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  • Spacecraft Design, Testing and Performance  (2)
  • assignment  (2)
  • Aerodynamics; Spacecraft Design, Testing and Performance  (1)
  • Electronics and Electrical Engineering  (1)
  • FABRICATION TECHNOLOGY  (1)
  • 1
    Electronic Resource
    Electronic Resource
    The singly constrained assignment problem: An AP basis algorithm (1995)
    Springer
    Computational optimization and applications 4 (1995), S. 347-374 
    Details
    ISSN: 1573-2894
    Keywords: mathematical programming ; assignment ; networks
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract This manuscript presents a specialized primal simplex algorithm to obtain near optimal integer solutions for the singly constrained assignment problem. An optimal solution for the continuous relaxation of the problem is obtained by generalizing the alternating basis algorithm of Barr, Glover, and Klingman for the pure assignment problem. Near optimal integer solutions are obtained by pivoting into the optimal basis the slack variable associated with the side constraint. Our empirical analysis indicated that for our test problems the soft-ware implementation of this algorithm was six times faster than CPLEX and four times faster than NETSIDE (a specialized code for network problems with side constraints). The integer solutions obtained in our tests were typically within 2% of the optimum of the continuous relaxation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01300862
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    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    The singly constrained assignment problem: A Lagrangian relaxation heuristic algorithm (1994)
    Springer
    Computational optimization and applications 3 (1994), S. 7-26 
    Details
    ISSN: 1573-2894
    Keywords: network programming ; assignment ; integer programming
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract This manuscript presents a new heuristic algorithm to find near optimal integer solutions for the singly constrained assignment problem. The method is based on Lagrangian duality theory and involves solving a series of pure assignment problems. The software implementation of this heuristic, ASSIGN+1, successfully solved problems having one-half million binary variables (assignment arcs) in less than 17 minutes of wall clock time on a Sequent Symmetry S81 using a single processor. In computational comparisons with MPSX and OSL on an IBM 3081D, the specialized software was from 100 to 1,000 times faster. In computational comparisons with the specialized code of Mazzola and Neebe, we found that ASSIGN+1 was 40 times faster. In computational comparisons with our best alternating path specialized code, we found that ASSIGN+1 was more than three times faster than that code. This new software proved to be very robust as well as fast. The robustness is due to an elaborate scheme used to update the Lagrangean multipliers and the speed is due to the fine code used to solve the pure assignment problems. We also present a modification of the algorithm for the case in which the number of jobs exceeds the number of men along with an empirical analysis of the modified software.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01299389
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    Paper (German National Licenses)
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  • 3
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    Ultra Lightweight Ballutes for Return to Earth from the Moon (2006)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Ultra lightweight ballutes offer revolutionary mass and cost benefits along with flexibility in flight system design compared to traditional entry system technologies. Under funding provided by NASA s Exploration Systems Research & Technology program, our team was able to make progress in developing this technology through systems analysis and design, evaluation of materials and construction methods, and development of critical analysis tools. Results show that once this technology is mature, significant launch mass savings, operational simplicity, and mission robustness will be available to help carry out NASA s Vision for Space Exploration.
    Keywords: Spacecraft Design, Testing and Performance
    Type: AIAA Paper 2006-1698 , 47th AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference; May 01, 2006 - May 04, 2006; Newport, RI; United States
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 4
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    Rolling Stitch Welder For Foil (1992)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: Hand-operated rolling spotwelder stitch-welds foil faster and more consistently than single-spotwelding gun without damaging it. Internal spring reacts against roller frame, exerting force on welding wheel when rollers contact workpiece.
    Keywords: FABRICATION TECHNOLOGY
    Type: MFS-29740 , NASA Tech Briefs (ISSN 0145-319X); 16; 6; P. 79
    Format: text
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  • 5
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    Aerocapture Systems Analysis for a Neptune Mission (2006)
    In:  CASI
    Details
    Publication Date: 2019-07-11
    Description: A Systems Analysis was completed to determine the feasibility, benefit and risk of an aeroshell aerocapture system for Neptune and to identify technology gaps and technology performance goals. The systems analysis includes the following disciplines: science; mission design; aeroshell configuration; interplanetary navigation analyses; atmosphere modeling; computational fluid dynamics for aerodynamic performance and aeroheating environment; stability analyses; guidance development; atmospheric flight simulation; thermal protection system design; mass properties; structures; spacecraft design and packaging; and mass sensitivities. Results show that aerocapture is feasible and performance is adequate for the Neptune mission. Aerocapture can deliver 1.4 times more mass to Neptune orbit than an all-propulsive system for the same launch vehicle and results in a 3-4 year reduction in trip time compared to all-propulsive systems. Enabling technologies for this mission include TPS manufacturing; and aerothermodynamic methods for determining coupled 3-D convection, radiation and ablation aeroheating rates and loads.
    Keywords: Spacecraft Design, Testing and Performance
    Type: NASA/TM-2006-214300 , L-19236
    Format: application/pdf
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  • 6
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    Flow Energy Piezoelectric Bimorph Nozzle Harvester (2014)
    In:  Other Sources
    Details
    Publication Date: 2019-08-26
    Description: There is a need for a long-life power generation scheme that could be used downhole in an oil well to produce 1 Watt average power. There are a variety of existing or proposed energy harvesting schemes that could be used in this environment but each of these has its own limitations. The vibrating piezoelectric structure is in principle capable of operating for very long lifetimes (decades) thereby possibly overcoming a principle limitation of existing technology based on rotating turbo-machinery. In order to determine the feasibility of using piezoelectrics to produce suitable flow energy harvesting, we surveyed experimentally a variety of nozzle configurations that could be used to excite a vibrating piezoelectric structure in such a way as to enable conversion of flow energy into useful amounts of electrical power. These included reed structures, spring mass-structures, drag and lift bluff bodies and a variety of nozzles with varying flow profiles. Although not an exhaustive survey we identified a spline nozzle/piezoelectric bimorph system that experimentally produced up to 3.4 mW per bimorph. This paper will discuss these results and present our initial analyses of the device using dimensional analysis and constitutive electromechanical modeling. The analysis suggests that an order-of-magnitude improvement in power generation from the current design is possible.
    Keywords: Electronics and Electrical Engineering
    Type: SPIE Smart Structures and Non-Destructive Evaluation; Mar 09, 2014 - Mar 13, 2014; San Diego, CA; United States
    Format: text
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    NASA TECHNICAL REPORTS
  • 7
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    A Survey of Titan Balloon Concepts and Technology Status (2011)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: This paper surveys the options for, and technology status of, balloon vehicles to explore Saturn's moon Titan. A significant amount of Titan balloon concept thinking and technology development has been performed in recent years, particularly following the spectacular results from the descent and landing of the Huygens probe and remote sensing observations by the Cassini spacecraft. There is widespread recognition that a balloon vehicle on the next Titan mission could provide an outstanding and unmatched capability for in situ exploration on a global scale. The rich variety of revealed science targets has combined with a highly favorable Titan flight environment to yield a wide diversity of proposed balloon concepts. The paper presents a conceptual framework for thinking about balloon vehicle design choices and uses it to analyze various Titan options. The result is a list of recommended Titan balloon vehicle concepts that could perform a variety of science missions, along with their projected performance metrics. Recent technology developments for these balloon concepts are discussed to provide context for an assessment of outstanding risk areas and technological maturity. The paper concludes with suggestions for technology investments needed to achieve flight readiness.
    Keywords: Aerodynamics; Spacecraft Design, Testing and Performance
    Type: AIAA Balloon Systems Conference; Sep 20, 2011 - Sep 22, 2011; Virginia Beach, VA; United States
    Format: text
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