The countdown at Cape Canaveral was halted at 12.36am (Florida time) less than half a second before Columbia's engines were due to ignite, after a warning about explosive gas. A second att empt is scheduled for tomorrow.
The abandoned launch wasa huge disappointment to Commander Eileen Collins and an audience that included Hillary Clinton, her daughter, Chelsea, 13 female members of Congress and the Health Secretary, Donna Shalala, as well as Sally Ride, the first female American astronaut, the US women's soccer team, and the folk singer Judy Collins. One female Nasa employee captured the mood, holding a sign reading: "Eileen - You go girl!!!"
The apparent build-up of explosive hydrogen gas was noticed by a ground controller with eight seconds left to take action to stop the countdown to Columbia's five-day mission, which involves carrying the pounds 930m Chandra X-ray observatory. It was later thought the detector had apparently malfunctioned. "We are convinced this is not a real leak," said Ralph Roe, the launch director.
Had the engines fired and then been stopped, it would have taken a full month to replace them - delaying the launch by up to a year, because other launches would have priority. If Thursday's launch does not succeed, that 12-month delay could still apply.
The mission will be the first to be commanded by a woman. Although women underwent tests for the astronaut programme in the 1960s, the US space agency, Nasa, rejected them in favour of male test pilots. For years, Nasa has struggled with ingrained chauvinism in its approach to women astronauts. Mrs Collins, 42, is Nasa's fourth female astronaut, after Ms Ride broke the male mould in June 1983.Reuse content