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NASA NTRS1988

AlGaAs heterojunction lasers

The characterization of 8300 A lasers was broadened, especially in the area of beam quality. Modulation rates up to 2 Gbit/sec at output powers of 20 mW were observed, waveform fidelity was fully adequate for low BER data transmission, and wavefront measurements showed that phase aberrations were less than lamda/50. Also, individually addressable arrays of up to ten contiguous diode lasers were fabricated and tested. Each laser operates at powers up to 30 mW CW in single spatial mode. Shifting the operating wavelength of the basic CSP laser from 8300 A to 8650 A was accomplished by the addition of Si to the active region. Output power has reached 100 mW single mode, with excellent far field wave front properties. Operating life is currently approx. 1000 hrs at 35 mW CW. In addition, laser reliability, for operation at both 8300 A and 8650 A, has profited significantly from several developments in the processing procedures.

Goldstein, B.↗

NASA NTRS1992

The 10 kW power electronics for hydrogen arcjets

A combination of emerging mission considerations such as 'launch on schedule', resource limitations, and the development of higher power spacecraft busses has resulted in renewed interest in high power hydrogen arcjet systems with specific impulses greater than 1000 s for Earth-space orbit transfer and maneuver applications. Solar electric propulsion systems with about 10 kW of power appear to offer payload benefits at acceptable trip times. This work outlines the design and development of 10 kW hydrogen arcjet power electronics and results of arcjet integration testing. The power electronics incorporated a full bridge switching topology similar to that employed in state of the art 5 kW power electronics, and the output filter included an output current averaging inductor with an integral pulse generation winding for arcjet ignition. Phase shifted, pulse width modulation with current mode control was used to regulate the current delivered to arcjet, and a low inductance power stage minimized switching transients. Hybrid power Metal Oxide Semiconductor Field Effect Transistors were used to minimize conduction losses. Switching losses were minimized using a fast response, optically isolated, totem-pole gate drive circuit. The input bus voltage for the unit was 150 V, with a maximum output voltage of 225 V. The switching frequency of 20 kHz was a compromise between mass savings and higher efficiency. Power conversion efficiencies in excess of 0.94 were demonstrated, along with steady state load current regulation of 1 percent. The power electronics were successfully integrated with a 10 kW laboratory hydrogen arcjet, and reliable, nondestructive starts and transitions to steady state operation were demonstrated. The estimated specific mass for a flight packaged unit was 2 kg/kW.

Hamley, John A.↗

DOE OSTI2020

Task 12 PV Sustainability - Life Cycle Inventories and Life Cycle Assessments of Photovoltaic Systems

Life Cycle Assessment (LCA) is a structured, comprehensive method of quantifying material- and energy-flows and their associated impacts in the life cycles of products (i.e., goods and services). One of the major goals of IEA PVPS Task 12 is to provide guidance on assuring consistency, balance, transparency and quality of LCA to enhance the credibility and reliability of the results. The current report presents the latest consensus life cycle inventories among the authors, PV LCA experts in North America, Europe, Asia and Australia. At this time consensus is limited to four technologies for which there are well-established and up-to-date life cycle inventory (LCI) data (mono- and multi-crystalline Si, CdTe, CIGS, as well as one emerging technology (perovskite silicon tandem). LCIs are necessary for LCA and the availability of such data is often the greatest barrier for conducting LCA. The Task 12 LCA experts have put great efforts in gathering and compiling the LCI data presented in this report. These include detailed inputs and outputs during manufacturing of cell, wafer, module, and balance-of-system (i.e., structural and electrical components) that were estimated from actual production and operation facilities. In addition, data are presented to enable analyses of various types of PV installations; these include operational data of rooftop and ground-mount PV systems and country-specific PV-mixes. The LCI datasets presented in this report are the latest that are available to the public describing the status in 2018 for crystalline Si (some manufacturing data from 2011 were not updated), 2015 and 2017-2018 for CdTe, 2010 for CIGS, 2010 for HCPV, and 2017 for perovskite silicon tandem technology.

14 SOLAR ENERGY↗

NASA NTRS1986

Optical techniques to feed and control GaAs MMIC modules for phased array antenna applications

A complex signal distribution system is required to feed and control GaAs monolithic microwave integrated circuits (MMICs) for phased array antenna applications above 20 GHz. Each MMIC module will require one or more RF lines, one or more bias voltage lines, and digital lines to provide a minimum of 10 bits of combined phase and gain control information. In a closely spaced array, the routing of these multiple lines presents difficult topology problems as well as a high probability of signal interference. To overcome GaAs MMIC phased array signal distribution problems optical fibers interconnected to monolithically integrated optical components with GaAs MMIC array elements are proposed as a solution. System architecture considerations using optical fibers are described. The analog and digital optical links to respectively feed and control MMIC elements are analyzed. It is concluded that a fiber optic network will reduce weight and complexity, and increase reliability and performance, but higher power will be required.

Bhasin, K. B.↗

NASA NTRS1986

Optical techniques to feed and control GaAs MMIC modules for phased array antenna applications

Bhasin, K. B.↗

NASA NTRS1990

System control of an autonomous planetary mobile spacecraft

The goal is to suggest the scheduling and control functions necessary for accomplishing mission objectives of a fairly autonomous interplanetary mobile spacecraft, while maximizing reliability. Goals are to provide an extensible, reliable system conservative in its use of on-board resources, while getting full value from subsystem autonomy, and avoiding the lure of ground micromanagement. A functional layout consisting of four basic elements is proposed: GROUND and SYSTEM EXECUTIVE system functions and RESOURCE CONTROL and ACTIVITY MANAGER subsystem functions. The system executive includes six subfunctions: SYSTEM MANAGER, SYSTEM FAULT PROTECTION, PLANNER, SCHEDULE ADAPTER, EVENT MONITOR and RESOURCE MONITOR. The full configuration is needed for autonomous operation on Moon or Mars, whereas a reduced version without the planning, schedule adaption and event monitoring functions could be appropriate for lower-autonomy use on the Moon. An implementation concept is suggested which is conservative in use of system resources and consists of modules combined with a network communications fabric. A language concept termed a scheduling calculus for rapidly performing essential on-board schedule adaption functions is introduced.

Dias, William C.↗

DOE OSTI2017

FINAL REPORT - Development of High Pressure Hydrogen Storage Tank for Storage and Gaseous Truck Delivery

The “Development of High Pressure Hydrogen Storage Tanks for Storage and Gaseous Truck Delivery” project [DE-FG36-08GO18062] was initiated on 01 July 2008. Hexagon Lincoln (then Lincoln Composites) received grant funding from the U.S. Department of Energy to support the design and development of an improved bulk hauling and storage solution for hydrogen in terms of cost, safety, weight and volumetric efficiency. The development of this capability required parallel development and qualification of large all-composites pressure vessels, a custom ISO container to transport and store said tanks, and performance of trade studies to identify optimal operating pressure for the system. Qualification of the 250 bar TITAN® module was completed in 2009 with supervision from the American Bureau of Shipping [ABS], and the equipment has been used internationally for bulk transportation of fuel gases since 2010. Phase 1 of the project was successfully completed in 2012 with the issuance of USDOT SP 14951, the special permit authorizing the manufacture, marking, sale and use of TITAN® Mobile Pipeline® equipment in the United States. The introduction of tube trailers with light weight composite tankage has meant that 2 to 3 times as much gaseous fuel can be transported with each trip. This increased hauling efficiency offers dramatically reduced operating costs and has enabled a profitable business model for over-the-road compressed natural gas delivery. The economic drivers of this business opportunity vary from country to country and region to region, but in many places gas distribution companies have realized profitable operations. Additional testing was performed in 2015 to characterize hydrogen-specific operating protocols for use of TITAN® systems in CHG service at 250 bar. This program demonstrated that existing compression and decompression methodologies can efficiently and safely fill and unload lightweight bulk hauling systems. Hexagon Lincoln and U.S. DOE agreed to continue into Phase 2 of the project without pursuing the development of higher pressure capabilities as originally planned. At 250 bar, development of equipment for hydrogen transport is supported by strong activity in the adjacent natural gas transportation sector. Trade studies performed since 2011 indicate optimization of hauling efficiency and system cost for hydrogen transport at about 350 bar (5076 psi). However, due to reduced efficiency of compression of natural gas above 250 bar, 350 bar operation is not an attractive option for natural gas transportation. The CHG market is not developed at this time, and it is difficult to forecast the arrival of significant revenues. On the investment side, the cost to fully qualify a large tank module at 350 bar is estimated at $3MM to $5MM. There is insufficient CHG market definition to support a stand-alone business case for this investment without near term revenue in the adjacent CNG transportation market. Therefore development of a 350 bar TITAN® system was deferred and not pursued under this project. Hexagon Lincoln continues to support the development of tankage and equipment for operation at 350 bar and above; with 700 bar vehicle tanks and 950 bar tanks for ground storage applications. Phase 2 activities were focused on reducing system cost, increasing system capacity, increasing system safety and characterization of polymer material performance specific to hydrogen pressure vessel usage. With the successful launch of TITAN® modules and trailers in natural gas transportation, over 600 units have been produced through the end of 2016, resulting in improved purchasing power for raw materials and manufactured components. This has allowed Hexagon Lincoln to approach the current project goals for system cost. At $590/kg of compressed hydrogen delivered, the system cost of the baseline TITAN® module is below the project’s 2015 target of $730/kg H2 delivered, and very close to the project’s 2020 target of $575/kg H2 delivered. [Based on product pricing in 1Q2017.] Emphasis was placed on configuration of larger capacity systems within the vehicle weights and dimensions allowed on federal and state highways in the United States and other countries. These activities resulted in the design and development of integrated tube trailer systems that have increased delivery capacities by 45%. The hydrogen delivery capacity of our largest system is 845 kg, exceeding the project’s 2015 target of 700 kg H2 delivered. Emerging technologies offering improvement of the safety systems used on the equipment were investigated, with particular focus on improving the reliability and cost of the emergency venting system for fire protection. Finally, investment in our materials laboratory improved detection and characterization of hydrogen-induced damage in polymer materials, supporting the development of operational protocols to avoid damage to pressure vessel liners and valve components.

08 HYDROGEN↗

DOE OSTI2012

Testing Protocol for Module Encapsulant Creep (Presentation)

Recently there has been an interest in the use of thermoplastic encapsulant materials in photovoltaic modules to replace chemically crosslinked materials, e.g., ethylene-vinyl acetate. The related motivations include the desire to: reduce lamination time or temperature; use less moisture-permeable materials; or use materials with better corrosion characteristics. However, the use of anythermoplastic material in a high-temperature environment raises safety and performance concerns, as the standardized tests currently do not expose the modules to temperatures in excess of 85C, yet modules may experience temperatures above 100C in operation. Here we constructed eight pairs of crystalline-silicon modules and eight pairs of glass/encapsulation/glass mock modules using differentencapsulation materials of which only two were designed to chemically crosslink. One module set was exposed outdoors with insulation on the back side in Arizona in the summer, and an identical set was exposed in environmental chambers. High precision creep measurements and performance measurements indicate that despite many of these polymeric materials being in the melt state at some of thehighest outdoor temperatures achievable, very little creep was seen because of their high viscosity, temperature heterogeneity across the modules, and in the case of the crystalline-silicon modules, the physical restraint of the backsheet. These findings have very important implications for the development of IEC and UL qualification and safety standards, and in regards to the necessary level ofcure during the processing of crosslinking encapsulants.

14 SOLAR ENERGY↗

DOE OSTI2024

FORCE Update 2024

The Framework for Optimization of Resources and Economics (FORCE) tool suite is the U.S. Department of Energy’s Nuclear Integrated Energy Systems (IES) Program flagship tool suite for technoeconomic IES analysis of IES. This tool suite is useful for analysis designed to evaluate and improve the technoeconomics of energy production systems, particularly for systems including nuclear technology. In this report, we document the development activity for the FORCE tool suite to extend its capabilities as performed during fiscal year 2024. In addition to reliability and accessibility, capability is one of the three standards guiding the development of the FORCE tool suite and the software codes that are its constituent parts. Extending the capabilities of the FORCE tool suite allows analysis both within the IES program as well as industry, university, and laboratory partners to perform analysis with more accuracy, insight, and impactful narrative. Four areas of capability development were the focus of activity this year: economic parameter uncertainty quantification, multiresolution analysis, components-to-optimization workflow automation, and statespace construction workflows for real-time optimal control. In economic parameter uncertainty quantification, the ability of HERON to capture risk due to scenarios (weather and energy demand uncertainty) was expanded to also include uncertainties in financial parameters such as capital cost or operation and maintenance costs. By including these sources of uncertainty, which are sometimes very large compared with scenario uncertainty, HERON is better able to capture the risk posed by investment in various IES technology. Because of this, analysts can also consider the reduction in risks that can be realized by choice of some technologies. In multiresolution analysis, development activity extended on work completed previously. In fiscal year 2023, methods for decomposing time series signals, such as demand, solar and wind availability, and price profiles, were analyzed and down-selected to those most effective at splitting signals into different resolutions. These resolutions allow considering the influence of different energy demand and supply behaviors across different time scales. For example, energy demand might be divided into seasonal, weekly, and hourly profiles. In fiscal year 2024, this preliminary work was extended and implemented within the Risk Analysis Virtual Environment (RAVEN) risk and uncertainty analysis platform, which is used throughout the FORCE framework. This development of the “multi-resolution time series analysis” (MR-TSA) module in RAVEN allows training synthetic history generators on complex time series. These synthetic history generators can then be used in HERON for generating scenarios that represent possible market and weather scenarios that can be analyzed on different time scales. We envision completing this work in the future, implementing multiresolution dispatch optimization strategies that can make the most beneficial use of these stratified time histories. In components-to-optimization workflow development, workflows for translating user inputs of components into algorithms for algebraic optimization were selected and implemented. Similar algorithms within the Holistic Energy Resource Optimization Network (HERON) were separated from the main code base of HERON and gathered with the components-to-optimization workflows in the new Dispatch Optimization Variable Engine (DOVE) software library. This modularization allows FORCE users to analyze dispatch optimization and energy system duty cycles independently of HERON, which previously was a burdensome task. Additionally, these dispatch optimization algorithms, set up in an independent library, can now be used across all software applications within FORCE, especially including the real-time optimal control software Optimization of Real-time Capacity Allocation (ORCA). Allowing FORCE software to share dispatch optimization algorithms within a single library allows for improved software maintenance and reliability. In statespace characterization workflow development, alternative workflows for optimizing dispatch with additional technical accuracy was the focus, particularly to improve the real-time optimization decision making in ORCA. Using algorithms and workflows initially developed for the Feasible Actuator Range Modifier (FARM), workflows for determining the statespace representation of IES were identified and demonstrated. The resulting dispatch optimization required a more robust optimization algorithm than that originally used in HERON (and moved to DOVE), which required adding an alternate workflow to DOVE that can more accurately match the behavior of physical systems using a partial differential equation representation. In conclusion, capability developments in the FORCE tool suite in fiscal year 2024 have improved the ability of the FORCE tool suite to perform

29 ENERGY PLANNING, POLICY, AND ECONOMY↗

NASA NTRS2011

Early Oscillation Detection Technique for Hybrid DC/DC Converters

Oscillation or instability is a situation that must be avoided for reliable hybrid DC/DC converters. A real-time electronics measurement technique was developed to detect catastrophic oscillations at early stages for hybrid DC/DC converters. It is capable of identifying low-level oscillation and determining the degree of the oscillation at a unique frequency for every individual model of the converters without disturbing their normal operations. This technique is specially developed for space-used hybrid DC/DC converters, but it is also suitable for most of commercial and military switching-mode power supplies. This is a weak-electronic-signal detection technique to detect hybrid DC/DC converter oscillation presented as a specific noise signal at power input pins. It is based on principles of feedback control loop oscillation and RF signal modulations, and is realized by using signal power spectral analysis. On the power spectrum, a channel power amplitude at characteristic frequency (CPcf) and a channel power amplitude at switching frequency (CPsw) are chosen as oscillation level indicators. If the converter is stable, the CPcf is a very small pulse and the CPsw is a larger, clear, single pulse. At early stage of oscillation, the CPcf increases to a certain level and the CPsw shows a small pair of sideband pulses around it. If the converter oscillates, the CPcf reaches to a higher level and the CPsw shows more high-level sideband pulses. A comprehensive stability index (CSI) is adopted as a quantitative measure to accurately assign a degree of stability to a specific DC/DC converter. The CSI is a ratio of normal and abnormal power spectral density, and can be calculated using specified and measured CPcf and CPsw data. The novel and unique feature of this technique is the use of power channel amplitudes at characteristic frequency and switching frequency to evaluate stability and identify oscillations at an early stage without interfering with a DC/DC converter s normal operation. This technique eliminates the probing problem of a gain/phase margin method by connecting the power input to a spectral analyzer. Therefore, it is able to evaluate stability for all kinds of hybrid DC/DC converters with or without remote sense pins, and is suitable for real-time and in-circuit testing. This frequency-domain technique is more sensitive to detect oscillation at early stage than the time-domain method using an oscilloscope.

Wang, Bright L.↗

DOE OSTI2017

Silanization of boron nitride nanosheets (BNNSs) through microfluidization and their use for producing thermally conductive and electrically insulating polymer nanocomposites

Chemical exfoliation of boron nitride nanosheets (BNNSs) from large flakes of specially synthesized micro-sized hexagonal boron nitride (h-BN) ceramics was carried out through microfluidization. The surface of BNNSs obtained was then functionalized with vinyl-trimethoxy silane (VTS) coupling agent through microfluidization once again in an effort to make them compatible with organic materials, especially those including polymers. The morphology of BNNSs with and without silane treatment was then systematically characterized by conducting various different analytical techniques, including Thermogravimetric analysis (TGA), X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Bright field Transmission Electron Microscopy (BF-TEM), Contact angle analyzer (CAA), Particle size analyzer (PSA) and Fourier Transmission Infrared (FTIR) spectroscopy attached with attenuated total reflectance (ATR) module. As a result, the silane treatment was determined to be properly and successfully carried out and to give rise to the irregularity of large flakes of the BNNSs by folding back their free edges upon themselves, which in turn assists in inducing further exfoliation of the few-layered nanosheets. To gain more insight into the effectiveness of the surface functionalization, thermal conductivity of polypropylene (PP) nanocomposites containing different amounts (1 wt% and 5 wt%) of BNNSs with and without silane treatment was experimentally investigated. Regardless of the weight content, PP nanocomposites containing silanized BNNSs were found to exhibit high thermal conductivity compared to PP nanocomposites containing BNNSs without silane treatment. It was concluded that microfluidization possesses the robustness to provide a reliable product quality, whether in small or large quantities, in a very time effective manner, when it comes to first exfoliating two-dimensional inorganic materials into few layered sheets, and functionalizing the surface of these sheets afterwards to make it possible to utilize them as promising filler constituent in manufacturing thermally conductive and electrically insulating polymer nanocomposites that could be considered as whole or a part of a heat-releasing device.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2019

Atomically engineering activation sites onto metallic 1T-MoS 2 catalysts for enhanced electrochemical hydrogen evolution

Engineering catalytic sites at the atomic level provides an opportunity to understand the catalyst’s active sites, which is vital to the development of improved catalysts. Here we show a reliable and tunable polyoxometalate template-based synthetic strategy to atomically engineer metal doping sites onto metallic 1T-MoS 2 , using Anderson-type polyoxometalates as precursors. Benefiting from engineering nickel and oxygen atoms, the optimized electrocatalyst shows great enhancement in the hydrogen evolution reaction with a positive onset potential of ~ 0 V and a low overpotential of –46 mV in alkaline electrolyte, comparable to platinum-based catalysts. First-principles calculations reveal co-doping nickel and oxygen into 1T-MoS 2 assists the process of water dissociation and hydrogen generation from their intermediate states. This research will expand on the ability to improve the activities of various catalysts by precisely engineering atomic activation sites to achieve significant electronic modulations and improve atomic utilization efficiencies.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2018

Thin-Film Module Reverse-Bias Breakdown Sites Identified by Thermal Imaging

Thin-film module sections are stressed under reverse bias to simulate partial shading conditions. Such stresses can cause permanent damage in the form of "wormlike" defects due to thermal runaway. When large reverse biases with limited current are applied to the cells, dark lock-in thermography (DLIT) can detect where spatially-localized breakdown initiates before thermal runaway leads to permanent damage. Predicted breakdown defect sites have been identified in both CIGS and CdTe modules using DLIT. These defects include small pinholes, craters, or voids in the absorber layer of the film that lead to builtin areas of weakness where high current densities may cause thermal damage in a partial-shading event.

14 SOLAR ENERGY↗

DOE OSTI2012

DEVELOPMENT OF A SOFTWARE DESIGN TOOL FOR HYBRID SOLAR-GEOTHERMAL HEAT PUMP SYSTEMS IN HEATING- AND COOLING-DOMINATED BUILDINGS

This project provides an easy-to-use, menu-driven, software tool for designing hybrid solar-geothermal heat pump systems (GHP) for both heating- and cooling-dominated buildings. No such design tool currently exists. In heating-dominated buildings, the design approach takes advantage of glazed solar collectors to effectively balance the annual thermal loads on the ground with renewable solar energy. In cooling-dominated climates, the design approach takes advantage of relatively low-cost, unglazed solar collectors as the heat rejecting component. The primary benefit of hybrid GHPs is the reduced initial cost of the ground heat exchanger (GHX). Furthermore, solar thermal collectors can be used to balance the ground loads over the annual cycle, thus making the GHX fully sustainable; in heating-dominated buildings, the hybrid energy source (i.e., solar) is renewable, in contrast to a typical fossil fuel boiler or electric resistance as the hybrid component; in cooling-dominated buildings, use of unglazed solar collectors as a heat rejecter allows for passive heat rejection, in contrast to a cooling tower that consumes a significant amount of energy to operate, and hybrid GHPs can expand the market by allowing reduced GHX footprint in both heating- and cooling-dominated climates. The design tool allows for the straight-forward design of innovative GHP systems that currently pose a significant design challenge. The project lays the foundations for proper and reliable design of hybrid GHP systems, overcoming a series of difficult and cumbersome steps without the use of a system simulation approach, and without an automated optimization scheme. As new technologies and design concepts emerge, sophisticated design tools and methodologies must accompany them and be made usable for practitioners. Lack of reliable design tools results in reluctance of practitioners to implement more complex systems. A menu-driven software tool for the design of hybrid solar GHP systems is provided that is based on mathematically robust, validated models. An automated optimization tool is used to balance ground loads and incorporated into the simulation engine. With knowledge of the building loads, thermal properties of the ground, the borehole heat exchanger configuration, the heat pump peak hourly and seasonal COP for heating and cooling, the critical heat pump design entering fluid temperature, and the thermal performance of a solar collector, the total GHX length can be calculated along with the area of a supplemental solar collector array and the corresponding reduced GHX length. An economic analysis module allows for the calculation of the lowest capital cost combination of solar collector area and GHX length. ACKNOWLEDGMENTS This project was funded by the United States Department of Energy DOE-DE-FOA-0000116, Recovery Act Geothermal Technologies Program: Ground Source Heat Pumps. The lead contractor, The University of Hartford, was supported by The University of Dayton, and the Oak Ridge National Laboratories. All funding and support for this project as well as contributions of graduate and undergraduate students from the contributing institutions are gratefully acknowledged.

14 SOLAR ENERGY↗

NASA NTRS1979

Lean, premixed, prevaporized fuel combustor conceptual design study

Four combustor concepts, designed for the energy efficient engine, utilize variable geometry or other flow modulation techniques to control the equivalence ratio of the initial burning zone. Lean conditions are maintained at high power to control oxides of nitrogen while near stoichometric conditions are maintained at low power for low CO and THC emissions. Each concept was analyzed and ranked for its potential in meeting the goals of the program. Although the primary goal of the program is a low level of nitric oxide emissions at stratospheric cruise conditions, both the ground level EPA emission standards and combustor performance and operational requirements typical of advanced subsonic aircraft engines are retained as goals as well. Based on the analytical projections made, two of the concepts offer the potential of achieving the emission goals; however, the projected operational characteristics and reliability of any concept to perform satisfactorily over an entire aircraft flight envelope would require extensive experimental substantiation before engine adaptation can be considered.

Fiorentino, A. J.↗

NASA NTRS2007

Optical Phased Array Antennas using Coupled Vertical Cavity Surface Emitting Lasers

High data rate communication links are needed to meet the needs of NASA as well as other organizations to develop space-based optical communication systems. These systems must be robust to high radiation environments, reliable, and operate over a wide temperature range. Highly desirable features include beam steering capability, reconfigurability, low power consumption, and small aperture size. Optical communication links, using coupled vertical cavity surface emitting laser radiating elements are promising candidates for the transmit portion of these communication links. In this talk we describe a mission scenario, and how the antenna requirements are derived from the mission needs. We describe a potential architecture for this type of antenna, and outline the advantages and drawbacks of this approach relative to competing technologies. The technology we are proposing used coupled arrays of 1550 nm vertical cavity surface emitting lasers for transmission. The feasibility of coupling these arrays together, to form coherent high-power beams that can be modulated at data rates exceeding 1 Gbps, will be explored. We will propose an architecture that enables electronic beam steering, thus mitigating the need for ancillary acquisition, tracking and beam pointing equipment such as needed for current optical communicatin systems. The beam-steering capability we are proposing also opens the possibility of using this technology for inter-satellite communicatin links, and satellite-to-surface links.

Mueller, Carl H.↗

NASA NTRSDate not supplied

Radiation and Nuclear Technology in Planetary Cave Environments

Many technological and environmental challenges must be resolved to enable successful lunar habitation and exploration, and to maximize scientific return. This presentation is intended as a preliminary discussion on three such areas of interest with the intent to identify likely areas of mutual benefit for collaboration and data sharing between the space nuclear and radiological disciplines with the planetary cave community. First is the previously identified and studied possible application of lunar lava tubes or pits to reduce the solar and cosmic radiation environment burden on crew health and hardware reliability. This is an area of continued interest, and should be kept in the forefront of discussion during the selection of sites for potential exploration or long-term habitation. In theory, the prospect of using existing morphology presents an enticing opportunity to reduce the requirements on landed mass or construction while also reducing dose or fluence of harmful natural radiation. However, such discussions should also include the practical implications of relocating habitation hardware and personnel from a landing site to a subsurface location. Inherent risks associated with landing in proximity to the relevant terrain must also be considered and weighed against those imposed by the natural radiation environment. Second is a discussion on the means by which a long-term habitation module or base of operations may be powered throughout the lunar day-night cycle. Fission surface power presents an opportunity to establish round-the-clock power in any lunar surface environment, including permanently shadowed regions where solar panels cannot operate, or in any other non-polar region where solar radiation is available for no more than two weeks per four-week cycle. Among the drawbacks of fission surface power is the need to either land and co-locate a heavy shield to minimize radiological consequences to personnel or equipment, land and operate construction equipment capable of restructuring the in-situ regolith to provide appropriate shielding, or to make use of existing topology features (e.g. craters or pits) to serve as pre-formed radiation barriers. A realistic assessment of the practicality of this third option should involve the selection of candidate features from existing surveys, and assess the effectiveness of the approach using modern radiation transport methodologies. Consideration must be made for the needs to reject waste heat in the thermal power conversion process, which typically requires the use of large area radiators. Energy must be exchanged from the reactor and power conversion system to such radiators, and the impacts on thermal efficiency and secondary scatter of nuclear radiation must be considered. Further consideration should be made for the implications of placement of a power source such that it does not sacrifice valuable scientific opportunity. Placement of a reactor is likely to thereafter prevent personnel access within that feature. Third is a discussion on the use of portable radioisotope power systems (RPS) within confined spaces, both with respect to the dose effects of emitted nuclear radiation and also performance associated with emitted thermal radiation. Radioisotope power systems provide a unique capability to power objects with no reliance upon solar radiance. However, their useable power production relies upon the flow of heat from ‘hot side’ (decaying radioisotope) to ‘cold side’ (radiators emitting heat to space). In the case of a confined volume in vacuum such as a lunar lava tube, that radiated energy will absorb into the wall, which is already above the ‘cold background’ temperature of dark space, and then gradually rises in temperature. That temperature rise, and its implications on availability of useable electrical power, will depend upon factors such as enclosure volume, thermal emissivity/absorptivity, and thermal conductivity through the depth of absorbing media. The advantages of nuclear technology may prove to enable unique scientific exploration opportunities, both above the lunar surface and below. In turn, the unique advantages of lunar lava tubes or pits may present unique opportunities to enhance the application of these technologies and to mitigate the effects of radiation from both natural and technological sources. A discussion on these pairings may prove to be valuable to all, in our endeavor to explore our neighboring worlds.

Radiation↗

DOE OSTI2012

Hybrid Solar GHP Simulator

Yavuzturk, Cy↗