Space Shuttle Columbia that remained fitted to the avionics suite, and an internal airlock that, originally fitted into the other orbiters, was later removed in favor of an external airlock to facilitate Shuttle/Mir and Shuttle/International Space Station dockings. Due to its weight, "Columbia" could not have used the planned Centaur-G booster (cancelled after the loss of "Challenger"). The retention of the internal airlock allowed NASA to use "Columbia" for the STS-109 Hubble Space Telescope servicing mission, along with the Spacehab double module used on STS-107. Due to "Columbia's" heavier weight, it was less ideal for NASA to use it for missions to the
Space Shuttle Independence display cases with shuttle program artifacts. On August 14, 2014, a heavy lift was completed to place "Independence" on top of NASA 905, which had been moved to Space Center Houston from Ellington Field on April 30, 2014. The combined exhibit, named "Independence Plaza", opened to the public on January 23, 2016, at an estimated cost of . Space Shuttle Independence Space Shuttle "Independence, formerly known as Explorer", is a full-scale, high-fidelity replica of the Space Shuttle. It was built by Guard-Lee in Apopka, Florida, installed at Kennedy Space Center Visitor Complex in 1993, and moved to Space Center Houston