Image above: The ISS Progress 26 on the launch pad at the Baikonur Cosmodrome in Kazakhstan. Image credit: NASA/Mark Bowman

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ISS Progress 26 prepares for liftoff

The ISS Progress 26 vehicle rolled to its launch pad Tuesday loaded with 5,111 pounds of food, fuel, air, water and supplies.

The cargo craft also contains new Russian computers, cables, connectors and a commanding unit. The commanding unit will replace an identical unit on the station when the upcoming STS-118 mission visits in August. The unit is suspected of causing the computer failure during the STS-117 mission in June.

On the eve of the undocking of the Progress 24 cargo ship from the Pirs docking compartment, the crew members completed the stowage of discarded items no longer needed on the station. They closed the hatch, conducted leak checks and activated the ship's systems for Wednesday’s undocking scheduled for 10:05 a.m. EDT. The Progress engines will be fired at about 2:40 p.m. to begin the descent to Earth's atmosphere, where it will burn up 30 minutes later.

The crew members also did a timeline review with flight controllers Tuesday as they prepare for the launch of Endeavour on the STS-118 mission Aug. 7.

The new Progress cargo carrier is scheduled to launch to the International Space Station at 1:34 p.m. EDT Thursday, Aug. 2, with more than 2.5 tons of fuel, air, water and other supplies and equipment aboard.

Image above: Backdropped by the blackness of space, an unpiloted Progress supply vehicle approaches the International Space Station in May 2007. Credit: NASA

The station's 26th Progress unpiloted spacecraft will bring to the orbiting laboratory almost 1,600 pounds of propellant, more than 100 pounds of air and oxygen, more than 465 pounds of water and 2,954 pounds of dry cargo. Total cargo weight is 5,111 pounds.

P26 will launch from the Baikonur Cosmodrome in Kazakhstan. It is scheduled to dock with the station Sunday, Aug. 5, at about 2:38 p.m.

The spacecraft will use the automated Kurs system to dock at the aft port of the Zvezda Service Module. Expedition 15 Commander Fyodor Yurchikhin, RN3FI, will be at the manual TORU docking system controls, should his intervention become necessary.

Once Expedition 15 crew members, Yurchikhin and flight engineers Oleg Kotov and Clay Anderson, KD5PLA, have unloaded the cargo, P26 will be filled with trash and station discards. It will be undocked from the station with its load of trash and deorbited, to burn in the Earth's atmosphere.

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