Unity (ISS module)
# Unity (ISS module)

The Unity connecting module, also known as Node 1, is the first U.S.-built component of the International Space Station (ISS). It connects the Russian and United States segments of the station, and is where crew eat meals together.

The module is cylindrical in shape, with six berthing locations (forward, aft, port, starboard, zenith, and nadir) facilitating connections to other modules. Unity measures 4.57 m (15.0 ft) in diameter, is 5.47 m (17.9 ft) long, made of steel, and was built for NASA by Boeing in a manufacturing facility at the Marshall Space Flight Center in Huntsville, Alabama. Unity is the first of the three connecting modules; the other two are Harmony and Tranquility.

## Launch and initial berthing

Unity (with its two attached PMAs) was carried into orbit as the primary cargo of the Space Shuttle Endeavour (OV 105) on STS-88, the first Space Shuttle mission dedicated to assembly of the station. On 6 December 1998, the STS-88 crew mated the docking port of the PMA on the aft berthing port of Unity with the forward hatch of the already orbiting Zarya module. (Zarya was a mixed Russian-U.S. funded and Russian-built component launched a few days before aboard a Russian Proton launch vehicle from Baikonur, Kazakhstan.) This was the first connection made between two station modules.

## Connecting modules and visiting vehicles

Unity has two axial and four radial Common Berthing Mechanism (CBM) ports. In addition to connecting to the Zarya module, Unity connects to the U.S. Destiny Laboratory Module (added on STS-98), the Z1 truss (an early exterior framework for the station added on STS-92), the PMA-3 (also added on STS-92), and the Quest Joint Airlock (added on STS-104). During STS-120 the Harmony module was temporarily berthed to the port-side hatch of Unity. Tranquility, with its multi-windowed cupola, was attached to Unity's port side during the STS-130 mission, and Leonardo was added to the nadir hatch during STS-133.

In addition, the Leonardo and Raffaello Multi-Purpose Logistics Modules were each berthed to Unity on multiple missions.

### Nadir

| Patch | Spacecraft | Docking | Undocking |
| - | - | - | - |
| | STS-97 | 2 December 2000 19:59 UTC | 9 December 2000 19:13 UTC |
| | STS-98 | 9 February 2001 16:51 UTC | 16 February 2001 14:05 UTC |
| Leonardo PMM, 2011-2015 ||||
| | Cygnus CRS OA-4 | 9 December 2015 14:26 UTC | 19 February 2016 10:38 UTC |
| | Cygnus CRS OA-6 | 26 March 2016 10:51 UTC | 14 June 2016 11:43 UTC |
| | Cygnus CRS OA-5 | 17 October 2016 23:45 UTC | 27 November 2016 23:36 UTC |
| | Cygnus CRS OA-7 | 22 April 2017 12:39 UTC | 4 June 2017 11:05 UTC |
| | Cygnus CRS OA-8E | 14 November 2017 12:15 UTC | 5 December 2017 17:52 UTC |
| | Cygnus CRS OA-9E | 24 May 2018 12:13 UTC | 15 July 2018 10:20 UTC |
| | Cygnus NG-10 | 19 November 2018 12:31 UTC | 8 February 2019 14:37 UTC |
| | Cygnus NG-11 | 19 April 2019 11:31 UTC | 6 August 2019 13:30 UTC |
| | Cygnus NG-12 | 4 November 2019 11:21 UTC | 31 January 2020 13:10 UTC |
| | Cygnus NG-13 | 18 February 2020 11:16 UTC | 11 May 2020 13:00 UTC |
| | Cygnus NG-14 | 5 October 2020 12:01 UTC | 26 January 2020 20:23 UTC |
| | Cygnus NG-15 | 20 February 2021 17:36 UTC | 29 June 2021 16:32 UTC |
| | Cygnus NG-16 | 12 August 2021 13:42 UTC | 15 December 2021 06:25 UTC |

### Forward

Via PMA-2

| Spacecraft | Docking | Undocking |
| - | - | - |
| STS-96 | 27 May 1999 10:49:42 UTC | 6 June 1999 02:02:43 UTC |
| STS-101 | 20 May 2000 04:30 UTC | 26 May 2000 23:03 UTC |
| STS-106 | 8 September 2000 12:45:47 UTC | 19 September 2000 07:56 UTC |
| STS-92 | 11 October 2000 23:17:00 UTC | 24 October 2000 20:59:47 UTC |

Not via PMA-2 (Relocated to front of Destiny during STS-98 and again to the front of Harmony during STS-120.)

* Destiny, 2001–Present

### Aft

* Zarya (via PMA-1), 1998–Present

### Starboard

* Quest, 2001-Present

### Port

* Tranquility, 2010-Present

### Zenith

* Z1 truss, 2000-Present

## Details

Essential space station resources such as fluids, environmental control and life support systems, electrical and data systems are routed through Unity to supply work and living areas of the station. More than 50,000 mechanical items, 216 lines to carry fluids and gases, and 121 internal and external electrical cables using six miles of wire were installed in the Unity node. The primary structure of Unity is constructed of aluminium.

During the space station construction, a crew member placed two speed limit signs on the hatch (leading into the FGB) in 2003, noting the orbital velocity in mph and km/h.

Prior to its launch aboard Endeavour, conical Pressurized Mating Adapters (PMAs) were attached to the aft and forward berthing mechanisms of Unity. Unity and the two mating adapters together weighed about 11,600 kg (25,600 lb). The adapters allow the docking systems used by the Space Shuttle and by Russian modules to attach to the node's hatches and berthing mechanisms. PMA-1 now permanently attaches Unity to Zarya, while PMA-2 provided a Shuttle docking port. Attached to the exterior of PMA-1 are computers, or multiplexer-demultiplexers (MDMs), which provided early command and control of Unity. Unity also is outfitted with an early communications system that allows data, voice and low data rate video with Mission Control Houston, to supplement Russian communications systems during the early station assembly activities. PMA-3 was attached to Unity's nadir berthing mechanism by the crew of STS-92.

## Other nodes

The two remaining station connecting modules, or nodes, were manufactured in Italy by Alenia Aerospazio, as part of an agreement between NASA and the European Space Agency (ESA). Harmony (also known as Node 2) and Tranquility (also known as Node 3) are slightly longer than Unity, measuring almost 6.4 m (21 ft) long in total. In addition to their six berthing ports, each can hold eight International Standard Payload Racks (ISPRs). Unity, in comparison, holds just four ISPRs. ESA built Nodes 2 and 3 as partial payment for the launch aboard the Shuttle of the Columbus laboratory module, and other ESA equipment.

