Email trail reveals Nasa fears over Columbia

A Nasa engineer warned days before the disaster that the condition of the Columbia shuttle was described within the organisation as "survivable but marginal".

Robert Daugherty, a 20-year veteran of Nasa, told a superior in an email on 29 January that he was concerned that a crash of debris against Columbia's left wing shortly after take-off on 16 January could have created a hole that could affect landing.

On 1 February, the shuttle broke up upon entering the earth's atmosphere, killing all seven astronauts on board.

One email from Mr Daugherty to a superior at Nasa's Langley Research Centre said discussion of the possible effect of the take-off incident was being treated "like the plague".

The emails, released by Nasa after requests from the The Washington Post, show there was suspicion within Nasa before the disaster that the take-off incident might cause trouble when the shuttle came to land.

An email from Mark Stuart, a colleague of Mr Daugherty, confirmed Nasa was keeping its concerns under wraps: "I am advised that the fact that this incident occurred is not being widely discussed."

Nasa has saidhigher ranks did not see the emails before the disaster. The correspondence has been passed to the investigating panel.