By Paul Rincon
BBC News science reporter, at the Kennedy Space Center
With a rumble like thunder that rattles the ribcage, Discovery soared off into the blue Florida sky on a plume of pale exhaust.
Nasa had a lot to prove with this mission
People jostled on the green opposite launch pad 39B as they tried to get the best view. But few could have been disappointed.
There were cheers and claps as the shuttle climbed high into the clouds, engines burning with violent intensity. There was a sense of national pride being restored.
The verdict from those onlookers? "Awesome." And so it was.
But there was a sense of relief, too, that this launch, of all launches, had gone smoothly.
As the first mission since the Columbia accident in 2003, Nasa had a lot to prove, to the nation, to its political masters and to itself.
Many safety improvements had been made for the return to flight, but the STS-114 mission was as much about restoring credibility to the embattled space agency as it was about testing Discovery's new features.
"My heart was in my throat the whole morning," said Wayne Hale, the shuttle's deputy programme manager.
"Here we are today with Americans back in flight on an American vehicle. It's a tremendous step, the first of many as we get into exploration of the Solar System, back to the Moon and on to Mars."
William Readdy, associate administrator for space operations, told journalists: "Today, mother nature smiled on us, and I also think the Columbia crew smiled on us. We owe them and their families a debt of
But he cautioned: "We've got 12 days of orbit operations to do, and then we've got to get Discovery and her crew safely back home."
In the post-launch news conference, Nasa acknowledged press reports describing the sighting of what appeared to be debris falling around the vehicle during the flight to orbit.
But panel members said they could not elaborate on a direct question about this sighting, to the visible frustration of some journalists.
They added they could only address the matter of debris in general once their experts had had time to assess pictures from cameras monitoring the launch.
Nasa officials were clearly keen that their buoyant mood not be spoiled in the wake of this historic lift-off.
Mr Readdy called Discovery the "best vehicle we have ever fielded" that had performed a "pristine launch".
But it was inevitable that this mission was going to be viewed through the prism of Columbia.
Indeed, it's unlikely that debris would ever have been such an issue were it not for the way that the Columbia investigation exposed the catastrophic damage that could be wreaked by a single piece of foam.
"You can never let down your guard and I think that was one of the lessons we learned after Columbia. It takes eternal vigilance to do what we do," admitted Mr Readdy.