Riding Rockets - Mike Mullane [156]
The question remaining was whether the crew had stayed conscious beyond the few seconds needed to activate their PEAPs and for Mike Smith to throw some switches on his panel. They could not have remained conscious if the cockpit had rapidly depressurized to ambient (outside) air pressure. Breakup occurred at 46,000 feet, an altitude 17,000 feet higher than Mount Everest, and the nearly Mach 2 upward velocity at breakup continued to carry the cockpit to an apogee of approximately 60,000 feet. To stay conscious in the low atmospheric pressure of these extreme heights, the crew would have needed pressurized pure oxygen in their lungs and the PEAPs only supplied sea levelair, a mixture of about 80 percent nitrogen and 20 percent oxygen. But had there been a cockpit depressurization?
An explosive depressurization—due to a window breaking, for example—would have been a blessing and I prayed fiercely that had been the case. ButChallenger ’s wreckage said it didn’t happen. If it had, the cockpit floor would have buckled upward as the air in the lower cockpit rapidly expanded. The wreckage revealed no such buckling. That news was a dagger in my heart.
Bagian and Carter explained there was still the possibility of a nonexplosive but rapid enough depressurization to cause quick unconsciousness. Such air leakage could have occurred due to numerous penetrations at the rear cockpit bulkhead. These provided pathways for wire bundles and fluid lines to pass between the cockpit and the rest of the orbiter. At breakup those wires and tubes were violently ripped apart, and it was possible the pressurization sealing for those manufactured penetrations could have failed. There was also evidence of breakup debris striking the cockpit from the outside. A piece of steel had been found jammed into a window frame. While that particular piece of debris did not penetrate the cockpit, other debris might have, resulting in a depressurization rapid enough to cause unconsciousness.
But it was all conjecture. There was no way to know the pressure integrity of the cockpit and, therefore, the state of crew consciousness. Bagian and Carter did have some ancillary evidence suggesting crew inactivity, which some thought could be a signature of crew blackout. Every piece of paper recovered from the wreckage was examined to see if any crewmembers had written a note. Nothing had been discovered. Neither had the cockpit overhead emergency escape hatch been blown. Some astronauts had suggested they would have jettisoned it as they neared the water to facilitate escape if impact was survived. The status