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  • 1
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    Derivation and test of elevated temperature thermal-stress-free fastener concept (1985)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Future aerospace vehicles must withstand high temperatures and be able to function over a wide temperature range. New composite materials are being developed for use in designing high-temperature lightweight structures. Due to the difference between coefficients of thermal expansion for the new composite materials and conventional high-temperature metallic fasteners, innovative joining techniques are needed to produce tight joints at all temperatures without excessive thermal stresses. A thermal-stress-free fastening technique is presented that can be used to provide structurally tight joints at all temperatures even when the fastener and joined materials have different coefficients of thermal expansion. The derivation of thermal-stress-free fasteners and joint shapes is presented for a wide variety of fastener materials and materials being joined together. Approximations to the thermal-stress-free shapes that result in joints with low-thermal-stresses and that simplify the fastener/joint shape are discussed. The low-thermal-stress fastener concept is verified by thermal and shear tests in joints using oxide-dispersion-strengthened alloy fasteners in carbon-carbon material. The test results show no evidence of thermal stress damage for temperatures up to 2000 F and the resulting joints carried shear loads at room temperature typical of those for conventional joints.
    Keywords: MECHANICAL ENGINEERING
    Type: Welding, Bonding and Fastening, 1984; p 105-122
    Format: application/pdf
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  • 2
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    Thermal-stress-free fasteners for joining orthotropic materials (1987)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Hot structures fabricated from orthotropic materials are an attractive design option for future high speed vehicles. Joining subassemblies of these materials with standard cylindrical fasteners can lead to loose joints or highly stressed joints due to thermal stress. A method has been developed to eliminate thermal stresses and maintain a tight joint by shaping the fastener and mating hole. This method allows both materials (fastener and structure), with different coefficients of thermal expansion (CTEs) in each of the three material directions, to expand freely with temperature yet remain in contact. For the assumptions made in the analysis, the joint will remain snug, yet free of thermal stress at any temperature. Finite element analysis was used to verify several thermal-stress-free fasteners and to show that conical fasteners, which are thermal-stress-free for isotropic materials, can reduce thermal stresses for transversely isotropic materials compared to a cylindrical fastener. Equations for thermal-stress-free shapes are presented and typical fastener shapes are shown.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-TM-100489 , NAS 1.15:100489
    Format: application/pdf
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  • 3
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    Transient thermal analysis of a titanium multiwall thermal protection system (1982)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The application of the SPAR thermal analyzer to the thermal analysis of a thermal protection system concept is discussed. The titanium multiwall thermal protection system concept consists of alternate flat and dimpled sheets which are joined together at the crests of the dimples and formed into 30 cm by 30 cm (12 in. by 12 in.) tiles. The tiles are mechanically attached to the structure. The complex tile geometry complicates thermal analysis. Three modes of heat transfer were considered: conduction through the gas inside the tile, conduction through the metal, and radiation between the various layers. The voids between the dimpled and flat sheets were designed to be small enough so that natural convection is insignificant (e.g., Grashof number 1000). A two step approach was used in the thermal analysis of the multiwall thermal protection system. First, an effective normal (through-the-thickness) thermal conductivity was obtained from a steady state analysis using a detailed SPAR finite element model of a small symmetric section of the multiwall tile. This effective conductivity was then used in simple one dimensional finite element models for preliminary analysis of several transient heat transfer problems.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Computational Aspects of Heat Transfer in Struct.; p 349-361
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  • 4
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    Theoretical basis for design of thermal-stress-free fasteners (1983)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A theoretical basis was developed for the design of fasteners which are free of thermal stress. A fastener can be shaped to eliminate the thermal stress which would otherwise result from differential thermal expansion between dissimilar fastener and sheet materials for many combinations of isotropic and orthotropic materials. The resulting joint remains snug, yet free of thermal stress at any temperature, if the joint is uniform in temperature, if it is frictionless, and if the coefficients of thermal expansion of the materials do not change with temperature. In general, such a fastener has curved sides; however, if both materials have isotropic coefficients of thermal expansion, a conical fastener is free of thermal stress. Equations are presented for thermal stress free shapes at both initial and final temperature, and typical fastener shapes are shown.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-TP-2226 , L-15658 , NAS 1.60:2226
    Format: application/pdf
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  • 5
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    Operational modules for space station construction (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Identification of an effective space construction concept is a current objective of NASA studies. One concept, described in this memorandum, consists of repetitive use of operational modules, which minimizes on-orbit stay time for the shuttle. A space station constructed of operational modules may benefit from fabrication and system checkout in ground-based facilities, and since the modules are the primary structure of the space station, a minimum of additional structure, and trips and on-orbit stay time of the shuttle are required.
    Keywords: SPACECRAFT DESIGN, TESTING AND PERFORMANCE
    Type: NASA-TM-85772 , NAS 1.15:85772
    Format: application/pdf
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  • 6
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    Design study of a slant-nose-cylinder aeroassisted orbital transfer vehicle (1985)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: A slant-nose-cylinder aeroassisted orbital transfer vehicle configuration is described and analyzed in this study. The vehicle is sized for a 12,000 lb roundtrip payload between low earth orbit and geosynchronous orbit and is assumed to be space based. The vehicle can be fabricated using near-term technologies and is fully reusable. Optional advanced technologies offer potential for improved performance. The vehicle can be assembled on the ground and carried to orbit in the Shuttle cargo bay. An enclosed payload bay is provided in the vehicle to protect payloads during the pass through the atmosphere. The payload bay capacity can be increased from a 10 ft to a 14 ft diameter payload by replacing a modular section of the payload bay in space. The results of calculations used to size the vehicle and to predict its performance and weight are presented.
    Keywords: LAUNCH VEHICLES AND SPACE VEHICLES
    Type: AIAA PAPER 85-0966
    Format: text
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  • 7
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    Fastening Parts Having Mismatched Thermal Coefficients (1985)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Fastener eliminates thermal stresses and maintains snug fit. Conicalhead bolt and metal washer main components of fastener that keeps constant tension on carbon/carbon parts regardless of thermal stress. Fastener used in cases where fastened parts have unmatched thermalexpansion coefficients. Does not become looser or tighter as conventional bolts and nuts or rivets do at elevated temperatures.
    Keywords: MACHINERY
    Type: LAR-13009 , NASA Tech Briefs (ISSN 0145-319X); 9; 1; P. 137
    Format: text
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  • 8
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    Viability of 3 D Woven Carbon Cloth and Advanced Carbon-Carbon Ribs for Adaptive Deployable Entry Placement Technology (ADEPT) for Future NASA Missions (2013)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: This paper describes aerothermodynamic and thermal structural testing that demonstrate the viability of three dimensional woven carbon cloth and advanced carbon-carbon (ACC) ribs for use in the Adaptive Deployable Entry Placement Technology (ADEPT). ADEPT is an umbrella-like entry system that is folded for stowage in the launch vehicle's shroud and deployed prior to reaching the atmeopheric interface. A key feature of the ADEPT concept is a lower ballistic coefficient for delivery of a given payload than seen with conventional, rigid body entry systems. The benefits that accrue from the lower ballistic coefficient incllude factor-of-ten reductions of deceleration forces and entry heating. The former enables consideration of new classes of scientific instruments for solar system exploration while the latter enables the design of a more efficient thermal protection system. The carbon cloth base lined for ADEPT has a dual use in that it serves as the thermal protection system and as the "skin" that transfers aerdynamic deceleration loads to its umbrella-like substructure. Arcjet testing described in this paper was conducted for some of the higher heating conditions for a future Venus mission using the ADEPT concept, thereby showing that the carbon cloth can perform in a relevant entry environment. Recently completed the thermal structural testing of the cloth attached to a representative ACC rib design is also described. Finally, this paper describes a preliminary engineering level code, based on the arcjet data, that can be used to estimate cloth thickness for future ADEPT missions and to predict carbon cloth performance in future arcjet tests.
    Keywords: Composite Materials
    Type: ARC-E-DAA-TN9793 , National Space and Missiles Materials Symposium; Jun 24, 2013 - Jun 28, 2013; Bellevue, WA; United States
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  • 9
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    Bending Stiffness of Multiwall Sandwich (1983)
    In:  CASI
    Details
    Publication Date: 2019-08-14
    Description: An analytical and experimental study was carried out to understand the extensional and flexural behavior of multiwall sandwich, a metallic insulation composed of alternate layers of flat and dimpled foil. The multiwall sandwich was structurally analyzed by using several simplifying assumptions combined with a finite element analysis. The simplifying assumptions made in this analysis were evaluated by bending and tensile tests. Test results validate the assumption that flat sheets in compression do not significantly contribute to the flexural stiffness of multiwall sandwich for the multiwall geometry tested. However, calculations show that thicker flat sheets may contribute significantly to bending stiffness and cannot be ignored. Results of this analytical approach compare well with test data; both show that the extensional stiffness of the dimpled sheet in he 0 deg direction is about 30 percent of that for a flat sheet, and that in the 45 deg direction, it is about 10 percent. The analytical and experimental multiwall bending stiffness showed good agreement for the particular geometry tested.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-TM-84613 , L-15549 , NAS 1.15:84613
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  • 10
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    Multiwall TPS - An emerging concept (1981)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Research on titanium multiwall used for thermal protection is reviewed. Continuing analytical and experimental studies yielding a fundamental understanding of the thermal and structural performance of the basic multiwall concept are presented noting that central to this understanding is a knowledge of the extensional behavior of the dimpled sheets since the thinner flat sheets will buckle and be relatively ineffective in supporting compressive loads. Results from radiant heating, aerothermal, vibration, acoustic and lightning strike tests are described as part of an effort to verify the performance of multiwall tiles under representative operating conditions. Flight tests of a large array of tiles are also planned as part of an orbiter experiments program. The research effort is being extended from flat all-titanium multiwall configurations limited to temperatures below 810 K to curved surfaces and higher temperature versions. Multi-wall concepts are found to offer the durability of metallic systems and to be mass competitive with the insulation system currently used on the Space Shuttle Orbiter.
    Keywords: SPACECRAFT DESIGN, TESTING AND PERFORMANCE
    Type: AIAA PAPER 81-0586 , Conference on Structures, Structural Dynamics and Materials; Apr 06, 1981 - Apr 08, 1981; Atlanta, GA
    Format: text
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