2007 shuttle flight doubled International Space Station interior volume

The International Space Station more than doubled its interior volume on October 23, 2007, when the space shuttle Discovery delivered the Harmony module. The delivery, part of the STS-120 mission, transformed the outpost from a space roughly the size of a three-bedroom house into one comparable to a five-bedroom house.

Harmony is a utility hub measuring 14 feet wide and 24 feet long, a length similar to a minibus. The module contains five common berthing mechanisms that serve as connection points for other station components. It was built by Italy-based Thales Alenia Space for NASA and was originally designated as Node 2, following the Unity module, or Node 1.

Astronauts initially attached Harmony to the Unity node upon arrival. After the shuttle departed, the crew used the station's robotic arm to move the shuttle docking port from the Destiny module. This action cleared the forward port of the Destiny laboratory for Harmony's permanent berth.

The installation of Harmony created a central link for future expansion. It connected the European Space Agency's Columbus laboratory on the starboard side and Japan's Kibo laboratory on the port side. The module also features a docking port on its roof where visiting vehicles can park, and some of its berthing points have hosted cargo ships.

Inside, Harmony houses eight payload racks. Four of these are dedicated to avionics, while the remaining four provide stowage or crew quarters. The sleeping quarters for American astronauts are located within this module. The name was selected through a public naming contest organized by NASA.

The arrival of Harmony ended a six-year gap in major station construction. The previous major addition was Russia's Pirs docking module, which was attached in 2001 and later discarded. The STS-120 flight lasted approximately two weeks before the shuttle returned to Earth.