Washington, Feb. 1: To sleeping Texans who heard the “boom-boom,” it was the sound of the sky falling. To the clinical-voiced controller at Nasa’s Mission Control, it was a “contingency.” To Americans already grappling with a confluence of threatening events, the instinctive reaction was: “What next?”

Like the space shuttle Challenger disaster 17 years ago this week and the attacks of September 11, the breakup of the Columbia unfolded in real time before a nationwide television audience, sparking many of the same unsettled feelings. Only because the crash began some 40 miles above the earth could the instinct to think of terrorism be repressed.

But to a nation still struggling with the aftermath of the most devastating terrorist attack in its history and the abiding threat of another, plus a sluggish economy, nuclear tension with North Korea and the prospect of war with Iraq, this morning’s tragedy fell as an especially harsh blow.

“We’ve grown used to the idea of space, and perhaps we forget that we’ve only just begun,” Ronald Reagan told the nation on January 28, 1986, when the Challenger exploded on takeoff. “I know it’s hard to understand, but sometimes painful things like this happen. It’s all part of taking a chance and expanding man’s horizons. The future doesn’t belong to the faint-hearted. It belongs to the brave.”

President Bush will surely need to summon all the courage he can muster and more important, summon the nation’s in the days and weeks ahead. For even as he tries to rally an anxious nation and doubting allies for a war, he will face a new, if predictable, challenge: public demands for answers and political demands for accountability.

The mourning will come first, of course. Like the Challenger, whose crew was a multiracial, multiethnic American mosaic, the Columbia had a diverse crew, including the first Israeli astronaut. One member was from Iowa and another was born in India.

Unlike the Challenger, which crashed at sea, the Columbia fell to earth this morning in fiery and potentially toxic bits over the cities in Bush’s home state, like a scene from War of the Worlds. Nasa spokesmen warned the public not to touch any debris, but report it instead to law enforcement authorities.

By late morning, Nasa was lowering flags to half-staff and television screens that had been full of the lulling ritual of Saturday morning cartoons were alive with charts, drawings and the endlessly replayed footage of the shuttle’s shockingly wrong multiple vapour trails as it streaked at six times the speed of sound toward a landing in Florida after a 16-day science mission.

John Glenn, the first American to orbit the earth 41 years ago, and his wife, Annie, had just turned on their television set to watch the landing. “Once you went for several minutes without any contact, you knew something was terribly wrong,” he said.

Government officials said there were no indications of possible terrorism, and the shuttle was out of range of surface-to-air missiles. Whatever the cause, there was no possibility of an emergency landing or ejection by the astronauts after the craft got in trouble at 200,000 feet, moving at 12,500 miles an hour.

In the initial aftermath of the Challenger disaster, the national and official mood was numbness. Only later did it become apparent that Nasa had long had evidence of the very vulnerability that caused that accident, the O-rings on the shuttle’s solid fuel rockets, which tended to become brittle and shrink in cold weather like that on the morning of Challenger’s ill-fated launch.

Engineers had warned of the possibility just hours before the launch.

So, too, in the days after September 11, 2001, there was enormous national unity and great reluctance to question the government missteps or intelligence failures that might have left the nation vulnerable to such brutal attack. But those questions have since surfaced with increasing urgency, and many remain unanswered today.

But for the moment, today there was only shock. Democratic leaders of the House of Representatives, meeting at a Pennsylvania resort to plan strategy for confronting President Bush on taxes, Medicare and the rest of his domestic agenda, instead began to pray.