Live at KSC: NASA Presses Toward Launch

Blogger note: Check back around 8:30 p.m. tonight to see the Rotating Service Structure back away from shuttle Discovery at launch pad 39A.

NASA still hasn't found the "smoking gun" -- the cause of the hydrogen leak that scrubbed Discovery's launch attempt last week -- but the agency nonetheless is pressing ahead with plans to send up the shuttle and seven astronauts Sunday night.

A fuel-loading operation set to begin at 10:28 a.m. Sunday will prove conclusively whether the agency has fixed the leak.

NASA mission managers, consequently, gave engineers a go-ahead to march toward a launch Sunday at 7:43 p.m. - the middle of a 10-minute opportunity to put the spaceship on course for a rendezvous with the International Space Station.

NASA officials are confident that the replacement of a suspect quick-disconnect valve and associated seals will fix a gaseous hydrogen leak in an area where a critical vent line connects to the shuttle's 15-story external tank.

"If it doesn't leak, we're going to be perfectly safe to fly," said NASA Shuttle Launch Director Mike Leinbach. "We should be good to go."

NASA is facing a launch deadline Tuesday. After that, the Discovery mission would be pushed back to at least April 7 so Russia can launch an already-scheduled station crew rotation mission that will involve a weeklong change-of-command at the outpost.

Tuesday is the last day NASA could launch Discovery and complete mission objectives before departing the station a day before the planned March 26 launch of the Expedition 19 crew and space tourist Charles Simonyi, who will be making a return trip to the outpost.

Simonyi, a billionaire who led the development of Microsoft Word and Excel software, flew a round trip to the station in April 2007 and is paying the Russian Federal Space Agency a reported $35 million to visit the outpost again.

NASA's prime mission objective for the Discovery flight is the delivery and installation of a fourth and final set of massive American solar wings. A new distillation assembly for a system that turns urine into potable water also will be hauled up. Both are key to plans to double the size of resident crews to six in May.

NASA scrubbed a launch attempt last Wednesday when a dangerous leak of gaseous hydrogen was detected at the end of a three-hour external tank propellant-loading operation.

The leak was traced to a seven-inch valve designed to vent excess gaseous hydrogen from the external tank. The excess is routed down a launch-pad line to a flare stack, where it is burned off.

NASA contractor technicians replaced the valve and two associated seals, but they ran in to trouble reconnecting the gaseous hydrogen vent line to the tank. That put NASA about three to four hours behind schedule today.

Leinbach said he expected the agency would be back on schedule early Sunday. That would clear the way for engineers to start filling Discovery's external tank with a half-million gallons of liquid hydrogen and liquid oxygen.

A launch Sunday would lead to a docking at the station around 5 p.m. Tuesday. The shuttle crew would depart the outpost on March 25 and land at KSC on March 28.

ABOUT THE IMAGES: Click to enlarge and save your own copies of these Florida Today photos taken by award-winning photographer Michael R. Brown earlier today as he and his colleagues set out remote cameras around the launch pad 39A area. You can also click the enlarged images to get even bigger, more detailed views.