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 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 in 2012. It was built using schematics, blueprints and archival documents provided by NASA and by shuttle contractors such as Rockwell International. While many of the features on the replica are simulated, some parts, including the landing gear's Michelin tires, have been used in the Space Shuttle program. The model is long, high, has a wingspan, and weighs