NASA Facts

National Aeronautics and
Space Administration

Lyndon B. Johnson Space Center

 IS-1999-01-ISS017JSC

Houston, Texas  77058

International Space Station

            January 1999

UNITY CONNECTING MODULE: CORNERSTONE FOR A HOME IN ORBIT

The First U.S.-Built International Space Station Component

The first U.S.-built component
of the International Space
Station, a six-sided connecting
module and passageway, or
node, named Unity, was the
primary cargo of  Space Shuttle
mission STS-88, launched in
December 1998 as the first
mission dedicated to assembly of
the station.

Now permanently attached to
the Zarya control module in
orbit, the Unity  connecting
module lays a foundation for all
future U.S. International Space

Station modules. Unity has six
berthing ports, one on each side,
one of which already is attached
to Zarya. Future U.S. station modules and station components will attach to the remaining five
ports. Built by The Boeing Company at a manufacturing facility at the Marshall Space Flight Center
in Huntsville, Alabama, Unity is the first of three such connecting modules that will be built for the
station. Sometimes referred to as Node 1, the Unity module measures 15 feet in diameter and 18
feet long. Including mating adapters attached at each end as is currently the case in orbit, the overall
component measures about 34 feet long.

Carried to orbit aboard the Space Shuttle Endeavour, Unity was mated on Dec. 6, 1998, with the
already orbiting Zarya, a U.S.-funded and Russian-built component launched earlier aboard a
Russian Proton rocket from Kazakstan. In addition to connecting to Zarya module, Unity eventually
will provide attachment points for the U.S. laboratory module; Node 3; an early exterior
framework, or truss for the station, called the Z-1 truss; an airlock; and a multi-windowed cupola.

Unity lifted from Endeavour's cargo bay to prepare for attachment to
the Zarya control module in December 1998 on shuttle mission STS-88

2

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. Unity is made of
aluminum.

Two conical docking adapters were attached to
each end of Unity prior to its launch aboard

Endeavour. The adapters, called pressurized
mating adapters (PMAs), allow the docking

systems used by the Space Shuttle and by Russian modules to attach to the node's hatches and
berthing mechanisms. One of the conical adapters now permanently attaches Unity to Zarya, while
the other provides a Shuttle docking port. Unity and the two mating adapters weigh about 25,600
pounds. Attached to the exterior of the mating adapter that permanently attaches Unity to Zarya are
computers, or multiplexer-demultiplexers (MDMs), which provide 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.

The two remaining station connecting modules, or nodes, are being built by the European Space
Agency (ESA) for NASA in Italy by Alenia Aerospazio. Nodes 2 and 3 will be slightly longer than
the Unity node, measuring almost 21 feet long, and each will hold eight standard space station
equipment racks in addition to six berthing ports. ESA is building the two additional nodes as
partial payment for the launch of the ESA Columbus laboratory module and other equipment on the
Space Shuttle. Unity holds four equipment racks.

Diagram of interior and exterior views of Unity connecting module

Unity, right, attached to Zarya in orbit