Riding Rockets

There was proof, in the form of Mike Smith’s Personal Emergency Air Pack (PEAP), that the crew had survived vehicle breakup. PEAPs were portable canisters intended to provide emergency breathing air to a crewmember escaping through toxic fumes in a ground emergency. They were not intended for use in flight. But Mike Smith’s PEAP, stowed on the back of his seat and only accessible in flight by mission specialist 1 or 2, had been found in the on position. Either El Onizuka (MS1) or Judy (MS2) had to have thrown the switch and there would have been only one reason to do so—they were suffocating. Breakup had ripped away their only source of oxygen, the tanks under the cargo bay. Within a couple breaths, the residual oxygen remaining in their helmets and in the feed lines would have been consumed. The fierce urge to breathe would have immediately driven all of the crew either to turn on their PEAPs or raise the faceplates of their helmets. Judy or El had turned on Mike Smith’s PEAP knowing he could not reach the switch himself. (Onizuka, sitting directly behind Mike, had the easiest access to the switch, though Judy, sitting to El’s left, could have reached it with some difficulty.) Enough pieces of one other PEAP were recovered to determine it had also been in the on position, but crash damage made it impossible to establish the seat location of that canister. The fact that two PEAPS had been turned on was proof the crew had survivedChallenger ’s breakup. I would later learn that some of the electrical system switches on Mike Smith’s right-hand panel had been moved out of their nominal positions. These switches were protected with lever locks that required them to be pulled outward against a spring force before they could be toggled to a new position. Tests proved the G-forces of the crash could not have moved them, meaning that Mike Smith made the switch changes, no doubt in an attempt to restore electrical power to the cockpit. This is additional proof the crew was conscious and functional immediately after the breakup. Mike Smith’s PEAP also provided proof the crew had been alive all the way to water impact. It had been depleted by approximately two and a half minutes of breathing, the time of the cockpit fall.

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.