Stock Photo - At NASA's Kennedy Space Center in Florida, space shuttle Atlantis' main engines and solid rocket boosters ignite on Launch Pad 39A as it lifts off on its STS-135 mission to the International Space Station. Atlantis with its crew of four; Commander Chris Ferguson, Pilot Doug Hurley, Mission Specialists Sandy Magnus and Rex Walheim, lifted off at 11:29 a.m. EDT on July 8, 2011 to deliver the Raffaello multi-purpose logistics module packed with supplies and spare parts for the station. Atlantis also will fly the Robotic Refueling Mission experiment that will investigate the potential for robotically refueling existing satellites in orbit. In addition, Atlantis will return with a failed ammonia pump module to help NASA better understand the failure mechanism and improve pump designs for future systems. STS-135 is the 33rd flight of Atlantis, the 37th shuttle mission to the space station, and the 135th and final mission of NASA's Space Shuttle Program.