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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 289 records · Page 16
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Eliminating Imaginary Vibrational Frequencies in Quantum-Chemical Cluster Models of Enzymatic Active Sites

In constructing finite models of enzyme active sites for quantum-chemical calculations, atoms at the periphery of the model must be constrained to stop unphysical rearrangements during geometry relaxation. A simple fixed-atom or “coordinate-lock” approach is commonly employed but leads to undesirable artifacts in the form of small imaginary frequencies. These preclude evaluation of finite-temperature free-energy corrections, limiting thermochemical calculations to enthalpies only. Full-dimensional vibrational frequency calculations are possible by replacing the fixed-atom constraints with harmonic confining potentials. Here, we compare that approach to an alternative strategy in which fixed-atom contributions to the Hessian are simply omitted. While the latter strategy does eliminate imaginary frequencies, it tends to underestimate both the zero-point energy and the vibrational entropy while introducing artificial rigidity. Harmonic confining potentials eliminate imaginary frequencies and provide a flexible means to construct active-site models that can be used in unconstrained geometry relaxations, affording better convergence of reaction energies and barrier heights with respect to the model size, as compared to models with fixed-atom constraints.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Electrostatics, Charge Transfer, and the Nature of the Halide–Water Hydrogen Bond

Binary halide–water complexes X – (H 2 O) are examined by means of symmetry-adapted perturbation theory, using charge-constrained promolecular reference densities to extract a meaningful charge-transfer component from the induction energy. As is known, the X – (H 2 O) potential energy surface (for X = F, Cl, Br, or I) is characterized by symmetric left and right hydrogen bonds separated by a C 2v -symmetric saddle point, with a tunneling barrier height that is <2 kcal/mol except in the case of F – (H 2 O). Our analysis demonstrates that the charge-transfer energy is correspondingly small (<2 kcal/mol except for X = F), considerably smaller than the electrostatic interaction energy. Nevertheless, charge transfer plays a crucial role determining the conformational preferences of X – (H 2 O) and provides a driving force for the formation of quasi-linear X··· H–O hydrogen bonds. Here, charge-transfer energies correlate well with measured O–H vibrational redshifts for the halide–water complexes and also for OH – (H 2 O) and NO 2 – (H 2 O), providing some indication of a general mechanism.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Molecular Dynamics Simulation Study of the Protonation State Dependence of Glutamic Acid Transport through a Cyclic Peptide Nanotube

The effect of the protonation state of glutamic acid on its translocation through cyclic peptide nanotubes (CPNs) was assessed by using molecular dynamics (MD) simulations. Anionic (GLU–), neutral zwitterionic (GLU0), and cationic (GLU+) forms of glutamic acid were selected as three different protonation states for an analysis of energetics and diffusivity for acid transport across a cyclic decapeptide nanotube. Based on the solubility-diffusion model, permeability coefficients for the three protonation states of the acid were calculated and compared with experimental results for CPN-mediated glutamate transport through CPNs. Potential of mean force (PMF) calculations reveal that, due to the cation-selective nature of the lumen of CPNs, GLU–, so-called glutamate, shows significantly high free energy barriers, while GLU+ displays deep energy wells and GLU0 has mild free energy barriers and wells inside the CPN. The considerable energy barriers for GLU– inside CPNs are mainly attributed to unfavorable interactions with DMPC bilayers and CPNs and are reduced by favorable interactions with channel water molecules through attractive electrostatic interactions and hydrogen bonding. Unlike the distinct PMF curves, position-dependent diffusion coefficient profiles exhibit comparable frictional behaviors regardless of the charge status of three protonation states due to similar confined environments imposed by the lumen of the CPN. The calculated permeability coefficients for the three protonation states clearly demonstrate that glutamic acid has a strong protonation state dependence for its transport through CPNs, as determined by the energetics rather than the diffusivity of the protonation state. In addition, the permeability coefficients also imply that GLU– is unlikely to pass through a CPN due to the high energy barriers inside the CPN, which is in disagreement with experimental measurements, where a considerable amount of glutamate permeating through the CPN was detected. To resolve the discrepancy between this work and the experimental observations, several possibilities are proposed, including a large concentration gradient of glutamate between the inside and outside of lipid vesicles and bilayers in the experiments, the glutamate activity difference between our MD simulations and experiments, an overestimation of energy barriers due to the artifacts imposed in MD simulations, and/or finally a transformation of the protonation state from GLU– to GLU0 to reduce the energy barriers. Altogether, our study demonstrates that the protonation state of glutamic acid has a strong effect on the transport of the acid and suggests a possible protonation state change for glutamate permeating through CPNs.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Acetate as a Platform for Carbon-Negative Production of Renewable Fuels and Chemicals (Final Technical Report)

This project was an industrial-academic collaboration between experts at the University of Wisconsin-Madison, the University of Kentucky, and LanzaTech, a world leader in the use of gas fermentation to sustainably produce fuels and chemicals. The project developed technologies to create an integrated process for converting carbon dioxide and renewable hydrogen into molecules that can be blended with liquid transportation fuels or used in an array of chemical applications. The project was motivated by the Program Objectives of eliminating carbon dioxide release in the production of chemicals by integrating the unique and efficient capabilities of two microorganisms into a single process. The first microbe, an acetogen, produces acetate from carbon dioxide and hydrogen while the second microbe upgrades acetate from acetogen fermentation permeates to higher-value chemical products. The carbon dioxide released in the upgrading process is recycled internally to produce more acetate. As such, the process can be designed to operate with zero carbon dioxide release and net positive carbon dioxide capture. The process has the potential to provide an alternative paradigm to the current bioeconomy – one in which acetate is the primary energy carrier instead of sugars. Our process by-passes photosynthesis and the barriers created by biomass as primary chemical feedstock. As such, the process can be scaled to meet existing sources of carbon dioxide emissions and located anywhere renewable hydrogen can be provided. Our work developed microorganisms with optimized metabolism for producing acetate and other microorganisms with improved conversion of acetate to dodecanol and dodecyl-acetate. We developed synthetic biology tools for a promising non-model bacterium that could enhance metabolic engineering efforts to convert acetate to chemical products. We conducted protein engineering studies to improve the activity of key enzymes involved in our metabolic pathways. We conducted a full technoeconomic analysis that set technical targets for each strain to meet economic goals. We identified key technical barriers in our process and proposed strategies to overcome them.

09 BIOMASS FUELS↗
NASA NTRS1980

Forward- and reverse-bias tunneling effects in n/+/p silicon solar cells

Excess currents due to field-assisted tunneling in both forward and reverse bias directions have been observed in n(+)-p silicon solar cells. These currents arise from the effect of conducting paths produced in the depletion layer by n(+) diffusion and cell processing. Forward-bias data indicate a small potential barrier with height of 0.04 eV at the n(+) end of conducting paths. Under reverse bias, excess tunneling currents involve a potential barrier at the p end of the conducting paths, the longer paths being associated with smaller barrier heights and dominating at the lower temperatures. Low-reverse-bias data give energy levels of 0.11 eV for lower temperatures (253-293 K) and 0.35 eV for higher temperatures (293-380 K). A model is suggested to explain the results.

Garlick, G. F. J.↗
DOE OSTI2021

Bringing Solar Energy to Low- and Moderate-Income Communities

The U.S. solar photovoltaics (PV) industry has taken off over the past decade, but without deliberate action low- and moderate-income communities could be left behind. Key recommendations for policymakers and funders in the renewable energy and community development fields that emerged from this process include the following: • Help to capitalize and support community-based lenders to provide flexible, low-cost, and long- term financing to mission-driven solar projects— including providing guarantees or other forms of credit enhancement. • Provide a grant-in-lieu-of-credits option for the Investment Tax Credit as was done during the last recession. • Develop pools of government and philanthropic support that can complement financing from community-based lenders to complete the capi- tal stack for mission-driven projects, as well as to support education and technical assistance to both consumers and potential project sponsors. • Create a national Renewable Energy Credits pro- gram that includes social equity targets to provide a baseline of support for clean energy generation. • Change utility regulations to remove barriers to low-income solar projects, provide greater certainty for developers, and measure progress toward equity in renewable energy policy implementation.

14 SOLAR ENERGY↗
DOE OSTI2021

Scaling Equitable Finance

Driven by dramatic declines in up-front cost, the U.S. solar photovoltaics (PV) industry has taken off over the past decade, growing from 1 gigawatt of installed capacity in 2009 to 89 gigawatts in 2020—or enough capacity to power roughly 19 million homes. The industry is expected to double in size over just the next 5 years.1 Much of the growth has been driven by large, utility-scale projects that can produce 5 mega- watts or more of power—enough to power at least 1,000 homes. The cost of electricity produced by these projects has decreased by more than 70 percent since 2010. As of Q3 2020, development costs of large, util- ity-scale solar PV power plants were under $1 per watt, down by more than 70 percent from 2010.2 A robust array of investors has come forward to efficiently deliver capital to these kinds of utility-scale projects including large banks, insurance companies, pension funds, and others. But low- and moderate-income communities, including communities of color, are at risk of being left behind in the transition to clean energy. Mission- driven solar project developers and financial institu- tions have been working alongside energy justice advocates to open up solar access for these communi- ties, using strategies ranging from community solar, to solar installations on affordable multifamily housing, to distributed solar and storage programs, and more. Their goals go beyond simply generating more green energy to advancing social equity by: • empowering communities to control their energy future • stabilizing energy prices, saving money, and build- ing wealth for low-income families • creating quality jobs • improving health by reducing pollution • providing energy resilience for vulnerable communities Mission-driven actors are successfully deploying a wide variety of strategies to meet these goals, from helping low-income homeowners get solar—and some- times battery storage, to developing solar projects serv- ing affordable rental housing and community facilities, to building larger “shared solar” projects to which households from across the community can subscribe. However, the financing ecosystem does not work nearly as well for these “mission driven” solar proj- ects as it does for utility-scale projects. For home rooftop solar, even if low-income consumers have a home and suitable roof, they may fail to qualify for federal tax incentives, lack adequate credit to qualify for a loan—or the mission-driven lenders seeking to serve them may not be adequately capitalized to make long-term loans. For mission-driven commercial or community-scale projects, assembling nearly every component of the project capital stack—whether bridging early-stage costs, attracting tax credit equity investors, securing long-term debt, or coming up with sponsor equity and filling gaps—can present challenges. A variety of obstacles contribute to the scarcity of financing for low-income solar, including small project sizes, lack of developer balance sheet capacity, both real and perceived issues with credit risk, elevated technical assistance needs, and greater subsidy requirements to pursue goals such as deep energy affordability, climate resilience, or job creation. Still other obstacles are regulatory: for example, not all states allow community solar projects or Power Purchase Agreements, common strategies used for providing low-income solar—and the potential for regulations to shift over time creates risks that mission-driven projects can ill afford. This report synthesizes information garnered from 47 key informant interviews, four focus group discus- sions involving 60 stakeholders, and a review of the substantial existing literature on low-income solar finance to assess the current landscape of mission- driven solar development in the United States, examine the roles that community-based financial institutions could play, and recommend public invest- ments and policy changes that could help to scale the provision of equitable solar finance. Key recommen- dations for policymakers and funders in the renew- able energy and community development fields that emerge from this process include the following: • Help to capitalize and support community-based lenders to provide flexible, low-cost, and long- term financing to mission-driven solar projects— including providing guarantees or other forms of credit enhancement. • Provide federal support for equitable solar, including a grant-in-lieu-of-credits option for the Investment Tax Credit to improve access to this critical government subsidy. • Develop pools of government and philanthropic support that can complement financing from community-based lenders to complete the capi- tal stack for mission-driven projects, as well as to support education and technical assistance to both consumers and potential project sponsors. • Create a national Renewable Energy Credits pro- gram that includes social equity targets to provide a baseline of support for clean energy generation. • Change utility regulations to remove barriers to low-income solar projects; lower permitting costs; provide greater certainty for developers, consumers and owners; and measure progress toward equity in renewable energy policy implementation.

14 SOLAR ENERGY↗
DOE OSTI2021

Microgrid's Role in Enhancing the Security and Flexibility of City Energy Systems

Smart cities depend on flexible and secure energy systems to ensure resilient power for critical infrastructure; however, recent weather-related events and cyberattacks have highlighted weaknesses in our energy systems, with the potential for widespread economic and security impacts. As stated by the Executive Office of the President, "the resilience of the US electric grid is a key part of the nation's defense against severe weather." To address the energy delivery security challenge, microgrids are rising as a viable solution that enhances the flexibility and resilience of the distribution grid and boosts the reliability of the local supply for the end-user. Traditionally, high capital investment has been a barrier to large-scale adoption of microgrid technology. Understanding the flexibility and resilience benefits of microgrids and accounting for the associated value streams can make the microgrid's proposition economically viable. In this chapter, microgrids' utility and their potential to serve as a flexible and resilient resource for the utility grid by providing capabilities such as peak shaving, demand response, and frequency regulation is presented. Moreover, other value streams, such as (1) their ability to island during a disaster and sustain critical loads which makes them a robust resilience solution for end-users, in the event of the utility grid outage and (2) microgrids also provide a flexible platform for integrating distributed energy resources in conjunction with storage and conventional generation technologies, strengthen microgrid's role in reducing the over-arching goal of emission reduction. Given the myriad of benefits associated with microgrids, we present strategies which can be employed for making microgrid itself resilient against physical and cyberthreats by employing hardware, software, and personnel training solutions to operate the microgrid before, during, and after a potential disaster. This chapter, thus, provides a holistic study of the microgrid as a resilience resource, for the utility grid, and a self-contained end-user for the end-user.

cyber-physical system↗
DOE OSTI2021

Polarization Effects in Water-Mediated Selective Cation Transport across a Narrow Transmembrane Channel

We report despite the progress in modeling complex molecular systems of ever-increasing complexity, a quantitatively accurate computational treatment of ion permeation through narrow membrane channels remains challenging. An important factor to reach this goal is induced electronic polarization, which is likely to impact the permeation rate of small ions through narrow molecular pores. In this work, we extended the recently developed polarizable force field based on the classical Drude oscillators to assess the role of induced polarization effects on the energetics of sodium and potassium ion transport across the gramicidin A (gA) ion channel. The inclusion of induced polarization lowers barriers present in 1D potential of mean force (PMF) for cation permeation by ~50% compared to those obtained with the additive force field. Conductance properties calculated with 1D PMFs from Drude simulations are in better agreement with experimental results. Polarization of single-file water molecules and protein atoms forming the narrow pore has a direct impact on the free-energy barriers and cation-specific solid-state NMR chemical shifts. Sensitivity analysis indicates that small changes to water–channel interactions can alter the free energy barrier for ion permeation. These results, illustrating polarization effects present in the complex electrostatic environment of the gA channel, have broad implications for revising proposed mechanisms of ion permeation and selectivity in a variety of ion channels.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2026

Space Cooling: Recovery, Reuse, Recycling and Supply Chain Impacts

The global cooling sector has undergone tremendous growth in recent years, and cooling demand is projected to double or triple by 2050. Surging air conditioning demand will continue to be driven by increased populations, incomes and occurrences of extreme heat and humidity events. Cooling equipment growth has important pollution and material implications as they are made up of critical metals and precious raw materials - including ferrous metals, copper, aluminum and printed circuit boards composed of copper, silver, gold and palladium - that generate significant electronic waste at end-of-life. Air conditioning equipment also contains fluorinated gas (F-gas) refrigerants, which are potent gases that are thousands of times more heat-trapping than carbon dioxide (CO2). While recovery, reuse, and recycling strategies have been assessed for cold chain and refrigeration, there is currently limited analysis on how these strategies could be adopted for the global space cooling industry and potential supply chain implications. This paper aims to address this research gap by qualitatively evaluating product and material recovery, reuse and recycling frameworks from both demand and supply-side perspectives and with the support of cooling-specific case studies. It also focuses on quantitatively assessing potential energy, emissions and resource benefits of such strategies for space cooling equipment. This paper first analyzes how existing recovery, reuse and recycling frameworks can be applied to space cooling, with emphasis on the demand-side enablers (e.g., innovative business models, supporting policies and regulations) and changes in supply-side production network throughout the supply chain (e.g., design, production and distribution, end-of-life recovery) needed to overcome existing barriers. It will present case studies of innovative business models for space cooling technologies, including reuse and recycling, and how effective refrigerant reclamation and recovery programs have been operationalized. Lastly, the paper will highlight global modeling results of energy, emissions and material recovery from scenario analysis of selected strategies for air conditioners. The findings of this paper are intended to inform the development of product and material recovery, reuse and recycling strategies for a rapidly growing stock of space conditioning equipment by addressing existing organizational, economic and regulatory barriers and potential supply-chain bottlenecks.

Khanna, Nina↗
DOE OSTI2025

Dynamic Capacitive Wireless Power Transfer System for Electric Vehicles (CRADA Final Report)

Road transportation accounts for 23% of our nation's total energy consumption, 59% of our petroleum consumption and 22% of our total emissions. Electric vehicles (EVs) have much higher well-to-wheel efficiency compared to gasoline vehicles and can reduce our dependence on oil, minimize emissions, improve local air quality and provide a platform for technological innovation and economic growth. While major progress has been made in the development of electric vehicles, their penetration remains under 1 The main hurdles in their widespread adoption are high cost, limited range and long charging times, due to limitations in battery technology. An approach to overcome these hurdles is to substantially reduce the on-board energy storage and instead deliver power wirelessly to the vehicle while it is in motion dynamic wireless power transfer (WPT). For EV charging applications, researchers have traditionally focused on inductive WPT. An issue with inductive WPT systems is that for magnetic flux guidance and shielding, they require ferrite cores, making them expensive, bulky and difficult to embed in the roadway. Under an ARPA-E IDEAS grant, the CU Boulder team has recently developed an alternative approach to WPT based on capacitive coupling that is much smaller, lighter, less expensive, and easier to embed in the roadway than inductive WPT; and have demonstrated a 1.2-kW 6.78-MHz version of this capacitive WPT system on a stationary platform. Under this seed grant program, preliminary work will be carried out on a dynamic capacitive WPT system to prepare a strong proposal for the ARPA-E OPEN 2018 FOA.

33 ADVANCED PROPULSION SYSTEMS↗
DOE OSTI2021

Adsorption of ethylenediamine on Cu surfaces: attributes of a successful capping molecule using first-principles calculations

The shape-controlled synthesis of Cu nanocrystals can benefit a wide range of applications, though challenges exist in achieving high and selective yields to a particular shape. Capping agents play a pivotal role in controlling shape, but their exact role remains ambiguous. In this study, the adsorption of ethylenediamine (EDA) on Cu(100) and Cu(111) was investigated with quantum density functional theory (DFT) to reveal the complex roles of EDA in promoting penta-twinned Cu nanowire growth. We find EDA has stronger binding on Cu(100) than on Cu(111), which agrees the general expectation that penta-twinned Cu nanowires express facets with stronger capping-molecule binding. Despite this stronger binding, ab initio thermodynamics reveals the surface energy of EDA-covered Cu(111) is lower than that EDA-covered Cu(100) at all solution-phase EDA chemical potentials, so there is no thermodynamic driving force for penta-twinned nanowires. We also investigated the capability of EDA to protect Cu surfaces from oxidation in water by quantifying energy barriers for a water molecule to diffuse through EDA layers on Cu(100) and Cu(111). The energy barrier on Cu(100) is significantly lower, which supports observations of faster oxidation of Cu(100) in electrochemical experiments. Thus, we elucidate another possible function of a capping agent – to enable selective oxidation of crystal facets. This finding adds to the general understanding of successful attributes of capping agents for shape-selective nanocrystal growth.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Evaluation of Microhole Drilling Technology for Geothermal Exploration, Assessment, And Monitoring

One of the greatest barriers to geothermal energy expansion is the high cost of drilling during exploration, assessment, and monitoring. Microhole drilling technology—small-diameter 2–4 in. (~5.1–10.2 cm) boreholes—is one potential low-cost alternative for monitoring and evaluating bores. However, delivering high weight-on-bit (WOB), high torque rotational horsepower to a conventional drill bit does not scale down to the hole sizes needed to realize the cost savings. Coiled tube drilling technology is one solution, but these systems are limited by the torque resistance of the coil system, helical buckling in compression, and most of all, WOB management. The evaluation presented herein will: (i) evaluate the technical and economic feasibility of low WOB technologies (specifically, a percussive hammer and a laser-mechanical system), (ii) develop downhole rotational solutions for low WOB drilling, (iii) provide specifications for a low WOB microhole drilling system, (iv) implement WOB control for low WOB drilling, and (v) evaluate and test low WOB drilling technologies.

15 GEOTHERMAL ENERGY↗
DOE OSTI2025

Research and Development on Advanced Electrochemical Energy Storage Devices Enabling a Spectrum of Electrified Vehicles

The USABC Advanced Battery development plan had the following three focus areas: 1. Existing technology validation, implementation, and cost reduction 2. Identification of the next viable technology with emphasis on the potential to meet USABC cost and energy density goals. 3. Support high-risk, high-reward battery technology R&D The primary aim of this project was focused on the barriers that most impede wider public adoption of electrification in vehicles-cost, energy density, low-temp performance, calendar life, and improvements in abuse tolerance. The specific objectives are as follows: Cost Reduction: drive to significantly reduce battery cost to be in-line with the $\$$100/kWh or less (by the end of calendar year 2020) DOE cost goals. Additionally, goals of $\$$75/KWh were set for 2023 aligned with fast charge and some offset of energy density. Energy Density Increase: focus on improving the cell-level specific energy and energy densities to >350 watt hours per kilogram (Wh/kg) and >750Wh/L. Low Temperature Performance Increase: strive toward developments that improve the discharge power and eliminate or dramatically reduce the life limiting lithium plating associated with regenerative braking at low temperatures, during the program. Calendar Life Increase: drive to achieve a 15-year calendar life. Abuse Tolerance Improvement: strive to develop improvements in Li-ion abuse tolerance and/or development of electrochemical energy storage technologies with inherently better response to abuse circumstances. Emerging Areas: initiate new programs that address emerging technologies that arise during the contract period.

25 ENERGY STORAGE↗
NASA NTRS1976

MCSCF potential energy surface for photodissociation of formaldehyde

The ground state potential energy surface for the dissociation of formaldehyde (H2CO to H2 and CO) is calculated with the ab initio MCSCF method with an extended (4-31G) basis set. The location, barrier height, and force constants of the transition state are determined, and the normal coordinate analysis is carried out. The calculated barrier height is 4.5 eV. Based on the calculated quantities, the detailed mechanism of the photochemical dissociation is discussed.

Jaffe, R. L.↗
DOE OSTI2022

Cold-Climate Packaged Heat Pumps - Resistance is Futile

The U.S. currently has a large market for room/zonal space conditioning equipment focused primarily on cooling, namely packaged terminal air conditioners (PTACs), packaged terminal heat pumps (PTHPs), and room air conditioners. This equipment largely relies on electric resistance for heating, particularly when outdoor temperatures fall to 40°F or below, presenting a compelling opportunity for energy savings and carbon reductions from reverse cycle heating. This paper provides an overview of cold climate packaged heat pump technologies in the market capable of high output down to outdoor temperatures of 5°F and identifies the technological and market barriers to adoption. For state-of-the-art cold climate packaged heat pumps sold in the retrofit market, defrost meltwater management is the principal barrier to implementation. An energy use analysis is conducted on state-of-the-art cold climate packaged heat pumps for heating and cooling loads by building vintage and climate zone. Potential solutions to defrost meltwater are proposed and modeled for their impact on heating energy efficiency. A national impact assessment estimates the aggregate energy savings and carbon reductions if cold climate packaged heat pumps were to replace existing PTACs and PTHPs in the U.S. building stock. A national, two-track approach is proposed for increasing market adoption in the replacement and new construction markets.

ACEEE Summer Study, cold climate, heat pumps, ccph↗
NASA NTRS2019

Experimental Demonstration and System Analysis for Plasmonic Force Propulsion

This project developed a higher-fidelity model of a recently envisioned small spacecraft propulsion system for precision pointing and proximity control. Plasmonic force propulsion harnesses solar light focused onto plasmon reactive subwavelength nanostructures to accelerate and expel nanoparticle propellant via strong optical forces. The goal of the project was to show that plasmonic space propulsion can provide the level of proximity and attitude control envisioned for future NASA nano/picosatellite missions, a level that is better than state-of-the-art approaches. We achieved this goal by showing that plasmonic force thrusters are feasible for a range of advanced mission concepts requiring swarm formations in a deep space environment. We performed three case studies that evaluated the performance of the plasmonic force propulsion thruster in a deep space, microsatellite swarm formation. These case studies assumed the propulsion system could generate thrust at the level predicted from our Phase 1 study (1.6 μN). Through these cases we were able to analyze the concept within a mission specific context through detailed orbital dynamics calculations. Results indicate that, with the Phase 1 estimated thrust level, the approach is promising for providing attitude control to swarm formation spacecraft. Further, we achieved goals related to technology development. Specifically, we experimentally demonstrated nanoparticle acceleration due to plasmonic forces with asymmetric nanostructures excited by focused laser light. Additionally, we investigated the thrust sensitivity and nanoparticle propellant injection dependencies upon thermal effects. As a result of our study, plasmonic force propulsion is at an early TRL 3. Active research and design has been conducted analytically and in the laboratory. Furthermore, practical applications such as the three case studies have been identified for the scientific basic principles that were observed. Future efforts related to fundamental understanding of these techniques should focus on 1) developing a standalone array of asymmetric nanostructures that can effectively interact with a stream or reservoir of particles or 2) experimentally evaluate a dielectrophoretic injector for nanoparticle propellant. The main limitation discovered about plasmonic propulsion regards performance estimates significantly below the Phase 1 estimations. Specifically, original assumptions in the Phase 1 project (notably, a linear array of asymmetric nanostructures) is not a viable approach to achieving significant acceleration, high exhaust velocity, of nanoparticles. More specifically, we assumed in Phase 1 that nanoparticles would be accelerated in series by a long linear array of asymmetric nanostructures. That is, the acceleration of the nanoparticle would build and increase with the kick received by each subsequent nanostructure. This is fundamentally flawed. The potential profile of a single nanostructure is such that it prohibits this phenomenon. The potential energy associated with the plasmon-generated dielectrophoretic force is a potential well, which is good for trapping nanoparticles, but cannot provide significant acceleration of particles to expel them out and away from the nanostructure. Further, a nanoparticle expelled from the first nanostructure would need to overcome the potential barrier for entry into the next nanostructure accelerating stage. Fundamentally, this effect means that a linear array of nanostructures is not a viable accelerating structure. Correspondingly then, acceleration can, or should, only be provided by one nanostructure, and the net acceleration and thrust force of a single nanostructure is small (~cm/s exhaust velocities, sub-nN level thrust vs. the 100’s m/s, μN originally envisioned). While our experiments demonstrated acceleration and manipulation of a nanoparticle using laser light in aqueous environment, the achievable energy and momentum addition to the nanoparticle from a single nanostructure stage is too low for useful propulsion. In terms of thrust prediction, the estimated thrust of 1.6 μN in Phase 1 is reduced to a few nN of thrust with this new insight and understanding of the concept. This thrust level is too small to achieve attitude control of swarms as originally envisioned.

Plasmonic Force↗