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  • Spacecraft Propulsion and Power  (12)
  • PROPELLANTS AND FUELS  (3)
  • tannic acid  (2)
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  • 1
    ISSN: 1573-1561
    Keywords: Dietary tannins ; tannic acid ; digestion ; absorption ; small intestine ; brush border membrane ; unstirred layer ; mucus ; Microtus, Mus.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract The acute effects of tannin (tannic acid; TA) on nutrient absorption were studied by measuring sugar and amino acid uptake across the brash border (luminal membrane) of intact intestine in the presence and absence of TA. Incubation of tissue for 4–9 min in TA solution (1 mg/ml) caused a reduction in passive influx ofl-glucose in voles and mice and a reduction in carrier-mediated influx ofd-glucose and total influx ofl-proline in mice, but not voles. In subchronic experiments, mice and voles were fed for 7–14 days a diet with 4% TA, but there was no significant effect on intestinal brush border uptake ofl-glucose,d-glucose, orl-proline (or three other amino acids tested in voles). In a synthesis of our study with others in the literature, three inferences are made from the patterns of effects across solutes, time scales of exposure, and species. First, the transport inhibitory effects following acute exposure are probably mediated by two processes: increased resistance to passive flux across an effective unstirred layer juxtaposed to the brush border membrane, perhaps due to tannin-mucin binding, and reduced Na+-coupled nutrient uptake across the intestinal brush border. Second, there is a species sensitivity difference in TA's effect on the second process. Third, the negative effects observed at the acute time scale in vitro do not necessarily occur in animals eating TA subchronically because little TA reaches the luminal membrane, or if it does its effects are quickly reversed when the tissue is removed and washed with solution free of TA.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Journal of chemical ecology 19 (1993), S. 1577-1585 
    ISSN: 1573-1561
    Keywords: Tannins ; tannic acid ; polyphenolics ; plant defense ; microtines ; Microtus ochrogaster ; reproduction ; resting metabolic rate ; digestibility reduction ; energetics ; growth rates
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract The hypothesis was tested that the reproductive performance of voles would be reduced when fed diets containing tannins either because of increased metabolic rates, decreased intake, or decreased digestive efficiency. We fed a ration containing 4% tannic acid (TA) (dry mass basis) to 24 pair of prairie voles (Microtus ochrogaster) and compared reproductive performance (litter size, birth weights, body mass of the young until weaning, and mass changes in the dams) to that of 24 pair of prairie vole fed a control ration. We also compared the intake rates, digestive efficiency, and metabolic rates [as measured by Vo2 consumption (cm3/hr)] of dams and young fed both rations. Voles consuming 4% TA diets produced litters of similar size and mass as did voles fed the control ration. Furthermore, the mass of the young of dams fed the tannic acid ration were similar to the young of dams consuming the control ration through day 19 postpartum. However, dams consuming the tannic acid ration lost mass throughout lactation while the control dams maintained mass. Because the Vo2 rates of both treated and control dams and litters were similar, we conclude increased metabolic costs were not the reason for the observed mass loss but, rather, reduced digestive efficiency, reduced intake of digestible dry mass, and apparent digestible nitrogen.
    Type of Medium: Electronic Resource
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  • 3
    Publication Date: 2019-06-28
    Description: The use of propellants manufactured from indigenous space materials has the potential to significantly reduce the amount of mass required to be launched from the Earth's surface. The extent of the leverage, however, along with the cost for developing the infrastructure necessary to support such a process, is unclear. Many mission analyses have been performed that have attempted to quantify the potential benefits of in situ propellant utilization. Because the planning of future space missions includes many unknowns, the presentation of any single study on the use of in situ propellants is often met with critics' claims of the inaccuracy of assumptions or omission of infrastructure requirements. The results of many such mission analyses are presented in one format. Each summarized mission analysis used different assumptions and baseline mission scenarios. The conclusion from the studies is that the use of in situ produced propellants will provide significant reductions in Earth launch requirements. This result is consistent among all of the analyses regardless of the assumptions used to obtain the quantitative results. The determination of the best propellant combination and the amount of savings will become clearer and more apparent as the technology work progresses.
    Keywords: PROPELLANTS AND FUELS
    Type: NASA-TM-105262 , E-6790 , NAS 1.15:105262
    Format: application/pdf
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  • 4
    Publication Date: 2019-06-28
    Description: NASA's LeRC has supported several efforts to understand how lunar and Martian produced propellants can be used to their best advantage for space exploration propulsion. A discussion of these efforts and their results is presented. A Manned Mars Mission Analysis Study identified that a more thorough technology base for propellant production is required before the net economic benefits of in situ propellants can be determined. Evaluation of the materials available on the moon indicated metal/oxygen combinations are the most promising lunar propellants. A hazard analysis determined that several lunar metal/LOX monopropellants could be safely worked with in small quantities, and a characterization study was initiated to determine the physical and chemical properties of potential lunar monopropellant formulations. A bipropellant metal/oxygen subscale test engine which utilizes pneumatic injection of powdered metal is being pursued as an alternative to the monopropellant systems. The technology for utilizing carbon monoxide/oxygen, a potential Martian propellant, was studied in subscale ignition and rocket performance experiments.
    Keywords: PROPELLANTS AND FUELS
    Type: IAF PAPER 91-669
    Format: text
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  • 5
    Publication Date: 2019-07-27
    Description: The activities and status of NASA Spacecraft Propulsion is presented including recent accomplishments.
    Keywords: Spacecraft Propulsion and Power
    Type: GRC-E-DAA-TN11245 , IHPRPT Steering Committee Meeting; 18 Sept. 2013; Edwards Air Force Base, California; United States
    Format: application/pdf
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  • 6
    Publication Date: 2019-07-13
    Description: Electrically heated tube tests were conducted to characterize the critical heat flux (transition from nucleate to film boiling) of subcritical ethanol flowing at conditions relevant to the design of a regeneratively cooled rocket engine thrust chamber. The coolant was SDA-3C alcohol (95% ethyl alcohol, 5% isopropyl alcohol by weight), and tests were conducted over the following ranges of conditions: pressure from 144 to 703 psia, flow velocities from 9.7 to 77 ft/s, coolant subcooling from 33 to 362 F, and critical heat fluxes up to 8.7 BTU/in(exp 2)/sec. For the data taken near 200 psia, critical heat flux was correlated as a function of the product of velocity and fluid subcooling to within +/- 20%. For data taken at higher pressures, an additional pressure term is needed to correlate the critical heat flux. It was also shown that at the higher test pressures and/or flow rates, exceeding the critical heat flux did not result in wall burnout. This result may significantly increase the engine heat flux design envelope for higher pressure conditions.
    Keywords: Spacecraft Propulsion and Power
    Type: NASA/TM-1998-206612 , E-11032 , NAS 1.15:206612 , AIAA Paper 98-1055 , Aerospace Sciences Meeting and Exhibit; Jan 12, 1998 - Jan 15, 1998; Reno, NV; United States
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  • 7
    Publication Date: 2019-07-13
    Description: The exponential increase of launch system size.and cost.with delta-V makes missions that require large total impulse cost prohibitive. Led by NASA fs Marshall Space Flight Center, a team from government, industry, and academia has developed a flight demonstration mission concept of an integrated electrodynamic (ED) tethered satellite system called PROPEL: \Propulsion using Electrodynamics.. The PROPEL Mission is focused on demonstrating a versatile configuration of an ED tether to overcome the limitations of the rocket equation, enable new classes of missions currently unaffordable or infeasible, and significantly advance the Technology Readiness Level (TRL) to an operational level. We are also focused on establishing a far deeper understanding of critical processes and technologies to be able to scale and improve tether systems in the future. Here, we provide an overview of the proposed PROPEL mission. One of the critical processes for efficient ED tether operation is the ability to inject current to and collect current from the ionosphere. Because the PROPEL mission is planned to have both boost and deboost capability using a single tether, the tether current must be capable of flowing in both directions and at levels well over 1 A. Given the greater mobility of electrons over that of ions, this generally requires that both ends of the ED tether system can both collect and emit electrons. For example, hollow cathode plasma contactors (HCPCs) generally are viewed as state-of-the-art and high TRL devices; however, for ED tether applications important questions remain of how efficiently they can operate as both electron collectors and emitters. Other technologies will be highlighted that are being investigated as possible alternatives to the HCPC such as Solex that generates a plasma cloud from a solid material (Teflon) and electron emission (only) technologies such as cold-cathode electron field emission or photo-electron beam generation (PEBG) techniques
    Keywords: Spacecraft Propulsion and Power
    Type: M12-1836 , M12-1798 , Global Space Exploration Conference; May 22, 2012 - May 24, 2012; Washinton, DC; United States
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  • 8
    Publication Date: 2019-07-13
    Description: NASA has created a roadmap for the development of advanced in-space propulsion technologies for the NASA Office of the Chief Technologist (OCT). This roadmap was drafted by a team of subject matter experts from within the Agency and then independently evaluated, integrated and prioritized by a National Research Council (NRC) panel. The roadmap describes a portfolio of in-space propulsion technologies that could meet future space science and exploration needs, and shows their traceability to potential future missions. Mission applications range from small satellites and robotic deep space exploration to space stations and human missions to Mars. Development of technologies within the area of in-space propulsion will result in technical solutions with improvements in thrust, specific impulse (Isp), power, specific mass (or specific power), volume, system mass, system complexity, operational complexity, commonality with other spacecraft systems, manufacturability, durability, and of course, cost. These types of improvements will yield decreased transit times, increased payload mass, safer spacecraft, and decreased costs. In some instances, development of technologies within this area will result in mission-enabling breakthroughs that will revolutionize space exploration. There is no single propulsion technology that will benefit all missions or mission types. The requirements for in-space propulsion vary widely according to their intended application. This paper provides an updated summary of the In-Space Propulsion Systems technology area roadmap incorporating the recommendations of the NRC.
    Keywords: Spacecraft Propulsion and Power
    Type: NASA/TM-2012-217641 , E-18195 , E-18195-1 , Space Propulsion 2012; May 07, 2012 - May 10, 2012; Bordeaux; France
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  • 9
    Publication Date: 2019-07-12
    Description: No abstract available
    Keywords: Spacecraft Propulsion and Power
    Type: E-664451
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  • 10
    Publication Date: 2019-07-13
    Description: This roadmap describes a portfolio of in-space propulsion technologies that can meet future space science and exploration needs.
    Keywords: Spacecraft Propulsion and Power
    Type: M11-0738 , 7th Symposium on Realistic Near-Term Advanced Scientific Space Missions; Jul 11, 2011 - Jul 14, 2011; Aosta; Italy
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