Space flight in 2008 saw several significant events and accomplishments. Four space shuttle missions were flown successfully. All of the international partner International Space Station (ISS) pressurized elements have now been placed in orbit. SpaceX Corporation flew the first commercially developed rocket to orbit. The National Aeronautics and Space Administration (NASA), in conjunction with the European Space Agency (ESA), continued to explore Mars and Saturn. China demonstrated its first spacewalk, and India launched its first spacecraft to the Moon. NASA also celebrated its 50th anniversary in 2008.