ISS Unity module.jpg
Unity as pictured by Space Shuttle Endeavour
Module statistics
COSPAR ID1998-069F [1]
Launch date4 December 1998,
08:35:34 UTC
Launch vehicleSpace Shuttle Endeavour
Docked6 December 1998
Mass11,612 kg (25,600 lb)
Length5.47 m (17.9 ft)
Diameter4.57 m (15.0 ft)
Unity-Zarya-Zvezda STS-106 (2).jpg

This image of the International Space Station (ISS) was taken when Space Shuttle Atlantis (STS-106) approached the ISS. At the bottom is the Russian Progress supply ship that is linked with Zvezda module. The Zvezda is connected with the Zarya module. The U.S. built Unity module is seen at the top.
The Unity module as seen in May 2011
The Unity module as seen in May 2011

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.

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
Orbital Sciences CRS Flight 4 Patch.png
Cygnus CRS OA-4 9 December 2015
14:26 UTC
19 February 2016
10:38 UTC
Orbital Sciences CRS Flight 6 Patch.png
Cygnus CRS OA-6 26 March 2016
10:51 UTC
14 June 2016
11:43 UTC
Orbital Sciences CRS Flight 5 Patch.png
Cygnus CRS OA-5 17 October 2016
23:45 UTC
27 November 2016
23:36 UTC
Orbital Sciences CRS Flight 7 Patch.png
Cygnus CRS OA-7 22 April 2017
12:39 UTC
4 June 2017
11:05 UTC
Orbital Sciences CRS Flight 8E Patch.png
Cygnus CRS OA-8E 14 November 2017
12:15 UTC
5 December 2017
17:52 UTC
Orbital Sciences CRS Flight 9E Patch.png
Cygnus CRS OA-9E 24 May 2018
12:13 UTC
15 July 2018
10:20 UTC
Cygnus NG-10 Patch.png
Cygnus NG-10 19 November 2018
12:31 UTC
8 February 2019
14:37 UTC
Cygnus NG-11 Patch.png
Cygnus NG-11 19 April 2019
11:31 UTC
6 August 2019
13:30 UTC
Cygnus NG-12 Patch.png
Cygnus NG-12 4 November 2019
11:21 UTC
31 January 2020
13:10 UTC
Cygnus NG-13 Patch.png
Cygnus NG-13 18 February 2020
11:16 UTC
11 May 2020
13:00 UTC
Cygnus NG-14 Patch.png
Cygnus NG-14 5 October 2020
12:01 UTC
26 January 2020
20:23 UTC
Cygnus NG-15 Patch.png
Cygnus NG-15 20 February 2021
17:36 UTC
29 June 2021

16:32 UTC

Cygnus NG-16 Patch.png
Cygnus NG-16 12 August 2021

13:42 UTC


Via PMA-2

Patch 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.[2])



Interior of Node 1 (As of 2005[update])
Interior of Node 1 (As of 2005)

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.[3] It is made of aluminium and stainless steel[dubious ],[4] or aluminium alloy.[5]

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.[6]

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.[3] 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

Node 3 (Tranquility) in space
Node 3 (Tranquility) in space

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.


  1. ^ "Display: Unity 1998-069F". NASA. 14 May 2020. Retrieved 31 January 2021. Public Domain This article incorporates text from this source, which is in the public domain.
  2. ^ "NASA - PMA-2 Move Readies Station for Harmony Relocation". nasa.gov. Retrieved 24 January 2021. Public Domain This article incorporates text from this source, which is in the public domain.
  3. ^ a b "Unity Node". NASA. Retrieved 8 November 2013. Public Domain This article incorporates text from this source, which is in the public domain.
  5. ^ "NASA Facts: Unity Connecting Module: cornerstone for a Home in Orbit" (PDF). NASA. January 1999. Archived from the original (PDF) on 17 August 2000. Public Domain This article incorporates text from this source, which is in the public domain.
  6. ^ "Space Station Science Picture of the Day: Speed Limit". www.spaceref.com. Retrieved 6 May 2022.