@Adrian Coward
"If you re-read the report (especially Fig 2.1-27) you will see that the G-forces were likely not so severe as to prevent closing the visors for 20 seconds or so. It only takes 4 or 5 seconds to close and lock the visors."
The obvious response to your point is 'OK, but they didn't. Why didn't they?'. And I cannot see that NASA have shown that this was because of unconsciousness.
If you read the report closely you will see comments that the astronauts spent their entire time on 'solving the problem' and none on 'preparing for survival'. They would have ignored minor bumps.
Why should you close a visor during the start of the tumbling? There is no problem with the shuttle air pressure at that point - the craft is not breaking up. The air only starts leaking out when the shuttle breaks up, and at that point the astronauts are unable to close their visors due to the high accelerations. It seems obvious to me that the astronauts were alive when the craft started breaking up, and the immediate cause of their deaths was trauma due to G force, impact with shuttle debris, or the slipstream.
The key sections for crew consciousness are the depresurisation sections (2.3.2 - 2.3.4, pp209-211). Here there are bland assurances that the crew were rapidly incapacitated, combined with a total lack of hard evidence about the depressurisation timeline. They reckon it started 'several seconds after 14:00.18', and was complete by 14:00.59. That could give almost any period of low air pressure, but I am struck by the poor evidence adduced - just ballistic data from crew suit patches. There is effectively no evidence about the onset of depressurisation, and the end of depressurisation is just assumed to be at total breakup!
If we look at your cite, we see 18 seconds of 'bumps', followed by 18 seconds of major tumbling, during which the craft was breaking up. Nasa's own figures suggest that you get about 14 seconds of consciousness when exposed to a vacuum, and die about 2 minutes later. http://imagine.gsfc.nasa.gov/docs/ask_astro/answers/970603.html refers. If a guess is taken that depressurisation was complete halfway through the tumbling process (and the NASA report suggests that the crew module stayed intact for longer), then the astronauts would have had approximately 5 seconds of consciousness left at the point when the craft completely disintegrated. (Assuming they were not unconscious or dead already from the battering they were receiving)
The more I look at this report, and compare it to the Soyuz 11 one, I am struck by how anxious the writers were to claim ' they didn't suffer'. The impression I get is that all space authorities are scared stiff of having marooned astro/cosmonauts dying slowly, and will do anything to avoid that circumstance. This may be good public relations but it is bad science, and it is bad journalism to read a report without noting the sort of discrepancies I have highlighted above...