NASA has scrubbed today's launch of Space Shuttle Discovery when high winds violated flight the tight rules for launching the space shuttle. Additional problems with a faulty thruster heater had also plagued the countdown throughout Saturday, with engineers unsure if the problem could be managed in orbit.
Crucial to the decision was whether it was better to launch with the faulty thruster heater or recycle the main cryogenic fuel tank. That dilemma has now changed with a recycle of the tank proceeding. A decision on whether to replace the faulty thruster heater will be taken by tomorrow morning.
The current launch window extends to July 19, and the estimate is that it will take 12 days to replace the thruster heater – reducing the window to barely a week in the middle of July.
The next launch window that meets all launches criteria is August 28 – September 14 – by which time the hurricane season will be in full force and introducing yet a further complication to making "Return to Flight Three" a success.
Flotsam and Jetsam
Whichever day Discovery launches all eyes will be on the orange-hued fuel tank, which shed devastating foam insulation during Columbia's launch and pierced the shuttle's protective heat shield.
NASA spent more than a billion dollars to fix the problem, but foam still fell off the tank during Discovery's launch last year, the first since the Columbia tragedy.
The debris missed the Discovery shuttle, but the incident prompted the space agency to ground the spacecraft until now.
NASA administrator Michael Griffin defended his controversial decision to schedule Saturday's launch despite opposition within his own staff, and expressed confidence that no large chunks of foam would peel off this time around.
"We are not expecting that. I do not feel vulnerable," he said, although he underscored that flying to space was never free of danger.
"Flying a shuttle is not without risk for many reasons," Griffin told reporters Friday.
"In fact, I worry that we spend so much time worrying about foam that we won't worry about other things which could get us," he said.
"Foam is a concern, but I very strongly feel that we are not risking the crew for foam in this case, or I wouldn't feel comfortable launching," Griffin added.
NASA chief safety officer Bryan O'Connor and chief engineer Chris Scolese had called for a six-month delay to the launch to redesign foam on the fuel tank. But the two officials later backed the launch.
NASA has installed more than 100 cameras to detect any loose debris and Discovery will perform a back flip before docking to the ISS so the space station can take pictures to see if its protective heat shield was damaged.
The images will allow officials to better understand the phenomenon and fix it, Griffin said.
"This is the first step back toward restoring the shuttle to regular (flights) … that will allow us to finish the space station project," Griffin said.
"Quite frankly, I think if we are unable to complete the project that we have before us, the space station, we will have a certain lack of credibility in encouraging others to join us in the exploration of Mars," Griffin said.
It would take years for a vessel to reach Mars, so the ISS is essential to understanding the effects of living in space for long periods of time, Griffin said.
He said "every single" shuttle flight was important since the fleet will be retired in 2010. Griffin said he wanted to conduct about four missions per year to finish the ISS before the 25-year-old shuttle is grounded.
NASA plans to replace the shuttle fleet with a Crew Exploration Vehicle (CEV) that could take astronauts all the way to Mars. But the space agency says the first manned flight would only take place in 2014, leaving the United States without a space vessel for at least four years.
The Discovery astronauts will deliver critical equipment and supplies to the ISS and drop off European Space Agency astronaut Thomas Reiter of Germany, adding a third crew member to the space station.
Bad weather has threatened to delay the liftoff by at least a day. The shuttle has a July 1-19 launch window.
