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  • Metals and Metallic Materials  (15)
  • Astrodynamics  (13)
  • 2010-2014  (13)
  • 2000-2004  (15)
  • 1925-1929
  • 1
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    Evaluation of Relative Navigation Algorithms for Formation-Flying Satellites (2001)
    In:  CASI
    Details
    Publication Date: 2017-09-27
    Description: Goddard Space Flight Center is currently developing advanced spacecraft systems to provide autonomous navigation and control of formation flyers. This paper discusses autonomous relative navigation performance for formations in eccentric, medium, and high-altitude Earth orbits using Global Positioning System (GPS) Standard Positioning Service (SPS) and intersatellite range measurements. The performance of several candidate relative navigation approaches is evaluated. These analyses indicate that the relative navigation accuracy is primarily a function of the frequency of acquisition and tracking of the GPS signals. A relative navigation position accuracy of 0.5 meters root-mean-square (RMS) can be achieved for formations in medium-attitude eccentric orbits that can continuously track at least one GPS signal. A relative navigation position accuracy of better than 75 meters RMS can be achieved for formations in high-altitude eccentric orbits that have sparse tracking of the GPS signals. The addition of round-trip intersatellite range measurements can significantly improve relative navigation accuracy for formations with sparse tracking of the GPS signals.
    Keywords: Astrodynamics
    Type: 2001 Flight Mechanics Symposium; 99-113; NASA/CP-2001-209986
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  • 2
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    Effects of Thermal Exposure on Properties of Al-Li Alloys (2003)
    In:  CASI
    Details
    Publication Date: 2018-06-12
    Description: The objective of this investigation is to evaluate the effects of thermal exposure on the mechanical properties of both production mature and developmental Al-Li alloys
    Keywords: Metals and Metallic Materials
    Type: 5th Conference on Aerospace Materials, Processes, and Environmental Technology; NASA/CP-2003-212931
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  • 3
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    Effects of Thermal Exposure on Properties of Al-Li Alloys (2002)
    In:  Other Sources
    Details
    Publication Date: 2019-07-18
    Description: Aluminum-Lithium (Al-Li) alloys offer significant performance benefits for aerospace structural applications due to their higher specific properties compared with conventional Al alloys. For example, the application of Al-Li alloy 2195 to the space shuffle external cryogenic fuel tank resulted in weight savings of over 7,000 lb, enabling successful deployment of International Space Station components. The composition and heat treatment of 2195 were optimized specifically for strength-toughness considerations for an expendable cryogenic tank. Time-dependent properties related to reliability, such as thermal stability, fatigue, and corrosion, will be of significant interest when materials are evaluated for a reusable cryotank structure. Literature surveys have indicated that there is limited thermal exposure data on Al-Li alloys. The effort reported here was designed to establish the effects of thermal exposure on the mechanical properties and microstructure of Al-Li alloys C458, L277, and 2195 in plate gages. Tensile, fracture toughness, and corrosion resistance were evaluated for both parent metal and friction stir welds (FSW) after exposure to temperatures as high as 300 F for up to 1000 hrs. Microstructural changes were evaluated with thermal exposure in order to correlate with the observed data trends. The ambient temperature parent metal data showed an increase in strength and reduction in elongation after exposure at lower temperatures. Strength reached a peak with intermediate temperature exposure followed by a decrease at highest exposure temperature. Friction stir welds of all alloys showed a drop in elongation with increased length of exposure. Understanding the effect of thermal exposure on the properties and microstructure of Al-Li alloys must be considered in defining service limiting temperatures and exposure times for a reusable cryotank structure.
    Keywords: Metals and Metallic Materials
    Type: AMPET; Sep 16, 2002 - Sep 18, 2002; Huntsville, AL; United States
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  • 4
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    B218 Weld Filler Wire Characterization for Al-Li Alloy 2195 (2000)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: NASA Marshall Space Flight Center, Lockheed Martin Space Systems- Michoud Operations, and McCook Metals have developed an aluminum-copper weld filler wire for fusion welding aluminum lithium alloy 2195. The aluminum-copper based weld filler wire has been identified as B218, a McCook Metals designation. B218 is the result of six years of weld filler wire development funded by NASA, Lockheed Martin, and McCook Metals. The filler wire chemistry was developed to produce enhanced 2195 weld and repair weld mechanical properties over the 4043 aluminum-silicon weld filler wire, which is currently used to weld 2195 on the Super Lightweight External Tank for the NASA Space Shuttle Program. An initial characterization was performed consisting of a repair weld evaluation using B218 and 4043 weld filler wires. The testing involved room temperature and cryogenic repair weld tensile testing along with fracture toughness testing. From the testing, B218 weld filler wire produce enhanced repair weld tensile strength, ductility, and fracture properties over 4043. B218 weld filler wire has proved to be a superior weld filler wire for welding aluminum lithium alloy 2195 over 4043.
    Keywords: Metals and Metallic Materials
    Type: Aeromat 2000 Conference; Jun 26, 2000 - Jun 29, 2000; Seattle, WA; United States
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  • 5
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    Test and Analysis of Sub-Components of Aluminum-Lithium Alloy Cylinders (2012)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Integrally machined blade-stiffened panels subjected to an axial compressive load were tested and analyzed to observe the buckling, crippling, and postcrippling response of the panels. The panels were fabricated from aluminum-lithium alloys 2195 and 2050, and both alloys have reduced material properties in the short transverse material direction. The tests were designed to capture a failure mode characterized by the stiffener separating from the panel in the postbuckling range. This failure mode is attributed to the reduced properties in the short transverse direction. Full-field measurements of displacements and strains using three-dimensional digital image correlation systems and local measurements using strain gages were used to capture the deformation of the panel leading up to the failure of the panel for specimens fabricated from 2195. High-speed cameras were used to capture the initiation of the failure. Finite element models were developed using an isotropic strain-hardening material model. Good agreement was observed between the measured and predicted responses for both alloys.
    Keywords: Metals and Metallic Materials
    Type: NF1676L-13166 , AIAA Paper-2012-1687 , 53rd AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics and Materials Conference; Apr 23, 2012 - Apr 26, 2012; Honolulu, HI; United States
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  • 6
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    Electromagnetic Characterization Of Metallic Sensory Alloy (2012)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Ferromagnetic shape-memory alloy (FSMA) particles undergo changes in both electromagnetic properties and crystallographic structure when strained. When embedded in a structural material, these attributes can provide sensory output of the strain state of the structure. In this work, a detailed characterization of the electromagnetic properties of a FSMA under development for sensory applications is performed. In addition, a new eddy current probe is used to interrogate the electromagnetic properties of individual FSMA particles embedded in the sensory alloy during controlled fatigue tests on the multifunctional material.
    Keywords: Metals and Metallic Materials
    Type: NF1676L-15575 , 39th Annual Review of Progress in Quantitative Nondestructive Evaluation (QNDE) Conference; Jul 15, 2012 - Jul 20, 2012; Denver, CO; United States
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  • 7
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    Magnetospheric Multiscale (MMS) Mission Navigation Concept (2011)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: No abstract available
    Keywords: Astrodynamics
    Type: GSFC.CPR.5479.2011 , Young Professional, Student, and Education Conference (YPSE-11); Nov 04, 2011; MD; United States
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  • 8
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    Comparison of Statistical Estimation Techniques for Mars Entry, Descent, and Landing Reconstruction from MEDLI-like Data Sources (2012)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Flight data from an entry, descent, and landing (EDL) sequence can be used to reconstruct the vehicle's trajectory, aerodynamic coefficients and the atmospheric profile experienced by the vehicle. Past Mars missions have contained instruments that do not provide direct measurement of the freestream atmospheric conditions. Thus, the uncertainties in the atmospheric reconstruction and the aerodynamic database knowledge could not be separated. The upcoming Mars Science Laboratory (MSL) will take measurements of the pressure distribution on the aeroshell forebody during entry and will allow freestream atmospheric conditions to be partially observable. This data provides a mean to separate atmospheric and aerodynamic uncertainties and is part of the MSL EDL Instrumentation (MEDLI) project. Methods to estimate the flight performance statistically using on-board measurements are demonstrated here through the use of simulated Mars data. Different statistical estimators are used to demonstrate which estimator best quantifies the uncertainties in the flight parameters. The techniques demonstrated herein are planned for application to the MSL flight dataset after the spacecraft lands on Mars in August 2012.
    Keywords: Astrodynamics
    Type: AIAA Paper 2012-0400 , NF1676L-14037 , 50th AIAA Aerospace Sciences Meeting and Exhibit; Jan 09, 2012 - Jan 12, 2012; Nashville, TN; United States
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  • 9
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    Mitigating Abnormal Grain Growth for Friction Stir Welded Al-Li 2195 Spun Formed Domes (2012)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Formability and abnormal grain growth (AGG) are the two major issues that have been encountered for Al alloy spun formed dome development using friction stir welded blanks. Material properties that have significant influence on the formability include forming range and strain hardening exponent. In this study, tensile tests were performed for two 2195 friction stir weld parameter sets at 400 F to study the effects of post weld anneal on the forming range and strain hardening exponent. It was found that the formability can be enhanced by applying a newly developed post weld anneal to heat treat the friction stir welded panels. This new post weld anneal leads to a higher forming range and much improved strain hardening exponent. AGG in the weld nugget is known to cause a significant reduction of ductility and fracture toughness. This study also investigated how AGG may be influenced by the heating rate to the solution heat treatment temperature. After post-weld annealing, friction stir welds were strained to 15% and 39% by compression at 400 F before they were subjected to SHT at 950 F for 1 hour. Salt bath SHT is very effective in reducing the grain size as it helps arrest the onset of AGG and promote normal recrystallization and grain growth. However, heat treating a 18 ft dome using a salt bath is not practical. Efforts are continuing at Marshall Space Flight Center to identify the welding parameters and heat treating parameters that can help mitigate the AGG in the friction stir welds.
    Keywords: Metals and Metallic Materials
    Type: M12-1469 , M12-1643 , M12-1818 , International Friction Stir Welding Symposium; May 15, 2012 - May 17, 2012; Huntsville, AL; United States
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  • 10
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    Procedure for Automated Eddy Current Crack Detection in Thin Titanium Plates (2012)
    In:  CASI
    Details
    Publication Date: 2019-07-12
    Description: This procedure provides the detailed instructions for conducting Eddy Current (EC) inspections of thin (5-30 mils) titanium membranes with thickness and material properties typical of the development of Ultra-Lightweight diaphragm Tanks Technology (ULTT). The inspection focuses on the detection of part-through, surface breaking fatigue cracks with depths between approximately 0.002" and 0.007" and aspect ratios (a/c) of 0.2-1.0 using an automated eddy current scanning and image processing technique.
    Keywords: Metals and Metallic Materials
    Type: NASA/TM-2012-217782 , L-20187 , NF1676L-15095
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