April 4, 2011 at 12:47 AM ET
Last updated 10:30 a.m. ET April 4:
NASA says the shuttle Endeavour's last scheduled launch will have to be postponed another 10 days to avoid a traffic jam in orbit.
Endeavour's April 19 liftoff will be put off until April 29 at the earliest because the Russians aren't willing to slow down the voyage of a robotic Progress cargo ship to the International Space Station. If both missions had proceeded as planned, the Progress would have shown up while Endeavour was still attached to the space station, which is an operational no-no.
For what it's worth, the delay means that Endeavour is currently due to blast off on the same day as Prince William's royal wedding to Kate Middleton at London's Westminster Abbey. (Sorry, your highness, I'll be attending the launch instead.)
NASA had hoped to persuade the Russians to put their Progress into a "parking orbit" for a few days after its April 27 launch. That would have given Endeavour time to finish its business and fly away from the space station before the cargo ship's automated docking. But the Russians held firm to their timetable for the Progress' arrival, forcing NASA to postpone Endeavour's launch.
Last month, NASASpaceflight.com's Chris Bergin noted that NASA and the Russians were in negotiations over the timing of the two missions. One of the sticking points: The Progress' cargo includes a time-sensitive biological experiment that has to be put in the space station's freezer within days of launch.
At the time, Bergin said it was "unlikely" that NASA would change Endeavour's launch date, but that's precisely what happened. The new launch time is 3:47 p.m. ET on April 29.
Endeavour's STS-134 mission is notable for at least three reasons: First, it would be Endeavour's final flight before it is retired and donated to a museum. Second, the shuttle is due to deliver a $2 billion international physics experiment known as the Alpha Magnetic Spectrometer. And third, the mission's commander, Mark Kelly, is the husband of U.S. Rep. Gabrielle Giffords, D-Ariz., who suffered a grave head injury in a shooting three months ago but now seems likely to attend the launch, whenever it is.
Endeavour and the Alpha Magnetic Spectrometer were originally due to go up into orbit last November as the final space shuttle mission, but NASA shuffled the launch schedule to give engineers more time to retrofit the physics experiment for extra years of service. Further slips pushed the STS-134 launch from February to April.
Last week, Kelly and his crewmates visited NASA's Kennedy Space Center in Florida for a launch rehearsal, just in time to see their spaceship pummeled by severe weather. NASA said Endeavour's external fuel tank suffered only "minor foam damage," and the shuttle orbiter itself was not affected. So the storm played no part in NASA's decision to delay the launch.
One more shuttle flight is scheduled after Endeavour's outing. Atlantis is due to take on the 30-year-old shuttle program's last mission in late June. NASA managers reportedly would prefer to delay that station resupply flight for a couple of months — but stretching out the shuttle program any further would require extra money, and it's not clear whether that funding could be made available.
Tip o' the Log to NBC News' Jay Barbree and NBC News space analyst James Oberg.
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