Engineers Debate Shuttle Leak

The space shuttle Discovery and the International Space Station flexed their robotic arms repeatedly Friday, racking up a record for robotics in space and taking yet one more look for damage to the shuttle’s heat shield.

Down at mission control, engineers debated what to do about a leaking auxiliary power unit, one of three needed to control the hydraulic steering and braking maneuvers for landing the shuttle. Discovery is to touch down Monday morning at Kennedy Space Center.

Deputy shuttle program manager John Shannon said it was unclear whether the unit was leaking harmless nitrogen or potentially dangerous hydrazine fuel. He suspects it is nitrogen, which would be “no issue at all.”

The leak is so small that even if it is hydrazine, it is well below any flammability threat, Shannon said. The power unit will be tested in orbit Sunday. If the leak worsens, it could affect touchdown plans.

Neither of Discovery’s two other power units appeared to be leaking, Shannon said. One, however, was getting close to overheating, considered a minor problem.