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| The space shuttle Atlantis is shown on launch pad 39A after the Rotating Service Structure was rolled back at the Kennedy Space Center in Cape Canaveral, Florida, July 7, 2011. Launch of Atlantis is scheduled for July 8 with a crew of four aboard the final STS-135 mission of the space shuttle program. (Xinhua/Reuters Photo) |
WASHINGTON, July 8 (Xinhua) -- Space shuttle Atlantis is expected to soar into the sky Friday on the 135th and final flight in NASA's shuttle program. Its return to Earth later this month will mark the end of the program.
The shuttle's primary payload is an Italian-built cargo hauler named Raffaello which is carrying 8,640 pounds (3,919 kg) of food, clothing, supplies and science equipment to sustain space station operations after the shuttles are retired.
Only four astronauts took to the skies because there is no shuttle available for a rescue flight should anything go wrong. Normally NASA sends six or seven astronauts on space shuttle flights -- with the last four-person shuttle crew launched 28 years ago.
But Atlantis' status as the final flight means there is no other space shuttle on standby, and the United States would have to call on Russia for any rescue operation. The Russian Soyuz capsules hold just three astronauts and at least one must be Russian, so two crew members would have to fly up and bring home the Americans from the International Space Station one at a time.
The crew will return an ammonia pump that recently failed on the station. Engineers want to understand why the pump failed and improve designs for future spacecraft.
The 12-day mission was not originally intended to include a spacewalk. But the desire to return the pump for analysis made one necessary. With only four people, however, the STS-135 crew was too small to perform a spacewalk on top of all of its other work. So members of the space station crew were recruited for the job, though the shuttle crew members will still support the spacewalk from inside the space station.
