Giorgio Mingotti

Optimal Low-Thrust Invariant Manifold Trajectories via Attainable Sets

A method to incorporate low-thrust propulsion into the invariant manifolds technique is presented in this paper. The low-thrust propulsion is introduced by means of special attainable sets that are used in conjunction with invariant manifolds to define a first-guess solution. This is later optimized in a more refined model where an optimal control formalism is used. Planar low-energy low-thrust transfers to the moon, as well as spatial low-thrust stable manifold transfers to halo orbits in the Earth–moon system, are presented. These solutions are not achievable via patched-conics methods or standard invariant manifolds techniques. The aim of the work is to demonstrate the usefulness of the proposed method in delivering efficient solutions, which are compared with known examples.

Optimal on-off cooperative manoeuvers for long-term satellite cluster flight

When a group of satellites is equipped with a particularly simple propulsion system (e.g., cold-gas thrusters), constraints on the thrust level and total propellant mass renders cluster keeping extremely challenging. This is even more pronounced in disaggregated space architectures, in which a satellite is formed by clustering a number of heterogonous free-flying modules. The research described in this paper develops guidance laws aimed at keeping the relative distances between the cluster modules bounded for long mission lifetimes, typically more than a year, while using constant-magnitude low thrust, with a characteristic on–off profile. A cooperative guidance law capable of cluster establishment and maintenance under realistic environmental perturbations is developed. The guidance law is optimized for fuel consumption, subject to relative distance constraints. Some of the solutions found to the optimal guidance problem require only a single maneuver arc to keep the cluster within relatively close dista...

Continuous-Thrust Cooperative Guidance Law for Disaggregated Satellites

The basic idea behind disaggregated satellites is to distribute the functionality of a single monolithic satellite among multiple physically-separated inter-communicating modules. The research described in this paper develops optimal guidance laws aimed at keeping the relative distances between the modules bounded for extended mission lifetimes while using constant-magnitude chemical low-thrust. A cooperative guidance law capable of cluster establishment and maintenance under environmental perturbations is proposed. The optimal guidance law is constructed using a bang-off-bang thrust profile. The cost functional is the total fuel consumption, and the constraints are maximum and minimum distances, balanced fuel utilization – so as to minimize differential drag – and stationkeeping about a nominal reference orbit.

A method to design efficient low-energy, low-thrust transfers to the Moon

In this work the novel technique of low-energy, low-thrust transfers is presented. These kind of orbits are used to design efficient Earth-to-Moon transfers requiring moderate time-of-flight and much less propellant than both classic patched-conics and low-energy solutions. The idea consists of merging notions of dynamical system theory with concepts of optimal control theory to combine the benefits coming from each area. A portion of trajectory recalls the exterior Earth–Moon transfer performing ballistic capture at the Moon. This is defined using the coupled restricted three-body problem approximation and invariant manifolds in the Sun–Earth problem. The low-thrust portion is instead handled by defining special attainable sets that mimic the role of invariant manifolds in propelled orbits. Attainable sets and invariant manifolds are combined together to define good first guess solutions which are later optimized in a four-body system under the formalism of optimal control problems. A new model, introducing the perturbation of the Moon in the Sun–Earth system is presented. This model allows us to consider lunar gravity assist at departure to further lower the propellant mass spent. Both high- and low-thrust solutions are presented and compared to the ones known literature.

Low-energy Earth-to-halo transfers in the Earth Moon scenario with Sun-perturbation

In this work, trajectories connecting LEOs with halos around libration points of the Earth–Moon CRTBP are investigated. Suitable first guess solutions are searched linking together the stable manifolds of the halo orbits (of the EM spatial CRTBP) with the Earth-departing trajectories (built in the SE planar CRTBP). As a first step, small discontinuities, in terms of Δv are allowed and bounded through the box-covering approach, implemented with the software GAIO. Then, the first guess solutions are optimized in the bicircular four-body problem: single-impulse and two-impulse transfers are presented and discussed.