One of several schemes can be chosen from the user interface to calculate inviscid fluxes across cell faces while central differences schemes are used to calculate the viscous fluxes. The flow domain is discretized by a structured grid and a finite-volume approach is used to discretize the conservation equations. Zero, one and two equation turbulence models have been implemented in the solver for turbulence modeling. Finite-rate reaction kinetics, thermal and chemical non-equilibrium and high temperature transport coefficients are all developed and incorporated into the solver. The flow solver is graphical user interface driven and platform independent as well. Sparta is a three-dimensional finite volume compressible Java based flow solver on multiple block structured grids. The eventual goal is the development of a rigorous link between TPS thermal margin process and the corresponding contribution to the overall heatshield reliability. This process is still a work in progress, and the paper discusses some of the key elements of it, along with potential ways by which the overall methodology could be improved. Examples of the application of this probabilistic process are given for Mars Pathfinder, Stardust, and the Mars Science Laboratory. The process is very data-dependent, and requires validation via a carefully crafted and executed test program including both ground and flight data. The current paper first reviews the history of margin application for several prior NASA missions ranging from Apollo to the Mars Exploration Rovers, then discusses a new probabilistic margin process, which was developed for the Mars Science Laboratory and Orion programs. Over the past several years, NASA has explored a more methodical technique through the application of statistically derived factors to various elements of the design. ![]() With the development of the human space vehicles presently underway, along with NASA’s return to a capsule concept for spaceflight, it may be more important than ever to record this history to help inform the NASA team of what has gone before and the lessons they may learn from those earlier efforts.Īfter over 50 years of spaceflight, the calculation of the necessary margin on the thermal protection system of an entering spacecraft remains a largely ad-hoc (in a tactical sense) process governed by engineering judgment. Moreover, the challenges, mystery, and outcomes wrestled with by those in programs that required safe reentry and return to Earth offer object lessons in how earlier generations of engineers sought optimal solutions and made trade-offs. Bits and pieces of this history exist in various disparate publications, but the critical role played by the researchers in developing the concepts that made possible a return to Earth have been generally overlooked. It is time that this important story is told in a compelling, sophisticated, and technically sound manner for a general audience. Rogallo at Langley developed creative parasail concepts that informed the development of the recovery systems of numerous reentry vehicles. Eggers at Ames pioneered blunt body reentry techniques and ablative thermal protection systems in the 1950s, while Francis M. ![]() This story extends back at least to the work of Walter Hohmann and Eugen Sänger in Germany in the 1920s and involved numerous NACA and NASA engineers at the Langley, Lewis, and Ames laboratories. ![]() Accordingly, this case study is intended as a means of highlighting the myriad technological developments that made possible the safe reentry and return from space and landing on Earth. Without this base of fundamental and applied research the capability to fly into space would not exist. Coming home after a flight into space is fundamentally a challenge that has involved over the years critical contributions from engineers working in aerodynamics, thermal protection, guidance and control, stability, propulsion, and landing systems. One of the most difficult tasks with which NASA has had to deal is how its space systems operate while transiting the atmosphere as they return to Earth.
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