Space Shuttle Columbia crew, left to right, front row, Rick Husband, Kalpana Chawla, William McCool, back row, David Brown, Laurel Clark, Michael Anderson and Israeli astronaut Ilan Ramon are shown in this undated crew photo.
The seven shuttle astronauts who died were in an 'unsurvivable' situation. But the space agency cites several equipment flaws in the 2003 disaster.
Astronauts on the shuttle Columbia were trying to regain control of their craft before it broke apart in 2003, but there was no chance of surviving the accident
From the crew's perspective, the shift from what appeared to be a normal descent on February 1, 2003, into disaster happened so fast that the astronauts didn't even have time to close the visors on their helmets.
Columbia broke apart about 12 miles over Texas as it headed for landing at the Kennedy Space Center. The cause of the accident was traced to a hole in one of the shuttle's wings, which was hit by a piece of falling foam insulation during launch 16 days earlier.
Seven astronauts, including Israel's first astronaut Ilan Ramon, were killed when superheated atmospheric gases blasted inside the breach like a blow torch, melting the ship's structure.
The crew cabin broke away from the ship and started spinning rapidly. Analysis of the wreckage indicated the crew members had flipped cockpit switches in response to alarms that were sounding. The astronauts had also reset the shuttle's autopilot system, the report said.
"We have evidence from some of the switch positions that the crew was trying very hard to regain control. We're talking about a very brief time in a crisis situation," said NASA's deputy associate administrator, Wayne Hale.
But rapid depressurization caused the Columbia crew to lose consciousness, and medical findings show that they could not have recovered, said the report, which took four years to compile.
"This report confirms that although the valiant Columbia crew tried every possible way to maintain control of their vehicle, the accident was not ultimately survivable," said Hale, who oversaw the shuttle program during its return to flight after the accident.
Analysis shows the astronauts' shoulder harnesses failed and their helmets did not adequately protect their heads. The lack of safety restraints caused traumatic injuries.
The investigation also found problems with the shuttle's seats and parachute landing system, which requires astronauts be conscious to operate manually.
Even if the safety gear had worked, the astronauts would have died due to the winds, shock waves and other extreme conditions in the upper atmosphere.
Designing spacesuits that are more automated and integrated into future spaceships is among 30 recommendations made in the report.
"I call on spacecraft designers from all the other nations of the world, as well as the commercial and personal spacecraft designers here at home to read this report and apply these hard lessons which have been paid for so dearly," Hale said.
Also killed in the accident were shuttle commander Rick Husband, pilot William McCool and astronauts Michael Anderson, David Brown, Kalpana Chawla and Laurel Clark.
Much of what is in the report was discovered by the Columbia accident investigation team, which released a series of findings and recommendations six months after the disaster.
The panel advised retiring the space shuttles as soon as NASA finishes using them to complete construction of the International Space Station, a $100 billion project of 16 partner countries that has been under way for more than a decade. The shuttle Challenger broke apart in 1986.
Since the accident, NASA has flown 11 shuttle missions and has nine left in its schedule. A 10th mission to fly a physics experiment to the space station is under consideration.
last moments of Columbia crew
Fixing the deficiencies would not have saved the astronauts because the accident -- occurring at high altitude and hypersonic speed -- was "unsurvivable," the report said. But such corrections could improve chances of survival in less serious accidents.
Even though parts of the report were redacted to protect the astronauts' families, it represents the most graphic and harrowing account of the crew's final moments.
NASA officials already knew the astronauts had died from either a lack of oxygen or from striking objects in the cabin, and the report was unable to distinguish between the two possibilities. But it does catalog all the things known to have gone wrong and provide new details about the crash.
One comforting conclusion in the 400-page report is that, after the first few seconds, the astronauts were probably unconscious and never knew what was happening.
"On behalf of their colleagues and families, I can say that we are relieved that we discovered this," astronaut Pamela Melroy, deputy project manager for the investigative team, said at a news conference.
The mission was doomed when a piece of foam broke off the external fuel tank during launch on Jan. 16, 2003, and damaged the leading edge of Columbia's wing. The wing was not inspected because the prevailing belief was that foam could not cause significant damage.
On its reentry to Earth's atmosphere on Feb. 1, Columbia broke up over Texas, killing all seven astronauts.
A 2003 report angrily blamed the accident on a "broken safety culture" at NASA.