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Wreckage of Columbia
On 1 February, 2003, Columbia was destroyed on re-entry during mission STS-107, resulting in the death of all seven crewmembers. A suitcase-sized block of insulating foam from the external tank had broken off during launch and punched a hole in the tiles on one wing, rendering it vulnerable to the super-heated gases of re-entry.
Pictured above, officials comb through the retrieved wreckage of Columbia.
The disaster spelled the beginning of the end of the shuttle programme. Discovery once again carried out the Return to Flight mission in 2005, but the programme was due to be wrapped up by 2010 (later extended to 2011), as Nasa cast about for new ways of travelling into space.
Critics of the shuttle said the design had been flawed from the very beginning. "The shuttle made America dependent on a fragile, expensive, risky launch system," space policy expert professor John Logsdon said in a Guardian interview. Logsdon noted that its design was influenced by the US Air Force, which insisted that the shuttle be able to fly at angle that would allow it to release spy satellites. While this never happened in practice, the shuttle was lumbered with a heavier heat shield than it needed.
As early as 1993, a Nasa report recommended replacing the already out-dated system by 2000. "The United States has advanced multiple proposals since at least the mid-1980s to build a space shuttle follow-on that would be less expensive and safer to operate," Nasa's chief historian, Roger Launius, wrote on his blog. "At the same time, the target date for space shuttle replacement shifted further into the future over the years."
Photo credit: Nasa