SEARCH · Engineering Papers

Results for “consumer”

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.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 379 records · Page 21

All sources NASA NTRS DOE OSTI

NASA NTRSDate not supplied

Integrated Trajectory, Habitat, and Logistics Analysis and Trade Study for Human Mars Missions

Environmental Control and Life Support System (ECLSS) architecture selection has profound implications for mission cost and mass extending far beyond the ECLSS itself. Similarly, other mission architecture decisions – particularly involving transportation systems – can influence optimal ECLSS architectures. Loop closure influences requirements for water, oxygen, and other consumables. System maintainability and reliability influences spares mass and risk. System, consumables, and spares mass interact with transportation system architectures, including propellant demands and propulsion element sizing. All these interactions with other systems must be considered when evaluating ECLSS options. Analyses that focus only on maximizing ECLSS loop closure – or minimizing ECLSS mass, or minimizing ECLSS life cycle cost – may lead to sub-optimal or even counterproductive system architecture and investment decisions at the mission level. For example, an ECLSS architecture that minimizes ECLSS life cycle cost but results in excessively high logistics mass could lead to significantly increased transportation system costs or make interplanetary transportation infeasible. Increased loop closure could result in higher development costs and higher mass if system/spares mass increases outweigh consumables reduction. In addition, systems mass and consumables mass are not directly comparable and have different impacts on propellant requirements, as consumables mass changes over the course of the mission. This paper presents an integrated analysis examining the overall impact of different ECLSS and transportation architectures on Earth departure mass for a crewed Mars mission, including the habitat and transportation systems as well as consumables, spares, and propellant. Key observations are discussed, along with opportunities for further sensitivity analysis and model development. Overall, ECLSS development activities must consider their impacts at the mission level, as part of an integrated system, rather than in isolation.

Mars↗

DOE OSTI2018

Environmental impact assessment of online advertising

Highlights: • A practical framework for assessing the environmental impact of any Internet service • Online advertising consumed between 20.38 to 282.75 TWh of energy and 11.53 – 159.93 million tons of CO{sub 2}e was emitted to produce the electricity consumed. • Invalid traffic associated with online advertising resulted in 2.65 – 36.78 million tons of CO{sub 2}e emissions. • The energy burden of online advertising is considerable and urgently requires attention from researchers and industries. - Abstract: There are no commonly agreed ways to assess the total energy consumption of the Internet. Estimating the Internet's energy footprint is challenging because of the interconnectedness associated with even seemingly simple aspects of energy consumption. The first contribution of this paper is a common modular and layered framework, which allows researchers to assess both energy consumption and CO{sub 2}e emissions of any Internet service. The framework allows assessing the energy consumption depending on the research scope and specific system boundaries. Further, the proposed framework allows researchers without domain expertise to make such an assessment by using intermediate results as data sources, while analyzing the related uncertainties. The second contribution is an estimate of the energy consumption and CO{sub 2}e emissions of online advertising by utilizing our proposed framework. The third contribution is an assessment of the energy consumption of invalid traffic associated with online advertising. The second and third contributions are used to validate the first. The online advertising ecosystem resides in the core of the Internet, and it is the sole source of funding for many online services. Therefore, it is an essential factor in the analysis of the Internet's energy footprint. As a result, in 2016, online advertising consumed 20–282 TWh of energy. In the same year, the total infrastructure consumption ranged from 791 to 1334 TWh. With extrapolated 2016 input factor values without uncertainties, online advertising consumed 106 TWh of energy and the infrastructure 1059 TWh. With the emission factor of 0.5656 kg CO{sub 2}e/kWh, we calculated the carbon emissions of online advertising, and found it produces 60 Mt CO{sub 2}e (between 12 and 159 Mt of CO{sub 2}e when considering uncertainty). The share of fraudulent online advertising traffic was 13.87 Mt of CO{sub 2}e emissions (between 2.65 and 36.78 Mt of CO{sub 2}e when considering uncertainty). The global impact of online advertising is multidimensional. Online advertising affects the environment by consuming significant amounts of energy, leading to the production CO{sub 2}e emissions. Hundreds of billions of ad dollars are exchanged yearly, placing online advertising in a significant role economically. It has become an important and acknowledged component of the online-bound society, largely due to its integration with the Internet and the amount of revenue generated through it.

54 ENVIRONMENTAL SCIENCES↗

DOE OSTI2022

13 C-metabolic flux analysis of Clostridium ljungdahlii illuminates its core metabolism under mixotrophic culture conditions

Carbon dioxide-fixing acetogenic bacteria (acetogens) utilizing the Wood-Ljungdahl Pathway (WLP) play an important role in CO 2 fixation in the biosphere and in the development of biological processes – alone or in cocultures, under both autotrophic and mixotrophic conditions – for production of chemicals and fuels. To date, limited work has been reported in experimentally validating and quantifying reaction fluxes of their core metabolic pathways. Here, the core metabolic model of the acetogen Clostridium ljungdahlii was interrogated using 13 C-metabolic flux analysis ( 13 C-MFA), which required the development of a new defined culture medium. Autotrophic, heterotrophic, and mixotrophic growth in defined medium was possible by adding 1 mM methionine to replace yeast extract. Our 13 C-MFA found an incomplete TCA cycle and inactive core pathways/reactions, notably those of the oxidative pentose phosphate pathway, Entner-Doudoroff pathway, and malate dehydrogenase. 13 C-MFA during mixotrophic growth using the parallel tracers [1– 13 C]fructose, [1,2– 13 C]fructose, [1,2,3– 13 C]fructose, and [U– 13 C]asparagine found that externally supplied CO 2 contributed the majority of carbon consumed. All internally-produced CO 2 from the catabolism of asparagine and fructose was consumed by the WLP. While glycolysis of fructose was active, it was not a major contributor to overall production of ATP, NADH, and acetyl-CoA. Gluconeogenic reactions were active despite the availability of organic carbon. Asparagine was catabolized equally via conversion to threonine and subsequent cleavage to produce acetaldehyde and glycine, and via deamination to fumarate and then the anaplerotic conversion of malate to pyruvate. Both pathways for asparagine catabolism produced acetyl-CoA, either directly via pyruvate or indirectly via the WLP. Cofactor stoichiometry based on our data predicted an essentially zero flux through the ferredoxin-dependent transhydrogenase (Nfn) reaction. Instead, nearly all of NADPH generated from the hydrogenase reaction was consumed by the WLP. Reduced ferredoxin produced by the hydrogenase reaction and glycolysis was mostly used for ATP generation via the RNF/ATPase system, with the remainder consumed by the WLP. NADH produced by RNF/ATPase was entirely consumed via the WLP.

13C metabolic flux analysis↗

DOE OSTI2019

Demographics, sleep, and daily patterns of caffeine intake of shift workers in a nationally representative sample of the US adult population

Abstract Study Objective Caffeine is the most widely consumed stimulant in the world, and sociodemographic factors including occupation are associated with intake. Shift work, required in various occupations, is associated with poor sleep, inadequate diet, and adverse health effects. Using a large nationally representative database, demographics, sleep, and caffeine intake of US adults working various shifts were assessed. Methods The 24-hour dietary recall data from NHANES 2005–2010 (N = 8,500) were used to estimate caffeine intake from foods and beverages. Work shifts were self-reported as follows: regular day shift; evening shift; night shift; rotating shift; or other shift. Regression analyses assessed associations of shift work with caffeine intake after adjustment for sociodemographic factors. Results Approximately 74% of employed adults were day-shift workers and 26% were nonday-shift workers. Night-shift workers slept for 6.25 ± 0.09 hours per day, somewhat less than day-shift workers who only slept 6.83 ± 0.02 hours (p < .0001). Mean 24-hour weekday caffeine intake of evening-, night-, and rotating-shift workers (217 ± 23, 184 ± 19, and 206 ± 15 mg, respectively) was similar (p > .3) to day-shift workers (203 ± 5 mg). Regardless of work schedule, individuals consumed the most caffeine during morning hours. Evening- and night-shift workers reported consuming 36%–46% less caffeine during their work hours and 72%–169% more during nonwork hours than day-shift workers (p < .01). Conclusions Total daily caffeine intake of shift workers is similar to nonshift workers; most caffeine is consumed in the morning regardless of shift. Because shift workers consume less caffeine during regular work hours and more during nonwork hours than day workers, they may be using caffeine to, in part, optimize off-duty alertness.

Lieberman, Harris R.↗

DOE OSTI2018

Extracellular Acidic pH Inhibits Acetate Consumption by Decreasing Gene Transcription of the Tricarboxylic Acid Cycle and the Glyoxylate Shunt

Escherichia coli produces acetate during aerobic growth on various carbon sources. After consuming the carbon substrate, E. coli can further grow on the acetate. This phenomenon is known as the acetate switch, where cells transition from producing acetate to consuming it. In this study, we investigated how pH governs the acetate switch. When E. coli was grown on a glucose-supplemented medium initially buffered to pH 7, the cells produced and then consumed the acetate. However, when the initial pH was dropped to 6, the cells still produced acetate but were only able to consume it when little (<10 mM) acetate was produced. When significant acetate was produced in acidic medium, which occurs when the growth medium contains magnesium, amino acids, and sugar, the cells were unable to consume the acetate. To determine the mechanism, we characterized a set of metabolic mutants and found that those defective in the tricarboxylic acid (TCA) cycle or glyoxylate shunt exhibited reduced rates of acetate consumption. We further found that the expression of the genes in these pathways was reduced during growth in acidic medium. The expression of the genes involved in the AckA-Pta pathway, which provides the principal route for both acetate production and consumption, was also inhibited in acidic medium but only after glucose was depleted, which correlates with the acetate consumption phase. On the basis of these results, we conclude that growth in acidic environments inhibits the expression of the acetate catabolism genes, which in turn prevents acetate consumption.

59 BASIC BIOLOGICAL SCIENCES↗

DOE OSTI2016

Market-Based and System-Wide Fuel Cycle Optimization

The Dynamic Resource Exchange (DRE) gives agency to consumer facilities to determine the preference of any particular trade that is offered by suppliers to satisfy its requests. This provides a natural balance of power in the relationship between consumers and suppliers. However, in situations in which suppliers have flexibility surrounding the way that they respond to individual requests, they have no mechanism to assess how different bids will be received by the consumer. Theoretically, a supplier can offer multiple bids to respond to a given request in an attempt to “cover their bases”, but this introduces more arcs into the underlying network flow problem, increasing the cost to solve the problem. In the extreme, when a supplier can continuously vary the characteristics of the bid, this can represent a large number of additional arcs and have real performance consequences. To remedy this inefficiency in the implementation of the market-level optimization, the definition of a request has been extended to include a function that can be used by the supplier to query the preference that would be assigned by a consumer for a potential bid. The supplier is then free to implement arbitrarily complex algorithms to revise/optimize its bid based on responses to this function. A supplier can chose to not invoke the function at all, mimicking the original DRE behavior, can use it to select among a small set of discrete choices, or can implement an internal algorithm to seek an optimum bid on a continuous parameter space. This capability was demonstrated with a storage facility that preferred material with a specific decay heat that was as close as possible to the maximum allowable decay heat, while requiring the specific decay heat to fall between a minimum and maximum level. This archetype was used to fill multiple storage roles in a simulation that also included a standard recipe reactor: wet storage with no maximum allowable specific decay heat, dry storage with a modest maximum allowable specific decay heat, and a geologic repository with a low maximum allowable specific decay heat. In such a simulation, the reactor, wet storage and dry storage always offer their material to be taken by one of the other storage facilities. The preference function of the consumer would always ensure that material only flowed when the decay heat was sufficiently low, but in the absence of objective function callbacks, would allow for many superfluous offers that exceeded those limits. If this archetype also uses a callback function to probe the preference of the receiving facility for each possible offer, it can avoid making offers that are not going to be accepted by the receiving facility.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗

DOE OSTI2017

Analysis of hydrogen as a Transportation Fuel FY17 Report

This report summarizes the results of literature reviews, surveys and analyses performed to evaluate the potential of hydrogen-fueled vehicles to be an economically viable transportation alternative. Five existing and important drivers of expanding hydrogen-fueled transportation adoption are multi-billion dollar sales reservations of Nikola Class 8 trucks, CALSTART viability analysis of hybrid-hydrogen drayage trucks in the shipyard cargo application, analysis showing economic advantages of Fuel Cell Electric Vehicles (FCEV)s over Battery Electric Vehicles (BEV)s beginning at 150-mile ranges, the announcement of a commercial 5kg electrolyzer, and commercial plans or vehicle availability by nine vehicle manufacturers of FCEV passenger vehicles. But hydrogen infrastructure availability needed to support broad adoption of hydrogen-fueled vehicles is limited to less than 50 publicly-available refueling stations, primarily in California. The demand side (consumer) economics associated with FCEV adoption showed strong economic sensitivity to the original vehicle’s fuel economy (mpg), distance traveled, and hydrogen (H2) generation costs. Seven use cases were used to evaluate the broad range of potential FCEV purchasers, including autonomous vehicle applications. Each consumer use case analysis resulted in a different hydrogen fuel cost that would be equivalent to the current fuel cost being paid by the consumer. The H2 generation costs (supply side) were sensitive to the volume of H2 supplied and H2 production costs needed to repay H2 supply facility capital costs and produce competitively-priced energy. H2FAST was used to more accurately incorporate capital, maintenance and production costs into a viable H2 supply cost to the consumer. When the H2 generation and consumer economics were combined, several applications with positive economics became clear. The availability of low-cost hydrogen pipeline connections, and therefore low-cost hydrogen, greatly benefits the California drayage truck application with hybrid-hydrogen retrofits being repaid within seven years. Class 8 trucks could also take advantage of these low-cost, but regional hydrogen supplies. In addition, the IVYS electrolyzer-based hydrogen generation product showed the potential to deliver hydrogen economically in an urban or freeway off-ramp setting to a limited number of passenger vehicles in areas with low-cost electricity. These positive, manually developed results show the need to develop more advanced tools to provide an expanded evaluation of the economics of hydrogen-based fuel applications. The use cases evaluated showed significant potential for hydrogen-fueled vehicles to have a sustainable impact as a transportation fuel. The positive impact is not limited to transportation fuels, but also grid resilience and flexibility through the use of controllable and variable electrolyzer output to rapidly adjust to changing grid conditions and enable greater integration of solar and wind generated power. This capability would directly enable alternative fuel vehicles to impact energy consumption, GHG emissions, and the economy at the regional and national levels.

08 HYDROGEN↗

DOE OSTI2024

Leveraging Observations of Untrained Panelists to Screen for Quality of Fresh-Cut Romaine Lettuce

Fresh-cut romaine lettuce’s high perishability challenges ready-to-eat (RTE) salad production. Selecting cultivars less prone to browning and decay is crucial for extending shelf life. Traditional quality evaluation methods using instrumentation and trained panelists are time-consuming and logistically complex. This study investigated the effectiveness of untrained volunteers in assessing fresh-cut romaine lettuce quality. Given that the average consumer in the USA is familiar with the flavor characteristics of romaine lettuce, this study proposed to investigate the value of having untrained volunteers discern the quality of fresh-cut romaine lettuce. Therefore, six romaine lettuce accessions (Green Forest, King Henry, Parris Island Cos, PI 491224, SM13-R2, and Sun Valley) were assessed for sensory quality attributes (browning, green color, decay, and overall quality) and compared with instrumentation analyses (gas composition including O2 and CO2, electrolyte leakage, and color). The results showed significant quality differences (p < 0.05) among the accessions, with some seasonal variability. Very importantly, the consumers’ (n = 159) assessments revealed similar results to those produced by either instrumentation or a trained panel. The consumers provided sensory scores that allowed for the grouping of accessions based on their postharvest quality, which efficiently matched their pedigree relationship. In conclusion, ad hoc consumer panels can be an effective way to characterize the quality of romaine lettuce for RTE salads.

Agriculture↗

DOE OSTI2018

Hunting and Game Consumption Patterns of Hunters in South Carolina

Not provided.

Biodiversity & Conservation↗

NASA NTRS1992

The reuse of logistics carriers for the first lunar outpost alternative habitat study

The Systems Definition Branch deals with preliminary concepts/designs of various projects currently in progress at NASA. One of these projects is called the First Lunar Outpost. The First Lunar Outpost (FLO) is a proposed permanent lunar base to be located on the moon. In order to better understand the Lunar Habitat, a detailed analysis of the lunar environment as well as conceptual studies of the physical living arrangements for the support crew is necessary. The habitat will be inhabited for a period of 45 days followed by a six month dormant period. Requirements for the habitat include radiation protection, a safe haven for occasional solar flare storms, an airlock module and consumables to support a crew of 4 with a schedule of 34 extra vehicular activities. Consumables in order to sustain a crew of four for 45 days ranges from 430 kg of food to only 15 kg for personal hygiene items. These consumables must be brought to the moon with every mission. They are transported on logistics carriers. The logistics carrier must be pressurized in order to successfully transport the consumables. Refrigeration along with other types of thermal control and variation in pressure are defined by the list of necessary consumables. The objective of the proposed work was to collaborate the Habitat Team with their study on Logistic Carriers as possible alternatives for additional habitable volume. Options for possible reuses was also determined. From this analysis, a recommended design is proposed.

Vargas, Carolina↗

NASA NTRS1992

A fuzzy set preference model for market share analysis

Consumer preference models are widely used in new product design, marketing management, pricing, and market segmentation. The success of new products depends on accurate market share prediction and design decisions based on consumer preferences. The vague linguistic nature of consumer preferences and product attributes, combined with the substantial differences between individuals, creates a formidable challenge to marketing models. The most widely used methodology is conjoint analysis. Conjoint models, as currently implemented, represent linguistic preferences as ratio or interval-scaled numbers, use only numeric product attributes, and require aggregation of individuals for estimation purposes. It is not surprising that these models are costly to implement, are inflexible, and have a predictive validity that is not substantially better than chance. This affects the accuracy of market share estimates. A fuzzy set preference model can easily represent linguistic variables either in consumer preferences or product attributes with minimal measurement requirements (ordinal scales), while still estimating overall preferences suitable for market share prediction. This approach results in flexible individual-level conjoint models which can provide more accurate market share estimates from a smaller number of more meaningful consumer ratings. Fuzzy sets can be incorporated within existing preference model structures, such as a linear combination, using the techniques developed for conjoint analysis and market share estimation. The purpose of this article is to develop and fully test a fuzzy set preference model which can represent linguistic variables in individual-level models implemented in parallel with existing conjoint models. The potential improvements in market share prediction and predictive validity can substantially improve management decisions about what to make (product design), for whom to make it (market segmentation), and how much to make (market share prediction).

Turksen, I. B.↗

NASA NTRS1993

Power optimization in logic isomers

Logic isomers are labeled, 2-isomorphic graphs that implement the same logic function. Logic isomers may have significantly different power requirements even though they have the same number of transistors in the implementation. The power requirements of the isomers depend on the transition activity of the input signals. The power requirements of isomorphic graph isomers of n-input NAND and NOR gates are shown. Choosing the less power-consuming isomer instead of the others can yield significant power savings. Experimental results on a ripple-carry adder are presented to show that the implementation using the least power-consuming isomers requires approximately 10 percent less power than the implementation using the most power-consuming isomers. Simulations of other random logic designs also confirm that designs using less power-consuming isomers can reduce the logic power demand by approximately 10 percent as compared to designs using more power-consuming isomers.

Panwar, Ramesh↗

NASA NTRS1995

Japan's electronic packaging technologies

The JTEC panel found Japan to have significant leadership over the United States in the strategic area of electronic packaging. Many technologies and products once considered the 'heart and soul' of U.S. industry have been lost over the past decades to Japan and other Asian countries. The loss of consumer electronics technologies and products is the most notable of these losses, because electronics is the United States' largest employment sector and is critical for growth businesses in consumer products, computers, automobiles, aerospace, and telecommunications. In the past there was a distinction between consumer and industrial product technologies. While Japan concentrated on the consumer market, the United States dominated the industrial sector. No such distinction is anticipated in the future; the consumer-oriented technologies Japan has dominated are expected to characterize both domains. The future of U.S. competitiveness will, therefore, depend on the ability of the United States to rebuild its technological capabilities in the area of portable electronic packaging.

Tummala, Rao R.↗

NASA NTRS2010

Effective Presentation of Metabolic Rate Information for Lunar Extravehicular Activity (EVA)

During human exploration of the lunar surface, a suited crewmember needs effective and accurate information about consumable levels remaining in their life support system. The information must be presented in a manner that supports real-time consumable monitoring and route planning. Since consumable usage is closely tied to metabolic rate, the lunar suit must estimate metabolic rate from life support sensors, such as oxygen tank pressures, carbon dioxide partial pressure, and cooling water inlet and outlet temperatures. To provide adequate warnings that account for traverse time for a crewmember to return to a safe haven, accurate forecasts of consumable depletion rates are required. The forecasts must be presented to the crewmember in a straightforward, effective manner. In order to evaluate methods for displaying consumable forecasts, a desktop-based simulation of a lunar Extravehicular Activity (EVA) has been developed for the Constellation lunar suite s life-support system. The program was used to compare the effectiveness of several different data presentation methods.

Mackin, Michael A.↗

NASA NTRS2011

Cassini Attitude Control Operations - Guidelines Levied on Science to Extend Reaction Wheel Life

The Cassini spacecraft was launched on October 15, 1997 and arrived at Saturn on June 30, 2004. It has performed detailed observations and remote sensing of Saturn, its rings, and its satellites since that time. Cassini deployed the European-built Huygens probe, which descended through the Titan atmosphere (Saturn's largest moon) and landed on its surface on January 14, 2005. The Cassini mission has recently been approved by NASA to continue through September of 2017. This 7-year extension is called the Solstice mission and it presents challenges to the spacecraft operations team and its ability to maintain the health of the spacecraft. To keep the spacecraft healthy for 7 more years, the spacecraft team must carefully manage hydrazine use (about 48% of the 132 kg launch load remains as of January 2011). A vital part of conserving hydrazine is to use the reaction wheel assembly (RWA) control system for precise pointing and slews wherever possible. In any given week, the Cassini spacecraft is commanded to use RWA control about 99% of the time, with about 1% of the time requiring reaction control system (RCS) thruster control (to perform Delta V course corrections or to bias the RWA momentum). Such extensive use of the RWA hardware throughout the mission requires that the RWAs be operated in a way that minimizes degradation in the RWA electronics, DC motor, and spin bearing for each reaction wheel. Three consumables in particular have been identified for the RWAs: (1) Total number of revolutions for each RWA. (2) Time spent at very low wheel speeds. At these low speeds, good elasto-hydrodynamic (EHD) film lubrication may be compromised. (3) Total number of on/off power cycles. The second of these consumables, minimizing the time spent at very low wheel speeds, is especially important to keep the spin bearing healthy and well-lubricated. These consumables are actively managed by the attitude control operations team throughout the mission. One vital management technique is to predict individual RWA momentum (given the pointing and slews that are needed to collect the best science) and to bias the RWA momentum in a way that reduces both the total number of revolutions as well as the time spent below EHD wheel speed. Another strategy to protect RWA health is to alter the planned pointing of the spacecraft (which can affect science collection) so that the RWA consumables are conserved. This paper focuses on why this second technique is needed, and discusses how guidelines have been developed by the attitude control team which affects the planned science pointing, so that science data can be most optimally collected while still minimizing RWA consumable usage.

interplanetary trajectory↗

NASA NTRS2017

Engineering of Methane Metabolism in Pichia Pastoris Through Methane Monooxygenase Expression

Exploration of the solar system is constrained by the cost of moving mass off Earth. Producing materials in situ will reduce the mass that must be delivered from earth. CO2 is abundant on Mars and manned spacecraft. On the ISS, NASA reacts excess CO2 with H2 to generate CH4 and H2O using the Sabatier System. The resulting water is recovered into the ISS, but the methane is vented to space. Thus, there is a capability need for systems that convert methane into valuable materials. Methanotrophic bacteria consume methane but these are poor synthetic biology platforms. Thus, there is a knowledge gap in utilizing methane in a robust and flexible synthetic biology platform. The yeast Pichia pastoris is a refined microbial factory that is used widely by industry because it efficiently secretes products. Pichia could produce a variety of useful products in space. Pichia does not consume methane but robustly consumes methanol, which is one enzymatic step removed from methane. Our goal is to engineer Pichia to consume methane thereby creating a powerful methane-consuming microbial factory.

Pichia↗

NASA NTRS2017

New Frontiers in Synthetic Biology for Spaceflight

Galazka, Jonathan M.↗

NASA NTRS2017

Methane Metabolism by Yeast for Solar System Exploration

Galazka, Jonathan M.↗