The TPSX Material Properties Database is a web-based tool that serves as a database for propertie... more The TPSX Material Properties Database is a web-based tool that serves as a database for properties of advanced thermal protection materials. TPSX provides an easy user interface for retrieving material property information in a variety of forms, both graphical and text. The primary purpose and advantage of TPSX is to maintain a high quality source of often used thermal protection material properties in a convenient, easily accessible form, for distribution to government and aerospace industry communities. Last year a major upgrade to the TPSX web site was completed. This year, through the efforts of researchers at several NASA centers, the Office of the Chief Engineer awarded funds to update and expand the databases in TPSX. The FY01 effort focuses on updating correcting the Ames and Johnson thermal protection materials databases. In this session we will summarize the improvements made to the web site last year, report on the status of the on-going database updates, describe the pla...
Experiments with deceleration from a Taylor-vortex flow
Physics of Fluids, 1986
ABSTRACT The behavior of a Taylor-vortex structure during a constant deceleration has been studie... more ABSTRACT The behavior of a Taylor-vortex structure during a constant deceleration has been studied experimentally. As expected, the results show a return to circular Couette flow at an instantaneous Reynolds number below the steady critical value.
Thermal protection materials used in spacecraft heatshields are subjected to severe thermal and m... more Thermal protection materials used in spacecraft heatshields are subjected to severe thermal and mechanical loading environments during re-entry into earth atmosphere. In order to investigate the reliability of PICA tiles in the presence of high thermal gradients as well as mechanical loads, the authors designed and conducted solar-tower tests. This paper presents the design and analysis work for this tests series. Coupled non-linear thermalmechanical finite element analyses was conducted to estimate in-depth temperature distribution and stress contours for various cases. The first set of analyses performed on isolated PICA tile showed that stresses generated during the tests were below the PICA allowable limit and should not lead to any catastrophic failure during the test. The tests results were consistent with analytical predictions. The temperature distribution and magnitude of the measured strains were also consistent with predicted values. The second test series is designed to test the arrayed PICA tiles with various gap-filler materials. A nonlinear contact method is used to model the complex geometry with various tiles. The analyses for these coupons predict the stress contours in PICA and inside gap fillers. Suitable mechanical loads for this architecture will be predicted, which can be applied during the test to exceed the allowable limits and demonstrate failure modes. Thermocouple and straingauge data obtained from the solar tower tests will be used for subsequent analyses and validation of FEM models.
10th AIAA/ASME Joint Thermophysics and Heat Transfer Conference, 2010
Many thermal protection system materials used for spacecraft heatshields have anisotropic thermal... more Many thermal protection system materials used for spacecraft heatshields have anisotropic thermal properties, causing them to display significantly different thermal characteristics in different directions, when subjected to a heating environment during flight or arcjet tests. The anisotropic effects are enhanced in the presence of sidewall heating. This paper investigates the effects of anisotropic thermal properties of thermal protection materials coupled with sidewall heating in the arcjet environment. Phenolic Impregnated Carbon Ablator (PICA) and LI-2200 materials (the insulation material of Shuttle tiles) were used for this study. First, conduction-based thermal response simulations were carried out, using the Marc.Mentat finite element solver, to study the effects of sidewall heating on PICA arcjet coupons. The simulation showed that sidewall heating plays a significant role in thermal response of these models. Arcjet tests at the Aerodynamic Heating Facility (AHF) at NASA Ames Research Center were performed later on instrumented coupons to obtain temperature history at sidewall and various radial locations. The details of instrumentation and experimental technique are the prime focus of this paper. The results obtained from testing confirmed that sidewall heating plays a significant role in thermal response of these models. The test results were later used to validate the two-dimensional ablation, thermal response, and sizing program, TITAN. The test data and model predictions were found to be in excellent agreement.
Thermal Stress Analysis of RCG-Tempered TUFI Tile TPS for Hypersonic Vehicles
This paper presents detailed results from linear and nonlinear finite-element thermal stress anal... more This paper presents detailed results from linear and nonlinear finite-element thermal stress analyses of a new tile, Thermal Protection Systems (TPS) concept. A very thin coating of Reaction Cured Glass (RCG) is used to "temper" the surface of Toughened Uni-Piece Fibrous Insulation ( ...
The Thermal Protection Branch at NASA Ames Research Center has developed a computer program for s... more The Thermal Protection Branch at NASA Ames Research Center has developed a computer program for storing, organizing, and accessing information about thermal protection materials. The program, called Thermal Protection Systems Expert and Material Property ...
Strong research and development programs in nanotechnology and Thermal Protection Systems (TPS) e... more Strong research and development programs in nanotechnology and Thermal Protection Systems (TPS) exist at NASA Ames. Conceptual studies have been undertaken to determine if new, nanostructured materials (composites of existing TPS materials and ...
Analytical modeling of thermal and mechanical response is a fundamental step in the design proces... more Analytical modeling of thermal and mechanical response is a fundamental step in the design process for ultra-high-temperature ceramic components, such as nose tips and wing leading edges for hypersonic applications. The purpose of the analyses is to understand the ...
Computational Modeling of Grain Boundaries in ZrB 2 : Implications for Lattice Thermal Conductivity
Journal of the American Ceramic Society, 2012
ABSTRACT A combination of ab initio, atomistic, and finite element methods (FEM) was used to inve... more ABSTRACT A combination of ab initio, atomistic, and finite element methods (FEM) was used to investigate fundamental properties of grain boundaries and grain boundary networks and their impact on lattice thermal conductivity in the ultra high‐temperature ceramic ZrB2. The structure, energetics, and lattice thermal conductance of certain low energy grain boundaries were studied. Atomic models of these boundaries were relaxed using density functional theory. Information about bonding across the interfaces was determined from the electron localization function. Interfacial thermal conductances were computed using nonequilibrium molecular dynamics. Microstructural models were used to determine the reduction in lattice thermal conductivity due grain boundary networks where FEM meshes were constructed on top of microstructural images.
Thermostructural Analysis of X-34 Wing Leading-Edge Tile Thermal Protection System
Journal of Spacecraft and Rockets, 1999
Finite element thermal and stress analyses are presented for ceramic tiles, assemblies, and arc j... more Finite element thermal and stress analyses are presented for ceramic tiles, assemblies, and arc jet models relevant to the thermal protection system for X-34 wing leading edge. The analyses are performed to verify thermal and structural models for silicone impregnated reusable ...
Thermal Protection System Materials and Costs for Future Reusable Launch Vehicles
Journal of Spacecraft and Rockets, 2001
... new reusable launch vehicles (RLVs) for reducing the cost of transporting payload to and from... more ... new reusable launch vehicles (RLVs) for reducing the cost of transporting payload to and from orbit.1"3 This work reviews 13 candidate ther-mal protection system (TPS) options currently available for RLVs. It is useful to begin with the current Space Shuttle TPS layout as a ...
Experiments on the onset of instability in unsteady circular Couette flow
Journal of Fluid Mechanics, 1985
ABSTRACT Thesis (M.S.)--Arizona State University, 1985. Vita. Includes bibliographical references... more ABSTRACT Thesis (M.S.)--Arizona State University, 1985. Vita. Includes bibliographical references (leaves [58]-60).
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Papers by Thomas Squire