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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 559 records · Page 31

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NASA NTRS2012

Thermally Resilient, Broadband Optical Absorber from UV to IR Derived from Carbon Nanostructures

Optical absorber coatings have been developed from carbon-based paints, metal blacks, or glassy carbon. However, such materials are not truly black and have poor absorption characteristics at longer wavelengths. The blackness of such coatings is important to increase the accuracy of calibration targets used in radiometric imaging spectrometers since blackbody cavities are prohibitively large in size. Such coatings are also useful potentially for thermal detectors, where a broadband absorber is desired. Au-black has been a commonly used broadband optical absorber, but it is very fragile and can easily be damaged by heat and mechanical vibration. An optically efficient, thermally rugged absorber could also be beneficial for thermal solar cell applications for energy harnessing, particularly in the 350-2,500 nm spectral window. It has been demonstrated that arrays of vertically oriented carbon nanotubes (CNTs), specifically multi-walled-carbon- nanotubes (MWCNTs), are an exceptional optical absorber over a broad range of wavelengths well into the infrared (IR). The reflectance of such arrays is 100x lower compared to conventional black materials, such as Au black in the spectral window of 350-2,500 nm. Total hemispherical measurements revealed a reflectance of approximately equal to 1.7% at lambda approximately equal to 1 micrometer, and at longer wavelengths into the infrared (IR), the specular reflectance was approximately equal to 2.4% at lambda approximately equal to 7 micrometers. The previously synthesized CNTs for optical absorber applications were formed using water-assisted thermal chemical vapor deposition (CVD), which yields CNT lengths in excess of 100's of microns. Vertical alignment, deemed to be a critical feature in enabling the high optical absorption from CNT arrays, occurs primarily via the crowding effect with thermal CVD synthesized CNTs, which is generally not effective in aligning CNTs with lengths less than 10 m. Here it has been shown that the electric field inherent in a plasma yields vertically aligned CNTs at small length scales (less than 10 m), which still exhibit broadband, and high-efficiency optical absorption characteristics from the ultraviolet (UV) to IR. A thin and yet highly absorbing coating is extremely valuable for detector applications for radiometry in order to enhance sensitivity. A plasma-based process also increases the potential of forming the optical absorbers at lower synthesis temperatures in the future, increasing the prospects of integrating the absorbers with flexible substrates for low-cost solar cell applications, for example.

Kaul, Anupama B.↗

NASA NTRS2014

Supersonic Wing Optimization Using SpaRibs

This research investigates the advantages of using curvilinear spars and ribs, termed SpaRibs, to design a supersonic aircraft wing-box in comparison to the use of classic design concepts that employ straight spars and ribs. The objective is to achieve a more efficient load-bearing mechanism and to passively control the deformation of the structure under the flight loads. Moreover, the use of SpaRibs broadens the design space and allows for natural frequencies and natural mode shape tailoring. The SpaRibs concept is implemented in a new optimization MATLAB-based framework referred to as EBF3SSWingOpt. This optimization scheme performs both the sizing and the shaping of the internal structural elements, connecting the optimizer with the analysis software. The shape of the SpaRibs is parametrically defined using the so called Linked Shape method. Each set of SpaRibs is placed in a one by one square domain of the natural space. The set of curves is subsequently transformed in the physical space for creating the wing structure geometry layout. The shape of each curve of each set is unique; however, mathematical relations link the curvature in an effort to reduce the number of design variables. The internal structure of a High Speed Commercial Transport aircraft concept developed by Boeing is optimized subjected to stress, subsonic flutter and supersonic flutter constraints. The results show that the use of the SpaRibs allows for the reduction of the aircraft's primary structure weight without violating the constraints. A weight reduction of about 15 percent is observed.

Locatelli, David↗

NASA NTRS2013

Ultimate Limits to Resource Efficiency in Photonic Communication

We review resource-efficiency metrics for transferring classical information with photon, present an overview of the ultimate limits to photon and dimensional efficiency permitted by quantum mechanics, as well as that acheived with structured transmitter-receiver pairs.

background noise↗

NASA NTRS1997

Optical Microactuation in Piezoceramics

Optically/electrically operable flexible film microactuators that can offer upto two orders higher efficiency of photonic to mechanical conversion compared to ceramic actuators are conceptualised.

Piezoceramics↗

NASA NTRS1998

Optical Microactuation in Piezoceramics

Optically/electrically operable flexible film microactuators that can offer up to two orders higher efficiency of photonic to mechanical conversion compared to ceramic actuators are conceptualized.

Piezoceramic↗

NASA NTRSDate not supplied

Coordination between Federated Scheduling and Conflict Resolution in UAM Operations

This work proposes a federated scheduling algorithm and explores two mechanisms for coordinating federated scheduling and conflict resolution functions - two core traffic management functions in urban air mobility operations. A federated scheduling algorithm is first developed, together with data that needs to be shared among schedulers. Two mechanisms for coordinating scheduling and conflict resolution functions are then introduced and studied as conflicts in high-density operations may not be completely resolved by conflict resolution function alone. The first coordination mechanism is constructed based on the arrival scheduler at the destination and another one utilizes the departure scheduler at the origin. Experiments and trade space studies are conducted to compare these two mechanisms using fast-time traffic simulations. Results show that both mechanisms perform well in coordinating scheduling and conflict resolution functions and helping resolve all potential conflicts. Experiments also show that with proper parameter selection, both mechanisms can achieve better efficiency (less delay) while maintaining zero losses of separation.

Federated scheduling↗

NASA NTRS2021

Coordination between Federated Scheduling and Conflict Resolution in UAM Operations

Federated scheduling↗

NASA NTRSDate not supplied

Production and Characterization of Additively Manufactured Radiator Panels with Integral Branching Heat Pipes for High-Temperature Heat Rejection

Emerging concepts for fission surface power and nuclear electric propulsion necessitate lightweight, mechanically robust, and thermally efficient heat rejection radiators. State-of-the-art intermediate-temperature (~400 K) composite radiator assemblies have been developed based on titanium-water heat pipes bonded to metal, graphite, and carbon-fiber-based panels. NASA has identified a need for new radiator concepts that can operate at even higher temperatures (500 – 600 K), minimize thermal resistances and thermal stress failures at bond interfaces, and approach areal densities of 2 – 3 kg m -2 . To meet these needs, our team is developing additively manufactured (AM) radiator panels with integral branching wicking heat pipe networks. Water is selected as the working fluid for this temperature range. Based on simulations and thermal vacuum experiments, these branching embedded heat pipe networks can efficiently distribute heat over panels for finned surface efficiencies of η f >70% at T H = 500 K input heat. This paper first presents laser powder-bed fusion AM strategies to produce embedded porous structures for wicking heat pipes in Inconel 718 and titanium alloys (commercially pure and Ti-6Al-4V alloys). Post-build chemical and thermal treatments are described that yield hydrophilic wicking surfaces for operation with water. Transient rate-of-rise experiments with water and acetone are reported that yield estimates for AM wick porosity (ϵ), permeability (K), and effective pore radius (r pore ). Based on the wick characterization results, small prototype radiator panels (75 × 125 mm) with integrated heat pipe networks were manufactured. Heat rejection performance data are presented from cold thermal vacuum testing, with heat input temperatures up to ~510 K. Future efforts will focus on improving heat pipe performance, optimizing radiator mass, and evaluating larger panels to assess scalability.

thermal management↗

NASA NTRS2024

Production and Characterization of Additively Manufactured Radiator Panels With Integral Branching Heat Pipes for High-Temperature Heat Rejection

Emerging concepts for fission surface power and nuclear electric propulsion necessitate lightweight, mechanically robust, and thermally efficient heat rejection radiators. State-of-the-art intermediate-temperature (~400 K) composite radiator assemblies have been developed based on titanium-water heat pipes bonded to metal, graphite, and carbon-fiber-based panels. NASA has identified a need for new radiator concepts that can operate at even higher temperatures (500 – 600 K), minimize thermal resistances and thermal stress failures at bond interfaces, and approach areal densities of 2 – 3 kg m -2 . To meet these needs, our team is developing additively manufactured (AM) radiator panels with integral branching wicking heat pipe networks. Water is selected as the working fluid for this temperature range. Based on simulations and thermal vacuum experiments, these branching embedded heat pipe networks can efficiently distribute heat over panels for finned surface efficiencies of η f >70% at T H = 500 K input heat. This paper first presents laser powder-bed fusion AM strategies to produce embedded porous structures for wicking heat pipes in Inconel 718 and titanium alloys (commercially pure and Ti-6Al-4V alloys). Post-build chemical and thermal treatments are described that yield hydrophilic wicking surfaces for operation with water. Transient rate-of-rise experiments with water and acetone are reported that yield estimates for AM wick porosity (ϵ), permeability (K), and effective pore radius ( r pore ). Based on the wick characterization results, small prototype radiator panels (75 × 125 mm) with integrated heat pipe networks were manufactured. Heat rejection performance data are presented from cold thermal vacuum testing, with heat input temperatures up to ~510 K. Future efforts will focus on improving heat pipe performance, optimizing radiator mass, and evaluating larger panels to assess scalability.

nuclear electric propulsion↗

DOE OSTI2020

Range-based memory system

A mechanism is provided for efficient coherence state modification of cached data stored in a range of addresses in a coherent data processing system in which data coherency is maintained across multiple caches. A tag search structure is maintained that identifies address tags and coherence states of cached data indexed by address tags. In response to a request from a device internal to or external from the coherence network, the tag search structure is searched to identify address tags of cached data for which the coherence state is to be modified and requests are issued in the data processing system to modify a coherence state of cached lines with the identified address tags. The request from the external device may specify a range of addresses for which a coherence state change is sought. The tag search structure may be implemented as search tree, for example.

97 MATHEMATICS AND COMPUTING↗

DOE OSTI2022

Multi-device cooling structure having assembly alignment features

A single device having both thermal and alignment features is provided to mechanically align and more efficiently cool multiple heat generating components. The device includes one or more thermal structures and assembly alignment features, in which the one or more thermal structures make thermal contact with a plurality of heat generating components. The assembly alignment features control the positions of the heat generating components during assembly of the heat generating components onto a common substrate.

42 ENGINEERING↗

DOE OSTI2023

Crosslinking of loose insulating powders

Described herein are materials and methods useful in the field of insulation, including building materials, refrigeration, cryogenics, and shipping, amongst others. Advantageously, the provided materials and method provide low thermal conductivities and increased mechanical strength, allowing for efficient insulating in a diverse range of applications. The provided materials and methods include individual particles connected by a polymer network that links individual particles and may include hollow or evacuated capsules and various strengthening agents.

Simpson, Lin Jay↗

DOE OSTI2022

Lead-Free Flexible Perovskite Solar Cells with Interfacial Native Oxide Have >10% Efficiency and Simultaneously Enhanced Stability and Reliability

Here we demonstrate an innovative compositional and interfacial engineering approach to achieve Pb-free flexible perovskite solar cells (f-PSCs) with an unprecedented combination of the highest efficiency reported to date (10.43%), together with enhanced operational stability and mechanical reliability. The key to this approach is alloying of an FASnI3 metal halide perovskite (MHP) thin film with Ge2+ to stabilize the Sn2+ oxidation state in the MHP, together with the use of a NiOx hole-transport layer. We show that this results in the in situ formation of a thin amorphous GeO2 native oxide layer at the NiOx/FASn0.9Ge0.1I3 interface. This layer not only passivates that critical interface but also enhances the interfacial mechanical bonding.

efficiency↗

NASA NTRS2009

Compact Deep-Space Optical Communications Transceiver

Deep space optical communication transceivers must be very efficient receivers and transmitters of optical communication signals. For deep space missions, communication systems require high performance well beyond the scope of mere power efficiency, demanding maximum performance in relation to the precious and limited mass, volume, and power allocated. This paper describes the opto-mechanical design of a compact, efficient, functional brassboard deep space transceiver that is capable of achieving megabyte-per-second rates at Mars ranges. The special features embodied to enhance the system operability and functionality, and to reduce the mass and volume of the system are detailed. System tests and performance characteristics are described in detail. Finally, lessons learned in the implementation of the brassboard design and suggestions for improvements appropriate for a flight prototype are covered.

DSOCT↗

NASA NTRS1975

High efficiency graded band-gap Al/x/Ga/1-x/As-GaAs p-on-n solar cell

A theoretical analysis of p-on-n (p/n) graded band-gap Al/x/Ga/1-x/As-GaAs solar cells including all practical energy loss mechanisms predicts air mass zero efficiencies of 17.3%. The energy losses include those due to spectral reflection, surface, bulk and junction recombination currents, and series resistance. The device consists of a layer of p-type Al/x/Ga/1-x/As 3.5-micron thick on top of an n-type GaAs substrate. The graded band-gap is achieved by decreasing x from 0.35 at the surface to zero at the junction. The same structure without the graded Al concentration, no longer an optimum device, has an efficiency of 10.4%. The primary function of the graded band-gap material is the reduction of surface and bulk recombination losses in the surface layer by a built-in electric field. A comparison of the p/n structure with an optimized n/p structure indicates that the latter has a slightly higher efficiency (17.7%) for assumed minority carrier diffusion lengths and surface recombination velocity.

Hutchby, J. A.↗

NASA NTRS1986

Electronic energy transfer and quenching in copolymers of styrene and 2-(2-prime-hydroxy -5-prime-vinylphenyl)-2H-benzotriazole Photochemical processes in polymeric systems. X

Intensity and lifetime quenching of the polystyrene monomer and excimer fluorescence emission by a pendant quencher have been studied in the solid state and in solution for a series of copolymers of styrene and 2-(2-prime-hydroxy-5-prime-vinylphenyl)-2H-benzotriazole. Two mechanisms of quenching have been identified. One involves interception of the migrating monomer excitation by the quencher, and the other involves a single-step Foerster energy-transfer process from the excimer traps to a quencher. The relative efficiencies of these two quenching mechanisms in the solid state and in solution have been compared and related to the efficiency of electronic energy migration. An estimate of the excimer trap concentration in solid polystyrene is also reported.

Coulter, D. R.↗

NASA NTRS1971

High efficiency telemetry method

Analog and digital mechanizations contain new combinations of known circuits that generate coefficients of Fourier series terms in accordance with harmonic content of waveform to be transmitted. Technique represents information signal more accurately that previous methods and requires fewer information bits.

Lim, L. Y.↗

NASA NTRS2012

Miniaturization of Planar Horn Motors

There is a great need for compact, efficient motors for driving various mechanisms including robots or mobility platforms. A study is currently underway to develop a new type of piezoelectric actuators with significantly more strength, low mass, small footprint, and efficiency. The actuators/motors utilize piezoelectric actuated horns which have a very high power density and high electromechanical conversion efficiency. The horns are fabricated using our recently developed novel pre-stress flexures that make them thermally stable and increases their coupling efficiency. The monolithic design and integrated flexures that pre-stresses the piezoelectric stack eliminates the use of stress bolt. This design allows embedding solid-state motors and actuators in any structure so that the only macroscopically moving parts are the rotor or the linear translator. The developed actuator uses a stack/horn actuation and has a Barth motor configuration, which potentially generates very large torque and speeds that do not require gearing. Finite element modeling and design tools were investigated to determine the requirements and operation parameters and the results were used to design and fabricate a motor. This new design offers a highly promising actuation mechanism that can potentially be miniaturized and integrated into systems and structures. It can be configured in many shapes to operate as multi-degrees of freedom and multi-dimensional motors/actuators including unidirectional, bidirectional, 2D and 3D. In this manuscript, we are reporting the experimental measurements from a bench top design and the results from the efforts to miniaturize the design using 2x2x2 mm piezoelectric stacks integrated into thin plates that are of the order of3 x 3x 0.2 cm.

horn actuation↗