Multi-Objective Optimization of Planetary Entry Vehicle Heat Shields with Reentry Trajectory Analysis
- Paper number
IAC-07-C2.7.09
- Author
Mr. Joshua Johnson, University of Maryland, United States
- Coauthor
Dr. Ryan P. Starkey, University of Maryland, United States
- Coauthor
Dr. Mark J. Lewis, University of Maryland, United States
- Year
2007
- Abstract
This research seeks to answer a fundamental question regarding re-entry vehicles: are yesterday’s heat shield designs optimal for tomorrow’s space exploration missions? A planetary entry vehicle such as the 1960’s-era Apollo Command Module, transports a payload from space to a planetary surface. NASA’s Orion crew exploration vehicle will re-enter the Earth’s atmosphere on a lunar or Martian return traveling at high velocities ranging from 10 to 20 km/s, corresponding to Mach numbers ranging from 30 to 50. This requires the heat shield to survive temperatures as high as 1800+ K at the stagnation points. The heat shield is the primary geometry defining the vehicle’s hypersonic aerodynamics and heat transfer limits. Its design enables mission scenarios, protects human life, enhances mission success, and facilitates the expansion of space access. This research seeks to determine optimal blunt-body re-entry forms by performing a gradient-based optimization analysis of heat shield designs maximizing aerodynamic and heat transfer performance. The present work advances entry vehicle design by augmenting design choices to include non-spherical geometries and skip trajectories. Although spherical designs have been applied over the past forty years, including Apollo, Viking, and Mars Exploration Rover missions, their advantages over non-spherical designs are not well characterized. Furthermore, it is unknown whether spherical designs provide optimal aerodynamic and heat transfer performance. Considered base cross-sections include oblate and prolate ellipses, rounded-edge polygons, and rounded-edge concave polygons. Axial profiles consist of the spherical-segment, spherically-blunted cone, and power law. Heat shield geometries are rendered using the superellipse formula to tailor an axial profile to match a base cross-section. Lower-order computational methods have been implemented to determine the aerodynamics and aerothermodynamics, balancing the need for fidelity with the desire to have practical computational times for optimization. Models are based on modified Newtonian impact theory with semi-empirical heat transfer correlations. They have been validated against Apollo and Fire II flight tests to be within 12-percent for aerodynamic coefficients and stagnation-point heat fluxes. Allowing for both circular and supercircular entry, non-oscillatory and oscillatory-type trajectories are generated using Loh’s modified second-order solution. Multi-objective function forms include maximizing the lift-to-drag ratio and minimizing heat load concurrently. With the inclusion of trajectory modeling, the present optimization can also minimize stagnation-point heat load, minimize g-loads, and optimize bank angle for maximum cross-range or minimum heat flux. Pareto frontiers of non-dominated solutions provide optimal aerothermodynamic characteristics, and optimal designs possess oblate eccentricity to generate lift-to-drag values greater than one.- Abstract document
- Manuscript document
IAC-07-C2.7.09.pdf (🔒 authorized access only).
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