Tuesday, July 20, 1999 Published at 04:25 GMT 05:25 UK
New shuttle launch attempt on Thursday
The igniters worked but launch was aborted just before the main engines fired
A second attempt to launch the first space shuttle mission to be commanded by a woman will be made early on Thursday morning.
The failure is a severe disappointment to Nasa who intended to celebrate the 30th anniversary of the first Moon landing with the launch. But the traumatic experience of the Challenger shuttle disaster in 1986 which killed seven astronauts still leads Nasa to place safety above any other consideration.
The order to halt the countdown came after instruments appeared to detect very high levels of explosive hydrogen gas in the aft engine compartment.
"The safety of the flight crew and orbiter were not compromised at any time," he added.
One more chance this month
The next launch attempt will be on Thursday morning at 0528 BST (0428 GMT). Nasa say the 48-hour delay is required to replace the igniters intended to start the shuttle's three main engines. The six igniters were fired just prior to the abort order.
Six seconds is not the record for a late shuttle launch abort. In 1994, Endeavour's first launch attempt was halted only 1.9 seconds before lift-off and, in 1993, two shuttles were shut down with only three seconds left on the countdown clock.
The crew began leaving the shuttle an hour after the scheduled launch time and will start again their pre-flight preparations.
First woman commander
The mission, called STS-93, is the first to be commanded by a woman, 42-year-old Air Force Colonel Eileen Collins.
The Chandra project is seen as being as significant as the groundbreaking Hubble Space Telescope, which revolutionised astronomy by providing a view of the stars unobscured by Earth-based pollutants.
The 25-tonne Chandra telescope, the heaviest shuttle cargo ever, will be deployed in space seven hours after take-off. It is expected to be operational for five years.
Columbia is the only shuttle big enough to carry such a weight, but it still had to be stripped of some 3,175 kg (7,000 pounds).
Once in position the Chandra telescope will enable scientists to study the most powerful sources of X-rays in the universe, including black holes, colliding galaxies and supernovae, huge stars that explode into space.
"It's an honour for me to be chosen, but I also see it as an evolutionary process. Eventually, having women in these roles won't be news anymore. It will be expected," she says.
"Inside of Nasa, I'm very accepted and I'm treated very much like the other astronaut commanders. I really don't notice a difference."
In 1995, Colonel Collins was the first woman to pilot a space shuttle. Much of the public's interest has focused on her dual role as an astronaut and a mother to her three-year-old daughter. The jobs are equally tough and equally rewarding, Colonel Collins says.