NASA astronaut Mike Hopkins will conduct his first spacewalk on Saturday.  He will wear the same spacesuit that European astronaut Luca Parmitano was wearing in July when the helmet filled with water for reasons that are still not fully understood.   Nonetheless, NASA has “high confidence” that measures they have taken will prevent a recurrence and, if not, they are adding an absorption pad and a snorkel to the spacesuit to mitigate the situation.

At a press conference today, International Space Station (ISS) program manager Mike Suffredini, ISS flight director Dina Contella, and lead spacewalk officer Allison Bollinger explained their reasoning that the spacewalk will be safe and why it needs to be conducted now.

The precipitating event is a problem in one of the two ISS coolant loops.  A flow control valve is not operating correctly, allowing the temperature of ammonia used as a coolant to drop too low to allow it to enter a heat exchanger that also is in contact with water, lest the water freeze.  The ISS uses water to cool the interior of the ISS, keeping the toxic ammonia on the outside of the station.   The flow control valve is part of a pump assembly that was replaced in 2010, so age is not a factor in its malfunction.   Suffredini said the problem likely is the valve’s electronics and he stressed that the pump itself is working fine and continues to cool equipment on the outside of the station.

The crew is not in danger and critical ISS systems have been moved to the functioning coolant loop, but NASA does not want to remain in that posture for long.   From December 30 to January 9, the Beta angle of the Sun vis a vis the ISS will preclude spacewalks as well as berthing of Orbital Sciences Corporation’s Cygnus spacecraft.  NASA decided yesterday to delay the Cygnus launch that was scheduled for tomorrow until January so the crew can focus on fixing the coolant loop issue before December 30.

Hopkins and fellow NASA astronaut Rick Mastracchio will conduct at least two and perhaps as many as four spacewalks while Japanese astronaut Koichi Wakata operates Canadarm2 in a complex ballet of steps needed to replace the pump assembly.   NASA is currently planning three 6.5 hour spacewalks on December 21, 23 and 25, but that schedule could change depending on how far the astronauts get during the first one. Although Hopkins is a rookie, Mastracchio is a veteran spacewalker with six spacewalks totaling 38 hours and 30 minutes.  

Parmitano provided a chilling account of feeling like “a goldfish in a fishbowl” during his spacewalk on July 16, 2013.  NASA still is not certain why his helmet filled with water.   Suffredini pointed out today that these spacesuits are 35 years old and they had not imagined that such a failure mode could occur.   Now that it has, engineers are trying to figure out exactly why and how.   They have been troubleshooting the issue since July and made some fixes, such as changing the fan pump separator unit, but the root cause remains elusive.  Suffredini said they believe it is related to water that is flowing through the suit that is high in silica content.

Contella said today that until the root cause is known, “we can’t rule out that we would have water in the helmet again,” which is why they have developed new operational procedures and two new pieces of hardware that will be added to the suit.   

Bollinger demonstrated the two items.   One is a “helmet absorption pad” that will be placed at the back of the astronaut’s head.  The pad can absorb 600-800 milliliters (ml) of water.  Astronauts testing it on the ground discovered that it begins to feel “squishy” when it has absorbed about 200 ml, so if a spacewalking astronaut notices squishiness, that’s a signal that he should return to the airlock quickly.  The pads were brought to the ISS on Orbital’s demonstration mission in September/October and on a Soyuz flight.

The other is a snorkel that was fabricated by the crew on orbit.  It will be installed in the spacesuit between the water restraint bag and the front side of the suit.  As “a last resort, if water is encroaching your face … the crewmember can lean down and use [the snorkel] to breathe, to receive fresh oxygen from down near his midsection,”  Bollinger explained.

All three currently planned spacewalks will begin at 7:10 am Eastern Standard Time, with NASA TV coverage beginning at 6:15 am EST.

The press conference is posted on NASA’s YouTube channel.

A problem with a flow control valve on one of the two International Space Station (ISS) coolant loops may delay the planned launch next week of Orbital Sciences Corporation’s Cygnus cargo resupply spacecraft.  The launch is currently scheduled for December 18.

Kenny Todd, ISS Mission Operations Integration Manager, said in an interview on NASA’s Space Station Live program this morning that the agency is still diagnosing the problem and determining what must be done to fix it.   Until more is known, he is delaying a “go/no-go” decision on Orbital’s launch because whenever another vehicle arrives at the ISS, certain levels of systems redundancy are required and NASA cannot meet those criteria under current circumstances.  NASA will revisit the situation on Monday and determine if a launch delay is necessary.

The launch window for this mission, designated Orbital-1 or simply Orb-1, is the company’s first flight of the Antares rocket and Cygnus spacecraft under NASA’s Commercial Resupply Services (CRS) contract.  Orbital has named this specific Cygnus spacecraft in honor of C. Gordon “Gordo” Fullerton, the former astronaut who passed away in August.  At one point in his career, Fullerton flew NASA NB-52B aircraft that were used to deploy Orbital’s air-launched Pegasus rocket.

Todd said the launch window for the Cygnus launch runs through December 21 or 22, and, if necessary, the launch could be delayed until the next launch window.   None of the 3,217 pounds of cargo on this mission is critical to ISS operations, Todd said.

The coolant loop malfunctioned yesterday.  ISS has two external thermal control loops that use ammonia as a coolant.  The ammonia must be kept at the proper temperature to ensure that when it flows through a heat exchanger, water that is also in the heat exchanger does not freeze.  If the ammonia becomes too cold, the system automatically shuts off.  That’s what happened yesterday. 

Ground-based engineers began to troubleshoot the issue and traced it back to a flow control valve in one of the loops, but they are still trying to determine exactly what went wrong and what is needed to fix it.   Meanwhile, the 6-person crew is safe and ISS is in a stable configuration, Todd said.  Still, NASA would like to get the loop working “sooner rather than later.”   All critical ISS systems can operate on just one loop, but both are needed for all systems to work and for redundancy.  NASA has moved all the critical systems over to the functioning loop, but some systems in Node 2 (Harmony), Japan’s Kibo module, and Europe’s Columbus module had to be turned off.

The ISS experienced a coolant loop problem in 2010 and Todd acknowledged that at first glance people might assume this is similar.  In 2010, however, a pump failed.  In this case, it is a flow control valve that “is in the same housing, but is a different piece of hardware” that regulates the temperature of the ammonia rather than moving the ammonia through the system like the pump.  NASA does not know whether a spacewalk is needed to repair the problem this time as it was in 2010, but, if so, Todd says the “choreography” will be similar and replacement pump modules are aboard.  He stressed that NASA needs to ensure that its spacesuits are in good order.   The last time the U.S. spacesuits were used, European Space Agency astronaut Luca Parmitano’s spacesuit filled with water because of a failure in its cooling system.

The video of this morning’s interview with Todd is posted on NASA’s YouTube channel.