Sunday, August 16, 2009

Discovery Rollback Decision Now Set For Tuesday

NASA sent landing teams Sunday to emergency runways in Spain and France despite the fact that Discovery might be rolled back from its launch pad to an assembly building for inspections and possibly repairs to suspect external tank foam insulation.

Another team will fly Monday to a back-up landing site at Edwards Air Force Base in California, and a decision on whether to proceed with a targeted Aug. 24 launch -- or roll back for repairs -- will not be made until after a traditional flight readiness review to be held Tuesday at Kennedy Space Center.

Discovery and seven astronauts are scheduled to launch at 1:58 a.m. Aug. 24 -- a week from Monday -- on a mission to haul supplies and equipment to the International Space Station.

The astronaut crew is scheduled to go in to quarantine at Johnson Space Center in Houston on Monday, and then fly to KSC on Wednesday evening. A launch countdown is slated to pick up at 11 p.m. Thursday. The shuttle's external tank is to be fueled for flight starting at 4:33 p.m. next Sunday.

NASA engineers are examining data from weekend tests on foam insulation in the central ribbed area of Discovery's external tank.

Thin strips peeled off that area on Endeavour's tank during a July 15 launch. Engineers think an adhesive did not adhere properly to a substrate primer on the aluminum-lithium skin of the tank.

NASA now has performed more than 200 plug pull tests on the so-called intertank area of Discovery's external tank. Test results are being reviewed.

One of 34 metal brackets that hold pressurization lines and electrical cabling to the outside of the external tank lost foam during the past two shuttle missions.

NASA conducted high-tech x-rays and found no evidence of cracks or voids on the same bracket on Discovery's tank. But NASA engineers think a process used to apply foam to that bracket and three others might be the cause of the foam loss on the past two flights. And the three other brackets on Discovery's tank were not x-rayed before the shuttle was rolled to launch pad 39A on Aug. 4.

NASA engineers ordered inspections of the four brackets on the tank being prepared in the Vehicle Assembly Building for the Nov. 12 launch of Atlantis. Data from those inspections is being reviewed by experts at Michoud Assembly Facility in New Orleans, the plant where shuttle external tanks are manufactured.

NASA's engineering community is split on the issue. At a shuttle program-level review this past week about 25 percent of the engineers thought Discovery should be rolled back to the VAB for inspections and possibly repairs.

Data and results from the latest tests and inspections will be presented Tuesday at a Flight Readiness Review -- the venue where NASA normally assigns firm launch dates for shuttle missions.

NASA is facing an Aug. 31 deadline to get the Discovery mission under way. After that, the agency would yield for the planned Sept. 10 debut launch of a robotic Japanese cargo carrier and the next Russian Soyuz crew rotation mission, now slated for launch Sept. 30.

NASA would have a short window Sept. 19 and Sept. 20 to launch Discovery and complete its supply run to the station in time to depart in advance of the Soyuz flight.

The next launch opportunity would come Oct. 17. A delay until then would push the planned Nov. 12 launch of Atlantis to Dec. 11 or 12.

NASA has seven shuttle missions to the station remaining on its manifest. The agency is supposed to finish those flights and retire the shuttle fleet by the end of 2010, but NASA, the Congress and the Obama Administration are starting to plan for a potential slip to 2011.

ABOUT THE IMAGE: Click to enlarge the NASA image of technicians watching on as Discovery's payload bay doors were closed for flight last week at Kennedy Space Center's launch pad 39A. You can also click the enlarged image to get a bigger, more detailed view. Seen inside the bay is an Italian-built multi-purpose logistics module named Leonardo. The cylindrical cargo carrier is filled with more than 15 tons of supplies and equipment for the International Space Station's newly expanded crew of six. Photo credit: NASA/Jack Pfaller.

No comments: