ETD

• cambiamento climatico
• climate change
• eliogiro
• four body problem
• heliogyro
• ottimizzazione di traiettoria
• planetary sunshade
• problema dei 4 corpi
• problema dei tre corpi
• solar sail
• three body problem
• trajectory optimization
• vela solare

Solar radiation management through space-based sunshades has been proposed as a potential contribution to long-term climate mitigation strategies. However, the feasibility of such large-scale space system, in terms of design, manufacturing, and control remains a challenge. The Planetary Sunshade Foundation (PSF) proposes to use heliogyro solar sails, positioned near the L1 Lagrangian point in the Sun-Earth system (SEL1), to reflect part of the solar radiation directed to the Earth.
The heliogyro architecture consists of a spinning hub with radial reflective blades, which can be individually controlled in pitch. This enables more controllability over a square sail, but at the same time a more challenging control system due to many degrees of freedom and rotational dynamics.
One of PSF proposals is to manufacture the heliogyros in space, near the Earth-Moon L4/L5 Lagrangian points, partly using material extracted from the lunar regolith. The heliogyros will then be transferred to their operational location at SEL1.
The study focuses on the design of heliogyro transfers from the EM system to sub-SEL1. First, we develop a dynamical model of the heliogyro in four-body solar-gravitational environment. In particular, solar radiation pressure forces and torques are quantified as a function of blade pitch and solar distance, and sub-SEL1 solar-gravitational equilibrium points are identified.
Then, we generate purely ballistic transfers by propagating families of trajectories backward from the operational location (in the Sun-Earth 3BP) and forward from the starting location (in the Sun-Earth-Moon 4BP), patching them at an appropriately-selected Poincaré section. This results in a small Δv to be applied at either end, and at the patching point. These trajectories serve as initial guesses for a set of final trajectories, which incorporate the thrust generated by a controlled heliogyro in the dynamical model.