NASA Weighs Spacewalk To Fix Cooling Problem On Station

NASA may allow its first spacewalk since summer to deal with a malfunction that crippled a cooling loop on the International Space Station.

If extravehicular activity is deemed necessary for a fix, it would be the first time NASA spacesuits were used “outside” since Luca Parmitano, an Italian astronaut, experienced a water leak in one that cut short a spacewalk in July. NASA suspended all spacewalks as a precaution while the cause was investigated.

Since then, the agency has put in place procedures to protect astronauts from it happening again, opening up a spacewalk or spacewalks as an option to deal with a balky control valve inside a pump on the station.

The valve is an essential part of an S1 (starboard) truss pump that helps maintain the correct temperature for space station electronics. Ammonia circulates through two external cooling loops and is put through radiators to bleed off heat. The valve is required to mix the cool and warm parts of liquid in the ammonia loop.

 Expedition 35 Flight Engineers Chris Cassidy (left) and Tom Marshburn completed a the 5-hour, 30-minute spacewalk on May 11 to inspect and replace a pump controller box on the International Space Station’s far port truss (P6) leaking ammonia coolant. Credit: NASA
Expedition 35 Flight Engineers Chris Cassidy (left) and Tom Marshburn completed a the 5-hour, 30-minute spacewalk on May 11 to inspect and replace a pump controller box on the International Space Station’s far port truss (P6) leaking ammonia coolant. Credit: NASA

A pump automatically shut down on Wednesday (Dec. 11) when the loop got too cold. As NASA began troubleshooting the issue, it powered down non-critical systems (including experiments and redundant systems) in the Columbus laboratory, Harmony node and Japanese Kibo laboratory. Primary systems are still online.

The astronauts are safe, NASA said today (Dec. 13), with the biggest impact to their activities being the science they perform. Expedition 38 astronaut Rick Mastracchio did a live media interview this morning (EST) where he similarly assured reporters that everyone on board is fine.

Cooling problems have happened on station before, most recently in May when an emergency spacewalk was needed to replace a pump controller box on the P6 (far port) truss. This particular cooling system experienced an issue in 2010, which required three contingency spacewalks to remove and replace a failed pump on the S1 truss.

Expedition 24 astronaut Douglas Wheelock exits the Quest airlock at the beginning of a spacewalk Aug. 11, 2010 to replace a failed ammonia pump on the International Space Station's S1 truss. Credit: NASA
Expedition 24 astronaut Douglas Wheelock exits the Quest airlock at the beginning of a spacewalk Aug. 11, 2010 to replace a failed ammonia pump on the International Space Station’s S1 truss. Credit: NASA

If a spacewalk is needed this time around, NASA has three spare pumps available on station for astronauts to use. NASA, however, is looking at all options before making a decision — including ways of controlling the errant valve from the ground. The agency is holding multiple meetings to decide what to do next after turning on and off the cooling loop yesterday and seeing the same malfunction.

On Monday, NASA will decide whether to move forward with a launch of a cargo spacecraft expected to head to the station on Dec. 18. The window for Orbital Sciences’ Cygnus spacecraft extends to Dec. 21 or 22, but as of Thursday (Dec. 12), the agency said the lack of redundant systems on station violates certain “commit criteria” for the launch to move forward.

While NASA spacewalks were suspended, activity using the Russian Orlan spacesuits has continued as usual. A spacewalk took place in November with the Olympic torch, amid other duties. Another spacewalk is planned Dec. 27 to install high- and medium-resolution cameras, put in a foot restraint, and remove and replace several external experiment packages.

UPDATE: NASA Pushes Back Cygnus Launch Decision Due To Space Station Cooling Problem

The decision to launch a cargo flight to the International Space Station next week has been pushed back until Monday (Dec. 16) because of a cooling problem on station that forced the shutdown of redundant systems, according to a NASA update.

Orbital Sciences’ Cygnus commercial spacecraft is expected to blast off on Dec. 18 from the Wallops Flight Facility in Virginia. However, with some station systems offline, the launch does not now meet certain “commit criteria” to make its journey to space next week, said Kenny Todd, the space station’s mission integration and operations manager.

“We haven’t lost any primary functionality,” he said in a NASA Television update today (Dec. 12), emphasizing that the six-person Expedition 38 crew is fine. “There is some redundancy that we’re down right now, but that’s not something I would call critical to day-to-day station operations.”

While a spacewalk is a possibility to fix the problem, it’s too early to say what NASA and other space station partners will decide to do.

NASA controllers spent the night examining a control valve blamed for causing an ammonia pump to shut down yesterday (Dec. 12). The space station uses liquid ammonia to maintain its temperature, pumping the ammonia through external radiators to bleed off heat. Astronauts have made periodic spacewalks to repair parts of the ammonia system, most recently in May when Expedition 35 replaced a pump controller box on the P6 (far port) truss just days before some crew members went home.

Expedition 35 Flight Engineers Chris Cassidy (left) and Tom Marshburn on a spacewalk on May 11 to inspect and replace a pump controller box on the International Space Station’s far port truss (P6) leaking ammonia coolant. Credit: NASA.
Expedition 35 Flight Engineers Chris Cassidy (left) and Tom Marshburn on a spacewalk on May 11 to inspect and replace a pump controller box on the International Space Station’s far port truss (P6) leaking ammonia coolant. Credit: NASA.

“The pump module on one of ISS two external cooling loops automatically shut down today when it got too cold,” stated the NASA Johnson Space Center Twitter feed yesterday (Dec. 11).

“The pump was brought back online, but they think a valve may not be working correctly inside it. Some of the station’s internal electrical systems were moved over to the second loop, and some noncritical things were powered down. The crew was always safe and will work with the ground teams as they figure out what caused the issue.”

Non-critical systems were powered down in the Harmony node, Columbus Laboratory and Japanese Kibo laboratory. After confirming that the new configuration was stable, controllers began this morning (EST) to move the troublesome valve to several positions and monitor the effect on cooling temperatures, according to a NASA TV update.

The Japanese Kibo module on the International Space Station as photographed by a member of the Expedition 38 crew in 2013. Credit: NASA
The Japanese Kibo module on the International Space Station as photographed by a member of the Expedition 38 crew in 2013. Credit: NASA

The crew is going about their activities as much as possible, although they’re on a “reduced timeline” because some of the experiments aren’t running as usual. (Science collected up to now is “not at risk”, Todd said.)

Responding to questions on social media, NASA astronaut Douglas Wheelock — who led three unplanned spacewalks in 2010 to replace a broken ammonia pump module on the S1 truss in the same cooling loop — said he is working with Mission Control to see what needs to be done next.

Of note, NASA has suspended spacewalks after a water leak in one of its spacesuits forced Italian astronaut Luca Parmitano back to the airlock during work in July. (Crewmate Chris Cassidy, who was on the spacewalk at the same time, later said he felt Parmitano was in no immediate danger, but felt the prudent thing to do was stop.)

NASA astronaut Douglas Wheelock during a contingency spacewalk Nov. 16, 2010 after an ammonia cooling pump failed aboard the International Space Station. During this spacewalk, Wheelock and fellow Expedition 24 crew member Tracy Caldwell installed a spare ammonia pump module on the S1 Truss on the space station. The duo did three contingency spacewalks during the mission to address the problem. Credit: NASA
NASA astronaut Douglas Wheelock during a contingency spacewalk Nov. 16, 2010 after an ammonia cooling pump failed aboard the International Space Station. During this spacewalk, Wheelock and fellow Expedition 24 crew member Tracy Caldwell installed a spare ammonia pump module on the S1 Truss on the space station. The duo did three contingency spacewalks during the mission to address the problem. Credit: NASA

Astronauts have been troubleshooting the suit periodically on board station, but NASA is planning to send it back on the next SpaceX Dragon flight to Earth for further investigation. SpaceX isn’t planning to get to the station again until late February, media reports say. Russian spacewalks can still continue as they use a separate suit; the most recent one took place in November with the Olympic torch.

While Todd didn’t quite say the ban on spacewalks has been lifted, he added that NASA has new procedures in place to guard against another crew member facing the same water issue. He did not elaborate on what those procedures are.

The current launch window for Cygnus extends as far as Dec. 21 and “possibly” the 22nd, Todd said, but emphasized more time is needed to come to a decision. “At this point, for lack of a better term, we’re going to kick the can a little bit and let the team work a little bit more,” he said.

Updates will follow as the situation and fix progresses.

Is Triton Hiding an Underground Ocean?

Voyager 2 mosaic of Neptune’s largest moon, Triton (NASA)

At 1,680 miles (2,700 km) across, the frigid and wrinkled Triton is Neptune’s largest moon and the seventh largest in the Solar System. It orbits the planet backwards – that is, in the opposite direction that Neptune rotates – and is the only large moon to do so, leading astronomers to believe that Triton is actually a captured Kuiper Belt Object that fell into orbit around Neptune at some point in our solar system’s nearly 4.7-billion-year history.

Briefly visited by Voyager 2 in late August 1989, Triton was found to have a curiously mottled and rather reflective surface nearly half-covered with a bumpy “cantaloupe terrain” and a crust made up of mostly water ice, wrapped around a dense core of metallic rock. But researchers from the University of Maryland are suggesting that between the ice and rock may lie a hidden ocean of water, kept liquid despite estimated temperatures of  -97°C (-143°F), making Triton yet another moon that could have a subsurface sea.

How could such a chilly world maintain an ocean of liquid water for any length of time? For one thing, the presence of ammonia inside Triton would help to significantly lower the freezing point of water, making for a very cold — not to mention nasty-tasting — subsurface ocean that refrains from freezing solid.

In addition to this, Triton may have a source of internal heat — if not several. When Triton was first captured by Neptune’s gravity its orbit would have initially been highly elliptical, subjecting the new moon to intense tidal flexing that would have generated quite a bit of heat due to friction (not unlike what happens on Jupiter’s volcanic moon Io.) Although over time Triton’s orbit has become very nearly circular around Neptune due to the energy loss caused by such tidal forces, the heat could have been enough to melt a considerable amount of water ice trapped beneath Triton’s crust.

Related: Titan’s Tides Suggest a Subsurface Sea

Another possible source of heat is the decay of radioactive isotopes, an ongoing process which can heat a planet internally for billions of years. Although not alone enough to defrost an entire ocean, combine this radiogenic heating with tidal heating and Triton could very well have enough warmth to harbor a thin, ammonia-rich ocean beneath an insulating “blanket” of frozen crust for a very long time — although eventually it too will cool and freeze solid like the rest of the moon. Whether this has already happened or still has yet to happen remains to be seen, as several unknowns are still part of the equation.

“I think it is extremely likely that a subsurface ammonia-rich ocean exists in Triton,” said Saswata Hier-Majumder at the University of Maryland’s Department of Geology, whose team’s paper was recently published in the August edition of the journal Icarus. “[Yet] there are a number of uncertainties in our knowledge of Triton’s interior and past which makes it difficult to predict with absolute certainty.”

Still, any promise of liquid water existing elsewhere in large amounts should make us take notice, as it’s within such environments that scientists believe lie our best chances of locating any extraterrestrial life. Even in the farthest reaches of the Solar System, from the planets to their moons, into the Kuiper Belt and even beyond, if there’s heat, liquid water and the right elements — all of which seem to be popping up in the most surprising of places — the stage can be set for life to take hold.

Read more about this here on Astrobiology.net.

Inset image: Voyager 2 portrait of Neptune and Triton taken on August 28, 1989. (NASA)