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  • Spacecraft Design, Testing and Performance  (72)
  • General Chemistry
  • 2010-2014  (40)
  • 2000-2004  (49)
  • 1975-1979  (44)
  • 1925-1929  (2)
  • 1
    Publication Date: 2019-07-12
    Description: The primary purpose of this study was to define a point-of-departure prephase A mission concept for the cryogenic propellant storage and transfer technology demonstration mission to be conducted by the NASA Office of the Chief Technologist (OCT). The mission concept includes identification of the cryogenic propellant management technologies to be demonstrated, definition of a representative mission timeline, and definition of a viable flight system design concept. The resulting mission concept will serve as a point of departure for evaluating alternative mission concepts and synthesizing the results of industry- defined mission concepts developed under the OCT contracted studies
    Keywords: Spacecraft Design, Testing and Performance
    Type: NASA/TM-2012-217467 , M-1343
    Format: application/pdf
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  • 2
    Publication Date: 2019-07-19
    Description: The Fusible Heat Sink is a novel vehicle heat rejection technology which combines a flow through radiator with a phase change material. The combined technologies create a multi-function device able to shield crew members against Solar Particle Events (SPE), reduce radiator extent by permitting sizing to the average vehicle heat load rather than to the peak vehicle heat load, and to substantially absorb heat load excursions from the average while constantly maintaining thermal control system setpoints. This multi-function technology provides great flexibility for mission planning, making it possible to operate a vehicle in hot or cold environments and under high or low heat load conditions for extended periods of time. This paper describes the model development and experimental validation of the Fusible Heat Sink technology. The model developed was intended to meet the radiation and heat rejection requirements of a nominal MMSEV mission. Development parameters and results, including sizing and model performance will be discussed. From this flight-sized model, a scaled test-article design was modeled, designed, and fabricated for experimental validation of the technology at Johnson Space Center thermal vacuum chamber facilities. Testing showed performance comparable to the model at nominal loads and the capability to maintain heat loads substantially greater than nominal for extended periods of time.
    Keywords: Spacecraft Design, Testing and Performance
    Type: JSC-CN-27335 , 43rd International Conference on Environmental Systems; Jul 14, 2013 - Jul 18, 2013; Vail, CO; United States
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  • 3
    Publication Date: 2019-08-13
    Description: For many years, the capabilities to determine the root-cause failure of component failures have been limited to the analytical tools and the state of the art data acquisition systems. With this limited capability, many anomalies have been resolved by adding material to the design to increase robustness without the ability to determine if the design solution was satisfactory until after a series of expensive test programs were complete. The risk of failure and multiple design, test, and redesign cycles were high. During the Space Shuttle Program, many crack investigations in high energy density turbomachines, like the SSME turbopumps and high energy flows in the main propulsion system, have led to the discovery of numerous root-cause failures and anomalies due to the coexistences of acoustic forcing functions, structural natural modes, and a high energy excitation, such as an edge tone or shedding flow, leading the technical community to understand many of the primary contributors to extremely high frequency high cycle fatique fluid-structure interaction anomalies. These contributors have been identified using advanced analysis tools and verified using component and system tests during component ground tests, systems tests, and flight. The structural dynamics and fluid dynamics communities have developed a special sensitivity to the fluid-structure interaction problems and have been able to adjust and solve these problems in a time effective manner to meet budget and schedule deadlines of operational vehicle programs, such as the Space Shuttle Program over the years.
    Keywords: Spacecraft Design, Testing and Performance
    Type: M10-0285 , 57th JANNAF Joint Propulsion Meeting; May 03, 2010 - May 07, 2010; Colorado Springs, CO; United States
    Format: text
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  • 4
    Publication Date: 2019-07-12
    Description: This briefing package contains the conceptual spacecraft design completed by the Advanced Concepts Office (ED04) in support of the Solar-C Study. The mission is to succeed Hinode (Solar B), and is designed to study the polar regions of the sun. Included in the slide presentation are sections that review the payload data, and overall ground rules and assumptions, mission analysis and trajectory design, the conceptual spacecraft design section includes: (1) Integrated Systems Design, (2) Mass Properties (3) Cost, (4) Solar Sail Systems, (6) Propulsion, (7) Structures, (8) Thermal (9) Power (10) Avionics / GN&C. There are also conclusions and follow-up work that must be done. In the Back-up section there is information about the JAXA H-11A Launch Vehicle, scalability and spiral development, Mass Projections, a comparison of the TRL assessment for two potential vendors of solar sails, and a chart with the mass properties,
    Keywords: Spacecraft Design, Testing and Performance
    Type: M11-0237
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  • 5
    ISSN: 1434-193X
    Keywords: Tetrakis(dimethylamino)naphthalenes ; Basicity ; Hydrogen bonds ; Cyclicvoltammetry ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---For comparison to the recently described 2,3,6,7-tetrakis(dimethylamino)naphthalene (1) the three isomers 2,3, and 4 were synthesized. The basicities of this group of isomers are strongly dependent upon the different mutual orientations of the pairs of dimethylamino substituents: only the isomers 3 and, partially, 4, both with dimethylamino groups in adjacent peri-positions of the naphthalene, are strong “proton sponges”. For the isomers 1 and 2 with the same number and kind of twofold dimethylamino substituents in neighbouring ortho-positions, however, no significant basicity increase is observed. To explain this difference between the two groups of isomers it is suggested that in the ortho-pairs of 1 and 2 the C-N bonds diverge considerably, leading to an increased N···N distance and consequently to less stable [N···H···N]+ hydrogen bonds in contrast to the parallel C-N bonds in the peri-substituted isomers 3 and 4. X-ray crystal structure analyses of the bases and of some of the salts derived therefrom were solved and are discussed. Cyclic voltammetry indicates that 1 to 4 are strong electron donors, reacting easily to radical cations or dications which with suitable acids have been obtained as salts.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1434-193X
    Keywords: Self-assembly ; Vapor-pressure osmometry ; Resorcin[4]arenes ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Resorcin[4]arene tetracarboxylic acids 5,6 (A) and resorcin[4]arene tetrapyridines 2,3 (P) self-assemble in chloroform solution to form stable heterotopic AP dimers. Data from NMR titration and dilution experiments, as well as from vapor-pressure osmometry (VPO), indicate that the AP dimer is formed with an association constant greater than 107 M-1. Solid-solution extraction experiments are indicative of the formation of a 2:1 trimer (A2P), while self-associated homotopic species (A2 and A3) can be detected by NMR and VPO. Analysis of the heterotopic noncovalent assembly process over a range of compositions shows that these other species are much less stable than the AP heterodimer, which is the exclusive species at an A/P concentration ratio of 1:1 (〉 99.7% of the total at 10 mM).
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 527-538 
    ISSN: 1434-193X
    Keywords: Furans ; Pyrans ; Dihydropyran-2-ylidenes ; Ring closure ; Addition reaction ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---On treatment with base the pentynones 8a-f undergo anionic addition reactions of the resulting enolate species to the alkyne moiety and afford the 2,5-disubstituted furans 10a-f in yields ranging from 10-91%. The proposed mechanism involves the 2-methylene-dihydrofurans 11 as intermediates which tautomerize to yield the observed products. In the case of the α-picolyl derivative 8g both possible enolates 12 and 13 are formed which are subsequently transformed to the products 10g and 14g, respectively. Starting with the hexynones 9a-e an analogous reaction takes place with the formation of the pyran derivatives 15 and 16 in comparable yields. Under the same reaction conditions the n-butyl ketone 9f gives rise to two isomeric compounds, namely the 4H-pyran 16f and the cyclohexenone 17. This result is explained by assuming initial formation of two isomeric enolates which react either by O- or C-attack on the carbon-carbon triple bond.
    Additional Material: 5 Tab.
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  • 8
    ISSN: 1434-193X
    Keywords: Amide linkage ; Phosphodiester ; Hammerhead ribozyme ; Oligonucleotides ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---A nucleoside dimer in which the natural phosphodiester bond is replaced by an isosteric amide linkage has been prepared. This dimer analogue was subsequently incorporated chemically at the cleavage position of a hammerhead ribozyme substrate. Although the resulting substrate analogue exhibited a high affinity for the ribozyme as shown by gel retardation assays, the amide bond proved to be fully resistant to cleavage under standard conditions of ribozyme cleavage activity.
    Additional Material: 3 Ill.
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  • 9
    ISSN: 1434-193X
    Keywords: Biotin ; Fullerenes ; Membranes ; Nanostructures ; Reflectometric interference spectroscopy ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -As a prototype for a new class of lipid membrane components, the lipophilic fullerene derivative (so-called lipofullerene) 1 was synthesized and characterized. This mixed [1:5]-hexakisadduct consists of ten long alkyl chains within five didodecyl malonate addends and a linker malonate carrying a (+)-biotin unit as part of an amphiphilic spacer. The malonates are attached to the fullerene core in an octahedral addition pattern, which was achieved by two successive cyclopropanation sequences with the functional precursor malonate 8 and dodecyl malonate 10. The final step of the synthesis of 1 was the attachment of activated biotin 5 with the deprotected precursor 11. Binding experiments followed by reflectometric interference spectroscopy [RIfS] proved the capability of 1 to bind specifically the protein streptavidin (SA) through the biotin unit. The amphiphilic behavior of 1 was demonstrated by Langmuir Blodgett (LB) film investigations.
    Additional Material: 3 Ill.
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  • 10
    ISSN: 1434-193X
    Keywords: Fullerenes ; Cycloadditions ; Donor-acceptor systems ; Cyclic voltammetry ; Photoinduced electron transfer ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The new C60 and C70 adducts 1b, 1d-1k, 1m, 6d, 7d, and 8d have been synthesized by [2+3] cycloadditions of the appropriate nitrile oxides. Variations in the distance and geometry of the donor and acceptor substituents are seen to have an influence on the redox behavior of the fullerene adducts in cyclic voltammetry experiments. The isoxazolo-fullerenes 1c, 1d, and 1i show shifts of about 30 mV or 40 mV to more negative values compared with the reference compound 1a. On the other hand, strong acceptor properties are detected in the case of compound 1e, which shows a positive shift of 30 mV relative to 1a. Moreover, time-resolved fluorescence spectroscopy has shown that upon excitation of the fullerene moiety in the polar solvent benzonitrile, an electron is transferred from the donor substituent to the first excited singlet state of the fullerene, thereby reducing the excited-state lifetime. Our data demonstrate that the electron-transfer rate in donor-substituted fullerenes can be controlled by the electron-donating property of the substituent as well as the electronic structure and/or length of the spacer used. The C70 regioisomers 6d, 7d, and 8d exhibit differences in their spectroscopic characteristics.
    Additional Material: 3 Ill.
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