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Fact sheet number: FS-2001-07-129-MSFC
Release date: 07/01

EXPRESS Racks 4 and 5

Missions: Expedition Three, ISS Mission 7A.1, STS-105 Space Shuttle Flight

Facility Location on ISS: Destiny

Project Manager: Annette Sledd, NASA's Marshall Space Flight Center, Huntsville, Ala M.

With its standardized hardware interfaces and streamlined approach, the EXPRESS Rack enables quick, simple integration of multiple payloads aboard the International Space Station.
With its standardized hardware interfaces and streamlined approach, the EXPRESS Rack enables quick, simple integration of multiple payloads aboard the International Space Station. (NASA)


The EXPRESS Rack is a standardized payload rack system that transports, stores and supports experiments aboard the International Space Station. EXPRESS stands for EXpedite the PRocessing of Experiments to the Space Station, reflecting the fact this system was developed specifically to maximize the Station's research capabilities.

The EXPRESS Rack system supports science payloads in several disciplines, such as biology, chemistry, physics, ecology and medicine, including commercial activities.

Facility Operations

With its standardized hardware interfaces and streamlined approach, the EXPRESS Rack enables quick, simple integration of multiple payloads aboard the International Space Station.

The system is comprised of elements that remain on the International Space Station, as well as elements that travel back and forth between the Space Station and Earth via the Space Shuttle. EXPRESS Racks stay on orbit continually, while experiments are exchanged in and out of the EXPRESS Racks as needed - remaining on the Space Station for three months to several years, depending on the experiment's time requirements.

The first two EXPRESS Racks were installed in the International Space Station during Expedition 2 on the STS-100 Space Shuttle Mission, ISS Mission 6A, in April 2001. EXPRESS Racks No. 4 and 5 will be installed during Expedition Three, ISS Mission 7A.1. Express Rack No. 3 is scheduled to be installed on the Space Station in April 2002.

Late load experiments are flown up in the Shuttle middeck and installed in the EXPRESS Racks on-orbit. Additional experiments will continue to be exchanged in the EXPRESS Racks, flying up in the Shuttle middeck, EXPRESS Transportation Racks, or launched in future EXPRESS Racks.

Each EXPRESS Rack is housed in an International Standard Payload Rack (ISPR) - a refrigerator-size container that acts as the EXPRESS Racks' exterior shell. Each rack can be divided into segments, whether as large as half the entire rack or as small as a breadbox. The first two EXPRESS Racks installed have eight middeck locker locations and two drawer locations each.

Payloads within EXPRESS Racks can operate independently of each other -- allowing for differences in temperature, power levels and schedules. EXPRESS Rack No. 2 is equipped with the Active Rack Isolation System (ARIS) -- a system that acts as a shock absorber for delicate science experiments that could be damaged by vibrational disturbances.

Experiments contained within EXPRESS Racks may be controlled by the Space Station crew or remotely from the ground by the Payload Rack Officer on-duty at the Payload Operations Center at NASA's Marshall Space Flight Center in Huntsville, Ala.

Seven days a week, 24 hours a day, a rack officer is on-hand to oversee rack maintenance and support experiments. Linked by computer to all payload racks aboard the Station, the officer routinely checks rack integrity, temperature control and the proper working conditions of Station experiments. The EXPRESS Rack system was developed by NASA's Marshall Center and built by the Boeing Co. in Huntsville. Eight EXPRESS Racks are being built for use on the International Space Station.

Background/Flight History

The EXPRESS Rack was successfully tested during the Space Shuttle STS-94 mission in 1997. A primary focus of mission STS-94 was to evaluate facilities associated with the Microgravity Science Laboratory-1 payload. The mission served to bridge the gap between the relatively short-duration work done on Shuttle Spacelab flights and the long-duration research to be performed on the International Space Station.

Two EXPRESS Rack experiments on the STS-94 mission were activated 14 hours into the flight and ran until the 15th day of the mission. As a result of these experiments, NASA determined the EXPRESS Rack system is able to successfully support subrack payload operations.

Aboard the International Space Station, EXPRESS Racks No. 1 and 2 are successfully supporting payloads operations for eight different experiments. These racks will continue to operate and support payload operations on Expedition Three, with the exchange of some experiments within the EXPRESS Rack. Seven additional experiments will be hosted by the EXPRESS Racks on Expedition Three.


The EXPRESS Racks are a host facility supporting multi-discipline science experiments with minimal interference from the force of gravity. The results of these various types of research and the effect of limited gravity on the associated processes will hopefully improve the lives of people on Earth. By housing, supporting and transporting these experiments, the EXPRESS Rack could play a key role in the development of better medicines, more powerful computer chips or lighter metals.

Similarly, by reducing the time, complexity and expense historically associated with orbital research, the EXPRESS Rack system will help universities and industry achieve these advances more quickly and for less money.

More Information

More information on EXPRESS Racks and the International Space Station can be found at: msl/science/express.html fd31.html

Steve Roy
Public Affairs Office
(256) 544-0034

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