STS-104

The primary purpose of the flight was to deliver and install the Quest airlock. The Joint Airlock is a pressurized flight element consisting of two cylindrical chambers attached end-to-end by a connecting bulkhead and hatch. Once installed and activated, the ISS airlock became the primary path for International Space Station spacewalk entry and departure for U.S. spacesuits, which are known as Extravehicular Mobility Units, or EMUs. In addition, the Joint Airlock is designed to support the Russian Orlan spacesuit for EVA activity.