National Aeronautics and Space Administration engineers have discovered a small leak in one of three auxiliary power units that controls the Discovery shuttle’s hydraulic steering and brakes, a rare complication that could alter the orbiter’s Monday morning landing plans.
At a news briefing Friday evening, deputy shuttle program manager John Shannon said circumstantial evidence suggests the leak involves nitrogen, which would not pose a flammability hazard and would be “no issue at all.”
But preliminary tests have not ruled out the possibility that the leak involves hydrazine, a volatile compound used as rocket fuel that could spark a fire if it accumulated in an adjacent compartment during the shuttle’s reentry and landing.
“To me, it is still a coin flip,” Shannon said of the nitrogen-or-hydrazine possibility.
He said the current rate of the leak – equivalent to about 1.2 tablespoons per hour – has resulted in a net loss of about two gallons of fuel. If that rate holds up, tests suggest, it would be 100,000 times lower than what NASA has established as the flammability danger rate for the shuttle.
“If it stays where it is now, I am very confident that things will be just fine,” Shannon said.
And if gets any worse?
Engineers will monitor the leak during a trial run of the power unit on Sunday, he said.
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