NASA ISS Astronauts' Emergency EVA appears Successful in fixing Coolant Leak

In this Saturday, May 11, 2013 photo made available by NASA, astronaut Chris Cassidy and Tom Marshburn, not pictured, perform a space walk to inspect and replace a pump controller box on the International Space Station after an ammonia coolant leak was discovered. 

Credit: NASA

NASA says an impromptu spacewalk seems to have fixed a big ammonia leak at the International Space Station.

The "gusher" erupted last Thursday. Two days later, spacewalking astronauts replaced a suspect ammonia pump. NASA is now calling the old, removed pump "Mr. Leaky."

On Thursday, a Mission Control official said the spacewalking repairs definitely took care of the big leak.

Engineers don't know whether the pump replacement also took care of a smaller leak that has plagued the system for years.

It will take at least a couple months of monitoring to know the full status. Ammonia is used as a coolant in the space station's radiator system.

The leak forced one of the station's seven power channels to go offline. NASA hopes to resume normal operations early next week.

NASA-International Space Station: Coolant Leak and EVAs

Image above: In the International Space Station’s Quest airlock, Expedition 24 Flight Engineer Doug Wheelock works on a spacesuit in preparation for the second spacewalk to remove a failed ammonia pump module on the station's S1 Truss. Credit: NASA TV

Flight controllers and engineers continue meetings to review the results from the first spacewalk conducted Saturday by International Space Station Expedition 24 Flight Engineers Doug Wheelock and Tracy Caldwell Dyson and to plan for the second of what now will be three spacewalks to complete the replacement of a failed pump module on the station’s starboard truss.

In the wake of an eight-hour, three-minute spacewalk Saturday that fell short of removing the failed pump module due to a leak in the fourth of four ammonia line connectors hooked up to the old pump, mission operations and station program officials laid out a series of procedures for Wheelock and Caldwell Dyson to perform at the beginning of the second spacewalk Wednesday designed to greatly reduce, or eliminate the possibility of ammonia leaking from the final fluid connector – called M3 – when it is demated to set the stage for the failed pump to be removed from the truss.

The plan would call for Wheelock and Caldwell Dyson to close other quick disconnect lines where the S1 and S0 trusses meet that will isolate ammonia upstream in the system from the final connector, preventing any recurrence of leakage while the new pump module is being installed. Additional work to configure lines and valves would be conducted by the spacewalkers prior to the final electrical demating of the old pump so it can be parked on a stowage bracket on the station’s Mobile Base System.

The goal Wednesday will be to remove the old pump and stow it on a payload attachment bracket on the Mobile Base System on the station’s truss while preparing the replacement pump for its removal from a stowage platform adjacent to the Quest airlock and its installation on the truss during a third spacewalk targeted for no earlier than next Sunday.

Mission and station managers are continuing meetings today to prepare for the second spacewalk before the station Mission Management Team meets Tuesday morning to provide its final approval to proceed.

The station’s systems remain in good condition operating on the second of two cooling loops available for the complex and the crew is well rested following Saturday’s spacewalk, spending the last two days recharging spacesuit batteries, reviewing spacewalk procedures and configuring tools for Wednesday’s excursion.

Toxic leak: space station repair fails

A toxic ammonia leak and a jammed fitting have foiled plans to fix a cooling pump on the International Space Station, forcing astronauts to delay the repairs until Wednesday at the earliest, reports NASA.

On Saturday, Expedition 24 Flight Engineers Doug Wheelock and Tracy Caldwell Dyson suffered setbacks that stretched their space walk to 8 hours 3 minutes - the longest in space station history and the sixth longest ever undertaken, according to NASA.

The astronauts began their excursion outside the International Space Station at 0719 EDT (1119 GMT) as the outpost flew 220 miles (354 km) above Earth.

They planned to remove a broken ammonia coolant pump and install a replacement, which involved disconnecting four ammonia hoses and five electrical cables from the pump on the station's truss.

Problems arose about 4 hours into the spacewalk when one of the hoses wouldn't come loose. Colonel Wheelock managed initially to open the "quick-disconnect" fitting mechanism on the hose by hitting it with a hammer, but then reported a clearly visible ammonia leak.

"I see little sparklets of ammonia coming from the line," he said. The astronauts compared the crystals of frozen ammonia coolant to tiny snowflakes.

Colonel Wheelock re-tightened the fitting before returning to the airlock, where he had to delay entering the station so any toxic ammonia on his suit had time to evaporate.

Michael T. Suffredini, manager of the space station program at the Johnson Space Center in Houston, said he was disappointed by the setbacks.

He said that these ammonia quick-disconnect fittings are complicated. "It's very high-pressure ammonia, you have to try to be able to disconnect and reconnect on a regular basis."

The space station is now running on a single cooling system. "The challenge is to get through this problem before the next problem hits the other system," Suffredini stated.