Expedition 9 Commander Gennady Padalka, left, and NASA ISS Science Officer Mike Fincke work on their Orlan spacesuits inside Pirs. Credit: NASA The 16-foot-long, 8,000-pound Pirs Docking Compartment is attached to the bottom, Earth-facing port of the Zvezda Service Module. It docked to the International Space Station on Sept. 16, 2001, and was configured during three spacewalks by the Expedition Three crew.
Pirs, also known as DC-1, launched Sept. 14, 2001, on a Russian Soyuz rocket. Pirs has two primary functions. It serves as a docking port for the docking of transport and cargo vehicles to the Space Station and as an airlock for the performance of spacewalks by two Station crewmembers using Russian Orlan spacesuits.
In addition, Pirs can transport fuel from the fuel tanks of a docked Progress resupply vehicle to either the Zvezda Service Module or Zarya It can also transfer propellant from the Zvezda and Zarya to the propulsion system of docked vehicles, whether it is a Soyuz or a Progress.
Image above: Diagram of the Pirs Docking Compartment. Credit: NASA