摘要 :
The preliminary feasibility of remote high-resolution infrared imagery of the Shuttle Orbiter lower surface during entry to obtain accurate measure¬ments of aerodynamic heat transfer to that vehicle has been examined. In general,...
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The preliminary feasibility of remote high-resolution infrared imagery of the Shuttle Orbiter lower surface during entry to obtain accurate measure¬ments of aerodynamic heat transfer to that vehicle has been examined. In general, it was determined that such images can be taken from an existing aircraft/telescope system (the C-141 AIRO) with a minimum modification or addition of systems using available technology. These images will have a spatial resolution of about 0.3 m and a temperature resolution much better than 2.5 percent. The data from these images will be at conditions and at a scale not reproducible in ground based facilities and should aid in the reduction of the prudent factors of safety required to account for phenomenological uncertainties on the thermal protection system design. Principal phenomena to be observed include laminar heating, boundary-layer transition, turbulent heating, surface catalysis, and flow separation and reattachment.
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Challenges to computational aerothermodynamic (CA) simulation and validation of hypersonic flow over planetary entry vehicles are discussed. Entry, descent, and landing (EDL) of high mass to Mars is a significant driver of new sim...
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Challenges to computational aerothermodynamic (CA) simulation and validation of hypersonic flow over planetary entry vehicles are discussed. Entry, descent, and landing (EDL) of high mass to Mars is a significant driver of new simulation requirements. These requirements include simulation of large deployable, flexible structures and interactions with reaction control system (RCS) and retro-thruster jets. Simulation of radiation and ablation coupled to the flow solver continues to be a high priority for planetary entry analyses, especially for return to Earth and outer planet missions. Three research areas addressing these challenges are emphasized. The first addresses the need to obtain accurate heating on unstructured tetrahedral grid systems to take advantage of flexibility in grid generation and grid adaptation. A multi- dimensional inviscid flux reconstruction algorithm is defined that is oriented with local flow topology as opposed to grid. The second addresses coupling of radiation and ablation to the hypersonic flow solver flight- and ground-based data are used to provide limited validation of these multi-physics simulations. The third addresses the challenges of retro-propulsion simulation and the criticality of grid adaptation in this application. The evolution of CA to become a tool for innovation of EDL systems requires a successful resolution of these challenges.
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The main premise driving our analysis of temperature data from a turbulentatmosphere is that it is a local power law process. This means that the power law itself the power (slope) and the multiplicative constant (log intercept) i...
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The main premise driving our analysis of temperature data from a turbulentatmosphere is that it is a local power law process. This means that the power law itself the power (slope) and the multiplicative constant (log intercept) is not a constant but a slowly varying function, deterministic or random. We estimate the slope and log intercept of the scale spectrum by appropriately segmenting the data and then removing segmentation effects by a filtering process. An important aspect of the model that we use is separation of scales in the variation of the estimate parameters (slope and log intercept) from the underlying process that generates the power law spectra. This will be the starting point for a detailed theoretical development of the methods that we have introduced here.
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Historically, the design of subsonic and supersonic aircraft has been divided into separate technical disciplines (such as propulsion, aerodynamics and structures) each of which performs their design and analysis in relative isola...
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Historically, the design of subsonic and supersonic aircraft has been divided into separate technical disciplines (such as propulsion, aerodynamics and structures) each of which performs their design and analysis in relative isolation from others. This is possible in most cases either because the amount of interdisciplinary coupling is minimal or because the interactions can be treated as linear. The design of hypersonic airbreathing vehicles, like NASA's X-43, is quite the opposite. Such systems are dominated by strong non-linear interactions between disciplines. The design of these systems demands that a multi-disciplinary approach be taken. Furthermore, increased analytical fidelity at the conceptual design phase is highly desirable as many of the non-linearities are not captured by lower fidelity tools. Only when these systems are designed from a true multi-disciplinary perspective can the real performance benefits be achieved and complete vehicle systems be fielded. Toward this end, the Vehicle Analysis Branch at NASA Langley Research Center has been developing the Integrated Design & Engineering Analysis (IDEA) Environment.
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A NASA team of engineers has been organized to design a crew return vehicle for returning International Space Station crew members from orbit. The hypersonic aerothermodynamic characteristics of the X-23/X-24A derived X-38 crew re...
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A NASA team of engineers has been organized to design a crew return vehicle for returning International Space Station crew members from orbit. The hypersonic aerothermodynamic characteristics of the X-23/X-24A derived X-38 crew return vehicle are being evaluated in various wind tunnels in support of this effort. Aerothermodynamic data from two NASA hypersonic tunnels at Mach 6 and Mach 10 has been obtained with cast ceramic models and a thermographic phosphorus digital imaging system. General windward surface heating features are described based on experimental surface heating images and surface oil flow patterns for the nominal hypersonic aerodynamic orientation. Body flap reattachment heating levels are examined. Computational Fluid Dynamics tools have been applied at the appropriate wind tunnel conditions to make comparisons with this data.
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A collaborative approach to software development is described. The approach employs the agile development techniques: project retrospectives, Scrum status meetings, and elements of Extreme Programming to efficiently develop a cohe...
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A collaborative approach to software development is described. The approach employs the agile development techniques: project retrospectives, Scrum status meetings, and elements of Extreme Programming to efficiently develop a cohesive and extensible software suite. The software product under development is a fluid dynamics simulator for performing aerodynamic and aerothermodynamic analysis and design. The functionality of the software product is achieved both through the merging, with substantial rewrite, of separate legacy codes and the authorship of new routines. Examples of rapid implementation of new functionality demonstrate the benefits obtained with this agile software development process. The appendix contains a discussion of coding issues encountered while porting legacy Fortran 77 code to Fortran 95, software design principles, and a Fortran 95 coding standard.
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A review of the experimental and computational studies performed at NASA Langley Research Center (LaRC) to support the optimization and benchmarking of the hypersonic aerodynamic and aerothermodynamic databases for the X-33 vehicl...
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A review of the experimental and computational studies performed at NASA Langley Research Center (LaRC) to support the optimization and benchmarking of the hypersonic aerodynamic and aerothermodynamic databases for the X-33 vehicle is presented. A synoptic of the testing, computational, and analysis capabilities at LaRC applied to these studies is given. Analyses of the hypersonic aerodynamic characteristics, control surface effectiveness, and reaction control system effects are discussed. Experimental measurement of the aerodynamic heating via the global thermographic phosphor technique and development of a hypersonic boundary-layer transition correlation for X-33 is described. Computational results used to complement the experimental program and to assess the vehicle aerodynamic and aerothermodynamic characteristics in flight are presented. The technical findings, impacts, and lessons learned from the studies are discussed.
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