Chapter 7

On Sol 63, Watney shifts to a long-term plan: reaching the Ares 4 MAV at Schiaparelli, 3,200 km away. He targets Rover 2 as a mobile Hab, focusing first on power. He calculates range with doubled batteries and no heater, estimating 90 km per full charge on flat ground, and plans to recharge using 14 solar panels carried on the roof.

On Sol 64, he removes Rover 1’s battery but finds no space to mount it. He fabricates external “saddlebags” from spare Hab canvas and resin, hoists the battery, and decides to swap cables manually between batteries as needed. On Sol 65, he relocates and secures the solar panels in two roof stacks, then harvests and reseeds his flourishing potatoes.

He begins “Sirius” rover tests. Sirius 1 (Sol 67) is aborted after an hour when disabling the heater leads to dangerous cabin cold. Seeking heat without draining power, he decides to use the RTG. On Sol 69, he retrieves the buried RTG four kilometers south (marked by Lewis’s green flag), confirms it provides ample heat, and tears out rover insulation until the RTG can maintain near-comfortable temperatures with brief heater assists.

On Sol 70, Sirius 3 validates the setup: he drives 81 km in 3 hours 27 minutes using two batteries, then recharges in 12 hours aided by the RTG’s 100-watt output. On Sol 71, he plans Sirius 4, a 20-day field test. He extends oxygen supply by bringing a Hab liquid O2 tank, relies on CO2 filters instead of the oxygenator, and arranges the Hab to sustain potatoes by saturating soil, turning off atmospheric systems, and venting compressed CO2 from the MAV fuel plant.

With power, heat, and life support logistics modeled, Watney sets the stage for multiday travel as a rehearsal for the eventual journey to Ares 4.