Electrical system of the International Space Station

Each wing is the largest ever deployed in space, weighing over 2,400 pounds and using nearly 33,000 solar arrays, each measuring 8-cm square with 4,100 diodes.

[1] When retracted, each wing folds into a solar array blanket box just 51 centimetres (20 in) high and 4.57 metres (15.0 ft) in length.

[citation needed] Over time, the photovoltaic cells on the wings have degraded gradually, having been designed for a 15-year service life.

STS-119 (ISS assembly flight 15A) delivered the S6 truss along with the fourth set of solar arrays and batteries to the station during March 2009.

To augment the oldest wings, NASA launched three pairs of large-scale versions of the ISS Roll Out Solar Array (IROSA) aboard three SpaceX Dragon 2 cargo launches from early June 2021 to early June 2023, SpaceX CRS-22, CRS-26 and CRS-28.

[7] Work to install iROSA's support brackets on the truss mast cans holding the Solar Array Wings was initiated by the crew members of Expedition 64 in late February 2021.

[8][9] After the first pair of arrays were delivered in early June, a spacewalk on 16 June by Shane Kimbrough and Thomas Pesquet of Expedition 65 to place one iROSA on the 2B power channel and mast can of the P6 truss ended early due to technical difficulties with the array's deployment.

On 9 June, astronauts Steve Bowen and Warren Hoburg of Expedition 69 installed the fifth iROSA on the 1A power channel and mast can on the S4 truss segment.

[17][18] On 15 June, Bowen and Hoburg installed the sixth iROSA on the 1B power channel and mast can on the S6 truss segment.

[19] The last pair of iROSAs, the seventh and eighth, are planned to be installed on the 2A and 3B power channels on the P4 and S6 truss segments in 2025.

Details on this subsystem can be found in the article External Active Thermal Control System.

Use of this system reduced usage of a shuttle's on-board power-generating fuel cells, allowing it to stay docked to the space station for an additional four days.

This was used in the initial construction of the space station to augment the power available from the Russian Zvezda service module.

[citation needed] In December 2006, during mission STS-116, PMA-2 (then at the forward end of the Destiny module) was rewired to allow for the use of the SSPTS.

Atlantis was the only surviving shuttle not equipped with the SSPTS, so it could only go on shorter length missions than the rest of the fleet.