Title: Aero-thermal Demise of Reentry Debris: A Computational Model
Author: Troy Owens
Major Advisor: Daniel R. Kirk, Ph.D.
The modeling of fragment debris impact is an important part of any space mission. Planned debris or failure at launch and reentry need to be modeled to understand the hazards to property and populations. With more accurate impact predictions, a greater confidence can be used to close areas for protection and generate destruct criteria for space vehicles. One aspect of impact prediction that is especially difficult to simulate in a simple yet accurate way is the aero-thermal demise of reentry debris. This thesis will attempt to address the problem by using a simple set of inputs and combining models for the earth, atmosphere, impact integration and stagnation-point heating.
Current tools for analyzing reentry demise are either too simplistic or too complex for use in range safety analysis. NASA’s Debris Assessment Software 2.0 (DAS 2.0) has simple inputs that a range safety analyst would understand, but only gives the demise altitude as output and no ability to specify breakup conditions. Object Reentry Survival Analysis Tool (ORSAT), the standard for reentry demise analysis, requires inputs that only the vehicle manufacturer knows and a trained operator. The output from ORSAT gives a full range of fragment properties and for numerous breakup conditions. This thesis details a computational model with simple inputs like DAS 2.0, but an output closer to that of ORSAT, that will be useful in many mission risk analysis scenarios.
This is achieved by using 1) WGS 84, a fourth order spherical harmonic model of the earth’s surface and gravity; 2) the 1976 U.S. Standard Atmosphere; 3) an impact integrator for a spherical rotating earth; and 4) a stagnation-point heating correlation based on the Fay-Riddell theory.