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Progress Docks With Space Station
A new Progress docked to the International Space Station at 12:25 p.m. EDT Monday with more than 2.5 tons of fuel, water and other supplies aboard.

The Progress 22 cargo spacecraft as it approaches the Pirs docking compartment Image to right: The Progress 22 cargo spacecraft as it approaches the Pirs docking compartment before docking. Image credit: NASA TV

The 22nd Progress unpiloted cargo carrier brings the station more than 1,900 pounds of propellant, just over 100 pounds of air and oxygen, almost 250 pounds of water and almost 2,860 pounds of dry cargo.

Its sister cargo carrier and a predecessor at the station, ISS Progress 20, was undocked from the station June 19. It was deorbited and destroyed with its load of trash and station discards on re-entry.

ISS Progress 21, which arrived at the station April 23, remains at the aft docking port of the Zvezda service module. It is scheduled to be undocked and deorbited on Sept. 13.

P22 may face a more dignified future than its predecessors, which in effect became big garbage cans. Plans call for P22 to be used after it is unloaded as a "closet." It will provide additional stowage space, rather than act as a trash receptacle.

Many items eventually to be stowed aboard will be delivered by Discovery on STS-121, scheduled to launch on July 1. Most P22 unloading will be done only after departure of Discovery.

The Progress is similar in appearance and some design elements to the Soyuz spacecraft, which brings crewmembers to the station, serves as a lifeboat while they are there and returns them to Earth. The aft module, the instrumentation and propulsion module, is nearly identical.

But the second of the three Progress sections is a refueling module, and the third, uppermost as the Progress sits on the launch pad, is a cargo module. On the Soyuz, the descent module, where the crew is seated on launch and which returns them to Earth, is the middle module and the third is called the orbital module.