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Fast-Running Physics-Based Models for Intercept Debris Aero-heating and Aero-thermal Demise


OBJECTIVE: Develop an approach for assessing the aero-thermal demise of the debris generated following a ballistic missile defense intercept DESCRIPTION: The intercept of a ballistic missile at high altitudes generates thousands of debris fragments, ranging in size from less than a millimeter to tens of centimeters. These pieces typically re-enter the atmosphere, and may or may not burn up before they strike the Earth. Assessment of this aero-thermal demise phenomenon can thus have a significant effect on sensor performance (discrimination, tracking, sensor loading, etc), particularly for lower-tier elements, consequences of intercept, as well as range safety issues for flight tests. Whether or not a particular fragment survives re-entry depends on a variety of factors, including the fragment (linear and angular) velocity just after intercept, the aerodynamic characteristics of the fragment, and the fragment material. The aerodynamic characteristics, in turn, are strongly coupled to the trajectory described by the fragment after the intercept. Most of these fragments are highly irregular in shape; therefore, simple analytical models are likely insufficient to predict the aerodynamic heating they experience. First-principles numerical techniques, such as computational fluid dynamics (CFD), could in theory be used to predict the aero-thermodynamic environment around each fragment. However, the time required per fragment for CFD grid generation and trajectory-coupled flow solution, combined with the large number of fragments associated with a single intercept, makes a"full-blown"CFD approach an impractical choice for supporting consequence management, scenario planning, and other high-level assessment functions. In light of the above observations, an approach is desired that incorporates a physics-based aerodynamic heating methodology into an aerodynamic trajectory framework capable of producing rapid predictions for large debris sets. The desired methodology must meet a number of requirements: (1) it must utilize realistic debris geometry, and not be restricted to simple geometric constructions; (2) it must be compatible with existing tools for debris generation and debris propagation; (3) it must be capable of extension to coupled phenomena such as surface recession; (4) it must be applicable to the full range of altitude and velocity regimes experienced during debris fly-down, from rarefied hypersonic to continuum supersonic/subsonic; (5) it must benchmarked using existing test data. PHASE I: Formulate an approach for predicting intercept debris aerodynamic heating and break-up that meets the requirements listed above. Perform proof-of-principle calculations using this approach for simple shapes, such as spheres and flat plates. Compare these predictions to high-fidelity results, theory, and/or test data. PHASE II: Perform further demonstration of the methodology proposed in Phase I through application to arbitrary fragment geometries. These results may be validated through comparison to test data (if available) or body-fitted CFD results. Integrate the validated aero-thermal analysis approach into an existing tool for intercept debris propagation, and apply it to a representative set of realistic debris. This debris set will be supplied from a high-fidelity finite-element calculation of a BMD engagement or flight test event. PHASE III: Extend and enhance the combined algorithm so that it can be used to provide more accurate debris footprints for a variety of BMDS functions. These would include debris mitigation measures for lower-tier elements, general consequence management and flight test range safety. COMMERCIALIZATION: Benefits to DoD, NASA, the commercial launch industry to understand if failed launches, or range safety launches, or re-entering orbital platforms will be a threat to air and ground based assets.
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