Preliminary capture trajectory design for Europa tomography probe

The objective of this work is the preliminary design of a low-DV transfer from an initial elliptical orbit around Jupiter into a final circular orbit around the moon Europa. This type of trajectory represents an excellent opportunity for a low-cost mission to Europa, accomplished through a small orbiter, as in the proposed Europa Tomography Probe mission, a European contribution to NASA’s Europa Multiple-Flyby Mission (or Europa Clipper). The mission strategy is based on the v-infinity leveraging concept, and the use of resonant orbits to exploit multiple gravity-assist from the moon. Possible sequences of resonant orbits are selected with the help of the Tisserand graph. Suitable trajectories are provided by an optimization code based on the parallel running of several differential evolution algorithms. Different solutions are finally compared in terms of propellant consumption and flight time

Spacecraft dynamics under the action of Y-dot magnetic control law

The paper investigates the dynamic behavior of a spacecraft when a single magnetic torque-rod is used for achieving a pure spin condition by means of the so-called Y-dot control law. Global asymptotic convergence to a pure spin condition is proven on analytical grounds when the dipole moment is proportional to the rate of variation of the component of the magnetic field along the desired spin axis. Convergence of the spin axis towards the orbit normal is then explained by estimating the average magnetic control torque over one orbit. The validity of the analytical results, based on some simplifying assumptions and approximations, is finally investigated by means of numerical simulation for a fully non-linear attitude dynamic model, featuring a tilted dipole model for Earth׳s magnetic field. The analysis aims to support, in the framework of a sound mathematical basis, the development of effective control laws in realistic mission scenarios. Results are presented and discussed for relevant test cases

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

Evolutionary Optimization for Active Debris Removal Mission Planning

Active debris removal missions require an accurate planning for maximizing mission payout, by reaching the maximum number of potential orbiting targets in a given region of space. Such a problem is known to be computationally demanding and the present paper provides a technique for preliminary mission planning based on a novel evolutionary optimization algorithm, which identifies the best sequence of debris to be captured and/or deorbited. A permutation-based encoding is introduced, which may handle multiple spacecraft trajectories. An original archipelago structure is also adopted for improving algorithm capabilities to explore the search space. As a further contribution, several crossover and mutation operators and migration schemes are tested in order to identify the best set of algorithm parameters for the considered class of optimization problems. The algorithm is numerically tested for a fictitious cloud of debris in the neighborhood of Sun-synchronous orbits, including cases with multiple chasers