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For direct reentry from a lunar or deep space mission, considerable variation in reentry plane, reentry point, and reentry angle must be anticipated. The returning vehicle must therefore, possess the ability to control its range after reentry in order to touch down in the desired recovery area. Recent studies have indicated that considerable ranging capability is available with even low lift-drag ratio vehicles operating wholly within the atmosphere if aerodynamic maneuvering is initiated while the vehicle still possesses greater than satellite velocity. In these studies, maneuvering was initiated shortly after the initial pull-up. Range control is also available during the initial pull-up, but such control results in little gain in longitudinal ranging capability in most cases. It is the purpose of the present thesis to investigate the feasibility of increasing lateral ranging capability by banking during the initial pull-up. Low lift-drag ratio vehicles reentering the atmosphere in a banked attitude are considered and the effects of such reentries on allowable corridor width, and lateral range capability are studied. Equations are developed for the motion of a vehicle reentering the atmosphere of a spherical, non-rotating earth, and some permissible approximations applicable for the present problems are discussed. Numerical results obtained for the developed system of equations through use of an IBM 7090 high-speed computer are used throughout the investigation to furnish accurate evaluations of the effects being studied and to check the validity of some of the approximations used. Particular emphasis is placed on reentry at escape velocity, but the effects determined apply in character to reentry at other supercircular velocities. / Master of Science

Supersonic deceleration has been identified as a critical deficiency in extending heritage technologies to the high-mass systems required to achieve long-term exploration goals at Mars. Supersonic retropropulsion (SRP), or the use of retropropulsive thrust while an entry vehicle is traveling at supersonic conditions, is an approach addressing this deficiency. The focus of this dissertation is aerodynamic and performance evaluation of SRP as a decelerator technology for high-mass Mars entry systems. This evaluation was completed through a detailed SRP performance analysis, establishment of the relationship between vehicle performance and the aerodynamic-propulsive interaction, and an assessment of the required fidelity and computational cost in simulating SRP flowfields, with emphasis on the effort required in conceptual design. Trajectory optimization, high-fidelity computational aerodynamic analysis, and analytical modeling of the SRP aerodynamic-propulsive interaction were used to define the fidelity and effort required to evaluate individual SRP concepts across multiple mission scales.

The reconstruction of entry, descent and landing (EDL) trajectories is significantly affected by the knowledge of the atmospheric conditions during flight. Away from Earth, this knowledge is generally characterized by a high degree of uncertainty, which drives the accuracy of many important atmosphere-relative states. One method of obtaining the in-flight atmospheric properties during EDL is to utilize the known vehicle aerodynamics in deriving the trajectory parameters. This is the approach taken by this research in developing a methodology for accurate estimation of ambient atmospheric conditions and atmosphere-relative states. The method, referred to as the aerodynamic database (ADB) reconstruction, performs reconstruction by leveraging data from flight measurements and pre-flight models. In addition to the estimation algorithm, an uncertainty assessment for the ADB reconstruction method is developed. This uncertainty assessment is a unique application of a fundamental analysis technique that applies linear covariance mapping to transform input variances into output uncertainties. The ADB reconstruction is applied to a previous mission in order to demonstrate its capability and accuracy. Flight data from the Mars Science Laboratory (MSL) EDL, having successfully completed on August 5th 2012, is used for this purpose. Comparisons of the estimated states are made against alternate reconstruction approaches to understand the advantages and limitations of the ADB reconstruction. This thesis presents a method of reconstruction for EDL systems that can be used as a valuable tool for planetary entry analysis.

A numerical method has been developed to predict the three-dimensional nonequilibrium flowfield past the space shuttle orbiter at high angles-of-attack (up to 50-deg). An existing viscous shock-layer method for perfect gas flows has been extended to include finite-rate chemical reactions of multi-component ionizing air. A general nonorthogonal computational grid system was introduced to treat the nonaxisymmetric geometry. At shuttle reentry flight conditions, nonequilibrium real gas effects on the surface-measurable quantities are significant. Computational solutions have been obtained for chemically reacting flowfields over the entire windward surface of the space shuttle orbiter at high angles-of-attack. Boundary conditions studied include noncatalytic wall, finite-catalytic wall, fully-catalytic wall, and nonequilibrium slip conditions at the wall and/or shock. The nonequilibrium solutions with a finite-catalytic wall are compared to both fully-catalytic and noncatalytic wall solutions. The present solutions are also compared to chemical equilibrium air solutions, perfect gas solutions, and the shuttle flight heating and pressure data. The comparisons show good agreement and correlations with flight-derived surface heat-transfer and pressure distributions. Three-dimensional effects are clearly shown in the flight-derived data for the first time based upon the results of this study. / Ph. D.

The present study was undertaken to determine the effects of the aerodynamics on a close earth orbit and reentry trajectory. The aerodynamic influence is compared to the effects of the earth’s oblateness, the sun, and the moon. In order to obtain maximum accuracy and computational speed Encke’s perturbative procedures were used during orbital periods and Cowell’s integration procedures during thrust and reentry periods. / M.S.

A computer program for predicting the three-dimensional nonequilibrium viscous shock-layer flows over blunt spherecones, straight. and bent mul ticonics at angle-of-attack has been developed. The method used is the viscous shock-layer approach- for nonequilibrium, multi-component ionizing air. A seven species chemical reaction model with single ionizing species and an eleven species chemical reaction model with five ionizing species are used to represent the chemistry. The seven species model considers 7 reactions whereas the eleven species model considers 26 reactions and the results obtained using these models are compared with perfect gas and equilibrium air results. This code is capable of analyzing shock-slip or no-shock-slip boundary conditions and equilibrium or non-catalytic wall boundary conditions. In this study the diffusion model is limited to binary diffusion. A sphere-cone-cylinder-flare with moderate flare angle, a straight biconic, and a bent biconic with seven deg. bend angle and a sphere-cone at various flight conditions are analyzed using this method. The bent biconic has been analyzed up to an angle-of-attack of 20 deg. with respect to the aft-cone axis and sample results are compared with inviscid and viscous results. The surface pressure distribution computed by this code compares well with that from a parabolized Navier-Stokes method. The diffusion heat transfer is about 15% of the total heat transfer for most cases. The aerodynamic forces and moments at the base of the body and computing time required for all cases are presented. The shock layer profiles at a streamwi se location of 8. 8 nose radii for one case computed using seven and eleven species models compare very well with each other. / Ph. D.

High Mach number, low-Reynolds number (high-altitude) reentry flowfield predictions are an important problem area in computational aerothermodynamics. Available numerical tools for handling such flows are very few and significantly limited in their applicability. A new implicit fully-iterative Parabolized Navier-Stokes (PNS) scheme is developed to accurately predict such low-Reynolds number flows. In this new approach the differential equations governing the conservation of mass, momentum and energy, and the algebraic equation of state for a perfect gas are solved simultaneously in a coupled manner. The idea is presented that by treating the governing equations in this manner (rather than eliminating the pressure terms in the governing equations by using appropriate differentiated forms of the equation of state) it may be possible to have an unconditionally time-like numerical scheme. The stability of a simplified version of this new PNS scheme is also studied, and it is demonstrated that these simplified equations are unconditionally time-like in the subsonic as well as the supersonic flow regions. A pseudo-time integration approach is used in addition to a new second-order accurate fully-implicit smoothing, to improve the efficiency of the solution algorithm. The new PNS scheme is used to predict the flowfield around a seven-deg sphere-cone vehicle under high- and low-Reynolds number conditions. Two test case, Case A and Case B, are chosen such that Case A has a large freestream Reynolds number (2.92x10⁵), whereas Case B has a freestream Reynolds number of 1.72x10³, which is smaller than the usual limit of applicability of the non-iterative PNS schemes (Re~10⁴ or larger). Comparisons are made with other available numerical schemes, and the results substantiate the stability, accuracy and efficiency claims of the new Parabolized Navier-Stokes scheme. / Ph. D.