Tuesday, August 15, 2006

Shuttle launch review under way

A two-day Flight Readiness Review is under way at Kennedy Space Center today while engineers study a potential problem with suspect bolts and load toxic propellant into the orbiter Atlantis.NASA still is targeting Aug. 27 for the launch of Atlantis and six astronauts on the first International Space Station assembly mission since late 2002. The February 2003 Columbia accident halted construction of the half-built outpost and NASA now faces a 2010 deadline to finish assembly work.A firm launch date traditionally is set at the conclusion of the review.Engineers still are studying a potential problem with four bolts securing a key communications antenna inside the shuttle's cargo bay.

The bolts are shorter than called for in engineering specifications. Engineers fear there might not be enough threads to keep the antenna in place during launch and the climb to orbit. If it broke free in flight, the antenna could plunge through the entire length of the cargo bay and cause critical damage.A plan to replace the bolts at the launch pad has been put in place. Should managers decide to swap them out, the work likely would be done late this week after engineers finish loading hypergolic propellants aboard the orbiter. Small pyrotechnic charges used to separate the shuttle from its launch platform, boosters and external tank likely would be installed prior to the replacement work, too.The propellant loading operation is continuing today at launch pad 39B. Engineers have finished loading hydrazine into the shuttle's Auxiliary Power Units, which provide the hydraulic power needed to steer the ship's three main engines in flight and control its aerosurfaces, rudder speedbrake, landing gear, brakes and nosewheel steering during atmospheric reentry and landing.Still to come: loading propellant into tanks that feed the shuttle's twin orbital manuevering engines and 44 nose-and-tail steering thrusters. The Forward Reaction Control System load was halted last weekend after a poppet valve failed. That work now is scheduled to be done Thursday, and ordnance installation is set for Friday. Any bolt replacement work likely would follow.One other option: Performing replacement work after the propellant load and before the installation of the explosive charges.

The replacement work likely would take two to four days to complete. A decision on whether to proceed is expected no later than Thursday.

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