Even with one main engine and two solid rocket boosters still firing, they would make it to orbit.

They had to abort the launch.

"Control, this is Endeavour," said Kittredge, his voice crisp steady.

Not a hint of apprehension. "Unable to throttle up. Left center MES went out at Max Q. We are stuck in the bucket. Going to RTLS abort."

"Roger, Endeavour. We confirm two MES out. Proceed to RTLS abort after SRB burnout." Emma was already rifling through the stack of checklists, and she retrieved the card for

"Return to Launch Site Abort." The crew knew every step of the procedure by heart, but in the frantic pace of an emergency abort, some vital action might be forgotten. The checklist was their security blanket.

Her heart racing, Emma scanned the appropriate path of action, clearly marked in blue. A two-engine-down RTLS abort was survivable -- but only theoretically. A sequence of near miracles had to happen next. First they had to dump fuel and cut off the last main engine before separating from the huge external fuel tank. Then Kittredge would pitch the orbiter around to a heads-up attitude, pointing back toward the launch site. He would have one chance, only one, to guide them to a safe touchdown at Kennedy. A single mistake would send Endeavour plunging into the sea.

Their lives were now in the hands of Commander Kittredge.

His voice, in constant communication with Mission Control, still sounded steady, even a little bored, as they approached the two-minute mark. The next crisis point. The CRT display flashed the Pc<50 signal. The solid rocket boosters were burning out, on schedule.

Emma felt it at once, the startling deceleration as the boosters consumed the last of the fuel. Then a brilliant flash of light in window made her squint as the SRBS exploded away from the tank.

The roar of launch fell ominously silent, the violent shudder calming to a smooth, almost tranquil ride. In the abrupt calm, she was aware of her own pulse accelerating, her heart thudding like fist against her chest restraint.