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Results for “dynamics of phase separation”

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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All sourcesNASA NTRSDOE OSTI
NASA NTRS1969

Ionene membrane battery separator

Ionic transport characteristics of ionenes, insoluble membranes from soluble polyelectrolyte compositions, are studied for possible application in a battery separator. Effectiveness of the thin film of separator membrane essentially determines battery lifetime.

Moacanin, J.↗
NASA NTRS1985

Development of a lithium secondary battery separator

A nonporous membrane based on the polymerization of 2,3-dihydrofuran followed by crosslinking in situ was prepared. The material is compatible with rechargeable Li battery components and, when swollen with an appropriate solvent such as tetrahydrofuran, exhibits separator resistance and Li transport equivalent to Celgard.

Moore, J. A.↗
NASA NTRS2025

Photophoretic Propulsion Enabling Mesosphere Exploration NIAC Phase I Final Report

This Phase I report presents a comprehensive study on photophoretic flyers—innovative, ultralight, solar-powered vehicles that harness photophoretic forces generated via Knudsen pumping to achieve sustained flight in the mesosphere (50–80 km altitude). By integrating advanced materials such as nanocardboard— characterized by its extremely low areal density (~1 g/m²) and high bending stiffness—with ultrathin light-absorbing coatings, the project converts incident solar radiation directly into a directed thrust. Extensive experimental investigations, coupled with high-fidelity computational fluid dynamics (CFD) simulations using ANSYS Fluent, validate the concept across various three-dimensional geometries, including spherical, conical, and rocket-shaped configurations. These simulations bridge the gap between free-molecular and continuum flow regimes, demonstrating that optimized designs can generate lift forces sufficient to support kilogram-scale payloads even in low-pressure environments. At the heart of this innovation is the use of Knudsen pumping, where temperature gradients across porous surfaces induce directional gas flow, creating a modest overpressure that provides lift. The report introduces an analytical framework that interpolates between the well-known low-Reynolds number drag regime and the high-Reynolds number momentum theory. This model accurately predicts lift based on design parameters such as microchannel dimensions, porous wall geometry, areal density, and nozzle exit area. For instance, simulations indicate that 10-meter-scale structures with carefully engineered porous walls can achieve the necessary pressure differential to support scientifically significant payloads (~1 kg). The study also explores a hybrid propulsion approach that combines solar buoyancy with photophoretic lift. Initially, solar heating creates a buoyant force that elevates the flyer to mesospheric altitudes. Once in the optimal pressure range, the photophoretic mechanism—powered by Knudsen pumping—takes over as the primary source of lift, ensuring stable, long-duration flight. This dual-mode operation not only facilitates the deployment of photophoretic flyers but also broadens the potential applications for mesospheric exploration. In addition to propulsion, the report investigates the integration of photophoretic thrusters for trajectory control of existing research balloons in the upper stratosphere. By dynamically adjusting the nozzle orientation and controlling the flow-through velocity, these thrusters provide precise maneuverability, enabling the flyers to counteract atmospheric disturbances and adjust their flight paths in real time. For example, a photophoretic thruster approximately 7.5 by 7.5 meters in size could be unfolded below a payload gondola of a 60 million-cubic-foot zero-pressure balloon. Such a thruster can provide horizontal speed control of approximately 1 m/s using only sunlight and no moving parts (except those needed to track the Sun and control the jet direction). Importantly, photophoretic thrusters operate more efficiently at higher altitudes, which is complementary to known trajectory control techniques, such as propellers and tethered wings, which are more effective at lower altitudes. Finally, the report identifies three scientific research thrusts where mesospheric aircraft technology can have a profound impact: atmospheric tides, characterization of gravity waves, and investigation of mesospheric instabilities. Overall, the findings of this Phase I project represent a significant advancement in photophoretic propulsion technology. By demonstrating that large-scale, ultralight structures can be powered solely by solar radiation—via carefully engineered Knudsen pumping—this work lays a robust foundation for scalable, near-space flight architectures. Future refinements in material fabrication, structural optimization, and integrated trajectory control are expected to further enhance performance, paving the way for operational demonstrations that could revolutionize atmospheric science, remote sensing, and communication networks.

Knudsen Pump↗
NASA NTRS2017

Novel Polyimide Battery Separator Imbibed with Room-Temperature Ionic Liquids

The journey to Mars will require advancements in many existing technologies, including space power and energy storage systems. According to the 2015 NASA Technology Roadmaps, energy storage is a critical technology area to develop for both terrestrial as well as future long-term space missions. Currently, batteries represent one of the major areas in need of advancement, both in terms of energy density as well as safety. Recently, concerns regarding the fire safety of commercial lithium-ion batteries have prompted efforts to produce nonflammable battery components, namely the electrolyte and separator. Commercial lithium-ion batteries utilize polyolefin separators imbibed with a lithium salt dissolved in cyclic carbonates. This separator/electrolyte combination imparts good ionic conductivities in the range of 10(exp -2) to 10(exp -3) S/cm. However, the cyclic carbonates and polyolefin separator are inherently flammable. Room-temperature ionic liquids (RTILs) appear to be a safer alternative to cyclic carbonates. They offer good ionic conductivities, similar to those observed in cyclic carbonates, but are inherently nonvolatile and nonflammable giving them a safety advantage. Many promising RTILs for battery electrolytes are not compatible with commercial polyolefin separator materials. Polyimide aerogels possess an open-porous, fibrillar network architecture which offers a high degree of porosity (typically greater than 85 porous), required for lithium ion conduction, as well as good mechanical properties. Furthermore, these materials are compatible with all tested RTILs. By creating a polyimide gel and imbibing the gel with a RTIL containing a lithium salt instead of super critically drying them to form aerogels, a nonflammable separator/electrolyte system with conductivities in the range of 1x10(exp -3) S/cm has been demonstrated.

Polyimide↗