ill consist of a series of lab modules and a solar array and mast. The 42,000-lb module is similar in layout to the Mir with three compartments: a small spherical transfer chamber forward, a cylindrical work room in the center, and a cylindrical transfer chamber aft. It can dock with a Soyuz or Progress. Zveda also has power-producing solar arrays and an unpressurized assembly area wrapped around the aft end.
Living spaces on Zveda include personal sleeping quarters for three, each with its own window, a toilet and hygiene facilities, a galley with a refrigerator, freezer, a table for eating meals, and a treadmill and stationary bike for exercise. There is a large 16-in viewing port in Zveda's working compartment and three 9-in. ports in the transfer compartment so the crew can watch docking activities. All together, Zveda boasts 14 windows. Astronauts will live in it until the U.S. Habitation module is delivered in 2005.
At the other end of Zarya is Node One, or Unity Node, connecting it and Zveda, along with future Russian modules, to the rest of the station. It also gives engineers five additional ports for planned expansion. The 22-ft-long, 18-ft-diameter node will provide a passage to the U.S. and European labs and living quarters, and be the main structural connection to the truss. Though seemingly simple, Unity contains more than 50,000 mechanical items, 216 lines for fluids and gases, 121 internal, and external cables using six miles of wiring.
The Joint Airlock Module, which connects to the Unity node, gives astronauts a way to access space without using the Shuttle. Before it is installed, there will only be Russian-built airlocks, which are incompatible with U.S. spacesuit umbilicals. The Joint Airlock will store suits and be used for overnight "camp outs" in preparation for spacewalks. Astronauts will sleep in the lock while pressure drops from the station's normal 14.7 to 10.2 psi. This purges their bloodstreams of nitrogen, increases the oxygen in their blood, and prevents decompression sickness, or the bends, when they go to the 4.3-psi pure-oxygen atmosphere inside the suit.
The U.S. space suit has been upgraded for station use. Internal parts are now more easily replaced, metal sizing rings let the suits adjust for different-sized crew members, and new gloves are more flexible and sport fingertip heaters. A new radio lets up to five people talk at once, and the helmet carries spot and floodlights. There's also a new jet-pack lifejacket, dubbed SAFER, that will help untethered spacewalkers get back to the station in emergencies. The new suits are rated for 25 space walks before they must be returned to Earth for refurbishing.
U.S. and European lab modules are connected to the ISS by the Unity node. They include the U.S. lab Destiny and Centrifuge Accommodation Module (CAM), the European lab Columbus, and the Japanese Kibo. Each lab has access to power, cooling, communication, vacuum, exhaust, gaseous nitrogen, and microgravity measurement tools. CAM will house an 8.2-ft-diameter centrifuge, an essential tool for exploring gravitational biology.
Space has its hazards, so Kevlar debris shields will cover the labs. Aluminum shields separated from the debris shield by a 4-in. gap will then cover the Kevlar for added protection. Russian modules are protected by an outer glass cloth covering a screened aluminum honeycomb shield, a small gap, and an inner carbon-plastic-coated screen. Protection is important since there are 20,000 object in low-Earth orbit larger than 1.97 in., according to NASA. There's at least a 7% chance one such object will penetrate a U.S. module while the ISS is in orbit. Chances are somewhat less for Russian modules.
The labs are similar in size, ranging from 21 to 36-ft long and 14.6 to 16.2 ft. in diameter, and are built to house research racks. Each rack is roughly the size of a large refrigerator with a curved back to fit the modules' cylindrical outer wall. In total, the European, Japanese, and U.S. labs hold 37 racks.
One such rack, for example, will house five inserts in half of i