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Results for “Surface Tethering”

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 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS1992

Polyethylene Glycol Propionaldehydes

New class of compounds derived from polyethylene glycol (PEG's) namely, PEG-propionaldehydes, offers two important advantages over other classes of PEG aldehyde derivatives: compounds exhibit selective chemical reactivity toward amino groups and are stable in aqueous environment. PEG's and derivatives used to couple variety of other molecules, such as, to tether protein molecules to surfaces. Biotechnical and biomedical applications include partitioning of two phases in aqueous media; immobilization of such proteins as enzymes, antibodies, and antigens; modification of drugs; and preparation of protein-rejecting surfaces. In addition, surfaces coated with PEG's and derivatives used to control wetting and electroosmosis. Another potential application, coupling to aminated surfaces.

Harris, Joe M.↗
DOE OSTI2024

Interfacial dynamics mediate surface binding events on supramolecular nanostructures

The dynamic behavior of biological materials is central to their functionality, suggesting that interfacial dynamics could also mediate the activity of chemical events at the surfaces of synthetic materials. Here, we investigate the influence of surface flexibility and hydration on heavy metal remediation by nanostructures self-assembled from small molecules that are decorated with surface-bound chelators in water. We find that incorporating short oligo(ethylene glycol) spacers between the surface and interior domain of self-assembled nanostructures can drastically increase the conformational mobility of surface-bound lead-chelating moieties and promote interaction with surrounding water. In turn, we find the binding affinities of chelators tethered to the most flexible surfaces are more than ten times greater than the least flexible surfaces. Accordingly, nanostructures composed of amphiphiles that give rise to the most dynamic surfaces are capable of remediating thousands of liters of 50 ppb Pb 2+ -contaminated water with single grams of material. These findings establish interfacial dynamics as a critical design parameter for functional self-assembled nanostructures.

42 ENGINEERING↗
DOE OSTI2020

The Role of Ligand–Ligand Interactions in Multimodal Ligand Conformational Equilibria and Surface Pattern Formation

Multimodal chromatography uses multiple modes of interaction such as charge, hydrophobic, or hydrogen bonding to separate proteins. Recently, we used molecular dynamics (MD) simulations to show that ligands immobilized on surfaces can interact and associate with neighboring ligands to form hydrophobic and charge patches, which may have important implications for the nature of protein–surface interactions. Here, we study interfacial systems of increasing complexity—from a single immobilized multimodal ligand to high density surfaces—to better understand how ligand behavior is affected by the presence of a surface and the presence of other ligands in the vicinity, and how this behavior scales to larger systems. Furthermore, we find that tethering a ligand to a surface restricts its conformations to a subset of those observed in free solution, yet the ligand maintains flexibility in the plane of the surface and can form contacts with neighboring ligands. We find that although the formation of a contact between two neighboring ligands is slightly unfavorable, three neighboring ligands exhibit a preference for the formation of a fully connected cluster. To explore how these trends in ligand association extend to a larger surface with high density of ligands, we performed coarse-grained Monte Carlo (MC) simulations of a 132-ligand surface using ligand interactions parametrized based on free energies obtained from the three-ligand MD simulations. Despite their simplicity, the coarse-grained simulations qualitatively capture the cluster size distribution of ligands observed in detailed MD simulations. Quantitative differences between the two suggest opportunities for improvements in the coarse-grained energy function for efficient predictions of cluster and pattern formations. Our approach presents a promising route to the engineering of multimodal patterns for future chromatographic resin design.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1989

Calculating the electromagnetic field on the earth due to an electrodynamic tethered system in the ionosphere

A method is presented for calculating the electromagnetic wave field on the earth's surface associated with the operation of an electrodynamic tethered satellite system of constant or slowly varying current in the upper ionosphere. The wave field at the ionospheric boundary and on the earth's surface is obtained by numerical integration. The results suggest that the ionospheric waves do not propagate into the atmosphere and that the image of the Alfven wings from a steady-current tether should be greatly broadened on the earth's surface.

Estes, Robert D.↗
NASA NTRS1982

An intense, quasi-steady thunderstorm over mountainous terrain. I - Evolution of the storm-initiating mesoscale circulation

The evolution of mesoscale systems that eventually lead to the formation of large quasi-steady storm systems is investigated. The morphological and turbulent structure of the quasi-steady storm is described. Data obtained during the South Park Area Cumulus Experiment from surface meteorological stations, rawinsondes and tethered balloons, conventional and Doppler radars, powered aircraft, and satellites, indicate that on July 19, 1977, a north-south oriented line of intense convective cells formed and remained within South Park. Elevated surface heating created a region of low-level convergence, importing Pacific moisture from west of the Rockies. The mesoscale thunderstorm line formed over this convergence zone, and a single large convective cell was observed to grow on the southern end of the mesoscale line, exhibiting supercell characteristics and substantial modifications of the environmental flow.

Cotton, W. R.↗
NASA NTRS1994

Biogenic nonmethane hydrocarbon emissions estimated from tethered balloon observations

A new technique for estimating surface fluxes of trace gases, the mixed-layer gradient technique, is used to calculate isoprene and terpene emissions from forests. The technique is applied to tethered balloon measurements made over the Amazon forest and a pine-oak forest in Alabama at altitudes up to 300 m. The observations were made during the dry season Amazon Boundary Layer Experiment (ABLE 2A) and the Rural Oxidants in the Southern Environment 1990 experiment (ROSE I). Results from large eddy simulations of scalar transport in the clear convective boundary layer are used to infer fluxes from the balloon profiles. Profiles from the Amazon give a mean daytime emission of 3630 +/- 1400 micrograms isoprene sq m/h, where the uncertainty represents the standard deviation of the mean of eight flux estimates. Twenty profiles from Alabama give emissions of 4470 +/- 3300 micrograms isoprene sq m/h, 1740 +/- 1060 micrograms alpha-pinene sq m/h, and 790 +/- 560 micrograms beta-pinene sq m/h, respectively. These results are in agreement with emissions derived from chemical budgets. The emissions may be overestimated because of uncertainty about how to incorporate the effects of the canopy on the mixed-layer gradients. The large variability in these emission estimates is probably due to the relatively short sampling times of the balloon profiles, though spatially heterogeneous emissions may also play a role. Fluxes derived using this technique are representative of an upwind footprint of several kilometers and are independent of hydrocarbon oxidation rate and mean advection.

Davis, K. J.↗
NASA NTRS2023

Results from InSight Robotic Arm Activities

The InSight lander carried an Instrument Deployment System (IDS) that included an Instrument Deployment Arm (IDA), scoop, five finger “claw” grapple, forearm-mounted Instrument Deployment Camera (IDC) requiring arm motion to image a target, and landermounted Instrument Context Camera (ICC), designed to image the workspace, and to place the instruments onto the surface. As originally proposed, the IDS included a previously built arm and flight spare black and white cameras and had no science objectives or requirements, or expectation to be used after instrument deployment (90 sols). During project development the detectors were upgraded to color, and it was recognized that the arm could be used to carry out a wide variety of activities that would enable both geology and physical properties investigations. During surface operations for two martian years, the IDA was used during major campaigns to image the surface around the lander, to deploy the instruments, to assist the mole in penetrating beneath the surface, to bury a portion of the seismometer tether, to clean dust from the solar arrays to increase power, and to conduct a surface geology investigation including soil mechanics and physical properties experiments. No other surface mission has engaged in such a sustained and varied campaign of arm and scoop activities directed at such a diverse suite of objectives. Images close to the surface and continuous meteorology measurements provided important constraints on the threshold friction wind speed needed to initiate aeolian saltation and surface creep. The IDA was used extensively for almost 22 months to assist the mole in penetrating into the subsurface. Soil was scraped into piles and dumped onto the seismometer tether six times in an attempt to bury the tether and ∼ 30% was entrained in the wind and dispersed downwind 1-2 m, darkening the surface. Seven solar array cleaning experiments were conducted by dumping scoops of soil from 35 cm above the lander deck during periods of high wind that dispersed the sand onto the panels that kicked dust off of the panels into suspension in the atmosphere, thereby increasing the power by ∼15% during this period. Final IDA activities included an indentation experiment that used the IDA scoop to push on the ground to measure the plastic deformation of the soil that complemented soil mechanics measurements from scoop interactions with the surface, and two experiments in which SEIS measured the tilt from the arm pressing on the ground to derive near surface elastic properties.

Mars↗
DOE OSTI2020

Colloidal Three-Dimensional Covalent Organic Frameworks and Their Application as Porous Liquids

Developing solid porous materials into free-flowing liquids with permanent porosity is a promising strategy for overcoming certain limitations of conventional sorbent materials employed in gas storage and separation applications. The ability to control the pore size and chemical functionalities of organic frameworks gives these particular nanoporous materials distinct advantages over other small cage-like molecules or hollow particles that have been developed into porous liquids. Here, we describe the synthesis of a 3D imine-linked colloidal covalent organic framework (COF)-based porous liquid, designed for efficient size-exclusion of solvent, as well as for long-term stability. By tethering ionic liquids to the colloid surface, the colloids can be dried, purified, and resuspended in a variety of solvents without irreversible aggregation typically observed of COF colloids. Colloid size could be controlled between 50 and 400 nm, with surface areas as high as 800 m2/g. The 3D intertwining morphology of the colloids had pore sizes ranging from 5 to 14 Å, allowing them to efficiently sizeexclude bulky ionic liquids. The COF colloids were stable towards flocculation in an ionic liquid for > 1 year. Permanent porosity was confirmed with a combination of 19F NMR measurements and gas sorption techniques. CO2 and CH4 uptake in these porous liquids increased more than 10 and 20-fold, respectively, over non-porous, neat ionic liquid control samples. The work not only advances the state of COF-based colloid science but also represents a practical advance towards developing more robust, tunable framework-based porous liquid materials for a host of gas storage and separation applications.

Mow, Rachel E.↗
NASA NTRS1992

Downward-deployed tethered satellite systems, measurement techniques, and instrumentation - A review

This paper describes a number of scheduled and proposed Shuttle-based downward-deployed tethered satellite systems (TSSs) the purpose of which is to determine the structure of the lower thermosphere and to measure the atmospheric and aerodynamic effects in the vicinity of the satellite, the aerothermodynamic effects on the satellite's surface, and the dynamics of the tether and its endmass, the satellite. The instruments for the downward-deployed tethered missions will include mass spectrometers and other density sensors, plasma instrumentation, optical spectrophotometers, magnetometers, and instrumentation to measure the effects on satellite surface (such as the surface temperature, heat transfer, and pressure; gas adsorption on surfaces, chemistry with other gas molecules and surface material, and desorption from the surface; and surface charging).

Brown, Kenneth G.↗
DOE OSTI2025

Mixed lipid bilayers enable enhanced stability and activity retention of Lipase A in low-pH environments

Lipase A (LipA) from Bacillus subtilis is a versatile and industrially relevant enzyme, but its activity is compromised under acidic conditions due to aggregation and deactivation. In this study, we investigated the use of mixed lipid bilayers to stabilize and improve activity retention of LipA at low pH. Attachment to lipid bilayers, particularly those containing cationic lipids, greatly enhanced the long-term stability of LipA in acidic conditions while also leading to improvements in activity. Tethering to cationic bilayers not only shifted the apparent pH activity profile toward more acidic conditions, but also significantly enhanced activity retention upon incubation at pH 6. Notably, this protective effect persisted even without direct tethering, indicating that reversible, non-covalent interactions with the bilayer surface are sufficient for long-term stability. Circular dichroism further revealed that the secondary structure of LipA was retained, while dynamic light scattering suggested that activity loss in solution was primarily due to aggregation of the native state. Together, these findings support a model in which lipid bilayers mitigate aggregation and stabilize LipA through transient interactions and electrostatic modulation of the local surface environment. Furthermore, this approach exemplifies a simple, tether-free strategy for enhancing enzyme performance in acidic or destabilizing conditions, with implications for biocatalysis, biosensing, and therapeutic delivery.

Biocatalysis↗
DOE OSTI2025

Ultrastable Gold Nanostars via Bottlebrush-like Block Copolymers

Gold (Au) nanostars are plasmonic nanostructures possessing potentials for small molecule detection, photocatalytic activities, and photothermal therapy. However, Au nanostars synthesized in the traditional way are often plagued by poor photo, thermal, and chemical stabilities. Here, we report an unconventional route to the synthesis of ultrastable colloidal Au nanostars enabled by bottlebrush-like block copolymers (BBCPs), dispensing with the need for Au seeds. Crafting of Au nanostars using BBCPs is rendered by bridging the latter with Au 3+ ions as cross-linkers that have multiple coordination sites. Notably, the presence of a covalently tethered polymer shell on the surface of Au nanostars (i.e., polymer-ligated Au nanostars) imparts remarkably high stability under high temperature and laser excitation over conventional cetyltrimethylammonium bromide (CTAB)-mediated Au nanostars. Due to enhanced laser stability, plasmonic fields near Au nanostars can be visualized under high laser fluence by ultrafast electron microscopy (UEM) without morphological degradation. Notably, the presence of insulating polystyrene chains does not compromise the plasmonic field distribution, with the highest field intensity observed along the star arms. In conclusion, the greatly improved long-term photo, thermal, and chemical stabilities make Au nanostars a prospective noble metal nanomaterial for a range of sensing applications.

Cellulose↗
DOE OSTI2026

Fluorescent Particle Vertical Profiles (Counts and Fractions) at SAIL

This dataset contains vertically resolved fluorescent aerosol number concentrations and fluorescent fractions of total aerosol number concentrations measured with the ARM Tethered Balloon System during the Surface Atmosphere Integrated Field Laboratory campaign near Gothic, Colorado. Measurements were collected during April and June 2023 as part of the ARM–EMSL FICUS project “Characterization of the Aerobiome during the ARM Surface-Atmosphere Integrated Laboratory Campaign,” which was designed to characterize the vertical distribution of bioaerosol-relevant particles in the Colorado River Basin. The dataset includes profiles of fluorescent particle concentrations measured with a Fluorescent Portable Optical Particle Sizer (FPOPS) in the approximately 0.5–3 µm diameter range. For fluorescent fractions of total aerosol number concentrations, we compare FPOPS measurements to POPS on the same TBS flight.

Fluorescent particle concentration↗
NASA NTRS1975

Drogue parachute deployment dynamics of the space shuttle solid rocket booster

Theoretical analysis and experimental investigations are presented for two deployment concepts of the drogue parachute deployment for the space shuttle solid rocket booster. The analysis represents the motion of three coupled rigid bodies, with one of the bodies having variable mass and moment of inertia. The unfurling process of the parachute from the bag is idealized as the flow of a continuum out of a control surface. The pilot parachute or tethered nose cap is modeled as a flexible pendulum with a nonlinear spring and a moving support. Measured wind tunnel test data compare reasonably well with the theory.

Banerjee, A. K.↗
DOE OSTI2021

A Lunar Farside Low Radio Frequency Array for Dark Ages 21-cm Cosmology

An array of low-frequency dipole antennas on the lunar farside surface will probe a unique, unexplored epoch in the early Universe called the Dark Ages. It begins at Recombination when neutral hydrogen atoms formed, first revealed by the cosmic microwave background. This epoch is free of stars and astrophysics, so it is ideal to investigate high energy particle processes including dark matter, early Dark Energy, neutrinos, and cosmic strings. A NASA-funded study investigated the design of the instrument and the deployment strategy from a lander of 128 pairs of antenna dipoles across a 10 kmx10 km area on the lunar surface. The antenna nodes are tethered to the lander for central data processing, power, and data transmission to a relay satellite. The array, named FARSIDE, would provide the capability to image the entire sky in 1400 channels spanning frequencies from 100 kHz to 40 MHz, extending down two orders of magnitude below bands accessible to ground-based radio astronomy. The lunar farside can simultaneously provide isolation from terrestrial radio frequency interference, the Earth's auroral kilometric radiation, and plasma noise from the solar wind. It is thus the only location within the inner solar system from which sky noise limited observations can be carried out at sub-MHz frequencies. Through precision calibration via an orbiting beacon and exquisite foreground characterization, the farside array would measure the Dark Ages global 21-cm signal at redshifts z~35-200. It will also be a pathfinder for a larger 21-cm power spectrum instrument by carefully measuring the foreground with high dynamic range.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
NASA NTRS2005

Elastic-Tether Suits for Artificial Gravity and Exercise

Body suits harnessed to systems of elastic tethers have been proposed as means of approximating the effects of normal Earth gravitation on crewmembers of spacecraft in flight to help preserve the crewmembers physical fitness. The suits could also be used on Earth to increase effective gravitational loads for purposes of athletic training. The suit according to the proposal would include numerous small tether-attachment fixtures distributed over its outer surface so as to distribute the artificial gravitational force as nearly evenly as possible over the wearer s body. Elastic tethers would be connected between these fixtures and a single attachment fixture on a main elastic tether that would be anchored to a fixture on or under a floor. This fixture might include multiple pulleys to make the effective length of the main tether great enough that normal motions of the wearer cause no more than acceptably small variations in the total artificial gravitational force. Among the problems in designing the suit would be equalizing the load in the shoulder area and keeping tethers out of the way below the knees to prevent tripping. The solution would likely include running tethers through rings on the sides. Body suits with a weight or water ballast system are also proposed for very slight spinning space-station scenarios, in which cases the proposed body suits will easily be able to provide the equivalency of a 1-G or even greater load.

Torrance, Paul↗
NASA NTRS1988

A two-dimensional theory of plasma contactor clouds used in the ionosphere with an electrodynamic tether

Plasma contactors have been proposed as a means of making good electrical contact between biased surfaces such as found at the ends of an electrodynamic tether and the space environment. A plasma contactor is a plasma source which emits a plasma cloud which facilitates the electrical connection. The physics of this plasma cloud is investigated for contactors used as electron collectors and it is shown that contactor clouds in space will consist of a spherical core possibly containing a shock wave. Outside of the core the cloud will expand anisotropically across the magnetic field leading to a turbulent cigar shape structure along the field. This outer region is itself divided into two regions by the ion response to the electric field. A two-dimensional theory of the motion of the cloud across the magnetic field is developed. The current voltage characteristic of an Argon plasma contactor cloud is estimated for several ion currents in the range of 1-100 Amperes. It is shown that small ion current contactors are more efficient than large ion current contactors. This suggests that if a plasma contactor is used on an electrodynamic tether then a miltiple tether array will be more efficient than a single tether.

Hastings, D. E.↗
DOE OSTI2025

Solution‐Like Water Transport Across Molecular to Macroscopic Length Scales in Crosslinked Poly(Ethylene Glycol Diacrylate) Networks With Tailored Sidechains

Poly(ethylene glycol) (PEG)‐based materials, like PEG‐diacrylate (PEGDA), are prized for their hydrophilic, inert properties, and leveraged in hydrogels and as membrane mimics. While network chemistry is often tuned for selective transport and antifouling, fundamental understanding of water dynamics at the network surface and the impact on bulk transport is limited. We utilize Overhauser dynamic nuclear polarization (ODNP) to measure nanoscale water diffusivity near a tethered spin label at the water‐polymer surface and compare it to bulk water diffusivity from pulsed field gradient (PFG) NMR. Via active ester chemistry, spin labels and varied sidechain chemistries are introduced, modulating network hydrophilicity. Tuning network hydration through crosslinker content and functional groups further impacts water diffusivity. Results show rapid nanoscale water transport at the polymer surface, reflecting network volumetric water content, with further modulation by sidechain functionality. These findings demonstrate PEGDA's utility as a membrane mimic and the critical impact of network chemistry on water transport.

hydrogels↗
NASA NTRS2000

A Subsurface Explorer for Deep Underground Exploration on Mars

A subsurface explorer (SSX) is being developed at the Jet Propulsion Laboratory which is suitable for exploration of the deep underground environments on Mars. The device is a self-contained piledriver which uses a novel 'spinning hammer' technology to convert a small continuous power feed from the surface over a two-wire tether into a large rotational energy of a spinning mass. The rotational energy is converted to translational energy by a novel mechanism described here. The hammer blows propagate as shock waves through a nosepiece, pulverizing the medium ahead of the SSX. A small portion of the pulverized medium is returned to the surface through a hole liner extending behind the SSX. This tube is 'cast in place' from two chemical feedstocks which come down from the surface through passages in the hole liner and which are reacted together to produce new material with which to produce the hole liner. The lined hole does not need to be the full diameter of the SSX: approximately 100 kilograms of liner material can create a tunnel liner with a three millimeter inside diameter and a six millimeter outside diameter with at total length of four kilometers. Thus it is expected that core samples representing an overlapping set of three-millimeter diameter cores extending the entire length of the SSX traverse could be returned to the surface. A pneumatic prototype has been built which penetrated easily to the bottom of an eight meter vertical test facility. An electric prototype is now under construction. It is expected that the SSX will be able to penetrate through sand or mixed regolith, ice, permafrost, or solid rock, such as basalt. For pure or nearly pure ice applications, the device may be augmented with hot water jets to melt the ice and stir any sediment which may build up ahead of the vehicle. It is expected that an SSX approximately one meter long, three to four centimeters in diameter, and with a power budget of approximately 200 Watts will be able to explore up to approximately five kilometers deep at the rate of about ten meters per day.

Wilcox, B. H.↗