NASA has released a Columbia Crew Survival Investigation Report (16.2 MB PDF – press release page) featuring a detailed description of the sequence of events for the crew and orbiter during its breakup. A summary from the report is below:
1.1.1 Events with lethal potential
There were five events identified with lethal potential to the crew.
The first event with lethal potential was depressurization of the crew module, which started at or shortly after orbiter breakup.The majority of the SCSIIT findings related to the first lethal event were connected to the operational incompatibilities of the advanced crew escape suit (ACES) with the orbiter. The launch and entry suit was added in response to the Challenger accident, rather than as a part of the original vehicle design. The ACES was the successor to that suit. The suit protects the crew in many scenarios; however, there are several areas where integration difficulties diminish the capability of the suit to protect the crew. Integration issues include: the crew cannot keep their visors down throughout entry because doing so results in high oxygen concentrations in the cabin; gloves can inhibit the performance of nominal tasks; and the cabin stow/deorbit preparation timeframe is so busy that sometimes crew members do not have enough time to complete suit-related steps prior to atmospheric entry.
As Columbia entered the atmosphere, one crew member was not yet wearing the ACES helmet and three crew members were not wearing gloves. Per nominal procedures, the crew wearing helmets had visors up. There was a period of about 40 seconds after the orbiter loss of control (LOC) but prior to depressurization when the crew was conscious and capable of action. Part of this short timeframe was undoubtedly employed in recognizing that a problem existed, as the indications of LOC developed gradually. The crew members could have closed their visors in this timeframe but did not. The SCSIIT attributed this to the training regimen, which separates vehicle systems training from emergency egress training and does not emphasize the transition between problem resolution and a survival situation. Once the cabin depressurization began, the rate of depressurization incapacitated the crew so quickly that even those crew members who had fully donned the ACES did not have time to lower their visors. Although circulatory systems functioned for a brief time, the crew could not have regained consciousness upon descent to lower altitudes due to the effects of the depressurization.
The second event with lethal potential was unconscious or deceased crew members exposed to a dynamic rotating load environment with nonconformal helmets and a lack of upper body restraint. The orbiter lost control, probably when the hydraulic systems failed due to hot gas intrusion in the left wing. The resulting motion was not lethal but did require bracing by the crew. The forebody (crew module and forward fuselage) eventually separated and the crew module lost pressure at orbiter break- up. When it separated, the forebody began a multi-axis rotation at approximately 0.1 revolution/second. Loads due to deceleration significantly decreased at the moment of breakup due to the change in ballistic number, but began to climb as the forebody continued to decelerate.
After the crew module depressurized and the crew lost consciousness, the seat inertial reel mechanisms failed to lock despite the off-nominal motion. The reels were not defective; they were simply not designed to lock under the conditions the forebody experienced. The upper harness straps failed at some point prior to the forebody breakup, causing the straps to recoil back into the inertial reel mech- anism. Because the reel mechanisms did not lock, the unconscious or deceased crew members were exposed to cyclical rotational motion while their upper bodies were inadequately restrained. Helmets that did not conform to the head and the lack of upper body restraint resulted in injuries and lethal trauma.
- The third event with lethal potential was separation from the crew module and the seats with associated forces, material interactions, and thermal consequences. This event is the least understood due to limitations in current knowledge of mechanisms at this Mach number and altitude. Seat restraints played a role in the lethality of this event. The breakup of the crew module and resultant exposure of the crew to entry conditions was an extremely significant event but was very difficult to characterize since many related events occurred in a short period of time. The consequences of exposure to entry conditions included traumatic injury related to seat restraints, high loads associated with deceleration due to a change in ballistic number, aero- dynamic loads, and thermal events. All crew were deceased before, or by the end of, this event. The ACES has no performance requirements for occupant protection from thermal events and may not provide adequate protection even for egress scenarios involving heat and flames. There is no known complete protection from the breakup event except to prevent its occurrence.
- The fourth event with lethal potential was exposure to near vacuum, aerodynamic accelerations, and cold temperatures. The ACES system is certified to operate at a maximum altitude of 100,000 feet, and certified to survive exposure to a maximum velocity of 560 knots equivalent air speed. The operating envelope of the orbiter is much greater than this. The actual maximum protection environment for the ACES is not known.
- The final event with lethal potential was ground impact. The ACES system provides protection from ground impact with a parachute system. The current parachute system requires manual action by a crew member to activate the opening sequence.
There are some “Redacted” sections; presumably containing details about the crew’s remains that the report authors didn’t want to be made public. There were reports of body parts found scattered over the landscape (sorry, this brings out my inner ghoul):
Reports of body parts being found started coming in Saturday night as emergency workers and residents searched hundreds of square miles of Texas and Louisiana for bits of what once was space shuttle Columbia.
In Hemphill, near the Louisiana state line, hospital employee Mike Gibbs reported finding what appeared to be a charred torso, thigh bone and skull on a rural road near what was believed to be other debris. Billy Smith, an emergency coordinator for three East Texas counties, confirmed the find.
“I wouldn’t want anybody seeing what I saw,” Gibbs said. “It was pretty gruesome.”
On a farm not far away, two young boys found a charred human leg, The Dallas Morning News reported Sunday. “From the hip to the foot, it’s all there, scorched from the fire,” said their father, Bob White.
I wonder if the bodies broke up during re-entry or on impact? Human bodies aren’t designed for high-g forces, as innumerable airplane crashes have demonstrated.
On a more cheerful note, Expedition 18 completed a spacewalk last week on 23 December wearing Russian Orlan spacesuits. Yurii Lonchakov (EV1, Orlan-M №26) and Michael Fincke (EV2, Orlan-M №27) were outside for 5h 38m (00:51-06:29 UTC). Reports: ISS Daily Report, NASA.
A random observation: I visit various spaceflight forums (see my links list) and it is rare to encounter other females! I don’t know why that is, as there are plenty of women in the aerospace industry (at least there are in the USA and Europe). (I did have a chance to begin a career in the industry a long time ago, but as with so much of my life, I botched that chance.)