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July 20, 1999
Web posted at: 9:42 a.m. EDT (1342 GMT)

In this story: First lady, VIPs, had gathered Telescope is heaviest payload ever Operator made the right call RELATED STORIES, SITES

CAPE CANAVERAL, Florida (CNN) -- NASA said it would try again Thursday to launch the space shuttle Columbia after Tuesday's liftoff was aborted with just 6 1/2 seconds left in the countdown.

Engineers first said the problem was a potentially dangerous buildup of hydrogen in the engine compartment, but later NASA officials said a faulty indicator may have caused the problem.

NASA rescheduled the launch for 12:28 a.m. EDT Thursday. There is a 90 percent chance of good weather for that launch, Cape Canaveral Air Station officials said. The forecast calls for scattered clouds at 3,000 and 25,000 feet, visibility of 7 miles and temperature of 80 degrees. The only concern is the slight chance of coastal showers.

Unless Columbia lifts off soon, the mission could be delayed until mid-August. The U.S. Air Force needs to halt launches for about a month to modify its rocket-tracking system.

The shuttle, commanded by Eileen Collins, the first woman to lead a U.S. space mission, was to have blasted off at 12:36 a.m. Also aboard was the world's most powerful X-ray telescope.

NASA equipment detected an increased concentration of hydrogen just before the three main engines ignited for liftoff.

"Cutoff," a launch controller said. "Cutoff was given," another replied.

Collins and the four other astronauts 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.

First lady Hillary Rodham Clinton and her daughter Chelsea, as well as Sally Ride, America's first woman in space, had gathered to watch the launch. A sign held by a female space worker lauded Collins on the 30th anniversary of the first manned moon landing, by Apollo 11: "Eileen -- You go girl!!!"

The lengthy VIP list also included Health and Human Services Secretary Donna Shalala; 15 members of Congress, 13 of them women; and folk singer Judy Collins, who wrote a song for the occasion.

The flight would have been the third in space for Collins, 42, an Air Force colonel and former test pilot.

The Chandra observatory is the biggest X-ray telescope ever built, measuring 13.5-meters (45-foot). It weighs 22,500 kilograms (50,000 pounds), with its attached rocked and support gear, and represents the heaviest payload ever put aboard a space shuttle.

Dozens of scientists who worked for decades on the program were gathered at the launch site in anticipation. The telescope should have flown last August but was grounded first by software problems, then bad circuit boards, then a suspect rocket motor.

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

NASA's top space scientist, Ed Weiler, noted that like the Hubble Space Telescope now orbiting Earth, Chandra has 1 million parts. Hubble was launched in 1990 with a flawed mirror that was discovered after the telescope was in orbit. Shuttle astronauts later fixed the telescope.

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.

Joining the team's scientists for the launch was the 88-year-old widow of the Nobel Prize-winning astrophysicist for whom the telescope is named, Subrahmanyan Chandrasekhar. The University of Chicago professor was known as Chandra, which is Sanskrit for "moon" or "luminous."

Before the next launch attempt, technicians will have to replace six igniters, needed to burn off hydrogen vapor below the engines before they are fired. At the same time, engineers will try to determine why one of two hazardous gas detectors gave an erroneous reading.

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. Launch Director Ralph Roe said the operator made the right call.

It was the first time in years that a countdown was called off so close to launch.

"Sorry about the delay. We'll do it in a couple days, hopefully," a launch controller told Collins as she exited the shuttle.

"We'll be ready whenever," she replied.

The Associated Press and Reuters contributed to this report, which was written by CNN Interactive Senior Writer Robin Lloyd.

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