The space shuttle disintegrated as it re-entered Earth's atmosphere
The US space agency (Nasa) has released a detailed report into the deaths of the crew of space shuttle Columbia.
It comes almost six years after the orbiter disintegrated when re-entering the Earth's atmosphere.
The report includes grim details of the crew's final moments as the shuttle broke up over the state of Texas.
It concludes that the accident was not survivable but makes the point that astronaut seat restraints, suits and helmets did not work well.
The failure of these safety features by themselves would have resulted in "lethal trauma", says the Columbia Crew Survival Investigation Report.
It recommends the lessons be taken up in future spacecraft designs.
"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 Nasa deputy associate administrator Wayne Hale.
The accident happened on 1 February 2003.
When the space shuttle Columbia blasted off from the Kennedy Space Center in Florida, the orbiter's left wing was damaged by a piece of insulating foam falling off the orbiter's external fuel tank.
That proved fatal for the seven astronauts when they re-entered the Earth's atmosphere days later.
The world watched as the shuttle disintegrated as hot atmospheric gases blasted inside the breach, melting the ship's structure.
COLUMBIA'S FATAL FOAM
Piece of insulating foam falls during launch, piercing one of shuttle's wings
On re-entry, hot atmospheric gases blast inside the breach and melt ship's structure
Crew cabin breaks away from ship and starts spinning rapidly
Astronauts try to regain control of craft, flipping cockpit switches as alarms sound
Rapid depressurization causes crew to lose consciousness
Lack of safety restraints cause crew traumatic injuries
Nasa's extensive 400-page report into their last moments found that the crew knew for as long as 41 seconds that they did not have control of the orbiter, and records that they went into problem-solving mode as they attempted to regain stability.
As a consequence, when the cabin structure failed, resulting in rapid depressurisation and loss of consciousness, some of the astronauts were not wearing their bulky protective gloves and still had their helmet visors open. Some were not fully strapped in.
Had the astronauts switched earlier to survival operations - getting all their gear on and preparing their suits properly - they might have survived a little longer and been able to take more actions. But, the report notes, they still would have died because of the extreme forces and conditions to which they were exposed.
The Spacecraft Crew Survival Integrated Investigation Team lists individual failures in training and equipment which should now be addressed.
The recommendations call for improved training, and better seat harness systems, helmets and pressurised suits; and more automated technology that can trigger actions if astronauts become incapacitated.
The report says some safety components, such as suits and helmets, need to be integrated "into the design of the vehicle and provide features that will protect the crew without hindering normal operations".
It draws some parallels with the restraint systems now used in motor racing to protect vulnerable areas of a driver's body, such as their head and neck.
The report says future spacecraft should be designed so that, when they do begin to break up in an accident, they experience the "most graceful degradation of vehicle systems and structure to enhance chances for crew survival".
Mr Hale, who oversaw the shuttle programme during its return to flight after the accident, urged spacecraft designers in the US and overseas to read the report and apply the "hard lessons which have been paid for so dearly".
A separate study undertaken by the Columbia Accident Investigation Board (CAIB) has already conducted a thorough review of both the technical and the organisational causes of the loss of the Columbia orbiter.
This led, among other things, to a redesign of the external fuel tank to minimise the shedding of foam on launch.
The remaining vehicles in Nasa's shuttle fleet are due to be retired in 2010, on completion of the construction phase of the International Space Station.