Search NASA⌕ Search

SEARCH · Search NASA

Results for “synthetic shells”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1994

Theoretical spectra of circumstellar dust shells around carbon-rich asymptotic giant branch stars

Realistic modeling of circumstellar dust shells around evolved stars has to include a physical treatment of the interaction among hydrodynamics, thermodynamics, radiative transfer, chemistry and dust formation and -growth. A self-consistent solution of this problem is presented in the case of stationary, spherical symmetric dust-driven winds. The resulting shell structure and the mass-loss rate are completely determined by the three fundamental stellar parameters stellar mass M(stellar), stellar luminosity L(stellar) and effective temperature T(sub eff) and by the element abundances epsilon(sub i). A detailed calculation of the transport coefficients of the dust component by means of the particle size distribution function and the solution of the non-grey radiative transfer problem provide realistic synthetic spectra of the dust shell models. We discuss the dependence of the resulting spectra on the stellar parameters in terms of infrared two color diagrams. Application of these model calculations to the prominent infrared object IRC +10216 yields best agreement with the observed spectrum and the visibility data at maximum light for the stellar parameters M(stellar) = 0.7 solar mass, L(stellar) = 2.4 x 10(exp 4) solar luminosity, T(stellar) = 2010K and a carbon to oxygen ratio of epsilon(sub c)/epsilon(sub o) = 1.40, which corresponds to a mass-loss rate of M-dot = 8 x 10(exp -5) solar mass/yr. In this model only amorphous carbon grains are considered as the main opacity source. From this model a distance to IRC +10216 of d = 170pc is deduced. The total mass contained in the circumstellar dust shell implies and initial main sequence mass of M(sub ZAMS) greater than or = 1.3 solar mass for IRC +10216.

Winters, J. M.↗
NASA NTRS1999

Backus Effect on a Perpendicular Errors in Harmonic Models of Real vs. Synthetic Data

Measurements of geomagnetic scalar intensity on a thin spherical shell alone are not enough to separate internal from external source fields; moreover, such scalar data are not enough for accurate modeling of the vector field from internal sources because of unmodeled fields and small data errors. Spherical harmonic models of the geomagnetic potential fitted to scalar data alone therefore suffer from well-understood Backus effect and perpendicular errors. Curiously, errors in some models of simulated 'data' are very much less than those in models of real data. We analyze select Magsat vector and scalar measurements separately to illustrate Backus effect and perpendicular errors in models of real scalar data. By using a model to synthesize 'data' at the observation points, and by adding various types of 'noise', we illustrate such errors in models of synthetic 'data'. Perpendicular errors prove quite sensitive to the maximum degree in the spherical harmonic expansion of the potential field model fitted to the scalar data. Small errors in models of synthetic 'data' are found to be an artifact of matched truncation levels. For example, consider scalar synthetic 'data' computed from a degree 14 model. A degree 14 model fitted to such synthetic 'data' yields negligible error, but amplifies 4 nT (rmss) added noise into a 60 nT error (rmss); however, a degree 12 model fitted to the noisy 'data' suffers a 492 nT error (rmms through degree 12). Geomagnetic measurements remain unaware of model truncation, so the small errors indicated by some simulations cannot be realized in practice. Errors in models fitted to scalar data alone approach 1000 nT (rmss) and several thousand nT (maximum).

Voorhies, C. V.↗
NASA NTRS2004

Discovering Planetary Nebula Geometries: Explorations with a Hierarchy of Models

Astronomical objects known as planetary nebulae (PNe) consist of a shell of gas expelled by an aging medium-sized star as it makes its transition from a red giant to a white dwarf. In many cases this gas shell can be approximately described as a prolate ellipsoid. Knowledge of the physics of ionization processes in this gaseous shell enables us to construct a model in three dimensions (3D) called the Ionization-Bounded Prolate Ellipsoidal Shell model (IBPES model). Using this model we can generate synthetic nebular images, which can be used in conjunction with Hubble Space Telescope (HST) images of actual PNe to perform Bayesian model estimation. Since the IBPES model is characterized by thirteen parameters, model estimation requires the search of a 13-dimensional parameter space. The 'curse of dimensionality,' compounded by a computationally intense forward problem, makes forward searches extremely time-consuming and frequently causes them to become trapped in local solutions. We find that both the speed and of the search can be improved by judiciously reducing the dimensionality of the search space. Our basic approach employs a hierarchy of models of increasing complexity that converges to the IBPES model. Earlier studies establish that a hierarchical sequence converges more quickly, and to a better solution, than a search relying only on the most complex model. Here we report results for a hierarchy of five models. The first three models treat the nebula as a 2D image, while the last two models explore its characteristics as a 3D object and enable us to characterize the physics of the nebula. This five-model hierarchy is applied to HST images of ellipsoidal PNe to estimate their geometric properties and gas density profiles.

Huyser, Karen A.↗
NASA NTRS2022

Quantifying Errors in 3D CME Parameters Derived from Synthetic Data Using White-Light Reconstruction Techniques

Current efforts in space weather forecasting of CMEs have been focused on predicting their arrival time and magnetic structure. To make these predictions, methods have been developed to derive the true CME speed, size, position, and mass, among others. Difficulties in determining the input parameters for CME forecasting models arise from the lack of direct measurements of the coronal magnetic fields and uncertainties in estimating the CME 3D geometric and kinematic parameters after eruption. White-light coronagraph images are usually employed by a variety of CME reconstruction techniques that assume more or less complex geometries. This is the first study from our International Space Science Institute (ISSI) team “Understanding Our Capabilities in Observing and Modeling Coronal Mass Ejections”, in which we explore how subjectivity affects the 3D CME parameters that are obtained from the Graduated Cylindrical Shell (GCS) reconstruction technique, which is widely used in CME research. To be able to quantify such uncertainties, the “true” values that are being fitted should be known, which are impossible to derive from observational data. We have designed two different synthetic scenarios where the “true” geometric parameters are known in order to quantify such uncertainties for the first time. We explore this by using two sets of synthetic data: 1) Using the ray-tracing option from the GCS model software itself, and 2) Using 3D magnetohydrodynamic (MHD) simulation data from the Magnetohydrodynamic Algorithm outside a Sphere code. Our experiment includes different viewing configurations using single and multiple viewpoints. CME reconstructions using a single viewpoint had the largest errors and error ranges overall for both synthetic GCS and simulated MHD white-light data. As the number of viewpoints increased from one to two, the errors decreased by approximately 4° in latitude, 22° in longitude, 14° in tilt, and 10° in half-angle. Our results quantitatively show the critical need for at least two viewpoints to be able to reduce the uncertainty in deriving CME parameters. We did not find a significant decrease in errors when going from two to three viewpoints for our specific hypothetical three spacecraft scenario using synthetic GCS white-light data. As we expected, considering all configurations and numbers of viewpoints, the mean absolute errors in the measured CME parameters are generally significantly higher in the case of the simulated MHD white-light data compared to those from the synthetic white-light images generated by the GCS model. We found the following CME parameter error bars as a starting point for quantifying the minimum error in CME parameters from white-light reconstructions: Δθ (latitude)=6° +2° -3° , Δϕ (longitude)=11° +18° -6° , Δγ (tilt)=25° +8° -7° , Δx (half-angle)=10° +12° -6° , Δh (height)=0.6 +1.2 -0.4 R ⨀ , and Δκ (ratio)=0.1 +0.03 -0.02 .

Coronal mass ejections↗
NASA NTRS2022

Quantifying Errors in 3D CME Parameters Derived From Synthetic Data Using White-Light Reconstruction Techniques

Current efforts in space weather forecasting of CMEs have been focused on predicting their arrival time and magnetic structure. To make these predictions, methods have been developed to derive the true CME speed, size, position, and mass, among others. Difficulties in determining the input parameters for CME forecasting models arise from the lack of direct measurements of the coronal magnetic fields and uncertainties in estimating the CME 3D geometric and kinematic parameters after eruption. White-light coronagraph images are usually employed by a variety of CME reconstruction techniques that assume more or less complex geometries. This is the first study from our International Space Science Institute (ISSI) team “Understanding Our Capabilities in Observing and Modeling Coronal Mass Ejections”, in which we explore how subjectivity affects the 3D CME parameters that are obtained from the Graduated Cylindrical Shell (GCS) reconstruction technique, which is widely used in CME research. To be able to quantify such uncertainties, the “true” values that are being fitted should be known, which are impossible to derive from observational data. We have designed two different synthetic scenarios where the “true” geometric parameters are known in order to quantify such uncertainties for the first time. We explore this by using two sets of synthetic data: 1) Using the ray-tracing option from the GCS model software itself, and 2) Using 3D magnetohydrodynamic (MHD) simulation data from the Magnetohydrodynamic Algorithm outside a Sphere code. Our experiment includes different viewing configurations using single and multiple viewpoints. CME reconstructions using a single viewpoint had the largest errors and error ranges overall for both synthetic GCS and simulated MHD white-light data. As the number of viewpoints increased from one to two, the errors decreased by approximately 4° in latitude, 22° in longitude, 14° in tilt, and 10° in half-angle. Our results quantitatively show the critical need for at least two viewpoints to be able to reduce the uncertainty in deriving CME parameters. We did not find a significant decrease in errors when going from two to three viewpoints for our specific hypothetical three spacecraft scenario using synthetic GCS white-light data. As we expected, considering all configurations and numbers of viewpoints, the mean absolute errors in the measured CME parameters are generally significantly higher in the case of the simulated MHD white-light data compared to those from the synthetic white-light images generated by the GCS model. We found the following CME parameter error bars as a starting point for quantifying the minimum error in CME parameters from white-light reconstructions: Δθ (latitude)=6° +2° -3° , Δϕ (longitude)=11° +18° -6° , Δγ (tilt)=25° +8° -7° , Δx (half-angle)=10° +12° -6° , Δh (height)=0.6 +1.2 -0.4 R ⨀ , and Δκ (ratio)=0.1 +0.03 -0.02 .

Coronal mass ejections↗
NASA NTRS1990

Bipolar supernova remnants and the obliquity dependence of shock acceleration

The diffusive shock acceleration mechanism proposed to explain the bipolarity observed in the synchrotron radio emission of young adiabatically expanding shell SNRs is investigated by means of numerical simulations. The theoretical basis of the SNR models and the numerical computation methods are explained, and the results are presented in graphs and synthetic radio maps and discussed in detail. It is found that the efficiency of the acceleration process depends on the obliquity angle theta(Bn) between the shock normal and the uniform magnetic field: models with theta(Bn) of about 90 deg can reproduce the observed azimuthal intensity ratios in most cases, but models with theta(Bn) near 0 deg cannot.

Fulbright, Michael S.↗
NASA NTRS1987

Mussel Glue

A mytilus edilus, a common blue ocean mussel is attaching itself to the underside of a wet glass in a laboratory. It secretes a glue like substance in the form of multiple threads which attach to surfaces such as shells, rocks, piers and ships. This natural super glue hardens within minutes and tightly affixes to its selected platform even in the roughest seas. Its superior adhesive properties suggest many practical applications. One company, Bio-Polymers, Inc., has developed a synthetic mussel glue for the commercial market.

Source record↗
NASA NTRSDate not supplied

BioNutrients: Microbial on-demand production of short shelf-life micronutrients in space

Long duration deep space missions pose a significant challenge when considering adequate nutrition for human spaceflight. Many micronutrients supplied in pre-packaged foods for low Earth orbit flights have a short shelf life and will degrade over multi-year missions. One strategy to mitigate the risk of micronutrient malnutrition is to grow fresh foods to supplement a pre-packaged diet. The BioNutrients project aims to develop systems for growing edible microorganisms that are genetically engineered to produce short shelf life micronutrients. BioNutrients-1 (BN-1) is a five-year spaceflight project currently underway on the International Space Station (ISS) that tests long-term storage and production of two carotenoids, β-carotene and zeaxanthin, in genetically engineered yeast strains. BN-1 on-orbit and ground control activities indicate that the nutrient production system will be stable for at least two years in ambient storage conditions. BN-1 is also testing the effects of long-term ISS storage on viability and gene expression using “stasis packs” containing a series of microorganisms useful in food and biomanufacturing processes. Stasis pack analysis is distinguishing microorganisms with full viability after two years of storage from other species that lose viability rapidly. In parallel, BioNutrients-2 (BN-2) is being developed as a six-month flight experiment that will expand the range of foods produced on ISS to include yogurt, kefir, and probiotic yeast. BN-2 will improve upon hardware design by transitioning from a hard-shell polycarbonate bioreactor to a flexible fluorinated ethylene propylene (FEP) bag. This change reduces the mass and volume required to store production packs. The long-term goal of BioNutrients is to develop the capability for rapid and safe delivery of multiple micronutrients in single-use production packs. We expect synthetic biology approaches similar to BioNutrients will play an important role for astronaut health in future NASA missions to the Moon and Mars.

Synthetic Biology↗
NASA NTRS2001

Multiwavelength Modeling of Nove Atmospheres

LMC 1988 #1 was a slow, CO type, dust forming classical nova. It was the first extragalactic nova to be observed with the IUE satellite. We have successfully fitted observed ultraviolet and optical spectra of LMC 1988 #1 taken within the first two months of its outburst (when the atmosphere was still optically thick) with synthetic spectra computed using PHOENIX nova model atmospheres. The synthetic spectra reproduce most of the features seen in the spectra and provide V band magnitudes consistent with the observed light curve. The fits are improved by increasing the CNO abundances to 10 times the solar values. The bolometric luminosity of LMC 1988 #1 was approximately constant at 2 x 10(exp 38) ergs per second at a distance of 47.3 kpc for the first 2 months of the outburst until the formation of the dust shell.

Huschildt, P. H.↗
NASA NTRS2015

3D Printing of Advanced Biocomposites on Earth and Beyond

Human exploration off planet is severely limited by the cost of launching materials into space and re-supply. Thus materials brought from earth must be light, stable and reliable at destination. Using traditional approaches a lunar or Mars base would require either transporting a hefty store of metals or heavy manufacturing equipment and construction materials for in situ extraction; both would severely limit any other mission objectives. Long-term human space presence requires periodic replenishment, adding a massive cost overhead. Even robotic missions often sacrifice science goals for heavy radiation and thermal protection. Biology has the potential to solve these problems because it can replicate and repair itself, and do a wide variety of chemical reactions including making food, fuel and materials. Synthetic biology can greatly enhance and expand life's evolved repertoire. Using natural and synthetically altered organisms as the feedstock for additive manufacturing could one day make possible the dream of producing bespoke tools, food, smart fabrics and even replacement organs on demand. To this end our lab has produced a proof-of-concept bioprinter with nearly one-cell resolution. Genetically engineering yeast cells to secrete bioproducts subsequent to printing allows the potential to make biomaterials with a fine microstructure. Imagine a production system that, at a few micron scale resolution, can add mollusk shell for compressive strength per unit mass, spider silk or collagen for tensile strength per unit mass, and potentially biologically-deposited wires. Now imagine what new products can be enabled by such a technology, on earth or beyond

Metals↗
NASA NTRS2014

3D Printing of Advanced Biocomposites on Earth and Beyond

Human exploration off planet is severely limited by the cost of launching materials into space and re-supply. Thus materials brought from earth must be light, stable and reliable at destination. Using traditional approaches a lunar or Mars base would require either transporting a hefty store of metals or heavy manufacturing equipment and construction materials for in situ extraction; both would severely limit any other mission objectives. Long-term human space presence requires periodic replenishment, adding a massive cost overhead. Even robotic missions often sacrifice science goals for heavy radiation and thermal protection. Biology has the potential to solve these problems because it can replicate and repair itself, and do a wide variety of chemical reactions including making food, fuel and materials. Synthetic biology can greatly enhance and expand life's evolved repertoire. Using natural and synthetically altered organisms as the feedstock for additive manufacturing could one day make possible the dream of producing bespoke tools, food, smart fabrics and even replacement organs on demand. To this end our lab has produced a proof-of-concept bioprinter with nearly one-cell resolution. Genetically engineering yeast cells to secrete bioproducts subsequent to printing allows the potential to make biomaterials with a fine microstructure. Imagine a production system that, at a few micron scale resolution, can add mollusk shell for compressive strength per unit mass, spider silk or collagen for tensile strength per unit mass, and potentially biologically-deposited wires. Now imagine what new products can be enabled by such a technology, on earth or beyond.

Biology↗
NASA NTRS1989

Measurement of wavelengths for inner-shell transitions in Ca XVII-XIX

The wavelengths of transitions in solar flare spectra in the region 3.12-3.24 A have been measured using data recorded by a crystal spectrometer on the Air Force P78-1 spacecraft. Appearing in this wavelength region are inner-shell transitions of the type n = 1-2 in Ca XVII-XIX and resonance transitions in Ar XVII, Ar XVIII, and Fe XXV. The hydrogenic Ar XVIII 1s-1p transition was used to establish an absolute wavelength scale with an estimated uncertainty of 0.3 mA, and the relative wavelengths were measured to an uncertainty that is typically less than 0.1 mA. The presently measured wavelengths are compared with previously measured and calculated wavelengths, and the observed flare spectra are compared with synthetic spectra.

Seely, J. F.↗
NASA NTRS2009

The Lunar Regolith as a Remote Sensing Target for the Lunar Reconnaissance Orbiter (LRO)

Of the 6 instruments and one technology demonstration aboard the LRO, only CRaTER does not measure some kind of interaction of particles with the lunar regolith. LEND detects neutron fluence that contains information about the number density of protons in the upper regolith. To infer the presence of protons, the PI must assume a model that characterizes the surface as a collection of atoms. Thus, LEND does not sense the regolith as a structure. LROC, LOLA, and LAMP sense reflected photons whose wavelength is much shorter than the median particle size in the regolith. The photons interact with electrons, either in atomic shells or in chemical bonds. These interactions occur within a nanometer or so of the surface of a particle. Thus, the particles are macroscopic objects and models of the reflection process invoke ray-tracing optics. DIVINER senses photons that have been emitted by surface particles through thermal phonon processes. The wavelengths detected by the instrument are of the same order as the median particle size, and the photons contain information on particle dimensions as well as the molecular bonds in the constituent compounds. The Mini-RF synthetic aperture radar generates and detects photons of a few centimeters wavelength that interact with the regolith as a dielectric, the dielectric properties of the particulate component being described through effective medium theory. However, the interaction with rocks (macroscopic objects of interest to geologists) can be characterized using Fresnel or Mie models of electromagnetic properties.

Mendell, Wendell W.↗
NASA NTRS2016

CME Flux Rope and Shock Identifications and Locations: Comparison of White Light Data, Graduated Cylindrical Shell Model, and MHD Simulations

Coronal mass ejections (CMEs) are major transient phenomena in the solar corona that are observed with ground-based and spacecraft-based coronagraphs in white light or with in situ measurements by spacecraft. CMEs transport mass and momentum and often drive shocks. In order to derive the CME and shock trajectories with high precision, we apply the graduated cylindrical shell (GCS) model to fit a flux rope to the CME directed toward STEREO A after about 19:00 UT on 29 November 2013 and check the quality of the heliocentric distance-time evaluations by carrying out a three-dimensional magnetohydrodynamic (MHD) simulation of the same CME with the Block Adaptive Tree Solar-Wind Roe Upwind Scheme (BATS-R-US) code. Heliocentric distances of the CME and shock leading edges are determined from the simulated white light images and magnetic field strength data. We find very good agreement between the predicted and observed heliocentric distances, showing that the GCS model and the BATS-R-US simulation approach work very well and are consistent. In order to assess the validity of CME and shock identification criteria in coronagraph images, we also compute synthetic white light images of the CME and shock. We find that the outer edge of a cloud-like illuminated area in the observed and predicted images in fact coincides with the leading edge of the CME flux rope and that the outer edge of a faint illuminated band in front of the CME leading edge coincides with the CME-driven shock front.

Schmidt, J. M.↗
NASA NTRS1993

The onset of Wolf-Rayet wind outflow and the nature of the hot component in the symbiotic nova PU Vulpecula

We have analyzed temporal variations in the far ultraviolet He II (1640), Si IV (1393, 1402), and C IV (1548, 1550) line profiles in eight high dispersion, International Ultraviolet Explorer Short Wavelength Prime spectra of the symbiotic nova PU Vul by comparatively examining these profiles on a common velocity scale. We see clear evidence of the onset of a Wolf-Rayet-like wind outflow from the bloated, contracting white dwarf hot component with terminal velocity of approximately equals -550 to -600 km/s. We have quantitatively analyzed the complicated He II (1640) emission region for the first time and show that the discrete absorption features seen in the He II region occur at precisely the same velocites in each spectrum, thus demonstrating that the absorbing source is steady and not affected by any orbital motion. We demonstrate that there is an underlying He II wind emission feature whose true shape is hidden by superposed absorption due to the foreground red giant wind flowing in front of the white dwarf and abscuring the white dwarf's wind outflow. We present synthetic spectra of He II emission behind an absorbing slab with u = 20 km/s, T = 5000 K, and column densities in the range N = 1 x 10(exp 22) and 1 x 10(exp 23)/sq cm which explain these absorptions. Our analysis of the Si IV and C IV resonance doublets, in velocity space, reveal temporal variations in the profile between 1987 and 1991 with the emergence of clear P Cygni profiles in Si IV by 1990. A nebular emission feature in C III 1909 also appears in the most recent spectra (e.g., SW42538H) while it was absent or extremely weak in the earliest spectra (e.g., SW36332H), thus strengthening evidence that the nebular emission, as seen in permitted and semiforbidden lines, intensities in step with the onset of the hot, fast, wind outflow. We also report the first detection of narrow interstellar (circumbinary shell?) absorption lines near -1 km/s, most strongly in Al III (1854, 1862) and Si IV (1392, 1402). We have carried out a rough quantitative analysis of the He II wind emission by using the theoretical He II Wolf-Rayet profiles of Hamann & Schmutz (1987). We obtain a lower limit to the He II net emission equivalent width of approximately 1 A, a hot component temperature in the range 25,000 to 35,000 K, a hot component radius in the range 5 solar radius to 30 solar radius, a maximum wind velocity of approximately equals -600 km/s and a rough upper limit to the mass-loss rate of less than 1 x 10(exp -5) solar mass/yr. To our knowledge, this is the first quantitative wind analysis, albeit crude, to be carried out for the hot component of a symbiotic nova or symbiotic variable.

Sion, Edward M.↗
NASA NTRS2005

Overview of Biomineralization and Nanobacteria

Biomineralization is a frequently used term in nanotechnology, astrobiology, geology, and medicine. In the process of biomineralization, a living organism provides a chemical environment that controls the nucleation and growth of unique mineral phases. Often these materials exhibit hierarchical structural order, leading to superior physical properties, not found either in their inorganic counterparts or in synthetic materials. Biomineralization is widespread in the biosphere and hundreds of different minerals are produced or assisted by a variety of organisms from bacteria to humans. Teeth, bones, kidney stones, and skeletons of algae, mussels, and magnetotactic bacteria are all examples of biomineralization. We do not fully understand the control mechanism of biomineralization either in primitive or in developed organisms. The presence of organic molecules, among other characteristics, can influence the coherence length for X-ray scattering in biogenic crystals. Control over biomineral properties can be accomplished at a myriad of levels, including the regulation of particle size, shape, crystal orientation, polymorphic structure, defect texture, and particle assembly. In the latter case, cellular processes enable control in both the spatial and temporal domain in such a way that hierarchical composite structures can be built which increase the toughness and durability of the material, which is invaluable for load-bearing materials such as bones, teeth, mollusk shells, etc. Durability of biominerals produces remarkably preserved bacterial and cyanobacterial microfossils from billions of years-old samples. The differentiation between microfossils and nonbiogenic artifacts has been a lively discussion subject in astrobiology especially in the last decade. Clearly, more detailed information on the mechanism of biomineralization, and the effect of organic matter on crystal formation/fossilization would help focus such discussions.

Ciftcioglu, N.↗
NASA NTRS2001

Rheology of Diabase: Implications for Tectonics on Venus and Mars

Two important goals of our experimental investigation of the rheological behavior of diabase rocks were: (1) to determine flow laws describing their creep behavior over wide ranges of temperature, stress and strain rate and (2) to develop an understanding of the physical mechanisms by which these rocks flow under laboratory conditions. With this basis, a primary objective then was to construct constitutive equations that can be used to extrapolate from laboratory to planetary conditions. We specifically studied the rheological properties of both natural rock samples and synthetic aggregates. The former provided constraints for geologic systems, while the latter defined the relative contributions of the constituent mineral phases and avoided the influence of glass/melt found in natural samples. In addition, partially molten samples of crustal rock composition were deformed in shear to large strains (greater than 200%) important in crustal environments. The results of this research yielded essential rheological properties essential for models of crustal deformation on terrestrial planets, specifically Venus and Mars, as well as on the geodynamical evolution of these planets. Over the past three years, we also completed our investigation of the creep behavior of water ice with applications to the glaciers, ice sheets and icy satellites. Constitutive equations were determined that describe flow over a wide ranged of stress, strain rate, grain size and temperature. In the case of ice, three creep regimes were delineate. Extrapolation demonstrates that dislocation glide and grain boundary sliding processes dominate flow in ice I under planetary conditions and that diffusion creep is not an important deformation mechanism either in the laboratory or on icy satellites. These results have already been incorporated by other investigators into models describing, for example, the thickness and stability of the ice shell on Europa and to unravel long-standing discrepancies between field observations on glaciers and laboratory results.

Kohlstedt, David L.↗
NASA NTRS2015

Biomaterials Out of Thin Air: in Situ, On-Demand Printing of Advanced Biocomposites

Upmass is the single most significant limitation of our current space mission capability. Although biomaterials and biocomposites have mass, strength, flexibility, and self-healing properties that could significantly reduce upmass, their use is limited by the following drawbacks: Expensive, specific production. Many biomaterials can only be produced as part of significant support ecosystem; Inaccessible functional customization. The grain of wood, the porosity of bone, and so on are an integral part of the materials' desired mechanical properties, but are not deterministic when the material is naturally grown; Limited compositions. Most biomaterials (unlike metal, plastic, etc.) cannot be easily combined or modified to produce new materials. This project builds on recent advances in: Synthetic biology. Libraries of standardized genetic parts which can be used for controlled cellular material production, delivery, and binding; 3D printing. Commercial off-the-shelf components which can be used to make of a pico- to nanoliter cell deposition system; Tissue engineering. Proven cell-compatible support hydrogels and scaffolds can be modified to bind the deposited biomaterials of interest. Objectives: Feasibility and benefit analysis. Two mission contexts span the concept's scope (see below); Proof-of-concept demonstration. A simple grid of two proteins, fluorescent for easy detection, to validate the core technology concept; Proposed implementations for follow-on work. Avenues for future work on each core component (host cell, production control, material delivery, material binding, etc.); Complementary studies exploration. A survey of other emerging areas (in situ resource utilization, protein engineering, etc.) with the potential to multiply our technology's impact. Potential Impacts: This application could dramatically expand manufacturing capabilities on Earth and in space: In situ resource utilization. A far greater range of materials and products will be available from the limited palette offered by in situ resource extraction techniques; Reduced equipment and material upmass for off-Earth habitats. Ready- to-use highly specialized construction materials (radiation hardened, compressive/tensile, light or dense) from an extremely low starting mass; Structured biomaterial production. New ready-to-use macro, micro, and molecular manufacturing techniques for traditional biomaterials such as wood, bone and shell; New and novel biocomposite creation. The ability to create completely novel material composites from any base material that cells can be engineered to produce. Suggested Mission Contexts: ISS part manufacturing. A 'minimal working example' making a finished biomaterial part aboard the International Space Station; A long-term Mars habitat. 'Cradle-to-grave' use at a hypothetical Mars habitat, covering everything from tools to construction materials. Alternate Abstract: Imagine being able to print anything from tools and composite building materials to food and human tissues. Imagine being on Mars with the ability to replace any broken part, whether it's a part of your spacesuit, your habitat, or your own body. We propose a technique that would allow just that. By printing 3D arrays of cells engineered to secrete the necessary materials, the abundant in situ resources of atmosphere and regolith become organic, inorganic, or organic-inorganic composite materials. Such materials include novel, biologically derived materials not previously possible to fabricate.

habitats↗