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Clocks to begin ticking toward Discovery's launch BY WILLIAM HARWOOD STORY WRITTEN FOR CBS NEWS "SPACE PLACE" & USED WITH PERMISSION Posted: August 21, 2009 
Engineers at the Kennedy Space Center geared up Friday for the 11 p.m. EDT start of the shuttle Discovery's countdown to launch Tuesday on a space station resupply mission. While some unplanned work will be carried into the countdown, engineers are optimistic and forecasters are predicting a 70 percent chance of good weather. "We've had a few challenges along the way, but I think we've gotten them behind us," said NASA Test Director Steve Payne. "As of the moment, our systems are in good shape, launch countdown preps are proceeding and we have no new issues to report. The flight crew, the vehicle and the launch team are ready to go." Engineers plan to load the shuttle's fuel cell system with liquid oxygen and hydrogen overnight Saturday and to rotate a protective gantry away from Discovery around 5 a.m. Monday. If all goes well, the shuttle will be loaded with liquid oxygen and hydrogen rocket fuel starting at 4:11 p.m. Monday and the crew will strap in around 10:16 p.m. Liftoff is targeted for 1:36:05 a.m. Tuesday, roughly the moment Earth's rotation carries the pad into the plane of the International Space Station's orbit.
Engineers worked Friday to close out the shuttle's aft engine compartment after replacement of a suspect electrical harness and to finish a few final items associated with replacement of a hydraulic power unit in Discovery's left solid-fuel booster. The only remaining technical issue of any significance is an analysis to make sure work-arounds are understood for any potential problems with a control assembly used to route power to various circuits through the shuttle's electrical buses. A faulty controller aboard Discovery was replaced earlier, but similar problems with other test units raised questions about possible generic issues. NASA's Mission Management Team plans to meet Sunday for a final review of launch processing. Forecasters are predicting a 70 percent chance of good weather Tuesday and Wednesday, dropping to 60 percent "go" on Thursday. The primary concerns are a chance of lightning near the pad during fueling and showers in the area at launch time. Assuming a good load for Discovery's fuel cell system, Payne said the shuttle should be able to make four launch attempts in five days. "It should be a spectacular launch," Payne said. "I'm hoping we put on a good show for you."
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The official crew patch for Discovery's flight to deliver and research gear to the space station
