Studies in the Fields of Space Flight and Guidance Theory

Compiled in this paper are 11 progress papers from 7 of the agencies working under contract to MSFC in the areas of guidance theory and space flight theory. This is the second paper of the "Progress Reports" and covers the period from December 1, 1961 to June 15, 1962. Extensive references are made to "Progress Report No. 1." This second progress report is referred to as "report" and "Progress Report No. 1" will be referred to as the "first report" in this introduction. Information given in the first report is not repeated herein. The reports of the various contractors will be referred to by index number as papers. There are two parallel series of publications covering the over-all activities at MSFC in the areas of guidance theory and space flight theory. One is the series of progress reports of which this paper is the second in the series. The other is the series of "Status Reports on Theory of Space Flight and Adaptive Guidance." These series along with a few other special reports, give a complete picture of the immediate objectives, accomplishments, and final goals of Aeroballistics Division and associated cont

Numerical Solution of Optimal Control Problems with Explicit and Implicit Switches

This dissertation deals with the efficient numerical solution of switched optimal control problems whose dynamics may coincidentally be affected by both explicit and implicit switches. A framework is being developed for this purpose, in which both problem classes are uniformly converted into a mixed–integer optimal control problem with combinatorial constraints. Recent research results relate this problem class to a continuous optimal control problem with vanishing constraints, which in turn represents a considerable subclass of an optimal control problem with equilibrium constraints. In this thesis, this connection forms the foundation for a numerical treatment. We employ numerical algorithms that are based on a direct collocation approach and require, in particular, a highly accurate determination of the switching structure of the original problem. Due to the fact that the switching structure is a priori unknown in general, our approach aims to identify it successively. During this process, a sequence of nonlinear programs, which are derived by applying discretization schemes to optimal control problems, is solved approximatively. After each iteration, the discretization grid is updated according to the currently estimated switching structure. Besides a precise determination of the switching structure, it is of central importance to estimate the global error that occurs when optimal control problems are solved numerically. Again, we focus on certain direct collocation discretization schemes and analyze error contributions of individual discretization intervals. For this purpose, we exploit a relationship between discrete adjoints and the Lagrange multipliers associated with those nonlinear programs that arise from the collocation transcription process. This relationship can be derived with the help of a functional analytic framework and by interrelating collocation methods and Petrov–Galerkin finite element methods. In analogy to the dual-weighted residual methodology for Galerkin methods, which is well–known in the partial differential equation community, we then derive goal–oriented global error estimators. Based on those error estimators, we present mesh refinement strategies that allow for an equilibration and an efficient reduction of the global error. In doing so we note that the grid adaption processes with respect to both switching structure detection and global error reduction get along with each other. This allows us to distill an iterative solution framework. Usually, individual state and control components have the same polynomial degree if they originate from a collocation discretization scheme. Due to the special role which some control components have in the proposed solution framework it is desirable to allow varying polynomial degrees. This results in implementation problems, which can be solved by means of clever structure exploitation techniques and a suitable permutation of variables and equations. The resulting algorithm was developed in parallel to this work and implemented in a software package. The presented methods are implemented and evaluated on the basis of several benchmark problems. Furthermore, their applicability and efficiency is demonstrated. With regard to a future embedding of the described methods in an online optimal control context and the associated real-time requirements, an extension of the well–known multi–level iteration schemes is proposed. This approach is based on the trapezoidal rule and, compared to a full evaluation of the involved Jacobians, it significantly reduces the computational costs in case of sparse data matrices

Time optimal control of a dissipative two level quantum system

In this thesis we investigate the controlled (coherent, i.e. without feedback from measurements) dynamics of a dissipative two-level quantum system subject to Generalized Amplitude Damping in the Markovian approximation. Our goal is to accelerate the relaxation of the system, starting from a state ``more pure'' than the fixed point. Roughly speaking, we want to speed up the heating of the system, when its initial state is colder than the bath. This problem may be of fundamental importance in quantum information and computation , where the two-level system play plays the role of qubit, the basic unit of information in quantum computation

Optimal manoeuvres and aeroservoelastic co-design of very flexible wings

The single shooting method is applied to the optimal control of very flexible aeroelastic wings and the combined structural and control design (co-design) of geometrically nonlinear beam models in vacuum. As large deflections occur, the dynamical properties of these systems can undergo substantial changes. Efficient actuation strategies require characterising, and possibly exploiting, these phenomena. With this purpose, geometrically-nonlinear models are built using composite beams and an unsteady vortex-lattice aerodynamics description. Optimal control is employed to identify actuations time-histories. Numerical solutions are obtained via single-shooting and sequential quadratic programming upon parametrisation of the control input. The approach is also extended to assess the feasibility of an integrated design strategy for active geometrically-nonlinear structures. Numerical studies are first presented for a very flexible actuated pendulum with large rigid-body motion. The impact of local (B-splines) and global (discrete sines) basis functions is investigated for increasing levels of actuation authority, underlining the importance of the time-frequency resolution of the parametrisation on the convergence properties and outcome quality of the process. Locking between control and structural vibrations around specific design points is found, thus highlighting the limitations of a sequential design approach. Simultaneous designing of control law and structure is seen, instead, to explore more efficiently larger portions of the design space. The lateral manoeuvring of very flexible partially-supported wings is then considered. A flight-dynamics model based on elastified stability derivatives is shown to capture the relevant dynamics either under slow actuation or for stiff wings, and it is hence used as a reference. Embedding the full aeroelastic description into the optimisation framework expands the space of achievable manoeuvres, allowing for quick wing response with low structural vibrations or large lateral forces with minimal lift losses.Open Acces

Mathematical Optimization Techniques

The papers collected in this volume were presented at the Symposium on Mathematical Optimization Techniques held in the Santa Monica Civic Auditorium, Santa Monica, California, on October 18-20, 1960. The objective of the symposium was to bring together, for the purpose of mutual education, mathematicians, scientists, and engineers interested in modern optimization techniques. Some 250 persons attended. The techniques discussed included recent developments in linear, integer, convex, and dynamic programming as well as the variational processes surrounding optimal guidance, flight trajectories, statistical decisions, structural configurations, and adaptive control systems. The symposium was sponsored jointly by the University of California, with assistance from the National Science Foundation, the Office of Naval Research, the National Aeronautics and Space Administration, and The RAND Corporation, through Air Force Project RAND

Numerical methods for low-thrust trajectory optimization

The spacecraft trajectory design process frequently includes the optimization of a quantity of importance such as propellant consumption or time of flight. A variety of methods for trajectory optimization are available, however the efficiency of an approach is dependent on the problem scenario it is applied to. Indirect and direct trajectory optimization methods are examined in this investigation with the goal of assessing the characteristics of each approach, and thereby determining the problem scenarios each is best suited for. Insight is gained from application of each optimization method to three sample problems; a circular-to-circular orbit transfer as well as two variants of a halo-to-halo orbit transfer, one that leverages manifold arcs and one that does not. The analytical theory underlying indirect optimization methods is presented as is the adjoint control transformation for determining initial costate values. Results from application of the indirect optimization approach to each of the sample problems are offered. The framework of a direct optimization scheme employing collocation is described including a mesh refinement process based on the de Boor update method. The direct optimization method is applied to the three sample problems and results are supplied. Quantitative comparisons of the results of the optimization methods are made based on the categories of accuracy, robustness, and efficiency. Findings from quantitative and qualitative comparisons of the optimization methods are employed to formulate guidelines on the problem scenarios each technique is most applicable to

Indirect Optimization of Bang-Bang Control Problems and Applications to Formation Flying Missions

This thesis is focused on indirect optimization methods for the design of space missions, and, in particular, to a specific class of optimal control problems whose solution exhibits a discontinuous control law: the so called bang-bang optimal control. Any attempt to solving such problems by using an indirect method without any specific treatment of the bang-bang control inevitably results into a failure, except for trivial problems. The thesis compares two techniques, conceptually quite different, that aim to handle (or just to reduce) issues related to the discontinuous profile of the optimal control: the Multi-Bound Approach and the Continuation-Smoothing Technique. These two approaches are first tried out/tested on a very simple case (the rocket-sled problem) and then applied to obtain the solution of two rather complex problems: the cooperative rendezvous and the deployment of a two-spacecraft formation that flies in a High Eccentricity Orbit (referring to the Simbol-X project). The general philosophy that stands behind either approach is outlined, as well as relative strength and weakness. Range of applicability, effort required to the user, computational time, and convergence radius are analyzed and discussed

Indirect Optimization of Bang-Bang Control Problems and Applications to Formation Flying Missions

This thesis is focused on indirect optimization methods for the design of space missions, and, in particular, to a specific class of optimal control problems whose solution exhibits a discontinuous control law: the so called bang-bang optimal control. Any attempt to solving such problems by using an indirect method without any specific treatment of the bang-bang control inevitably results into a failure, except for trivial problems. The thesis compares two techniques, conceptually quite different, that aim to handle (or just to reduce) issues related to the discontinuous profile of the optimal control: the Multi-Bound Approach and the Continuation-Smoothing Technique. These two approaches are first tried out/tested on a very simple case (the rocket-sled problem) and then applied to obtain the solution of two rather complex problems: the cooperative rendezvous and the deployment of a two-spacecraft formation that flies in a High Eccentricity Orbit (referring to the Simbol-X project). The general philosophy that stands behind either approach is outlined, as well as relative strength and weakness. Range of applicability, effort required to the user, computational time, and convergence radius are analyzed and discussed

Lectures in Applied Mathematics. Volume VI - Space Mathematics, Part 2

Applied mathematics in celestial mechanics - theory of librational motions, earth shape, and satellite orbit calculation

Multiobjective Problems of Mathematical Programming; Proceedings of an International Conference, Yalta, USSR, October 26 - November 2, 1988

IIASA's approach to research in Multiple Objective Decision Support, Multiple Criteria Optimization (MCO) and related topics assumes a high level of synergy between three main components: methodological and theoretical backgrounds, computer implementation and decision support systems and real life applications. This synergy is reflected in the subjects of papers presented at the Conference as well as in the structure of the Proceedings which is divided into three main sections. In the first section, "Theory and Methodology of Multiple Criteria Optimization," 21 papers discussing new theoretical developments in MCO are presented. The second section, "Applications of Multiple Criteria Optimization, " contains nine papers dealing with real-life applications of MCO. Five papers on the application of MCO in the development of Decision Support Systems are included in the final section, "Multiple Criteria Decision Support." Among the important outcomes of this Conference were conclusions regarding further directions of research for Multiple Criteria Optimization, in particular, in the context of cooperation between scientists from Eastern and Western countries