Spacewalking repair halts station leak - for now

Astronauts making a rare, hastily planned spacewalk have replaced a pump outside the International Space Station in hopes of plugging a serious ammonia leak.
The prospects of success grew as the minutes, then hours passed and no frozen flecks of ammonia appeared. Mission Control said it appeared as though the leak may have been plugged, although additional monitoring over the coming weeks will be needed before declaring a victory.
"I will tell you that we're happy. We're very happy," said Joel Montalbano yesterday, NASA's deputy space station program manager.
"We didn't see any obvious signs of a leak, but it's going to take some time ... For us to look at the system, evaluate the system and make sure we did, indeed, stop the leak."

Montalbano expects it will take "a good four weeks, five weeks, maybe even a few weeks longer."
"Obviously, the longer you go, the more confidence you get," he told reporters.

Christopher Cassidy and Thomas Marshburn installed the new pump after removing the old one suspected of spewing flakes of frozen ammonia coolant two days earlier. They uncovered "no smoking guns" responsible for the leak and consequently kept a sharp lookout for any icy flecks that might appear from the massive frame that holds the solar panels on the left side.
"Let us know if you see anything," Mission Control urged as the fresh pump was cranked up. Thirty minutes later, all was still well. "No snow," the astronauts radioed.

"We have our eyes on it and haven't seen a thing," Marshburn said.
NASA said the leak, while significant, never jeopardised crew safety. But managers wanted to deal with the trouble now, while it's fresh and before Marshburn returns to Earth in just a few days.
The space agency never before staged such a fast, impromptu spacewalk for a station crew. Even during the shuttle program, unplanned spacewalks were uncommon.
The ammonia pump was the chief suspect going into yesterday's spacewalk. So it was disheartening for NASA, at first, as Cassidy and Marshburn reported nothing amiss on or around the old pump.

"All the pipes look shiny clean, no crud," Cassidy said as he used a long, dentist-like mirror to peer into tight, deep openings.