Countdown to shuttle launch begins

The Discovery space shuttle is scheduled to launch at 3:51 p.m. EDT on Wednesday, marking the first shuttle flight since the Columbia disaster of 2003 and NASA's first concerted attempt to demonstrate that it's fixed the problems that caused the high-profile mishap.

NASA said that it's ready for Discovery's 13-day mission. During the 29 months that the shuttle fleet has been grounded, the agency has scanned shuttle panels for cracks with ultrasound and X-rays, redesigned the external tanks, added new sensors, and created a new level of bureaucratic strata focused on mission safety.

Also, a contingency plan, dubbed "Safe Haven," would permit the seven-person crew to take refuge temporarily at the International Space Station if its orbiter vehicle were critically damaged. The station is estimated to have enough air and "consumables" for between 50 days and 60 days, though it would take about a month to launch the Atlantis shuttle on a rescue mission.

Some last-minute glitches caused worries but have not postponed the scheduled launch. Around 7:10 a.m. EDT Wednesday, a heater failure delayed filling the shuttle's large orange external tank, and on Tuesday evening a window cover fell about six stories and damaged orbiter tiles that were subsequently replaced.

Yahoo has signed an agreement to provide official coverage of the launch and around-the-clock video footage of the 12-day mission, including take-off, space walks and shuttle landing. The company will provide a co-branded Windows Media Player that will stream the online video on the Web sites of Yahoo and NASA.

In addition, phone company SBC said it is offering its DSL customers VIP access to streaming video of the shuttle launch, as well as exclusive behind-the-scenes footage of news clips and interviews with the astronauts via SBC's "Members Only" Web site.

Discovery's launch will test whether these precautions work--that is, if weather at Florida's Kennedy Space Center permits. A NASA spokeswoman said Tuesday that there's a "30 percent chance that the launch will have to be postponed, and a 70 percent chance that it will proceed."

If the launch succeeds, Discovery's crew will deliver a cargo container full of supplies to the space station, perform three spacewalks, and conduct routine maintenance on the station's equipment. NASA says a "top priority" will be to inspect the Reinforced Carbon-Carbon panels on the leading edge of Discovery's wing for cracks.

In August 2003, a government review board reported that Columbia's break-up was caused by a piece of insulating foam that broke loose from the external fuel tank during the climb to orbit. That suitcase-sized foam block slammed into the leading edge of the orbiter's wing--an area of the spacecraft subject to intense heat--and eventually weakened it enough to cause a breakup at an altitude of 40 miles on re-entry.

If a catastrophic accident results in engine failure soon after takeoff, Discovery Commander Eileen Collins and Pilot Jim Kelly could land in Zaragoza, Spain; Moron, Spain; or Istres, France--or even do a U-turn and return to the Kennedy Space Center. NASA's procedures require that the weather must be acceptable at one of the European emergency landing sites before a launch can take place. (Alternate U.S. landing sites include Edwards Air Force Base in California, and White Sands Space Harbor in New Mexico.)

Safety questions remain
After the Columbia disaster, NASA came under steady fire even from usual allies in Congress.

In 2003, Rep. Dana Rohrabacher, a California Republican who chaired a space subcommittee, said: "The Shuttle has failed miserably to meet its original goals. Our reliance on such a complex and high-risk technology has drained billions of dollars from our treasury and other space programs, and has regrettably cost too many lives."

One reason for the pointed criticism is that NASA was warned about lack of attention to shuttle safety. A September 2001 report by outside government auditors--about a year and a half before the loss of Columbia--had raised alarms about the shuttle fleet. "NASA still needs to fully staff areas critical to shuttle safety," the Government Accountability Office warned at the time.

Even with NASA's pre-launch preparations, an oversight panel reported last month that the agency still does not comply with all of the recommendations made by Columbia accident investigators two years ago.

The costly space shuttle missions and alleged management problems have sparked opposition from taxpayer groups, which say that it's time to retire the shuttle and let the private sector take the lead.

The free-market Cato Institute's handbook for Congress says that NASA should "sell off the space shuttle."

"Mankind's future in space no longer depends on politicized bureaucracies and tax-funded boondoggles," Tom Schatz, president of Citizens Against Government Waste, said in a statement. "The success of SpaceShipOne, start-up space companies, and the advent of space tourism have opened the door to an exciting future of private enterprise in space. Such endeavors are economical, realistic, and more likely to yield tangible benefits for mankind and taxpayers."

Instead, however, the Bush administration has requested a modest increase--about 2.4 percent, to $16.45 billion--in NASA's budget for the fiscal year that begins in October 2005.

CNET News.com's Elinor Mills contributed to this report.