Each of the refrigerator-size (73-in. high, 42-in. wide, 53 cu. ft. of volume) "International Standard Payload Racks" contains test tubes, beakers, and the other stuff of laboratory experiments.
But the racks still provide flexibility. For instance, experiments are housed in easily replaced container drawers and lockers that can be popped out and sent back to Earth with their experiments intact. The Space Station is capable of carrying 37 payload racks.
Use of a rack begins with the process of outfitting it on the ground. It can carry more than 1,540 lbs. of experiment hardware. When outfitting is completed, the rack is loaded into one of NASA's three Italian-built Multi-Purpose Logistics Vehicles and rocketed to the ISS aboard the Space Shuttle.
Upon its arrival at the ISS, the rack will be placed in one of four laboratory modules: the U.S. Laboratory, Japanese Experiment Module, Columbus Orbital Facility, or Centrifuge Accommodations Module. It will be hooked up to outlets for water, power and gas (nitrogen), connected to some other equipment -- readied for research.
Individual experiments will be designed to fit part or all of a rack, or a number of racks.
Experiments that need only part of a rack's space will be housed in special EXPRESS (EXpedite the PRocessing of Experiments to Space Station) racks. NASA studies have shown that a substantial number of users will not need an entire International Standard Payload Rack.
EXPRESS racks can hold up to five experiments, each of which can differ in size and discipline from any of the others. Like Standard racks, they are built around a common set of software, avionics and structures and provide standard hookups. Boeing is building EXPRESS racks at the Marshall Space Flight Center in Huntsville, Alabama.
Racks that are long-term or permanent ISS fixtures are termed "facilities." They allow easy changes of experiments and provide physical support hardware, data and video handling, and other services.
Comprising one or more racks, these facilities serve specific disciplines or research areas. Among the major facilities on the ISS are the centrifuge, furnace, and optical window rack. Others will be used for experiments in gravitational biology, human research, biotechnology, and fluids and combustion.
These facilities were developed with the advice of scientists from around the world who participated in Science Working Groups sponsored by NASA.