Search

A supervised stochastic learning method called the Gaussian Process Regression (GPR) is used to design an autonomous guidance law for low-thrust spacecraft. The problems considered are both of the time- and fuel-optimal regimes and a methodology based on "perturbed back-propagation" approach is presented to generate optimal control along neighboring optimal trajectories which form the extremal bundle constituting the training data-set. The use of this methodology coupled with a GPR approximation of the spacecraft control via prediction of the costate n-tuple or the primer vector respectively for time- and fuel-optimal trajectories at discrete time-steps is demonstrated to be effective in designing an autonomous guidance law using the open-loop bundle of trajectories to-go. The methodology is applied to the Earth-3671 Dionysus time-optimal interplanetary transfer of a low-thrust spacecraft with off-nominal thruster performance and the resulting guidance law is evaluated under different design parameters using case-studies. The results highlight the utility and applicability of the proposed framework with scope for further improvements. [ABSTRACT FROM AUTHOR]

Impulsive trajectories provide time- and ΔV -reachability insights. Two novel homotopy-based methods are proposed for generating optimal many-impulse, multirevolution maneuvers. The first method is based on the continuation over the specific impulse value, which is shown to enhance convergence performance of the resulting two-point boundary-value problems. The second method is based on the formulation of impulsive trajectories using a linear acceleration term. The two methods are used in a hybrid framework. The utility of the proposed methods is demonstrated on four problems: Two interplanetary trajectories 1) from Earth to Mars, 2) from Earth to asteroid Dionysus, 3) a planet-centric transfer maneuver from a geostationary transfer orbit (GTO) to geostationary orbit (GEO) consisting of 21 revolutions, and 4) a 50-revolution transfer from the considered GTO to a circular orbit at the first Lagrange point (L1) of the Earth-moon system. The last two problems leading to 18 and 50 impulses are tackled to give an optimal near-impulsive solution. The impulsive solution with 18 impulses is shown to satisfy Lawden's conditions. [ABSTRACT FROM AUTHOR]

In this paper, we investigate the manifolds of three Near-Rectilinear Halo Orbits (NRHOs) and optimal low-thrust transfer trajectories using a high-fidelity dynamical model. Time- and fuel-optimal low-thrust transfers to (and from) these NRHOs are generated leveraging their 'invariant' manifolds, which serve as long terminal coast arcs. Analyses are performed to identify suitable manifold entry/exit conditions based on inclination and minimum distance from the Earth. The relative merits of the stable/unstable manifolds are studied with regard to time- and fuel-optimality criteria, for a set of representative low-thrust family of transfers. [ABSTRACT FROM AUTHOR]

In this work, end-to-end low-thrust transfers from a GTO orbit to a low-altitude lunar orbit by exploiting the manifolds of a chosen Earth–Moon L 1 halo orbit has been studied. The practicality of piece-wise, minimum-time transfers that exploit halo orbit manifolds is demonstrated, which offers more flexibility to meet mission objectives. It is known that the structure of the manifolds varies substantially due to the presence of the Sun and its contribution has to be considered to obtain more realistic trajectories. To incorporate Sun's perturbation, we study (1) manifolds' behavior within a Bi-Circular Problem (BCP) dynamics and (2) Sun's impact on the previously converged trajectories obtained using the standard Circular Restricted Three-Body Problem (CR3BP). Comparisons of the resulting trajectories using the CR3BP and BCP are presented. • Analyzed invariant manifolds in the CR3BP and BCP. • Methodology to analyze patch points on manifold for transfer trajectories. • Demonstrated feasibility of low-thrust transfer using invariant manifolds. • Designed Earth GTO to 1000 km circular lunar polar orbit via patching to manifolds. • Framework to merge periodic orbits and manifolds with indirect optimal control. [ABSTRACT FROM AUTHOR]