designed to accommodate pressurized payloads and has a capacity for 24 rack locations, of which the International Standard Payload Racks (ISPRs) will occupy 13 (see Figure 3.1).

The ISPRs inside the ISS pressurized modules provide the only means of accommodating payload experiments. Each ISPR consists of an outer shell that holds interchangeable racks and that maintains a set of standard interfaces, a support structure, and equipment for housing research hardware. It can accommodate one or several experiments. Through the ISPRs, the ISS payload experiments will be able to interface with the following ISS resources contained on Destiny:

• Electrical power,

• Thermal control,

• Command/data/video,

• Vacuum exhaust/waste gas, and

• Gaseous nitrogen.

The EXPRESS (expedite the processing of experiments to space station) Rack System was developed to provide ISS accommodations and resources such as power, data, and cooling to small, subrack payloads and is housed within ISPRs aboard the space station. An EXPRESS rack accommodates payloads originally fitted to shuttle middeck lockers and International Subrack Interface Standard drawer payloads, allowing previously flown payloads to evolve to flight on the ISS.

Figure 3.2 depicts one possible standard EXPRESS rack configuration with eight middeck size drawers and two smaller, International Subrack Interface Standard drawers. The EXPRESS Rack System provides payload accommodations that allow quick, simple integration by using standardized hardware interfaces through which ISS resources can be distributed to the experiment, experiment commands can be given, and data and video can be transmitted.

Facility-Class Payloads

A facility-class payload is a long-term or permanent ISS-resident facility that provides services and accommodations for experiments in a particular science discipline. It includes general capabilities for main areas of science research. Facility-class payloads are located on ISPRs. These facilities are designed to allow easy change-out of experiments by the crew and to accommodate varied experiments in the same area of research. There are facility-class payload racks dedicated to life sciences, material sciences, and fluids and combustion.

Window Observational Research Facility. The Window Observational Research Facility (WORF)1 provides a crew workstation window in the U.S. Destiny module to support research-quality optical Earth observations. Some of these observations include “rare and transitory Earth surface and atmospheric phenomena.”2

Life Sciences Glovebox. This glovebox, which occupies one rack location, provides a sealed workspace3 within which biological specimens and chemical agents can be handled while remaining isolated from the ISS cabin. Its design was based on experience with other gloveboxes flown on previous Spacelab§ missions aboard the space shuttle.

Microgravity Science Glovebox. The Microgravity Science Glovebox (MSG) also provides a sealed environment and is intended to enable scientists from multiple disciplines to participate actively in the assembly and operation of experiments in space with much the same degree of involvement that they have in their own research laboratories.4 The MSG core work volume slides out of the rack to provide additional crew access capability from the side ports.5

Cold Storage: Minus Eighty Degree Laboratory Freezer for the ISS, Glacier, and Microgravity Experiment Research Locker/Incubator. The Minus Eighty Degree Laboratory Freezer for the ISS (MELFI)6 is designed


§ Spacelab was a reusable laboratory module flown in the space shuttle’s cargo bay and used for microgravity experiments that were operated and/or monitored by astronauts.

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