Space Shuttle design process refurbishment, and the agency studied resupplying the satellite in space. The Air Force planned on having its own fleet of shuttles, and re-built a separate launch facility originally derived from the canceled Manned Orbiting Laboratory program at Vandenberg called Space Launch Complex Six (SLC-6). However, for various reasons, due in large part to the loss of the space shuttle "Challenger" on January 28, 1986, work on SLC-6 was eventually discontinued with no shuttle launches from that location ever taking place. SLC-6 was eventually used for launching the Lockheed Martin-built Athena expendable launch vehicles, which included the successful IKONOS commercial Earth
Space Shuttle of "Atlantis"s final flight on July 21, 2011. The U.S. has since relied primarily on the Russian Soyuz spacecraft to transport astronauts to the International Space Station. The Space Shuttle was a partially reusable human spaceflight vehicle capable of reaching low Earth orbit, commissioned and operated by the U.S. National Aeronautics and Space Administration (NASA) from 1981 to 2011. It resulted from shuttle design studies conducted by NASA and the U.S. Air Force in the 1960s and was first proposed for development as part of an ambitious second-generation Space Transportation System (STS) of space vehicles to follow the Apollo program