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  • Polymer and Materials Science  (3)
  • SPACECRAFT PROPULSION AND POWER  (3)
  • AIRCRAFT DESIGN, TESTING AND PERFORMANCE  (2)
  • 1990-1994  (7)
  • 1970-1974  (1)
Collection
Keywords
Publisher
Years
Year
  • 1
    Electronic Resource
    Electronic Resource
    Calculation of the glass transition temperatures of polymers. Part I. Homopolymers and copolymers with alkyl side chains (1970)
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 8 (1970), S. 555-570 
    Details
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Four equations, relating the glass transition temperatures Tg of homopolymers and copolymers to invariant additive temperature parameters (ATP) associated with their constituent groups, but weighted in different ways, have been applied to the calculation of the Tg of seven series of polymers having alkyl side chains. It is shown that the Tg of the 32 polymers considered may be calculated, within 7°K of the observed values, without the use of interaction coefficients from 15 independent variables, representing summations of the ATP's. The present calculations are confined to those structures which may be formed by a recombination of the structures corresponding to these independent variables. It is an essential feature of the approach that a distinction is made between groups with different nearest neighbors. Alternative methods of calculation are considered. The temperature parameter for a sequence of three or more methylene groups is estimated as 141°K, in conformity with the transition in polyethylene at 148°K. Nearest-neighbor interactions, stereoregularity, and crystallinity effects are discussed.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1970.160080407
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    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    The preparation and characterization of new polyether ketone-tetraethylorthosilicate hybrid glasses by the sol-gel method (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 40 (1990), S. 1177-1194 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: In recent years, tetraethyl orthosilicate (TEOS) has been used as a precursor in preparing inorganic glasses. The technique, known as the sol-gel process involves a two step poly(hydrolysis-condensation)reaction sequence. The work presented here is concerned with the utilization of a suitably functionalized oligomeric “glassy” organic polymeric component in this two step sequence. In particular, an amine terminated amorphous poly(arylene ether) ketone, (PEK), end capped with isocyantonropyl triethoxy silane was used to synthesize a hybrid network with TEOS. Low incorporation of the PEK oligomers into the network caused by early vitrification can be eliminated by carrying out reactions at elevated temperatures. A systematic change in mechanical and physical properties of the hybrid glass has been found with TEOS content and the annealing temperatures. A model for the network has been proposed based on structural and morphological evidence.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1990.070400709
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Physical characteristics of Ti-6Al-4V implants fabricated by electrodischarge compaction (1991)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 25 (1991), S. 1417-1429 
    Details
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Physical characteristics of a Ti-6Al-4V implant were evaluated following fabrication using a new electrodischarge compaction technique. Ti-6Al-4V atomized powders were loaded into Pyrex tubes (3.3 mm ID) and subjected to a highvoltage, high-current-density pulse in air for a period of less than 300 μs. Single pulses (1.0, 1.5, 2.0 and 2.5 KJ/grampowder) were applied from a capacitor bank (240, 480 or 720 μF) to produce solid core implants with porous surface layers. Implants were evaluated microscopically for core size, neck size, pore size, grain structure, and incorporated oxide film. Hardness was also evaluated. Implants were compared with Ti-6Al-4V commercial powders. Core size increased and pore size decreased with increases in energy and capacitance. The cores were composed of equiaxed grains which were free of oxide at the grain boundary. Porous layers, consisting of particles connected in three dimensions by necks, were free of oxide films at the connecting interfaces. Neck size increased with increases in input energy and capacitance. Hardness readings of the core, necks, and porous particles resulted in readings higher than or similar to control materials. Electrodischarge compaction did not alter the physical characteristics during compaction.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jbm.820251202
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    Paper (German National Licenses)
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  • 4
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    Propulsion technology discipline (1990)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: Viewgraphs on propulsion technology discipline for Space Station Freedom are presented. Topics covered include: water electrolysis O2/H2 system; hydrazine system advancements; common technology; fluids disposal; and storable bipropellant system.
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: NASA, Washington, Technology for Space Station Evolution. Executive Summary and Overview; p 179-196
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 5
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    Propulsion for the lunar mission (1990)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The paper describes the selection process utilized by NASA during the conduct of the 90-day study of the mission set that is known as the Space Exploration Initiative (SEI). It is directed specifically toward propulsion system definition and selection, with emphasis on the proposed Lunar Transfer Vehicle and the Lunar Exploration Vehicle. Results of trade studies show that selection cannot be readily made on the basis of engine performance alone, because the cost of launching hardware elements and the required propellant are very high. A decision must be made to use either life-cycle costs or annual program costs as the economic figure of merit, because they drive the selection in opposite directions.
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: AIAA PAPER 90-3709
    Format: text
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  • 6
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    Engine selection for the Space Exploration Initiative (1990)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The process used by NASA in the selection of the engine for the Space Exploration Initiative mission is described. The major propulsion requirements of the engine are addressed along with the engine options and key drivers and trades. Special attention is given to the requirements of the propellant feed system and the reaction control system. As a result of the 90-study, four moderate chamber pressure expander-cycle oxygen/hydrogen engines with a thrust level of 20,000 lbf each were selected for the lunar transfer vehicle. The paper also presents results of architecture studies and of advanced engine test bed studies.
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: AIAA PAPER 90-1880
    Format: text
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  • 7
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    Optimal trajectories for an aerospace plane. Part 2: Data, tables, and graphs (1990)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Data, tables, and graphs relative to the optimal trajectories for an aerospace plane are presented. A single-stage-to-orbit (SSTO) configuration is considered, and the transition from low supersonic speeds to orbital speeds is studied for a single aerodynamic model (GHAME) and three engine models. Four optimization problems are solved using the sequential gradient-restoration algorithm for optimal control problems: (1) minimization of the weight of fuel consumed; (2) minimization of the peak dynamic pressure; (3) minimization of the peak heating rate; and (4) minimization of the peak tangential acceleration. The above optimization studies are carried out for different combinations of constraints, specifically: initial path inclination that is either free or given; dynamic pressure that is either free or bounded; and tangential acceleration that is either free or bounded.
    Keywords: AIRCRAFT DESIGN, TESTING AND PERFORMANCE
    Type: NASA-CR-187848 , NAS 1.26:187848 , AAR-248-PT-2 , 1990 American Control Conference; May 23, 1990 - May 25, 1990; San Diego, CA; United States
    Format: application/pdf
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  • 8
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    Optimal trajectories for an aerospace plane. Part 1: Formulation, results, and analysis (1990)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The optimization of the trajectories of an aerospace plane is discussed. This is a hypervelocity vehicle capable of achieving orbital speed, while taking off horizontally. The vehicle is propelled by four types of engines: turbojet engines for flight at subsonic speeds/low supersonic speeds; ramjet engines for flight at moderate supersonic speeds/low hypersonic speeds; scramjet engines for flight at hypersonic speeds; and rocket engines for flight at near-orbital speeds. A single-stage-to-orbit (SSTO) configuration is considered, and the transition from low supersonic speeds to orbital speeds is studied under the following assumptions: the turbojet portion of the trajectory has been completed; the aerospace plane is controlled via the angle of attack and the power setting; the aerodynamic model is the generic hypersonic aerodynamics model example (GHAME). Concerning the engine model, three options are considered: (EM1), a ramjet/scramjet combination in which the scramjet specific impulse tends to a nearly-constant value at large Mach numbers; (EM2), a ramjet/scramjet combination in which the scramjet specific impulse decreases monotonically at large Mach numbers; and (EM3), a ramjet/scramjet/rocket combination in which, owing to stagnation temperature limitations, the scramjet operates only at M approx. less than 15; at higher Mach numbers, the scramjet is shut off and the aerospace plane is driven only by the rocket engines. Under the above assumptions, four optimization problems are solved using the sequential gradient-restoration algorithm for optimal control problems: (P1) minimization of the weight of fuel consumed; (P2) minimization of the peak dynamic pressure; (P3) minimization of the peak heating rate; and (P4) minimization of the peak tangential acceleration.
    Keywords: AIRCRAFT DESIGN, TESTING AND PERFORMANCE
    Type: NASA-CR-187868 , NAS 1.26:187868 , AAR-247 , American Control Conference; May 23, 1990 - May 25, 1990; San Diego, CA; United States
    Format: application/pdf
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