Editing Space Shuttle Columbia (section)

===Weight===
As the second orbiter to be constructed and the first able to fly into space, ''Columbia'' was roughly {{convert|8000|lb|abbr=on}} heavier than subsequent orbiters such as [[Space Shuttle Endeavour|''Endeavour'']] when she was first constructed, which had benefited from advances in materials technology.<ref>{{cite web|url=http://spaceflightnow.com/shuttle/features/000414overhaul/weightloss.html |title=Orbiter Overhaul: The Columbia weight loss plan |publisher=Spaceflight Now |date=April 14, 2000 |access-date=July 17, 2009}}</ref> In part, this was due to heavier wing and fuselage spars, the weight of early test instrumentation 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.<ref>{{cite web|url=http://spaceflightnow.com/shuttle/features/000414overhaul/future.html |title=Orbiter Overhaul: Flying into the future |publisher=Spaceflight Now |date=April 14, 2000 |access-date=July 17, 2009}}</ref>.''Columbia'' was not modified for the planned [[Centaur (rocket stage)|Centaur-G]] booster (canceled after the loss of ''Challenger'').<ref>{{cite book|last=Lardas|first=Mark|title=Space Shuttle Launch System: 1972-2004|year=2012|publisher=Osprey Publishing|pages=35}}</ref> The retention of the internal airlock allowed NASA to use ''Columbia'' for the [[STS-109]] [[Hubble Space Telescope]] servicing mission, along with the [[Astrotech Corporation|Spacehab]] double module used on [[STS-107]].{{Citation needed|date=December 2017|reason=An external airlock would have fit fine on Columbia's last two missions, but there was no need. Columbia would have carried Endeavour's external airlock on its next mission (to ISS) if they had made it home safely from STS-107.}} Due to ''Columbia's'' higher weight, it was less ideal for NASA to use it for missions to the International Space Station due the performance decreases needed to carry the heavy payloads to the high inclination orbit, though modifications were made to the Shuttle during its last refit in case the spacecraft was needed for such tasks.