Weather looks favorable for Thursday shuttle launch

Shuttle commander Eileen Collins is strapped in before launch
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By Robin Lloyd
CNN Interactive Senior Writer

July 22, 1999
Web posted at: 12:59 a.m. EDT (0459 GMT)

In this story: Collins ready for flight Telescope is heaviest payload ever Crucial timing in countdown cutoff RELATED STORIES, SITES

CAPE CANAVERAL, Florida (CNN) -- An instrument that gave a faulty reading and caused operators to abort Tuesday's shuttle launch needs no repairs and Columbia is ready for a second liftoff attempt early Thursday morning, NASA officials said.

Offshore thunderstorms held up Columbia's launch, which had been scheduled for 12:28 a.m. Thursday. NASA had 46 minutes to launch the shuttle.

Tuesday's liftoff was aborted 6 1/2 seconds before the shuttle's three main engines were to ignite because a hydrogen detector indicated excess gas in one of the engines.

Engineers later discovered that the reading was inaccurate -- there was no gas problem.

The spiked reading that threw off the launch Tuesday is typical of the instrument, which constantly corrects itself, said NASA spokesman Joel Wells.

But with precious seconds left before liftoff and the potential for a disaster, the operator could not afford to wait for an updated reading and made the right decision to call for engine cutoff, he said.

The space shuttle Columbia sits on the launch pad Wednesday night

"Everything is ready for flight -- both the shuttle itself, the main propulsion system and the hazardous gas detection system which picked up the false indication," Wells said.

Engineers reviewed the propulsion and gas detection systems Tuesday and reported that everything is in working order.

"Everyone feels very confident with no changes in system, and there are no modifications necessary to go out to the pad and try again," Wells said.

Wednesday morning, technicians spent four hours replacing six igniters, also known as sparklers, that already had burned during Tuesday's countdown.

The sparklers burn off hydrogen vapor below the shuttle's engines before they are fired.

Shuttle commander Eileen Collins, set to be the first woman to head up a U.S. space mission, also gave the thumbs up for a second attempt when she exited the shuttle after Tuesday's abort.

"We'll be ready whenever," she said. If all goes well Thursday, the STS-93 flight will be the third in space for Collins, 42, an Air Force colonel and former test pilot.

If the launch is scrubbed again Thursday, the mission will have to wait until mid-August because an unmanned rocket and a ground equipment modernization project will have priority.

The shuttle was to have blasted off Tuesday at 12:36 a.m. Collins and the four other astronauts in her crew were safe and never in danger, officials said, but the crew hurriedly turned off all shuttle systems. The rocket was filled with more than 500,000 gallons of highly explosive liquid hydrogen fuel and liquid oxygen.

Columbia is slated to carry the most powerful X-ray telescope ever built into space.

The Chandra observatory measures 13.5-meters (45-foot) long. It weighs 22,500 kilograms (50,000 pounds) with its attached rocket and support gear, and represents the heaviest payload ever put aboard a space shuttle.

The Columbia is the only shuttle big enough to hold it.

The telescope should have flown last August but was grounded first by software problems, then bad circuit boards, then a suspect rocket motor.

The entire Chandra project, including the shuttle ride and five years of orbital operations, costs $2.8 billion, making it one of NASA's most expensive projects.

The launch controller monitoring the gas detectors first noticed a hydrogen spike with 16 seconds remaining in the countdown. He began a manual cutoff at the eight-second mark, as quickly as he could, and computers shut everything down one second later.

Had Columbia's three main engines fired, it would have forced a full month's delay in order to replace them.

The Copyright 1999   The Associated Press. All rights reserved.