 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 its volume. Each insert is equipped with a furnace to process materials. NASA and the European Space Agency will each supply two inserts, with the German Space Agency proving the fifth. The German furnace, unlike the others, will use a rotating magnetic field to control flow inside molten samples.
Japan's Kibo is unique in that part of the lab is "outside," to expose experiments to the environment of space. An airlock allows moving equipment in and out of the station without depressurizing the entire lab. Researchers will control a robotic arm with grippers and a camera to observe experiments exposed to space and move equipment.
A device called the Express pallet (Expedite the Processing of Experiments to Space Station) will hold up to six payloads or experiments that call for exposure to space. Built by the Brazilian Space Agency, the pallet can be located almost anywhere along the main truss, and will get its power and data handling from the ISS. Robots, such as the Canadian and European robotic arms, or spacewalks will be used to remove, replace, and service payloads.
A habitation module will connect to Node 2, which will be below, or Earthward of, Unity node. It will contain living quarters for seven crew members, eating and hygiene facilities, as well as medical and exercise equipment.
Keeping it in place
Completing the station will take more than 40 shuttle flights and a host of Progress launches. Future payloads are also scheduled for delivery on Japan's Hope spacecraft and the European Automated Transfer Vehicle. The Italian Space Agency is providing three multipurpose logistics modules named Leonardo, Rafaello, and Donatello after famed Italians, not Ninja Turtles. The modules fit inside the Shuttle bay and carry 9.1 tons of cargo packed in a pressurized environment. The modules also provide power, data, and cooling fluid to some cargo containers.
Due to the small but constant presence of atmosphere at ISS's orbiting altitude (217 to 285 miles) and the large size of the ISS, it will fall about 1 mile/wk o