Systems

How the station works, system by system

Six systems keep the International Space Station powered, breathable, cool, pointed and in touch. Each page below explains every reading the station publishes for it — 162 in all — and each reading is live on the console.

• Power 30 readings

  Eight 34-metre solar wings provide 75 to 90 kW. Two joints keep them facing the Sun: the SARJ turns once per orbit, the BGA compensates for the seasonal tilt.

• Life support 32 readings

  The ISS makes its own air and recycles its water. Oxygen is produced by electrolysis, carbon dioxide is scrubbed out, and 98 % of the water is reused — a figure reached in 2023, when the brine processor took it up from 93–94 %.

• Thermal 16 readings

  Surfaces outside cycle between −120 °C and +120 °C, sixteen times a day. Two ammonia loops carry equipment heat out to large steerable radiators.

• Attitude & orbit 49 readings

  The station holds its orientation with four 100 kg gyroscopes spinning at 6,600 rpm. They absorb disturbing torques without burning any propellant.

• Communications 19 readings

  The station does not talk to the ground directly: it aims at TDRS relay satellites 35,800 km up. Between two relays, contact drops for a few minutes.

• Command & data 16 readings

  Around fifty redundant computers run the station, in three tiers. The top tier is two-fault tolerant: three identical command-and-control machines, one hot, one warm backup processing data without commanding, and one cold.