Space Shuttle Discovery and its seven-member crew launched at 2:38 p.m. (EDT) to begin the two-day journey to the International Space Station (ISS) on the historic Return to Flight STS-121 mission. The shuttle made history as it was the first human-occupying spacecraft to launch on Independence Day. During its 12-day mission, this utilization and logistics flight delivered a multipurpose logistics module (MPLM) to the ISS with several thousand pounds of new supplies and experiments. In addition, some new orbital replacement units (ORUs) were delivered and stowed externally on the ISS on a special pallet. These ORUs are spares for critical machinery located on the outside of the ISS. During this mission the crew also carried out testing of Shuttle inspection and repair hardware, as well as evaluated operational techniques and concepts for conducting on-orbit inspection and repair.