Astronauts from NASA’s space shuttle Atlantis are installing a new truss element on the International Space Station so the orbital laboratory will have continuous electrical power, even when eclipsed by the Earth’s shadow.
The Starboard 3 (S3) and 4 (S4) truss element, designed by Boeing, has two solar arrays for collecting electrical power from the sun, a solar rotary joint to keep the arrays permanently pointing towards the sun and 12 batteries to power the station for the 35 minutes during its 92-minute circuit around the Earth when it cannot receive sunlight.
During the seven-hour installation, astronauts will need to carefully remove the hardware from Atlantis‘ payload bay and transfer it to the space station using one of the shuttle’s robotic arm. Once captured by the station’s arm, the astronauts will manoeuvre and attach the element to the right side of the station. The crew will activate the element during an additional scheduled spacewalk.
At nearly 16,200kg, the S3/S4 assembly is the largest space station cargo the US has flown to date. Each battery is as big as a large suitcase, and the solar arrays will provide a total operating power capability of about 20kW.
After this mission, the total ISS power output will be about 50-60kW, depending on the station’s attitude and the angle of the sun. The new arrays will contribute about half that power.