NASA will remove and replace a leaky gaseous hydrogen valve and then attempt to launch shuttle Discovery and seven astronauts on an International Space Station assembly mission on Sunday.The 18-story shuttle and its crew are tentatively scheduled to blast off from Kennedy Space Center at 7:43 p.m. EDT Sunday, setting sail on a shortened mission that would feature three rather than four spacewalks. The work to be done on the fourth would be shifted to a resident crew on the outpost.
An Air Force Atlas V rocket launch now set for Saturday likely will be moved to the middle of next week to allow NASA to try to get Discovery and its crew into orbit before a deadline Tuesday.
After that, the Discovery launch would have to be postponed until April 7 so that Russia could carry out an already scheduled crew rotation and change-of-command at the orbiting outpost.
The valve swap will get under way early Friday. The replacement valve then will be retested before performing leak checks. If all goes well, an abbreviated countdown would pick up Sunday morning for a launch Sunday night.
"We have confidence that we will be able to launch Sunday night," said KSC spokeswoman Candrea Thomas.
The U.S. Air Force and United Launch Alliance are continuing to step toward an already scheduled Saturday night launch of an Atlas V rocket with a new-generation military communications satellite.
But ULA is willing to forgo their launch opportunity Saturday if NASA can put itself in position to pick up a countdown and try to send up the shuttle on Sunday.
"We're pressing ahead with preparations to launch on Saturday. But there's not a national imperative that we launch on that day, so we can adjust," said ULA spokesman Mike Rein.
As it stands, an Atlas V and its payload -- a Wideband Global SATCOM spacecraft -- are scheduled to blast off from Launch Complex 41 at Cape Canaveral Air Force Station at 9:25 p.m. Saturday. The launch window that night will extend until 10:03 p.m.
If NASA presses ahead with a launch attempt Sunday, then the Atlas launch would be postponed until the middle of next week.
The reason: It typically takes about 48 hours to reset Eastern Range tracking and range safety systems between the launches of different vehicles flying different flight profiles. Range users typically are allowed a back-up launch date in case weather or a minor technical problem prompts a scrub.
So NASA would be allotted launch attempts on Sunday and Monday, and in this case, the agency probably would be given an opportunity on Tuesday if need be. The earliest the Atlas could launch then would be next Wednesday or Thursday.
An initial attempt to launch Discovery on Wednesday was scrapped when a gaseous hydrogen leak was detected near the end of fuel-loading operations.
The leak was traced to a seven-inch quick-disconnect valve that links a gaseous hydrogen vent line with the shuttle's external tank. The vent line is designed to route excess gaseous hydrogen from the liquid hydrogen tank within the ET to a flare stack in the pad 39A area. The flare stack burns off the hydrogen.
The temperature of supercold liquid hydrogen is Minus 423 degrees Fahrenheit and the propellant boils off -- turns from a liquid to a gas -- within the external tank. The gaseous hydrogen keeps pressures within the tank at proper levels, but when too much builds up, it is vented through the quick-disconnect valve to a line that routes it down the Fixed Service Structure at the launch pad to a nearby "flare stack," where the excess is burned off.
NASA mission managers plan to meet Saturday to review the replacement work and the results of leak checks on the valve.
ABOUT THE IMAGE: Click to enlarge and save the cell phone photo that shows a Kennedy Space Center closed-circuit television view of NASA contractor technicians working around the area where a leaky gaseous hydrogen valve is located on the shuttle Discovery stack. Photo credit: James Dean, Florida Today.
3 comments:
In these difficult economic times, the space program is nothing more than a HUGE waste of money and resources.
You obviously have no idea what you are talking about. Try getting educated and then you can make an informed comment. The government is spending more bailing out businesses that ran themselves into the ground than they are are spending on the shuttle program.
OPINIONS are like rear ends every one has one good job todd keep up the good work
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