Smart polymeric materials, such as piezoelectric polymers which deform by application of an electric field, are of interest for use in controllable mirrors as large, lightweight space optics. An important consideration when using any organic material in a space application is their extreme vulnerability to the space environment. In LEO the presence of atomic oxygen, large thermal extremes, hard vacuum, short wavelength ultraviolet and particulate radiation can result in erosion, cracking and outgassing of most polymers. While much research has been performed examining the physical and chemical changes incurred by polymers exposed to actual and simulated LEO environments, little work has focused on the effects of the space environment on the performance of piezoelectric polymers. The most widely used piezoelectric polymers are those based on poly(vinylidene fluoride) (PVDF) and include copolymers synthesized from vinylidene fluoride and trifluoroethylene, hexafluoropropylene or chlorotrifluoroethylene. The presence of a comonomer group can greatly influence on the crystalline phase, melting point, Curie point, modulus and processing required for piezoelectricity. After a rigorous pre-selection process only two polymers, namely the PVDF homopolymer and a TrFE copolymer (80% comonomer content), satisfied most of the requirements for operation in the temperature/radiation environment of LEO. Based on this initial materials selection, we have now performed a detailed study of the effects of temperature, atomic oxygen and vacuum UV radiation simulating low Earth orbit conditions on these two polymers. Both polymers exhibited diminished but very stable piezoelectric performance up to 130 C despite the upper use temperatures suggested by industry of 80 C (PVDF) and 100 C (P(VDF-TrFE)). We believe that the loss of piezoelectric response in samples conditioned at 130 C compared with non-exposed samples is partly due to the depoling process which occurs when the highly stressed films undergo contraction via relaxation. The TrFE copolymer, which does not need to be stretched for the polar phase to be present, has better retention of piezoelectric properties at 130 C compared with the highly oriented homopolymer. AO/VUV exposure caused significant surface erosion and pattern development for both polymers. Erosion yields were 2.8 x 10{sup -24} cm{sup 3}/atom for PVDF and 2.5 x 10{sup -24} cm{sup 3}/atom for P(VDF-TrFE). The piezoelectric properties of the residual material for both polymers were largely unchanged after exposure, although a slight shift in the Curie transition of the P(VDF-TrFE) was observed. A lightly crosslinked network was formed in the copolymer, presumably due to penetrating VUV radiation, while the homopolymer remained uncrosslinked. These differences were attributed to different levels of crystallinity and increased VUV absorption by P(VDF-TrFE) over PVDF. In this paper a summary of the performance limiting effects of temperature, radiation, atomic oxygen and VUV on the piezoelectric response of PVDF based polymers will be presented.
With multipath routing in mobile ad hoc networks (MANETs), a source can establish multiple routes to a destination for routing data. In MANETs, mulitpath routing can be used to provide route resilience, smaller end-to-end delay, and better load balancing. However, when the multiple paths are close together, transmissions of different paths may interfere with each other, causing degradation in performance. Besides interference, the physical diversity of paths also improves fault tolerance. We present a purely distributed multipath protocol based on the AODV-Multipath (AODVM) protocol called AODVM with Path Diversity (AODVM/PD) that finds multiple paths with a desired degree of correlation between paths specified as an input parameter to the algorithm. We demonstrate through detailed simulation analysis that multiple paths with low degree of correlation determined by AODVM/PD provides both smaller end-to-end delay than AODVM in networks with low mobility and better route resilience in the presence of correlated node failures.
We report a simple, rapid approach to synthesize water-soluble and biocompatible fluorescent quantum dot (QD) micelles by encapsulation of monodisperse, hydrophobic QDs within surfactant/lipid micelles. Analyses of UV-vis and photo luminescence spectra, along with transmission electron microscopy, indicate that the water-soluble semiconductor QD micelles are monodisperse and retain the optical properties of the original hydrophobic QDs. The QD micelles were shown to be biocompatible and exhibited little or no aggregation when taken up by cultured rat hippocampal neurons.
The effects of atomic oxygen (AO) and vacuum UV radiation simulating low Earth orbit conditions on two commercially available piezoelectric polymer films, poly(vinylidene fluoride) (PVDF) and poly(vinylidene fluoride-trifluoroethylene) P(VDF-TrFE), have been studied. Surface erosion and pattern development are significant for both polymers. Erosion yields were determined as 2.8 x 10{sup -24} cm{sup 3}/atom for PVDF and 2.5 x 10{sup -24} cm{sup 3}/atom for P(VDF-TrFE). The piezoelectric properties of the residual material of both polymers were largely unchanged after exposure, although a slight shift in the Curie transition of the P(VDF-TrFE) was observed. A lightly cross-linked network was formed in the copolymer presumably because of penetrating vacuum ultraviolet (VUV) radiation, while the homopolymer remained uncross-linked. These differences were attributed to varying degrees of crystallinity and potentially greater absorption, and hence damage, of VUV radiation in P(VDF-TrFE) compared with PVDF.
Pellets of Fe/KClO{sub 4} mixtures are used as a heat source for thermally activated ('thermal') batteries. They provide the energy necessary for melting the electrolyte and bringing the battery stack to operating temperature. The effects of morphology of the Fe and the heat-pellet density and composition on both the physical properties (flowability, pelletization, and pellet strength) and the pyrotechnic performance (burn rate and ignition sensitivity) were examined using several commercial sources of Fe.
We report the demonstration of a terahertz quantum-cascade laser that operates up to 164 K in pulsed mode and 117 K in continuous-wave mode at approximately 3.0 THz. The active region was based on a resonant-phonon depopulation scheme and a metal-metal waveguide was used for modal confinement. Copper to copper thermocompression wafer bonding was used to fabricate the waveguide, which displayed improved thermal properties compared to a previous indium-gold bonding method.
Nano photonic materials are synthetically manufactured crystals at the nano scale with the target of creating a microstructure with a special electro-magnetic periodicity. Such nano photonic materials have the ability to control light propagation and thus are capable of creating photonic bandgaps in the frequency domain. We propose using nano photonic crystals as sensors to detect microdamage in composite materials. We demonstrate using a simulation model that a nano photonic sensor attached to a composite bar experiences a significant change in its bandgap profile when damage is induced in the composite bar. The model predicts the frequency response of the nano photonic sensor using the transfer matrix method. A damage metric to evaluate the change in the frequency response is developed. Successful developments of nano photonic sensors allow damage identification at scales not attainable using current sensing technologies.
This slide presentation outlines information on a technology acquisition strategy for the security of water distribution networks. The Department of Homeland Security (DHS) has tasked a multi-laboratory team to evaluate current and future needs to protect the nation's water distribution infrastructure by supporting an objective evaluation of current and new technologies. The primary deliverables from this Operational Technology Demonstration (OTD) are the following: establishment of an advisory board for review and approval of testing protocols, technology acquisition processes and recommendations for technology test and evaluation in laboratory and field settings; development of a technology acquisition process; creation of laboratory and field testing and evaluation capability; and, testing of candidate technologies for insertion into a water early warning system. The initial phase of this study involves the development of two separate but complementary strategies to be reviewed by the advisory board: a technology acquisition strategy; and, a technology evaluation strategy. Lawrence Livermore National Laboratory and Sandia National Laboratories are tasked with the first strategy, while Los Alamos, Pacific Northwest, and Oak Ridge National Laboratories are tasked with the second strategy. The first goal of the acquisition strategy is the development of a technology survey process that includes a review of current test programs and development of a method to solicit and select existing and emerging sensor technologies for evaluation and testing. The second goal is to implement the acquisition strategy to provide a set of recommendations for candidate technologies for laboratory and field testing.
We have conducted an extensive study of the evolution of surface morphology of single crystal diamond surfaces during sputtering by 20 keV Ga{sup +} and Ga{sup +} + H{sub 2}O. We observe the formation of well-ordered ripples on the surface for angles of incidence between 40 and 70{sup o}. We have also measured sputter yields as a function of angle of incidence, and ripple wavelength and amplitude dependence on angle of incidence and ion fluence. Smooth surface morphology is observed for <40{sup o}, and a transition to a step-and-terrace structure is observed for >70{sup o}. The formation and evolution of well-ordered surface ripples is well characterized by the model of Bradley and Harper, where sputter-induced roughening is balanced by surface transport smoothing. Smoothing is consistent with an ion-induced viscous relaxation mechanism. Ripple amplitude saturates at high ion fluence, confirming the effect of nonlinear processes. Differences between Ga{sup +} and Ga{sup +} + H{sub 2}O in ripple wavelength, amplitude, and time to saturation of amplitude are consistent with the increased sputter yield observed for Ga{sup +} + H{sub 2}O. For angle of incidence <40{sup o}, an ion bombardment-induced 'atomic drift' mechanism for surface smoothing may be responsible for suppression of ripple formation. For Ga{sup +} + H{sub 2}O, we observe anomalous formation of very large amplitude and wavelength, poorly ordered surface ridges for angle of incidence near 40{sup o}. Finally, we observe that ripple initiation on smooth surfaces can take place by initial stochastic roughening followed by evolution of increasingly well-ordered ripples.
Nuclear fuel cycle transparency can be defined as a confidence building approach among political entities to ensure civilian nuclear facilities are not being used for the development of nuclear weapons. Transparency concepts facilitate the transfer of nuclear technology, as the current international political climate indicates a need for increased methods of assuring non-proliferation. This research develops a system which will augment current non-proliferation assessment activities undertaken by U.S. and international regulatory agencies. It will support the export of nuclear technologies, as well as the design and construction of Gen. IV energy systems. Additionally, the framework developed by this research will provide feedback to cooperating parties, thus ensuring full transparency of a nuclear fuel cycle. As fuel handling activities become increasingly automated, proliferation or diversion potential of nuclear material still needs to be assessed. However, with increased automation, there exists a vast amount of process data to be monitored. By designing a system that monitors process data continuously, and compares this data to declared process information and plant designs, a faster and more efficient assessment of proliferation risk can be made. Figure 1 provides an illustration of the transparency framework that has been developed. As shown in the figure, real-time process data is collected at the fuel cycle facility; a reactor, a fabrication plant, or a recycle facility, etc. Data is sent to the monitoring organization and is assessed for proliferation risk. Analysis and recommendations are made to cooperating parties, and feedback is provided to the facility. The analysis of proliferation risk is based on the following factors: (1) Material attractiveness: the quantification of factors relevant to the proliferation risk of a certain material (e.g., highly enriched Pu-239 is more attractive than that of lower enrichment) (2) The static (baseline) risk: the quantification of risk factors regarding the expected value of proliferation risk under normal (not proliferating) operations. (3) The dynamic (changing) risk: the quantification of risk factors regarding the observed value of proliferation risk, based on monitor signals from facility operations. This framework could be implemented at facilities which have been exported (for instance, to third world countries), or facilities located in sensitive countries. Sandia National Laboratories is currently working with the Japan Nuclear Cycle Development Institute (JNC) to implement a demonstration of nuclear fuel cycle transparency technology at the Fuel Handling Training Model designed for the Monju Fast Reactor at the International Cooperation and Development Training Center in Japan. This technology has broad applications, both in the U.S. and abroad. Following the demonstration, we expect to begin further testing of the technology at an Enrichment Facility, a Fast Reactor, and at a Recycle Facility.
This paper presents a 3D facial recognition algorithm based on the Hausdorff distance metric. The standard 3D formulation of the Hausdorff matching algorithm has been modified to operate on a 2D range image, enabling a reduction in computation from O(N2) to O(N) without large storage requirements. The Hausdorff distance is known for its robustness to data outliers and inconsistent data between two data sets, making it a suitable choice for dealing with the inherent problems in many 3D datasets due to sensor noise and object self-occlusion. For optimal performance, the algorithm assumes a good initial alignment between probe and template datasets. However, to minimize the error between two faces, the alignment can be iteratively refined. Results from the algorithm are presented using 3D face images from the Face Recognition Grand Challenge database version 1.0.
Low-temperature co-fired ceramic (LTCC) enables development and testing of critical elements on microsystem boards as well as nonmicroelectronic meso-scale applications. We describe silicon-based microelectromechanical systems packaging and LTCC meso-scale applications. Microfluidic interposers permit rapid testing of varied silicon designs. The application of LTCC to micro-high-performance liquid chromatography (?-HPLC) demonstrates performance advantages at very high pressures. At intermediate pressures, a ceramic thermal cell lyser has lysed bacteria spores without damaging the proteins. The stability and sensitivity of LTCC/chemiresistor smart channels are comparable to the performance of silicon-based chemiresistors. A variant of the use of sacrificial volume materials has created channels, suspended thick films, cavities, and techniques for pressure and flow sensing. We report on inductors, diaphragms, cantilevers, antennae, switch structures, and thermal sensors suspended in air. The development of 'functional-as-released' moving parts has resulted in wheels, impellers, tethered plates, and related new LTCC mechanical roles for actuation and sensing. High-temperature metal-to-LTCC joining has been developed with metal thin films for the strong, hermetic interfaces necessary for pins, leads, and tubes.
Combinatorial algorithms have long played a pivotal enabling role in many applications of parallel computing. Graph algorithms in particular arise in load balancing, scheduling, mapping and many other aspects of the parallelization of irregular applications. These are still active research areas, mostly due to evolving computational techniques and rapidly changing computational platforms. But the relationship between parallel computing and discrete algorithms is much richer than the mere use of graph algorithms to support the parallelization of traditional scientific computations. Important, emerging areas of science are fundamentally discrete, and they are increasingly reliant on the power of parallel computing. Examples include computational biology, scientific data mining, and network analysis. These applications are changing the relationship between discrete algorithms and parallel computing. In addition to their traditional role as enablers of high performance, combinatorial algorithms are now customers for parallel computing. New parallelization techniques for combinatorial algorithms need to be developed to support these nontraditional scientific approaches. This chapter will describe some of the many areas of intersection between discrete algorithms and parallel scientific computing. Due to space limitations, this chapter is not a comprehensive survey, but rather an introduction to a diverse set of techniques and applications with a particular emphasis on work presented at the Eleventh SIAM Conference on Parallel Processing for Scientific Computing. Some topics highly relevant to this chapter (e.g. load balancing) are addressed elsewhere in this book, and so we will not discuss them here.
In this article we describe stress nets, a technique for exploring 2D tensor fields. Our method allows a user to examine simultaneously the tensors eigenvectors (both major and minor) as well as scalar-valued tensor invariants. By avoiding noise-advection techniques, we are able to display both principal directions of the tensor field as well as the derived scalars without cluttering the display. We present a CPU-only implementation of stress nets as well as a hybrid CPU/GPU approach and discuss the relative strengths and weaknesses of each. Stress nets have been used as part of an investigation into crack propagation. They were used to display the directions of maximum shear in a slab of material under tension as well as the magnitude of the shear forces acting on each point. Our methods allowed users to find new features in the data that were not visible on standard plots of tensor invariants. These features disagree with commonly accepted analytical crack propagation solutions and have sparked renewed investigation. Though developed for a materials mechanics problem, our method applies equally well to any 2D tensor field having unique characteristic directions.
Smart polymeric materials, such as piezoelectric polymers which deform by application of an electric field, are of interest for use in controllable mirrors as large, lightweight space optics. An important consideration when using any organic material in a space application is their extreme vulnerability to the space environment. In LEO the presence of atomic oxygen, large thermal extremes, hard vacuum, short wavelength ultraviolet and particulate radiation can result in erosion, cracking and outgassing of most polymers. While much research has been performed examining the physical and chemical changes incurred by polymers exposed to actual and simulated LEO environments, little work has focused on the effects of the space environment on the performance of piezoelectric polymers. The most widely used piezoelectric polymers are those based on poly(vinylidene fluoride) (PVDF) and include copolymers synthesized from vinylidene fluoride and trifluoroethylene, hexafluoropropylene or chlorotrifluoroethylene. The presence of a comonomer group can greatly influence on the crystalline phase, melting point, Curie point, modulus and processing required for piezoelectricity. After a rigorous pre-selection process only two polymers, namely the PVDF homopolymer and a TrFE copolymer (80% comonomer content), satisfied most of the requirements for operation in the temperature/radiation environment of LEO. Based on this initial materials selection, we have now performed a detailed study of the effects of temperature, atomic oxygen and vacuum UV radiation simulating low Earth orbit conditions on these two polymers. Both polymers exhibited diminished but very stable piezoelectric performance up to 130 C despite the upper use temperatures suggested by industry of 80 C (PVDF) and 100 C (P(VDF-TrFE)). We believe that the loss of piezoelectric response in samples conditioned at 130 C compared with non-exposed samples is partly due to the depoling process which occurs when the highly stressed films undergo contraction via relaxation. The TrFE copolymer, which does not need to be stretched for the polar phase to be present, has better retention of piezoelectric properties at 130 C compared with the highly oriented homopolymer. AO/VUV exposure caused significant surface erosion and pattern development for both polymers. Erosion yields were 2.8 x 10{sup -24} cm{sup 3}/atom for PVDF and 2.5 x 10{sup -24} cm{sup 3}/atom for P(VDF-TrFE). The piezoelectric properties of the residual material for both polymers were largely unchanged after exposure, although a slight shift in the Curie transition of the P(VDF-TrFE) was observed. A lightly crosslinked network was formed in the copolymer, presumably due to penetrating VUV radiation, while the homopolymer remained uncrosslinked. These differences were attributed to different levels of crystallinity and increased VUV absorption by P(VDF-TrFE) over PVDF. In this paper a summary of the performance limiting effects of temperature, radiation, atomic oxygen and VUV on the piezoelectric response of PVDF based polymers will be presented.
A new approach to optical time-domain reflectometry (OTDR) is proposed that will enable distributed fault monitoring in singlemode VCSEL-based networks. In situ OTDR uses the transmitter VCSEL already resident in data transceivers as both emitter and resonant-cavity photodiode for fault location measurements. Also valuable at longer wavelengths, the concept is demonstrated here using an 850 nm oxide-confined VCSEL and simple electronics. The dead times and sensitivity obtained are adequate to detect the majority of faults anticipated in local- and metropolitan-area networks.
Leaders around the world and across the ideological spectrum agree that the global nonproliferation regime is facing a serious test. The emergence of sophisticated terrorist networks, black markets in nuclear technology, and technological leaps associated with globalization have conspired to threaten one of the most successful examples of international cooperation in history. The rampant proliferation of nuclear weapons that was predicted at the start of the nuclear age has been largely held in check and the use of those weapons avoided. Nonetheless, with the thirty-fifth anniversary of the Treaty on the Nonproliferation of Nuclear Weapons (NPT), the threat of nuclear proliferation seems more serious than ever. Although experts readily concede that there exist many pathways to proliferation, the threat posed by the misuse of the civilian nuclear fuel cycle has received considerable recent attention. While the connection between nuclear energy and nonproliferation has been a topic of discussion since the dawn of the nuclear age, world events have brought the issue to the forefront once again. United States President George W. Bush and International Atomic Energy Agency (IAEA) Director General Mohammad ElBaradei are among those who have highlighted proliferation risks associated with civilian nuclear power programs and called for revitalizing the nuclear nonproliferation regime to address new threats. From the possibility of diversion or theft of nuclear material or technology, to the use of national civilian programs as a cover for weapons programs - what some have called latent proliferation - the fuel cycle appears to many to represent a glaring proliferation vulnerability. Just as recognition of these risks is not new, neither is recognition of the many positive benefits of nuclear energy. In fact, a renewed interest in exploiting these benefits has increased the urgency of addressing the risks. Global energy demand is expected to at least double by the middle of the century and could increase even more quickly. Much of the new demand will come from the rapidly expanding economies in China and India, but much of the developing world stands poised to follow the same path. This growth in demand is paralleled by concerns about global warming and the long-term reliability of carbon-based fuel supplies, concerns which expanded use of nuclear power can help to address. For these reasons and others, many countries in Asia have already clearly signaled that nuclear energy will play a key role for years to come. Numerous proposals have been made in the last two years for reducing the proliferation risk of the civilian nuclear fuel cycle. These range from a ban on export of enrichment and reprocessing technology to countries not already possessing operational capabilities to multinational management of the nuclear fuel cycle and strengthening existing monitoring and security mechanisms. The need for international willingness to enforce nonproliferation commitments and norms has also been emphasized. Some of these proposals could significantly impact the production of nuclear energy. Because the successful strengthening of the nonproliferation regime and the expansion of nuclear energy are so closely related, any successful approach to resolving these issues will require the creative input of experts from both the nuclear energy and nonproliferation communities. Against this backdrop, Sandia National Laboratories organized its 14th International Security Conference (ISC) around the theme: Strengthening the Nuclear Nonproliferation Regime: Focus on the Civilian Nuclear Fuel Cycle. The goal of the conference was to begin a constructive dialogue between the nuclear energy and nuclear nonproliferation communities. The conference was held in Chantilly, Virginia, just outside Washington, D.C. on April 4-6, 2005, and was attended by approximately 125 participants from fifteen countries. The ISC agenda was structured to produce a systematic review of the connection between civilian nuclear energy programs and the proliferation of nuclear weapons and to identify constructive approaches to strengthen the nonproliferation regime. The conference began by reviewing the energy and security context that has, once again, raised the profile of this issue. A discussion of the risks associated with the civilian nuclear fuel cycle was then used to inform the analysis of several potential risk-management tools. The conference concluded by looking for lessons from the past as well as looking forward to future opportunities, with a particular focus on East Asia. In this paper we summarize the debates and ideas that emerged during the conference. Although we have drawn on material presented by speakers and comments made by participants, we do not quote or cite the specific contributions of individuals.
We propose a new class of Discontinuous Galerkin (DG) methods based on variational multiscale ideas. Our approach begins with an additive decomposition of the discontinuous finite element space into continuous (coarse) and discontinuous (fine) components. Variational multiscale analysis is used to define an interscale transfer operator that associates coarse and fine scale functions. Composition of this operator with a donor DG method yields a new formulation that combines the advantages of DG methods with the attractive and more efficient computational structure of a continuous Galerkin method. The new class of DG methods is illustrated for a scalar advection-diffusion problem.
This paper analyzes the accuracy of the shift-invert Lanczos iteration for computing eigenpairs of the symmetric definite generalized eigenvalue problem. We provide bounds for the accuracy of the eigenpairs produced by shift-invert Lanczos given a residual reduction. We discuss the implications of our analysis for practical shift-invert Lanczos iterations. When the generalized eigenvalue problem arises from a conforming finite element method, we also comment on the uniform accuracy of bounds (independent of the mesh size h).
A unique nanocrystalline, mesoporous PdO-SnO{sub 2} film exhibiting high sensitivity and selectivity to hydrogen gas at room temperature has been developed.
Numotech Inc. has developed the Numobag{trademark}, a disposable, lightweight, wound healing device which produces Topical Hyperbaric Oxygen Therapy (THOT). The Numobag{trademark} is cost effective and has been clinically validated to heal large skin lesions rapidly and has proven to arrest wound advancement from several insidious forms of biological attack including dermal anthrax, small pox, necrotizing fasciitis etc. The Numobag{trademark} can treat mass casualties wounded by chemical/radiological burns or damaging biological exposures. The Numobag{trademark} can be a frontline tool as an isolation unit, reducing cross-contamination and infection of medical personnel. The heightened oxygen content kills organisms on the skin and in the wound, avoids expensive hospital trash disposal procedures, and helps the flesh heal. The Numobag{trademark} requires high purity oxygen. Numotech Inc. is teaming with Sandia National Laboratories and Spektr Conversion in Russia to develop a cost effective, portable, low power oxygen generator.
Diversionary devices also known as flash bangs or stun grenades were first employed about three decades ago. These devices produce a loud bang accompanied by a brilliant flash of light and are employed to temporarily distract or disorient an adversary by overwhelming their visual and auditory senses in order to gain a tactical advantage. Early devices that where employed had numerous shortcomings. Over time, many of these deficiencies were identified and corrected. This evolutionary process led to today's modern diversionary devices. These present-day conventional diversionary devices have undergone evolutionary changes but operate in the same manner as their predecessors. In order to produce the loud bang and brilliant flash of light, a flash powder mixture, usually a combination of potassium perchlorate and aluminum powder is ignited to produce an explosion. In essence these diversionary devices are small pyrotechnic bombs that produce a high point-source pressure in order to achieve the desired far-field effect. This high point-source pressure can make these devices a hazard to the operator, adversaries and hostages even though they are intended for 'less than lethal' roles. A revolutionary diversionary device has been developed that eliminates this high point-source pressure problem and eliminates the need for the hazardous pyrotechnic flash powder composition. This new diversionary device employs a fuel charge that is expelled and ignited in the atmosphere. This process is similar to a fuel air or thermobaric explosion, except that it is a deflagration, not a detonation, thereby reducing the overpressure hazard. This technology reduces the hazard associated with diversionary devices to all involved with their manufacture, transport and use. An overview of the history of diversionary device development and developments at Sandia National Laboratories will be presented.
Solar power towers can be used to make hydrogen on a large scale. Electrolyzers could be used to convert solar electricity produced by the power tower to hydrogen, but this process is relatively inefficient. Rather, efficiency can be much improved if solar heat is directly converted to hydrogen via a thermochemical process. In the research summarized here, the marriage of a high-temperature ({approx}1000 C) power tower with a sulfuric acid/hybrid thermochemical cycle was studied. The concept combines a solar power tower, a solid-particle receiver, a particle thermal energy storage system, and a hybrid-sulfuric-acid cycle. The cycle is 'hybrid' because it produces hydrogen with a combination of thermal input and an electrolyzer. This solar thermochemical plant is predicted to produce hydrogen at a much lower cost than a solar-electrolyzer plant of similar size. To date, only small lab-scale tests have been conducted to demonstrate the feasibility of a few of the subsystems and a key immediate issue is demonstration of flow stability within the solid-particle receiver. The paper describes the systems analysis that led to the favorable economic conclusions and discusses the future development path.