Wednesday, April 23, 2014
By MARCIA DUNN The Associated Press
CAPE CANAVERAL, Fla. - Astronauts making a rare, hastily planned spacewalk replaced a pump outside the International Space Station on Saturday in hopes of plugging a serious ammonia leak.
Christopher Cassidy, who grew up in York, pumps his fist before taking off for the International Space Station March 28. Cassidy was part of a hastily planned spacewalk Saturday that repaired a serious ammonia leak on the station.
Associated Press file photo
In this image made from video provided by NASA, astronaut Christopher Cassidy, foreground, holds a power wrench as he stows away a suspect coolant pump on the International Space Station on Saturday. Thomas Marshburn is at left. The two astronauts made the spacewalk to replace the pump after flakes of frozen ammonia coolant were spotted outside the station on Thursday.
The Associated Press
The prospects of success grew as the minutes 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 days, if not weeks, will be needed before declaring a victory.
"No evidence of any ammonia leakage whatsoever. We have an airtight system -- at the moment," Mission Control reported.
Christopher Cassidy, who grew up in York, 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 jeopardized 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 days, unplanned spacewalks were uncommon.
The ammonia pump was the chief suspect going into Saturday'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.
"I can't give you any good data other than nominal, unfortunately. No smoking guns."
Engineers determined there was nothing to lose by installing a new pump, despite the lack of visible damage to the old one. The entire team -- weary and stressed by the frantic pace of the past two days -- gained more and more confidence as the 51/2-hour spacewalk drew to a close with no flecks of ammonia popping up.
"Gloved fingers crossed," space station commander Chris Hadfield said in a tweet from inside. "No leaks!" he wrote a half-hour later.
Flight controllers in Houston worked furiously to get ready for Saturday's operation, completing all the required preparation in under 48 hours. The astronauts trained for just such an emergency scenario before they rocketed into orbit; the repair job is among NASA's so-called Big 12.
This area on the space station is prone to leaks.
The ammonia coursing through the plumbing is used to cool the space station's electronic equipment. There are eight of these power channels, and all seven others were operating normally. The loss of two power channels, however, could threaten science experiments and backup equipment.
"We may not have found exactly the smoking gun," Cassidy said, "but to pull off what this team did yesterday and today, working practically 48 straight hours, it was a remarkable effort on everybody's behalf."