Weight As the second orbiter to be constructed and the first able to fly into space,
Columbia was roughly heavier than subsequent orbiters such as
Endeavour when she was first constructed, which had benefited from advances in materials technology. 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..
Columbia was not modified for the planned
Centaur-G booster (canceled 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'' 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.
Thermal protection system in the underside of
Columbia as seen in a visible (left side) and infrared (right side) image which was taken by the
Kuiper Airborne Observatory on
STS-3 Externally,
Columbia was the first orbiter in the fleet whose surface was mostly covered with High & Low Temperature Reusable Surface Insulation (HRSI/LRSI) tiles as its main
thermal protection system (TPS), with white silicone rubber-painted
Nomex – known as Felt Reusable Surface Insulation (FRSI) blankets – in some areas on the wings, fuselage, and payload bay doors. FRSI once covered almost 25% of the orbiter; the first upgrade resulted in its removal from many areas, and in later flights, it was only used on the upper section of the payload bay doors and inboard sections of the upper wing surfaces. The upgrade also involved replacing many of the white LRSI tiles on the upper surfaces with Advanced Flexible Reusable Surface Insulation (AFRSI) blankets (also known as Fibrous Insulation Blankets, or FIBs) that had been used on
Discovery and
Atlantis. , accompanied by a
T-38 Talon flying in formation. Originally,
Columbia had 32,000 tiles – the upgrade reduced this to 24,300. The AFRSI blankets consisted of layers of pure silica felt sandwiched between a layer of silica fabric on the outside and S-Glass fabric on the inside, stitched together using pure silica thread in a 1-inch grid, then coated with a high-purity silica coating. The blankets were semi-rigid and could be made as large as 30" by 30". Each blanket replaced as many as 25 tiles and was bonded directly to the orbiter. All of this work was performed during ''Columbia's
first retrofitting and the post-Challenger'' stand-down. Though the orbiter's thermal protection system and other enhancements had been refined,
Columbia would never weigh as little unloaded as the other orbiters in the fleet. The next-oldest shuttle,
Challenger, was also relatively heavy, although lighter than
Columbia.
Markings and insignia Columbia was the only operational orbiter with black
chines. These were added because at first, shuttle designers did not know how reentry heating would affect the craft's upper wing surfaces. The chines allowed
Columbia to be easily recognized at a distance, unlike the subsequent orbiters. The black chines were a late modification and were a high temperature paint over the white FRSI. The chines were modified on
Columbia shortly before rollover to the Vehicle Assembly Building in late 1980 for STS-1. The only other orbiter with black chines was
Pathfinder, but it was a cosmetic
test article and only gained them when it was refurbished. Additionally, until its last refit,
Columbia was the only operational orbiter with wing markings consisting of an
American flag on the port (left) wing and the letters "USA" on the starboard (right) wing.
Challenger,
Discovery,
Atlantis, and
Endeavour all, until 1998, bore markings consisting of the letters "USA" above an American flag on the left-wing, and the pre-1998
NASA "worm" logotype afore the respective orbiter's name on the right-wing.
Enterprise, the test vehicle which was the prototype for
Columbia, originally had the same wing markings as
Columbia but with white chines and the "USA" letters on the right-wing spaced closer together.
Enterprise's markings were modified to match
Challenger in 1983. The name of the orbiter was originally placed on the payload bay doors much like
Enterprise but was placed on the crew cabin after the
Challenger disaster so that the orbiter could be easily identified while in orbit. From its last refit following the conclusion of STS-93 to its destruction,
Columbia bore markings identical to those of its operational sister orbiters–the
NASA "meatball" insignia on the left-wing and the American flag afore the orbiter's name on the right-wing.
Columbia only flew twice with these markings, STS-109 and STS-107.
SILTS pod Another unique external feature, termed the "SILTS" pod (Shuttle Infrared Leeside Temperature Sensing), was located on the top of ''Columbia's'' vertical stabilizer, and was installed after
STS-9 to acquire infrared and other thermal data. Though the pod's equipment was removed after initial tests, NASA decided to leave it in place, mainly to save costs, along with the agency's plans to use it for future experiments. The vertical stabilizer was later modified to incorporate the drag chute first used on
Endeavour in 1992.
OEX/MADS "black box" One unique feature that permanently stayed on
Columbia from
STS-1 to
STS-107 was the OEX (Orbiter Experiments) box or MADS (Modular Auxiliary Data System) recorder. On March 19, 2003, this "black box" was found slightly damaged but fully intact by the
U.S. Forest Service in
San Augustine County in
Texas after weeks of search and recovery efforts after the
Space Shuttle Columbia disaster. The OEX/MADS was not designed to survive a catastrophic loss like an airplane
black box.
Other upgrades (
STS-62 mission)
Columbia was originally fitted with
Lockheed-built ejection seats identical to those found on the
SR-71 Blackbird. These were active for the four orbital test flights, but deactivated after
STS-4, and removed entirely after
STS-9.
Columbia was the only spaceworthy orbiter not delivered with
head-up displays for the Commander and Pilot, although these were incorporated after STS-9. Like its sister ships,
Columbia was eventually retrofitted with the new MEDS "
glass cockpit" display and lightweight seats.
Planned future Had
Columbia not been destroyed, it would have been fitted with the
external airlock/docking adapter for
STS-118, an
International Space Station assembly mission, originally planned for November 2003.
Columbia was scheduled for this mission due to
Discovery being out of service for its Orbital Major Modification, and because the ISS assembly schedule could not be adhered to with only
Endeavour and
Atlantis.
Columbia's career would have started to wind down after
STS-118. It was to service the
Hubble Space Telescope two more times between 2004 and 2005. Following the
Columbia accident, NASA flew the
STS-125 mission using
Atlantis, combining the planned fourth and fifth servicing missions into one final mission to Hubble. Because of the retirement of the Space Shuttle fleet, the batteries and gyroscopes that keep the telescope pointed will eventually fail, which would result in its reentry and breakup in Earth's atmosphere. A "Soft Capture Docking Mechanism", based on the docking adapter that was to be used on the
Orion spacecraft, was installed during the last servicing mission in anticipation of this event. ==Flights==