Realistic sunshade system at L1 for global temperature control

So far, space-based geoengineering has rarely been studied from a practical point of view, considered unrealistic as a near-future alternative to fight climate change. This paper evaluates the feasibility of implementing a space sunshade in the vicinity of the first Lagrange point of the Sun-Earth system by the middle of the century. The analysis considers the necessary technological development, the possible trajectories for the shades, and an approximation of the size and cost of the system. It is strongly dependent on the possible optical properties of future solar sails, so an optimal and a more conservative alternative have been studied. With the latter, the shade will be formed by 1.5 × 109 sailcraft with a sail area of 2500 m2 and a total mass of 8.3 × 1010 kg. In the optimal case, the total mass is 3.4 × 1010 kg. Each one of these sails will be launched to a 2000 km orbit, from where they will travel for about 600 days to the equilibrium point using solar radiation pressure. The total cost of the mission is estimated to be five to ten trillion dollars, based on a launch cost of US$50/kg. There are two main technological challenges for this to become a reality: the low TRL of the solar sails proposed and the necessary development in the launch vehicle industry given the dimensions of the mission.