charge distributions in nuclear fragmentation. This angular momentum independent statistical decay model also describes the momentum and energy distribution of emitted particles (n, p, d, t, h, and a) from a prefragment nucleus.

Cucinotta, Francis A.↗
NASA NTRS1988

Characteristics of satellite breakups from radar cross section and plane change angle

A problem of considerable interest in orbital debris research is the determination of the cause of the fragmentation of a satellite from the observed radar cross section and orbital element data. In this paper, analytic representations of the observed distribution functions of the radar cross section and the orbital plane change angle are derived. This then allows for the extraction of a small number of features that describe the observed data. Based on the known cause of fragmentation of a subset of satellites, a linear classifier is trained on these derived features. The discriminant function derived from this training is used to determine the previously unknown cause of the satellite breakup. the technique developed is objective and has been applied to the study of the cause of a number of unknown satellite breakup events.

Badhwar, Gautam D.↗
NASA NTRS1992

Bohemian circular structure, Czechoslovakia: Search for the impact evidence

Test of the impact hypothesis for the origin of the circular, 260-km-diameter structure of the Bohemian Massif led to the discovery of glasses and breccias in the Upper Proterozoic sequence that can be compared to autogeneous breccias of larger craters. The black recrystallized glass contains small exsolution crystals of albite-oligoclase and biotite, regularly dispersed in the matrix recrystallized to quartz. The occurrence of these rocks is limited to a 1-sq-km area. It is directly underlain by the breccia of the pelitic and silty rocks cemented by the melted matrix, found on several tens of square kilometers. The melt has the same chemistry as rock fragments in major and in trace elements. It is slightly impoverished in water. The proportion of melted rocks to fragments varies from 1:5 to 10:1. The mineralogy of melt viens is the function of later, mostly contact metamorphism. On the contact of granitic plutons it abounds on sillimanite, cordierite, and small bullets of ilmenite. Immediately on the contact with syenodiorites it contains garnets. The metamorphism of the impact rock melt seems the most probable explanation of the mineralogy and the dry total fusion of rocks accompanied by the strong fragmentation. Other aspects of this investigation are discussed.

Rajlich, Petr↗
NASA NTRS1980

Emission line shapes produced by dissociative excitation of atmospheric gases

The spectral line shapes of the radiation emitted from O atoms produced by the dissociative excitation of O2, CO, CO2 and NO are investigated. Doppler line shapes are derived from time-of-flight spectra of O (5S0) atoms decaying by the emission of 1356-A radiation after being produced in electron impact experiments at incident electron energies from 25 to 300 eV. It is shown that the effective line width of the radiation is large compared with the Doppler absorption widths of ambient O atoms in both photoelectron and auroral excitation, and thus the dissociatively excited component of the O I 1304-A airglow will behave as though it were optically thin, exhibiting pronounced limb brightening effects and a scale height characteristic of the initial, local source function. It is found that the average kinetic energy of the dissociation fragments inferred from O I (5S) time-of-flight spectra is in good agreement with that of O I (3S) atoms in the electron impact dissociation of CO2, although not for O2. Finally, it is suggested that although electron impact dissociation of CO and CO2 contributes to the 1304-A emission in the upper atmosphere of Venus, it cannot be the dominant source of this radiation since the absolute cross sections for the reaction are too small.

Zipf, E. C.↗
NASA NTRS1981

Laboratory measurements of the cometary photochemical phenomena

Laboratory experiments are described that provide fundamental information about photochemical processes in comets. The yield of cometary radicals such as CN, OH, etc. can be determined as a function of photolyzing wavelength. Quantum state distributions of the internal energy of the cometary radicals can also be measured as a function of wavelength permitting one to define the recoil velocity of the fragments. This type of information supplies the data needed for more elaborate models to interpret the data being obtained on comets.

Jackson, W. M.↗
NASA NTRS2006

Isotopic Dependence of GCR Fluence behind Shielding

In this paper we consider the effects of the isotopic composition of the primary galactic cosmic rays (GCR), nuclear fragmentation cross-sections, and isotopic-grid on the solution to transport models used for shielding studies. Satellite measurements are used to describe the isotopic composition of the GCR. For the nuclear interaction data-base and transport solution, we use the quantum multiple-scattering theory of nuclear fragmentation (QMSFRG) and high-charge and energy (HZETRN) transport code, respectively. The QMSFRG model is shown to accurately describe existing fragmentation data including proper description of the odd-even effects as function of the iso-spin dependence on the projectile nucleus. The principle finding of this study is that large errors (+/-100%) will occur in the mass-fluence spectra when comparing transport models that use a complete isotopic-grid (approx.170 ions) to ones that use a reduced isotopic-grid, for example the 59 ion-grid used in the HZETRN code in the past, however less significant errors (<+/-20%) occur in the elemental-fluence spectra. Because a complete isotopic-grid is readily handled on small computer workstations and is needed for several applications studying GCR propagation and scattering, it is recommended that they be used for future GCR studies.

Cucinotta, Francis A.↗
DOE OSTI2026

The Myth of Fungible FTE: A Quantitative Assessment of Matrixed Resource Allocation

Matrix organizations allow scientific facilities to share specialized personnel across projects, operations, maintenance, and strategic initiatives. Nominal staffing allocations, however, may not capture the schedule consequences of fragmented individual commitments, limited access to specialist groups, and intermittent availability of key decision makers. We developed a stochas- tic, daily-time-step simulation of a hypothetical medium-sized accelerator-facility project com- prising sequential phases and parallel tasks. Each task requires role-specific work measured in FTE-days. Ordinary personnel may be unavailable because they contribute concurrently to other institutional activities, while designated key roles have independently specified daily un- availability probabilities. An organization-wide priority factor scales the number of people from each functional group who can effectively contribute to the project. It is interpreted as a composite proxy for project access and workforce fragmentation across competing commit- ments. We examined project completion time as a function of this factor and Project Lead unavailability using 100 Monte Carlo runs per condition. Increasing priority factor from 0.1 to 1.0 reduced median completion time from 1708.5 days (interquartile range 1681.5–1735.25) to 390 days (interquartile range 379–399). At priority factor = 0.1, increasing Project Lead unavailability from 0.5 to 0.9 increased median completion time from 1713.5 days (interquartile range 1691–1733.25) to 4,417 days (interquartile range 4271.75–4550.5). The model quantifies the commonly expected sensitivity of project schedules to fragmented resource commitments and limited coordination availability. Within this model, the results also indicate a possible threshold regime in which small increases in workforce availability yield only modest sched- ule improvements until sufficient capacity becomes accessible, after which project performance improves sharply. With further validation and calibration, this quantitative framework could support resource-allocation decisions during initial project planning and subsequent schedule rebaselining.

Bai, Mei [SLAC National Accelerator Laboratory (SL↗
DOE OSTI2024

Determining Key Factors for the Open-Loop Control of Molecular Fragmentation Using Shaped Strong Fields

Pulse shaping has long been employed for tailoring femtosecond laser pulses to study and control the fragmentation of polyatomic molecules. In many cases, a physical explanation connecting the properties of the field to the observed control is difficult to ascertain. We utilized 80 bit binary spectral phase functions to parametrize and map the search space, gaining insight into which pulse parameters most impact the ion yield and fragmentation pattern for the relatively large triethylamine [N(C 2 H 5 ) 3 ] molecule. Pulse structures used to control the m/z 86 branching ratio beyond a simple intensity dependence are identified and compared to pump–probe results. All of these findings are explained in terms of control via a dissociative Rydberg state in the neutral molecule. This methodology may be used to discover new control mechanisms and shed light onto which pulse parameters most influence the interaction between strong field lasers and matter.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS2005

Conservation of Fold and Topology of Functional Elements in Thiamin Pyrophosphate Enzymes

Thiamin pyrophosphate (TPP)-dependent enzymes are a highly divergent family of proteins binding both TPP and metal ions. They perform decarboxylation-hydroxyaldehydes. Prior -ketoacids and of a common - (O=)C-C(OH)- fragment of to knowledge of three-dimensional structures of these enzmes, the GDGY25-30NN sequence was used to identify these enzymes. Subsequently, a number of structural studies on those enzymes revealed multi-subunit organization and the features of the two duplicate cofactor binding sites. Analyzing the structures of 44 structurally known enzymes, we found that the common structure of these enzymes is reduced to 180-220 amino acid long fragments of two PP and two PYR domains that form the [PP:PYR]2 binding center of two cofactor molecules. The structures of PP and PYR are arranged in a similar fold-sheet with triplets of helices on both sides.Dconsisting of a six-stranded Residues surrounding the cofactors are not strictly conserved, but they provide the same interatomic contacts required for the catalytic functions that these enzymes perform while maintaining interactive structural integrity. These structural and functional amino acids are topological counterparts located in the same positions of the conserved fold of sets of PP and PYR domains. Additional parallels include short fragments of sequences that link these amino acids to the fold and function. This report on the structural commonalities amongst TPP dependent enzymes is thought to contribute new approaches to annotation that may assist in advancing the functional proteomics of TPP dependent enzymes, and trace their complexity within evolutionary context.

Dominiak, P.↗