NASA - National Aeronautics and Space Administration

Crewmembers say they can smell the fresh foods aboard a Progress, things like apples taken for granted on Earth, shortly after the unpiloted cargo craft docks with the International Space Station.

Image to right: A Progress spacecraft approaches the Station.

A Progress arrival is an occasion, not only because of the treats for the crew but also because of the valuable and necessary equipment and supplies it brings to the Station.

The ISS Progress 18 spacecraft is no exception. It lifted off June 16 from the Baikonur Cosmodrome in Kazakhstan and docked at 8:42 p.m. June 18. Among its 4,662 pounds of cargo is 397 pounds of propellant, 242 pounds of oxygen and 926 pounds of water.

Also aboard is a camera to be used to photograph thermal protection tiles of Discovery as the orbiter approaches the Station on the Space Shuttle's Return to Flight mission, STS-114. It is a replacement for a similar camera found to be not working after it was sent to the Station aboard ISS Progress 17, which docked to the orbiting laboratory March 2.

Discovery is scheduled to launch no earlier than July 13.

Also aboard ISS Progress 18 is about 3,100 pounds of dry cargo, including food, other equipment and supplies and experiment hardware. Among that dry cargo are spare parts for the Russian Elektron oxygen generation system, which has been out of operation for several weeks. Additional Solid Fuel Oxygen Generators (SFOGs) or "candles," each of which can provide enough oxygen for one crewmember for one day, also are among cargo items.

The Progress is similar in appearance and some design elements to the Soyuz spacecraft, which brings three 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.

The undocking of the previous Progress cargo ship begins the sequence of events replacing the old cargo craft with the new. The Progress craft being replaced is typically undocked the day before launch of the new cargo capsule, and later commanded to deorbit by Russian flight controllers, clearing the aft port of Zvezda for the new Progress. Filled with trash and discarded items, the departing Progress burns up in the Earth's atmosphere soon afterward.

+ Read more about Expedition 11
+ Read more about the Progress spacecraft