NASA retired the Space Shuttle fleet on July 21, 2011 after completing the ISS and the final flight and subsequent landing of Atlantis . The Shuttle's replacement, Orion , was to have consisted of an Apollo-derived spacecraft launched on the Ares I rocket, which would use a Space Shuttle Solid Rocket Booster as its first stage. Orion would not face the dangers of either an O-ring failure (due to the presence of a launch escape system  ) or shedding foam (as the spacecraft would be launched in a stack configuration). In addition to ferrying crews to the ISS, the Orion spacecraft was to (as part of Project Constellation ) allow NASA to return to the Moon.  President Obama signed the NASA Authorization Act 2010 on October 11 which officially brought the Constellation program to an end, replacing it with the Space Launch System (SLS) and Multi-Purpose Crew Vehicle (MPCV) programs to develop the launch vehicle and spacecraft to enable human exploration missions beyond low-Earth orbit.