Blogger Note: This is an updated version of a post below.
NASA aims to fix dangerous gaseous hydrogen leaks and carry out a fuel-loading test next Wednesday -- moves that would clear the way for a July 11 launch of Endeavour on an International Space Station assembly mission.
But if the repairs don't work, and elevated levels of the highly flammable gas are detected again, NASA could be forced to switch out the shuttle's external tank and solid rocket boosters.
Such a swap would trigger significant delays and make it more difficult for NASA to fly eight remaining shuttle missions and finish station assembly by the end of 2010.
NASA is hopeful that a recovery plan briefed to managers Wednesday will halt the leaks, which caused back-to-back launch scrubs June 13 and June 17 and another in March.
"There's a very high degree of confidence that we understand this problem, and it's a very simple problem," said Kyle Herring, a spokesman for NASA's Johnson Space Center in Houston. "It's not a simple problem to correct."
Engineers load the external tank with 526,000 gallons of liquid hydrogen and liquid oxygen -- propellants that power the shuttle's three main engines during ascent.
Some liquid hydrogen -- which is Minus 423 degrees Fahrenheit -- turns from a liquid to a gaseous state as the tank is filled.
The Endeavour leaks were detected around a seven-inch vent line designed to keep pressures within the tank at proper levels by routing excess hydrogen gas to a nearby flare stack, where it is safely burned off.
A slight misalignment in an attachment assembly on the outside of the tank apparently created a tiny leak path in a Teflon seal when the vent line was fixed to it. So an alternate seal and specially designed washers will be put in place to stop the leak.
NASA will have just four days between July 11 and July 14 to get Endeavour off the ground.
A robotic Russian Progress space freighter is scheduled to launch June 24 on a supply run to the station. It can loiter five days but must dock at the orbiting outpost by July 29.
Endeavour consequently must launched by July 14 to complete 12 days of assembly work and then depart the outpost before the Russian resupply ship arrives. The next Endeavour launch opportunity after that would be July 27.
Herring said it would be a challenge to roll Endeavour back to its assembly building, swap its external tank-and-booster set, and then be in position to make a July 27 launch attempt.
Endeavour and seven astronauts aim to deliver the third and final segment of the $1 billion Japanese Kibo science research facility to the station.
Its launch delay from June to July already pushed back a subsequent station outfitting mission. The planned Aug. 7 launch of shuttle Discovery on that flight has been bumped to Aug. 18.
2 comments:
What will happen to the tank if it is swapped? Scrapped or repaired?
Apart from the delay if a swap is needed, would the resulting shortage of tanks cause problems?
Since that's a brand new $40 million dollar tank, which they have been building for almost thirty years, I would never expect the problem to be with it.
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