Sometimes the main computer system breaks down on Mir (as it did 7 times in 1997), the gyrodynes which align the solar panels towards the sun is then automatically shut down, causing a big reduction in power production. The power also stops flowing to Mir's modules except the Core module, these modules then starts using the power in the batteries which soon becomes depleted. The batteries is normaly used when Mir heads into the shadow of the Earth (every 90 minutes) when the solar panels canīt produce power. When a computer breakdown happens the Soyuz spacecraft docked at the station can use its thrusters to maintain attitude control of the station.