NASA released a detailed engineering study Tuesday outlining lessons learned about astronaut survival based on an analysis of the 2003 Columbia disaster. The study does not provide any significant new details about the fate of Columbia's crew - investigators earlier concluded the seven astronauts died of sudden oxygen loss and blunt force trauma as the crew module broke up - but a new timeline provides a wealth of data showing the pilots attempted to troubleshoot a cascade of problems in the final moments before the spacecraft's computers lost control. The timeline also shows, in grim detail, the forces acting on the shuttle's crew module in the final seconds before it broke apart, subjecting the astronauts to a sudden loss of air pressure that occurred so rapidly they did not have time to close their helmet visors.

The study, the most detailed astronaut survival analysis ever conducted, includes 30 recommendations for improving crew safety on future flights based on a review of the safety equipment and procedures used during Columbia's mission.

"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," said former shuttle Program Manager Wayne Hale, now serving as a NASA associate administrator. "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."

As part of its support for the Columbia Accident Investigation Board, NASA set up a Crew Survival Working Group in the wake of the Feb. 1, 2003, disaster that later evolved into the Spacecraft Crew Survival Integrated Investigation Team. The crew survival team began its study in October 2004 with the goals of expanding the earlier working group analysis and making recommendations to improve safety on future vehicles.

The Columbia breakup was not survivable, but the new report sheds light on how various shuttle safety systems performed and what sort of changes may be needed to improve safety in future spacecraft like the Orion capsules that will replace the shuttle after the fleet is retired in 2010.

The report was completed earlier this month, but its release was delayed "out of respect for the Columbia crew families," said veteran shuttle commander Pam Melroy, deputy project manager of the investigation. "At their request, we released it after Christmas but while the children were still out of school and home with their family members so they could discuss the findings and the elements of the report with some privacy. That's what drove the timing of today."

Columbia was destroyed by a breach in the leading edge of the shuttle's left wing that was caused by the impact of foam insulation from the ship's external tank during launch 16 days earlier. The wing melted from the inside out and eventually failed, either folding over or breaking away. The shuttle's flight computers then lost control and the crippled spacecraft went into a catastrophic spin. The nose section housing the crew module ripped away from the fuselage relatively intact, but the module broke apart within a few moments due to thermal stress and aerodynamic forces.

The analysis of Columbia's breakup identified five "lethal events:"

• Depressurization: Shortly after Columbia's flight computers lost control due to the failure of the shuttle's heat-damaged left wing, the crew module broke away from the fuselage. The astronauts are believed to have survived the initial breakup. But within a few moments, the crew module lost pressure "so rapidly that the crew members were incapacitated within seconds, before they could configure the (pressure) suit for full protection from loss of cabin pressure," the new study concluded. "Although circulatory systems functioned for a brief time, the effects of the depressurization were severe enough that the crew could not have regained consciousness. This event was lethal to the crew."

  Recommendations: Improve crew training to increase emphasis on the transition between problem solving and survival operations; future spacecraft must integrate pressure suit operations into the design of the vehicle.

• Exposure of the unconscious or deceased astronauts to unexpected rotating forces without sufficient upper body restraints and helmets: When Columbia lost control, the resulting motion was not violent enough, in and of itself, to be lethal. The crew module separated from the fuselage "and continued to rotate," the study concluded. "After the crew lost consciousness due to the loss of cabin pressure, the seat inertial reel mechanisms on the crews' shoulder harnesses did not lock. As a result, the unconscious or deceased crew was exposed to cyclical rotational motion while restrained only at the lower body. Crew helmets do not conform to the head. Consequently, lethal trauma occurred to the unconscious or desceased crew due to the lack of upper body support and restraint."

  Recommendations: Re-evaluate crew procedures; future seats and suits should be "integrated to ensure proper restraint of the crew in off-nominal situations."

• Separation of the crew from the crew module and the seat: "The breakup of the crew module and the crew's subsequent exposure to hypersonic entry conditions was not survivable by any currently existing capability," the study says. ... "The lethal-type consequences of exposure to entry conditions included traumatic injury due to seat restraints, high loads associated with deceleration due to a change in ballistic number, aerodynamic loads, and thermal events. Crew circulatory functions ceased shortly before or during this event."

  Recommendation: Optimize future spacecraft design for "the most graceful degradaton of vehicle systems and structure to enhance chances for crew survival."

• Exposure to near vacuum, aerodynamic acceleration and low temperatures: Shuttle pressure suits are certified to a maximum altitude of 100,000 feet and a velocity of about 560 knots. "It is uncertain whether it can protect a crew member at higher altitudes and air speeds," the study says.

  Recommendation: Pressure suits should be evaluated to determine weak points; improvements should be made as warranted.

• Ground impact: The current parachute system requires manual action by the astronauts.

  Recommendation: "Future spacecraft crew survival systems should not rely on manual activation to protect the crew."

"The SCSIIT investigation was performed with the belief that a comprehensive, respectful investigation could provide knowledge that would improve the safety of future space flight crews and explorers," the group wrote. "By learning these lessons and ensuring that we continue the journey begun by the crews of Apollo 1, Challenger and Columbia, we help to give meaning to their sacrifice and the sacrifice of their families. it is for them, and for the future generations of explorers, that we strive to be better and go farther."

The 400-page report is posted on line here.

One striking aspect of the initial 2003 accident board study was similarities between how the shuttle Challenger broke up during launch in 1986 and how Columbia met its fate during re-entry in 2003. In both cases, the reinforced crew modules broke away from the shuttle fuselage relatively intact. And in both cases, the astronauts are believed to have survived the initial breakup.

In an appendix to the Columbia accident board report, investigators concluded "acceleration levels seen by the crew module prior to its catastrophic failure were not lethal. LOS (loss of signal) occurred at 8:59:32 (a.m. EST). The death of the crew members was due to blunt force trauma and hypoxia. The exact time of death - sometime after 9:00:19 a.m. Eastern Standard Time - cannot be determined because of the lack of direct physical or recorded evidence."

"Failure of crew module was precipitated by thermal degradation of structural properties that resulted in a catastrophic sequential structural failure that happened very rapidly as opposed to a catastrophic instantaneous 'explosive' failure," the report said. "Crew module separation from the forward fuselage is not an anomalous condition in the case of a vehicle loss of control as has been the case in both 51-L (Challenger) and STS-107 (Columbia)."

But the shuttle crew module, on its own, has no power and no systems were present that could have saved either crew after breakup occurred.

Even so, "it is irrefutable, as conclusively demonstrated by items that were recovered in pristine condition whose locations were within close proximity to some crew members, that it was possible to attenuate the potentially hostile environment that was present during CM (crew module) break-up to the point where physically and thermally induced harmful effects were virtually eliminated," the CAIB concluded.

"This physical evidence makes a compelling argument that crew survival under environmental circumstances seen in this mishap could be possible given the appropriate level of physiological and environmental protection."

The CAIB went on to recommend that NASA "investigate techniques that will prevent the structural failure of the CM due to thermal degradation of structural properties to determine the feasibility for application. Future crewed vehicles should incorporate the knowledge gained from the (Challenger) and (Columbia) mishaps in assessing the feasibility of designing vehicles that will provide for crew survival even in the face of a mishap that results in the loss of the vehicle."

Columbia blasted off on mission STS-107 on Jan. 16, 2003. On board were commander Rick Husband, pilot William "Willie" McCool, Michael Anderson, David Brown, Kalpana Chawla, Laurel Clark and Ilan Ramon, the first Israeli to fly in space.

Some 81.7 seconds after liftoff, a briefcase-size chunk of foam insulation broke away from Columbia's external tank. Long-range tracking cameras showed the foam disappearing under the left wing and a cloud of debris emerging an instant later.

No one knew it at the time, but the foam had hit the underside of the left wing's reinforced carbon carbon leading edge, punching a ragged hole four to six inches across. During re-entry 16 days later, superheated air entered the breach and melted the wing from the inside out.

In the moments leading up the catastrophic failure, telemetry from the damaged shuttle indicated problems with the left wing, including loss of data from hydraulic line sensors and temperature probes and left main landing gear pressure readings. The astronauts - Husband, McCool, Chawla and Clark strapped in on the upper flight deck, Anderson, Brown and Ramon seated on the lower deck - presumably were unaware of anything unusual until just before the left wing either folded over or broke away and the vehicle's flight computers lost control.

The final words from Columbia's crew came at 8:59:32 a.m. when Husband, presumably responding to a tire alarm acknowledgement from mission control, said "Roger, uh, buh..." At that point, the shuttle was nearly 38 miles above Central Texas and traveling at 18 times the speed of sound. No more voice transmissions were received. But telemetry, some of it garbled, continued to flow for a few more moments.

That data, combined with stored telemetry on a data recorder that was found in the shuttle's wreckage and analysis of recovered debris, eventually allowed engineers to develop a rough timeline of events after the initial loss of signal.

In the new study, data show the crew received multiple indications of problems in the minute prior to loss of control, which probably occurred right around the time of Husband's last transmission. Fifty-eight seconds before that event, the first of four tire pressure alert messages was displayed. Thirty-one seconds before loss of control, the left main landing gear indicator changed state. Seven seconds before LOC, a pulsing yaw thruster light came on as the jets began firing continuously to keep the shuttle properly oriented. Less than one second before LOC, aileron trim exceeded 3 degrees.

"For the crew, the first strong indications of the LOC would be lighting and horizon changes seen through the windows and changes on the vehicle attitude displays," the report says. "Additionally, the forces experienced by the crew changed significantly and began to differ from the nominal, expected accelerations. The accelerations were translational (due to aerodynamic drag) and angular (due to rotation of the orbiter). The translational acceleration due to drag was dominant, and the direction was changing as the orbiter attitude changed relative to the velocity vector (along the direction of flight).

"Results of a shuttle LOC simulation show that the motion of the orbiter in this timeframe is best described as a highly oscillatory slow (30 to 40 degrees per second) flat spin, with the orbiter's belly generally facing into the velocity vector. It is important to note that the velocity vector was still nearly parallel to the ground as the vehicle was moving along its trajectory in excess of Mach 15. The crew experienced a swaying motion to the left and right (Y-axis) combined with a pull forward (X-axis) away from the seatback. The Z-axis accelerations pushed the crew members down into their seats. These motions might induce nausea, dizziness, and disorientation in crew members, but they were not incapacitating. The total acceleration experienced by the crew increased from approximately 0.8 G at LOC to slightly more than 3 G by the CE (catastrophic event).

"The onset of this highly oscillatory flat spin likely resulted in the need for crew members to brace as they attempted to diagnose and correct the orbiter systems. ... One middeck crew member had not completed seat ingress and strap-in at the beginning of this phase. Seat debris and medical analyses indicate that this crew member was not fully restrained before loss of consciousness. Only the shoulder and crotch straps appear to have been connected. The normal sequence for strap-in is to attach the lap belts to the crotch strap first, followed by the shoulder straps. Analysis of the seven recovered helmets indicated that this same crew member was the only one not wearing a helmet. Additionally, this crew member was tasked with post-deorbit burn duties. This suggests that this crew member was preparing to become seated and restrained when the LOC dynamics began. During a dynamic flight condition, the lap belts hanging down between the closely space seats would be difficult to grasp due to the motion of the orbiter, which may be why only the shoulder straps were connected."

Recovered cockpit switch panels indicate McCool attempted to troubleshoot hydraulic system problems. Either Husband or McCool also returned the shuttle's autopilot to the automatic setting at 9:00:03 a.m. after one of the two hand controllers apparently was inadvertently bumped. "These actions indicate that the CDR or the PLT was still mentally and physically capable of processing display information and executing commands and that the orbiter dynamics were still within human performance limitations," the study concludes.

"It was a very short time," Hale said. "We know it was very disorienting motion that was going on. There were a number of alarms that went off simultaneously. And the crews, of course, are trained to maintain or regain control in a number of different ways and we have evidence from (recovered debris that they) were trying very hard to regain control. We're talking about a very brief time, in a crisis situation, and I'd hate to go any further than that."

Said Melroy: "I'd just like to add we found that those actions really showed the crew was relying on their training in problem solving and problem resolution and that they were focused on attempting to recover the vehicle when they did detect there was something off nominal. They showed remarkable systems knowledge and problem resolution techniques. Unfortunately, of course, there was no way for them to know with the information they had that that was going to be impossible. But we were impressed with the training, certainly, and the crew."

From the point the crew cabin broke away from the fuselage to the point where depressurization occurred "can be narrowed to a range of 17 seconds, from between GMT 14:00:18 (9:00:18 a.m.) to GMT 14:00:35," the report states. "Crew module debris items recovered west of the main crew module debris field were 8 inches in diameter or smaller, were not comprised of crew module primary structure, and originated from areas above and below the middeck floor. This indicates that the crew module depressurization was due to multiple breaches (above and below the floor), and that these breaches were initially small.

"When the forebody separated from the midbody, the crew members experienced three dramatic changes in their environment: 1. all power was lost, 2. the motion and acceleration environment changed; and 3. crew cabin depressurization began within 0 to 17 seconds. With the loss of power, all of the lights and displays went dark (although each astronaut already had individual chem-lights activated). The intercom system was no longer functional and the orbiter O2 system was no longer available for use, although individual, crew worn Emergency Oxygen System (EOS) bottles were still available.

"As the forebody broke free from the rest of the orbiter, its ballistic number underwent a sharp change from an average ballistic number of 41.7 pounds per square foot (psf) (out of control intact orbiter) to 122 psf (free-flying forebody). The aerodynamic drag of the forebody instantaneously decreased, resulting in a reduction in the translational deceleration from approximately 3.5 G to about 1 G."

As experienced by the astronauts, the change from a normal re-entry to loss of control and separation of the crew module from the fuselage "all occurred in approximately 40 seconds. Experience shows that this is not sufficient time to don gloves and helmets."

"Histological (tissue) examination of all crew member remains showed the effects of depressurization. Neither the effects of CE nor the accelerations immediately post-CE would preclude the crew members who were wearing helmets from closing and locking their visors at the first indication of a cabin depressurization. This action can be accomplished in seconds. This strongly suggests that the depressurization rate was rapid enough to be nearly immediately incapacitating. The exact rate of cabin depressurization could not be determined, but based on video evidence complete loss of pressure was reached no later than (NLT) GMT 14:00:59 (9:00:59 a.m.), and was likely much earlier. The medical findings show that the crew could not have regained consciousness after this event. Additionally, respiration ceased after the depressurization, but circulatory functions could still have existed for a short period of time for at least some crew members."

For background, here are the results of the original Crew Survival Working Group's assessment, as reported in "Comm Check: The Final Flight of Shuttle Columbia" by Michael Cabbage and William Harwood (Free Press, 2004; some of the conclusions may change based on the new study):

The study concluded the shuttle's heavily reinforced crew module and nose section broke away from the fuselage relatively intact, separating at the bulkhead that marks the dividing line between the cargo bay and the forward fuselage. Challenger's crew module had also broken away in one piece when the shuttle disintegrated during launch 17 years earlier. As with Challenger, the forces acting on Columbia's crew during this period were not violent enough to cause injury, and investigators believe the astronauts probably survived the initial breakup of the orbiter.

Presumably, the cabin maintained pressure. But there was no electrical power. The shuttle's fuel cells were located under the floor of the cargo bay, and even though it wouldn't have helped at this point, Husband had no way to contact Mission Control. The lights were out on the lower deck, and without power, the intercom system no longer worked.

Like Challenger's crew, the Columbia astronauts met their fates alone and the details will never be known. Clark presumably was still videotaping on the flight deck when the alarms began blaring and the shuttle yawed out of control. But the outer portions of the tape ’Äì the portions that might have shown at least the initial moments of the shuttle's destruction ’Äì were burned away.

To determine what happened after the module broke away from Columbia's fuselage, investigators analyzed recovered cabin wreckage and calculated the trajectories the debris items must have followed based on weight and other factors. A sophisticated computer program then used those data to run those trajectories back in time to the point where they intersected, the point where the cabin must have started breaking apart.

On the basis of those data, investigators concluded the module fell intact for 38 seconds after main vehicle breakup, plunging 60,000 feet to an altitude of 26 miles before it began to disintegrate from the combined effects of aerodynamic stress and extreme temperatures. From the debris analysis, investigators believe the module was probably destroyed over a 24-second period beginning at 9:00:58 a.m. During that period, or window, the module fell another 35,000 feet, to an altitude of 19 miles or so.

Investigators believe the module began breaking up at the beginning of that window. If any of the astronauts were still alive at that point, death would have been instantaneous, the result of blunt force trauma, including hypersonic wind blast, and lack of oxygen. Pathologists found no evidence of lethal injuries from heat.

"The most western piece of crew equipment found was a helmet from the mid-deck," according to an appendix to the CAIB report. "The breakdown as to the location of the remaining crew equipment showed that the mid-deck crew equipment was the farthest west and the flight deck crew equipment was at the eastern end of the debris field. Therefore, it seems reasonable to conclude that the crew equipment on the mid-deck separated from the CM [crew module] before the flight deck equipment."

About 45 percent of the crew module was recovered near Hemphill, Texas, including pieces of the forward and aft main bulkheads, the frames from the forward cockpit windows, the crew airlock, and all of the hatches. About three quarters of the flight deck instrument panels were found, along with 80 percent of the mid-deck floor panels and numerous parts from the crew's seats and attached safety equipment. Wreckage from the ship's galley was recovered, along with parts of the toilet, bailout equipment, tools, one of the crew's sleeping compartments and items that had been stored in middeck lockers. Remarkably, the wristwatch Dave Brown had carried aloft as a belated birthday present for Kennedy engineer Ann Micklos was found, its faceplate missing and its hands frozen at 9:06 a.m.

Condition of the items varied from "highly melted, twisted and torn to near pristine," investigators concluded, noting that crew module debris "experienced noticeably less aerodynamic heating than other portions of the vehicle."

From an analysis of pressure suit components and helmets, investigators concluded three astronauts had not yet donned their gloves when breakup began and one was not wearing his or her helmet. In the end, however, having sealed pressure suits would have made no difference.

Additional details about the Challenger and Columbia accidents can be found on the CBS News space pages: here.