Potential Shuttle Launch Slip To April 29

NASA is expected to make an announcement at the top of the hour on a potential 10-day delay in the upcoming launch of shuttle Endeavour and six astronauts on that orbiter's 25th and final flight.

Senior NASA officials are at Baikonur Cosmodrome in Kazakhstan today for the planned launch of a Russian Soyuz rocket and the final three members of the Expedition 27 crew. Russian officials have been negotiating with NASA for a delay until April 29 in the shuttle launch, a move that would clear the way for the comings and goings of two Russian Progress space freighters at the International Space Station.

The Russians hope to undock Progress 41 on April 26 and then launch Progress 42 a day later. The Progress 42 spacecraft then would arrive at the station on April 29.

NASA and the Russians avoid "dual docked operations" at the station, which means that the arrival and departures of different vehicles are generally departed by two or three days. NASA had hoped the Progress could launch and loiter in orbit until Endeavour departed the station. But there will be time-critical science experiments on Progress 42, so that's not an option.