Doubling Sunlight for a Human Mars Base With Orbiting Solar Reflectors
The Sun's faintness at Mars' orbit makes producing energy, melting ice, and staying warm more difficult. Orbiting solar reflectors (OSRs) can augment sunlight at Mars, but the area of OSRs needed to double sunlight at a Mars base is not known. Here, we analyze Sun-synchronous Mars orbits to find the OSR area that doubles insolation to a Mars base. We show that the reflectors can deliver sunlight and maintain a stable orbit via attitude control and solar-sail propulsion, with no propellant. We also show that these Mars orbits can be reached via solar sailing from low Earth orbit, reducing delivery cost. Doubling sunlight is viable with an orbiting solar reflector areal density of $20 {\rm g/m^2}$, a 7-fold improvement over flight-proven solar sails. However, designing a spacecraft with low areal density, agile maneuverability (for accurate pointing), high tension in the sail membrane (to smooth wrinkles), and mass-manufacturability (to enable a constellation of reflectors) would be challenging. Still lower areal density of $<5 {\rm g/m^2}$ would be needed for more ambitious applications, such as sublimating the CO$_2$ ice at Mars' south pole to aid in terraforming.