NASA scrubbed the last scheduled launch of the space shuttle Endeavour on Friday, citing problems with failed heaters. Astronauts on buses heading to the shuttle turned around mid-route.
The next possible launch date is Sunday. Commander Mark Kelly, husband of injured Rep. Gabrielle Giffords, D-Ariz., was leading the mission and Giffords was scheduled to watch the launch, along with President Obama and his family.
Space shuttle launches are often delayed and re-scheduled.
The shuttle is loaded with a $2 billion particle physics detector that will seek out antimatter and dark energy across the universe. Many in and outside NASA say the experiment, if successful, could validate science operations at the decade-old orbiting lab.
As many as 750,000 people were expected to crowd nearby coastal communities for the liftoff, the Associated Press reported. The very last shuttle mission is scheduled for June 28. After that, the United States will rely on Russian spacecraft to get astronauts in and out of orbit.
The Kennedy Space Center was groaning with 45,000 guests, including more than three dozen members of Congress, at least two former NASA administrators, and a score of high-level academic and space industry officials.
President Obama, who was touring tornado-struck Alabama, had not yet arrived.
NASA is ending the shuttle program this summer, after the last trip by Atlantis. Obama is pushing private space initiatives and encouraging robotic scientific mission.
NEXT STORY HP wins $2.5B NASA services contract