There are questions to be asked about the shuttle tragedy, not least about its safety and its cost, writes Conor O'Clery, North America Editor
It fell from the sky in pieces of metal, circuit boards, ceramics and human bones, slicing through fir trees, tearing holes in rooftops and ripping into the fabric of the America psyche, still not fully recovered from September 11th.
The fall to earth of the shuttle Columbia on Saturday morning and the death of its seven crew members heightened the sense of vulnerability that has possessed the United States since the attacks on New York and the Pentagon.
Once again the national mood has turned to pain and grief. It happened at a time when nerves were stretched as an anxious nation anticipated war with unforeseen tragedies yet to come. As on September 11th, there were the same heart-stopping phone calls across the country at about 9 a.m. eastern time as people rang friends and relatives to say: "Turn on your television."
Once again the nation heard bad news from sombre anchors like Dan Rather of CBS, his voice quivering on the verge of tears. Scheduled TV programmes were cancelled to show over and over again the multiple white plumes of vapour spiralling unevenly across the blue Texan sky.
Viewers heard the recordings of mission control talking laconically with Columbia about tyre pressure and then a flight specialist saying: "We did not copy your last . . ." and the reply: "Roger, ah . . ." followed by static.
On NBC, Peter Jennings recalled that Libyan leader Col Moamar Gadafy had broadcast pictures of the shuttle Challenger exploding in January 1986 to be shown over and over again to underline the vulnerability of American technology and speculated that Iraqi President Saddam Hussein might do the same this time.
President Bush, pondering war plans at Camp David in Maryland, was told of the disaster in a telephone call from NASA chief Sean O'Keeffe. Mr Bush returned to the White House in a speeding convoy of limousines.
From the Oval Office, he spoke over speaker-phone to shocked relatives holding hands at the Kennedy Space Centre in Florida.
A few hours before they had been waiting for the moment of joy when they would greet the crew on their return from a 16-day mission. "I wish I was there to hug and cry and comfort you right now," said the president.
The tragedy was made more poignant by the fact that the crew was the most representative group of earthlings yet to travel together in space. They included an Indian-born teacher, an Israeli pilot and an African-American astronaut.
Col Ilan Ramon's presence on the shuttle had led to greater security before the launch, but sabotage was quickly dismissed as a cause (ironically the spacecraft disintegrated near an East Texas town called Palestine).
In an address from the Cabinet Room Mr Bush, looking drawn and weary, informed viewers, "The Columbia is lost, there are no survivors." His eyes glistening, he said: "The same Creator who names the stars also knows the names of the seven souls we mourn today. The crew of the shuttle Columbia did not return safely to Earth, but we can pray that all are safely home."
At times of national tragedy, American presidents assume an enhanced stature as the nation's comforter. Ronald Reagan was transformed when he told Americans after the Challenger disaster in 1986 that "the future doesn't belong to the faint-hearted; it belongs to the brave" and that they would never forget those who "slipped the surly bonds of earth" to "touch the face of God".
Bill Clinton's rallied people shocked by the Oklahoma bombing in 1995 with St Paul's admonition: "Let us not be overcome with evil, but overcome evil with good." Mr Bush's speech was made more difficult by the likelihood that in a few weeks he will address the nation once more, about sending American soldiers into a new war.
This weekend at least, the tensions over Iraq were put to one side. French President Jacques Chirac, who opposes the war, was one of the first foreign leaders to call Mr Bush with condolences, followed by President Vladimir Putin of Russia.
By the time Mr Bush spoke on television, five hours after the shuttle disintegrated, the whole of America knew for sure that the astronauts were dead. Flags were lowered to half mast. The television news switched to the ground in Texas where police had tied cordons of yellow tape around bits of debris to prevent people taking them for souvenirs.
People spoke of hearing a loud bang in the sky as the shuttle disintegrated at 18 times the speed of sound,and then seeing objects plummeting to earth with streams of vapour like a spectacular scene from War of the Worlds.
John Hughes, a worker at a fibreglass factory, watched the pyrotechnics and described a four-foot object floating to earth. "At first I was saying this is probably the coolest thing I have ever seen," he said. "Then we found out what it was and it was like, this is not the coolest thing I have seen any more."
NASA officials warned people not to touch the pieces of wreckage because of toxic hydraulic propellants carried on the spaceship.
The charred helmet of one of the crew members was found lying in a garden in Norwood Texas.
Crowds of onlookers laid wreaths of flowers beside a chunk of metal in Nacogdpoches. A burnt metal cylinder spewed yellow smoke on Route 155. Troopers paused to pray over human remains in a field near Hemphill.
Miraculously, no one else was injured or killed. As in any tragedy, a few scavengers tried to make a profit and several items described as debris from the space shuttle were advertised on an auction website before the day was out, though yesterday they were taken off.
In Houston, home of generations of professional astronauts, the tragedy was felt most keenly.
At the Outpost Tavern near the Lyndon Johnson Space Centre, where there is a wall dedicated to the crew of the Challenger, bar-owner Stan Aden said another wall would now be dedicated to the Columbia crew. As happened after the Challenger tragedy, people came to lay flowers in great heaps at the foot of the sign for the space centre.
The shuttle programme director, Ron Dittemore and NASA's chief flight director, James Heflin, held a news conference four hours after all hope was lost. They disclosed that there was no way of survival for the crew, as the spacecraft did not have an escape pod.
They also revealed that there had been some low-level concern over a piece of foam hitting the left wing on take-off and that all future flights of space shuttles would be put on hold until they found and corrected the cause of the disaster.
Mr Dittemore promised: "We're going to fix this problem, we're going to get back to the launch pad". The period of mourning would be followed by "getting on with the job which is the best therapy".
This may not be so easy. It was 32 months after Challenger before the next launch. Questions will have to be answered again, such as why Columbia, the oldest shuttle of the NASA fleet, was not retired in 2001 as recommended.
Questions will be asked about whether the programme is now too risky and whether it is draining funds away from investment in a modern, safer and cheaper system.
Questions will be asked why manned flight is necessary, underlined by the launch by Russia yesterday of an unmanned flight.
The shuttle design is more than 30 years old, is much more cumbersome and complex than new rocket designs and uses pre-Pentium technology. Each shuttle voyage costs about half a billion dollars - big business for Boeing and Lockheed Martin - compared to a projected $5 million.
Terrible as this tragedy is, there was also a sense that this was a trauma which the nation could cope with more easily than the shock of Challenger, which exploded 72 seconds after take-off in full view of a watching television audience.
Everyone knew the names of the astronauts on board Challenger, especially school teacher Christa McAuliffe, whose presence captivated children across the US. Challenger was a symbolof America's technological achievements at a time of Cold War, a metaphor for America's striving for dominance. Since then shuttle flights have become routine, even humdrum.
The voyage of Columbia was the 113th shuttle journey into space since 1981. Once again it was felt safe enough to allow a school teacher to join the crew. Most Americans were in fact barely aware that Columbia was due to land on Saturday morning.
It was in India and Israel and in Jewish communities like that in Brooklyn where everyone followed this flight which carried their heroes, Kalpana Chawla and Ilan Ramon. But just as in 1986, the impact will be particularly upsetting for thousands of children in schools from Pennsylvania to California who had a personal connection with Columbia, like the students from a New York school who had sent a magnetic card to see if it changed in space.
For these children, the Columbia disaster has provided a different lesson - the fragility of human endeavour.
Some of the romance had gone from space travel, except when bad things happened, said John Logsdon, director of the space policy at George Washington University's Elliott School of International Affairs, "then we remember these are brave people willingly taking risks".
Astronaut Thomas Jones, who has flown four missions, commented: "At times like this you always ask, why are you doing it?" But, he told National Public Radio, "it would be unnatural not to have people in space."