Tranquility (ISS module)

Tranquility, also known as Node 3, is a module of the International Space Station (ISS). It contains environmental control systems, life support systems, a toilet, exercise equipment, and an observation cupola.

The European Space Agency (ESA) and the Italian Space Agency (ASI) had Tranquility manufactured by Thales Alenia Space. A ceremony on November 20, 2009, transferred ownership of the module to NASA. On February 8, 2010, NASA launched the module on the Space Shuttle's STS-130 mission.

Tranquility was built within the ESA–NASA ISS bartering system. Under this arrangement, ESA agreed to provide NASA with the fully integrated Harmony and Tranquility node modules, along with additional equipment and parts, in exchange for the launch of ESA’s Columbus module and its initial payload aboard the Space Shuttle. This barter allowed ESA to secure launch services without a direct financial transaction, and enabling those funds to remain within ESA member states.

To build the nodes, ESA partnered with the Italian Space Agency and Thales Alenia Space, which manufactured them at its facility in Turin, Italy. The module’s pressure shell is constructed from 2219 aluminum, while its debris shield is made from hardened 6061 aluminum. The metal is heat-treated, giving the shield ballistic resistance comparable to stainless steel.

Tranquility provides six berthing locations with power, data and commanding, thermal and environmental control, and crew access for more attached habitable volumes or for crew transportation vehicles or stowage, or an appropriate combination of all of these. One of the berthing locations is used by the Cupola, which houses a Robotic Work Station inside it to assist in the assembly/maintenance of the ISS, and offers a window for Earth observations. Tranquility was launched with the Cupola attached to its port-facing Common Berthing Mechanism (CBM). After mating Tranquility with the port CBM of Unity, the Cupola was transferred to the nadir facing port of Tranquility where it will stay.

The module has three redundant berthing ports that were not scheduled to be used prior to the end of the Space Shuttle program, although there is a Power Data Grapple Fixture reserved for the Special Purpose Dexterous Manipulator (Dextre), which is located on the zenith berthing location. In the current ISS configuration Tranquility is docked to the port berthing location of Unity. As such, the three unused berthing locations of Tranquility were disabled as the node's close proximity to other segments would prohibit the port's direct use for cargo spacecraft or using the docking module PMA-3, which was relocated from Harmony to the port berthing location of Tranquility for storage. At the time, the move of PMA-3 to the port location of Tranquility was required because NASA decided to leave the Multi-Purpose Logistics Module (MPLM) Leonardo permanently attached to the ISS, which will be located at the nadir side of Unity.

In 2001, NASA considered changing the design of the module. This idea for an extended or "stretched" module, was a result of the deferral/deletion of the Habitation Module. The stretched module would have held 16 racks, compared with the baseline capacity of eight racks. This modification was not funded and the plans were abandoned.

The module's life-support system (ECLSS) recycles waste water for crew use and generates oxygen for the crew to breathe. In addition, Tranquility contains an atmosphere revitalization system to remove contaminants from the atmosphere and monitor/control the atmosphere constituents of the ISS. Tranquility also contains a Waste and Hygiene Compartment (toilet) for supporting the on-board crew.