Exactly ten years ago, the International Space Station unfurled its second set of wings for the first time.
A decade ago, the beloved space station was just a fledgling in orbit, not yet equipped with all the goodies current astronauts take for granted. The crew of the Space Shuttle Atlantis installed a brand-new set of solar array wings to the P3/P4 truss on September 12th. After passing tests with flying colours, the wings fully extended for the first time on September 14, 2006 at 8:44 am eastern time.
The wings are 35 meters (120 feet) long and 11.6 meters (38 feet) wide, paired to create an array with a wingspan over 73 meters (240 feet) long. Each solar array wing is a long mast with a pair of retractable “blankets” of solar arrays on either side, with nearly 33,000 individual solar cells.
The arrays track the Sun, spinning along the alpha gimbal to follow primary rotation, and the beta gimbal to compensate for the space station’s angle with respect to the ecliptic. Different tracking modes are used to maximize solar power (full Sun-tracking mode), to reduce drag (Night-glider or Sun-slicer modes), or even to maximize drag if the station needs to shed altitude.
It is still in use today as one of eight solar array wings on the space station, generating a combined total of 84 to 120 kilowatts of electricity from 262,400 solar cells. About 60% of that energy is used to charge batteries to keep the station going when the arrays are in the shade.