NASA releases post-Columbia crew survival study
BY WILLIAM HARWOOD
STORY WRITTEN FOR CBS NEWS "SPACE PLACE" & USED WITH PERMISSION
Posted: December 30, 2008;
Updated following NASA news conference
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:"
"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.
Additional details about the Challenger and Columbia accidents can be found on the CBS News space pages: here.