Keep the shuttle flying: Fwd: Coolant system repair EVA begin Saturday

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Subject: FW: Coolant system repair EVA begin Saturday

NASA preps for spacewalk to repair ISS
Dec. 18, 2013 |
International Space Station Plagued With Cooling S...: NASA will determine if a spacewalk is necessary to repair a problem with a cooling pump aboard the Space Station. Linda So reports.
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Written by
James Dean
FLORIDA TODAY
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The International Space Station. / NASA
Equipped with the latest in spacesuit technology — sponges and snorkels — a pair of NASA astronauts are set to perform a series of spacewalks to repair a critical International Space Station cooling system.
But at the first sign of "squishiness" in their helmets, Mike Hopkins and Rick Mastracchio will cut short any of the three planned excursions, which are scheduled to start Saturday and wrap up Christmas Day.
The new equipment and procedures are a response to a frightening incident last summer when Italian astronaut Luca Parmitano's helmet began to fill with water, resulting in a safe abort of the most recent U.S.-led spacewalk.
Although NASA managers haven't conclusively determined the cause of that suit malfunction, they don't expect it to reoccur and are confident the spacewalkers can return to an airlock if necessary, as Parmitano did.
"We're ready to go out the door on Saturday," said Dina Contella, an ISS flight director.
Mastracchio and Hopkins will attempt to remove and replace a pump module that suffered a valve failure last week, leaving it unable to regulate temperatures in one of the two coolant loops running outside the station.
That put a stop to most science research as non-critical systems inside the U.S. segment were shut down to prevent overheating.
It also left the station and its six-person crew vulnerable to a total cooling system shutdown if the second loop failed — what managers called the potential "next worst failure."
"We've always known that was a big concern, and so we try not to leave ourselves in that posture very long," said Mike Suffredini, NASA's ISS program manager.
It's possible only two spacewalks will be necessary to remove the pump module and replace it with one of three spares, but spacewalkers needed three in 2010 to install the module now experiencing trouble.
They struggled to remove the 780-pound module, which is the size of a large kitchen appliance, when coolant hoses wouldn't disconnect easily and leaked highly toxic ammonia.
Mastracchio is a veteran of six previous spacewalks totaling more than 38 hours.
Hopkins, on his first spacewalk, will wear the same suit as Parmitano but with many of its internal components replaced.
Both astronauts installed pads in the back of their helmets that can absorb up to 27 ounces of water. The pads represent the "first line of defense" against any Parmitano-like leaks, said Allison Bolinger, NASA's lead officer for the upcoming spacewalks.
When the spacewalkers routinely examine their spacesuit gloves for nicks and scrapes, they now will also check whether the helmet pads feel "squishy." If they do, it's back to the airlock.
The spacewalkers also fashioned "snorkels" from tubes already used to vent water inside their suits. Faced with spreading water, they could nod their heads down and suck oxygen from the snorkel to breathe.
"This is your last resort if water is encroaching your face," said Bolinger.

ISS spacewalkers to pack new safety gear
Coolant system repair walks begin Saturday
Dec. 19, 2013 9:21 AM |
Rick Mastracchio (left) and Mike Hopkins check a U.S. spacesuit inside the Quest airlock Image Credit: NASA TV
Written by
James Dean
FLORIDA TODAY
Equipped with the latest in spacesuit technology — sponges and snorkels — a pair of NASA astronauts are set to perform a series of spacewalks to repair a critical International Space Station cooling system.
But at the first sign of "squishiness" in their helmets, Mike Hopkins and Rick Mastracchio will cut short any of the three planned excursions, which are scheduled to start Saturday and wrap up Christmas Day.
The new equipment and procedures are a response to a frightening incident this past summer when Italian astronaut Luca Parmitano's helmet began to fill with water, resulting in a safe abort of the most recent U.S.-led spacewalk.
Although NASA managers haven't conclusively determined the cause of that suit malfunction, they said they don't expect it to reoccur and are confident the spacewalkers can return to an airlock if necessary, as Parmitano did.
"We're ready to go out the door on Saturday," said Dina Contella, an ISS flight director.
Mastracchio and Hopkins will attempt to remove and replace a pump module that suffered a valve failure this past week, leaving it unable to regulate temperatures in one of the two coolant loops running outside the station.
That put a stop to most science research as non-critical systems inside the U.S. segment were shut down to prevent overheating.
It also left the station and its six-person crew vulnerable to a total cooling system shutdown if the second loop failed — what managers called the potential "next worst failure."
"We've always known that was a big concern, and so we try not to leave ourselves in that posture very long," said Mike Suffredini, NASA's ISS program manager.
It's possible only two spacewalks will be necessary to remove the pump module and replace it with one of three spares, but spacewalkers needed three in 2010 to install the module now experiencing trouble.
They struggled to remove the 780-pound module, which is the size of a large kitchen appliance, when coolant hoses wouldn't disconnect easily and leaked highly toxic ammonia.
Mastracchio is a veteran of six previous spacewalks totaling more than 38 hours.
Hopkins, on his first spacewalk, will wear the same suit as Parmitano but with many of its internal components replaced.
Both astronauts installed pads in the back of their helmets that can absorb up to 27 ounces of water. The pads represent the "first line of defense" against any Parmitano-like leaks, said Allison Bolinger, NASA's lead officer for the upcoming spacewalks.
When the spacewalkers routinely examine their spacesuit gloves for nicks and scrapes, they now also will check whether the helmet pads feel "squishy." If they do, it's back to the airlock.
The spacewalkers also fashioned "snorkels" from tubes already used to vent water inside their suits. Faced with spreading water, they could nod their heads down and suck oxygen from the snorkel to breathe.
"This is your last resort if water is encroaching your face," said Bolinger.
Contact Dean at 321-242-3668 or jdean@floridatoday.com.

Copyright © 2013 www.floridatoday.com. All rights reserved.

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NASA confident spacesuits ready for cooling system repair work
12/18/2013 05:56 PM
By WILLIAM HARWOOD
CBS News

Engineers have not yet figured out the root cause of a leak in a spacesuit that flooded an astronaut's helmet during a spacewalk last summer. But NASA managers said Wednesday they are confident the suit in question, and another that will be used for urgent space station coolant repair work starting Saturday, will operate safely without any dangerous leakage.

Just in case, Rick Mastracchio and Mike Hopkins, scheduled to begin the first of up to three spacewalks Saturday morning, will have water-absorbing pads positioned in their helmets just behind their heads and homemade snorkel-like tubes that would allow them to breathe on the way back to the station's airlock if any flooding occurs.

"We think that's an extremely clean suit and it's ready to go," space station Flight Director Dina Contella said of the suit that leaked in July. "We have high confidence that it's essentially just like a unit that was refurbished on the ground."

She said she asked flight controllers Wednesday if anyone had any concerns about pressing ahead and "there was not much to be said. I think we're ready to go out the door Saturday and our team has no lingering, outstanding, show-stopping issues that we're working right now."

Mastracchio, call sign EV-1, will be wearing a spacesuit with red stripes while Hopkins, EV-2, will be wearing an unmarked suit. They plan to switch their suits to battery power at 7:10 a.m. EST (GMT-5) Saturday to officially kick off a planned 6.5-hour spacewalk.

A second spacewalk is planned for Monday with a third on tap, if necessary, Christmas day.

This will be the seventh spacewalk for Mastracchio, a shuttle veteran, and the first for Hopkins, who is making his first space flight. He will be wearing spacesuit No. 3011, the same suit worn by European Space Agency astronaut Luca Parmitano during a frightening excursion in July.

During that outing, the suit's internal plumbing developed a leak, flooding Parmitano's helmet with a steadily growing, floating blob of water that wrapped around his head, blocking his ears, obscuring his vision and threatening to cover his nose and mouth.

Parmitano safely made it back to the station's airlock, but the leak prompted a major engineering investigation to find -- and fix -- whatever had gone wrong.

After extensive troubleshooting, engineers concluded the leak most likely was caused by contamination that blocked a filter and allowed water to back up in the system, moving into a line that feeds air to the helmet.

The source of the contamination is not yet known, but critical components in Parmitano's suit -- the one Hopkins will wear during the upcoming spacewalks -- were replaced and Contella said engineers are confident the suit's system's are pristine.

Mastracchio's suit also was inspected and engineers believe its internal filters are not saturated with contaminants that could cause similar leakage.

Even so, lead spacewalk officer Allison Bolinger said both men would use a helmet absorption pad, or HAP, and the homemade snorkel. Just in case.

"It's a modified absorbent pad that's designed to be installed in back of the crew member's helmet," she said of the HAP. "This is our first line of defense, that if water were to enter the helmet again ... this is designed to hold anywhere from between 600 and 800 milliliters of water."

The crew will periodically tilt their heads back to determine whether the pads are "squishy."

"That's the technical term we're using to define whether we think water has entered the helmet," Bolinger said. Based on testing on the ground, astronauts can first detect "squishiness" around the 200-milliliter mark.

"As soon as the crew member experiences squishiness in his HAP, that's the sign there is a problem in the (spacesuit) and it's time to come inside," she said.

The snorkel was fashioned from plastic lines that were cut to fit and wrapped in Velcro. The lines will extend from the front of the helmet, within easy reach of the astronaut's mouth, down into the chest area.

If water floods the helmet and exceeds the capacity of the absorbent pad, the astronaut as a last resort could breathe fresh air from lower in the suit while making his way back to the airlock.

The goal of the spacewalks is to replace a refrigerator-size ammonia pump module on the right side of the station's power truss. Last week, a valve inside the 780-pound module malfunctioned, preventing the station's computer from properly regulating the coolant's temperature.

The partial loss of coolant loop A forced flight controllers to power down a variety of non-essential systems and left the station one failure away from a much more serious problem if some other malfunction disabled coolant loop B.

As it turns out, this is the second problem with a coolant loop A pump module in the past three years. But space station Program Manager Mike Suffredini said different components in the module malfunctioned and "this is not an ISS-aging-vehicle issue."

"It's an unfortunate anomaly ... with a relatively young pump," he said. "But when you do mean time between failures, it's all about the averages, and so these are the kinds of things that can happen. We're prepared to deal with it."

The space station relies on a complex cooling system to dissipate the heat generated by the lab's myriad electronic systems. Components inside the station's habitable modules are cooled by water circulating through "cold plates" to absorb the heat produced by components bolted to them.

That warmed water then flows through interface heat exchangers where the "thermal load" is transferred to ammonia coolant from the station's external thermal control system. Toxic ammonia is not allowed inside the habitable modules and the coolant flowing through the heat exchangers is physically isolated from the internal water loops.

The station is equipped with two independent external ammonia coolant circuits. Both of them pick up heat from the station's water-cooled interior components and both directly cool major electrical components mounted in the station's solar power truss, including circuit breakers, voltage converters and other equipment associated with the lab's solar power grid.

The two external coolant loops include separate ammonia pump modules that push the coolant through complex plumbing and out to huge radiators where the heat is radiated away into space. The cooled ammonia then flows back through the heat exchangers and other equipment to begin a new cooling cycle.

The station can operate with just one coolant loop, but only essential life support equipment, communications gear, computers and other critical systems can remain powered. Non-essential systems must be powered down to reduce the thermal "load" on the system.

In August 2010, coolant loop A went into a sudden shutdown when its ammonia pump shorted out, triggering an emergency power down. In that case, the coolant loop no longer worked at all, and flight controllers had to shut down a variety of critical systems, including a communications channel, two of four stabilizing gyroscopes, a GPS navigation sensor and several computer control boxes and heaters.

The pump module was replaced during three spacewalks, using one of four spares that were on board at the time. The failed unit was shipped back to Earth on the final shuttle mission in 2011 for refurbishment and eventual relaunch.

In this case, the loop A pump is still operational and continues to provide cooling to components mounted in the station's solar power truss. While non-essential systems have been shut down, many more systems remain up and running thanks to the partial cooling provided to the truss components.

Even so, research gear and other components in the station's three forward modules -- NASA's Harmony, or Node 2, module, the European Space Agency's Columbus laboratory and Japan's Kibo research module -- have been shut down, interrupting scientific experiments.

Flight controllers initially hoped to correct the problem in coolant loop A by implementing a software patch that would enable another valve in the system to control the ammonia's temperature. While the patch appeared to work during preliminary tests, mission managers decided they could not afford to rely on it and ordered the spacewalks instead.

The loop A pump module is mounted on the forward face of the station's main power truss, just above and to the right of the Destiny laboratory module, in the starboard 1, or S1, truss segment. Its loop B counterpart is mounted to the left of Destiny in the port 1 truss segment.

The Boeing-built pump modules are roughly the size of refrigerators, measuring 5-and-a-half feet long, 4 feet wide and 3 feet high.

During the first spacewalk Saturday, Mastracchio and Hopkins plan to set up tools, disconnect four fluid lines and hook up two others to a "jumper" box that will prevent the loop A coolant system from over pressurizing during temperature swings in orbit.

During the second spacewalk Monday, the astronauts plan to remove the faulty pump module and temporarily mount it on a storage fixture. The replacement pump then can be installed and electrical connections restored. During the third spacewalk on Christmas day, the fluid lines will be connected to the replacement pump module and the old unit will be moved to a more secure storage platform.

Bolinger said the astronauts possibly could complete the pump module swap out in two spacewalks if everything goes as planned and no major problems develop. But that is far from certain.

During the 2010 pump replacement, two spacewalkers ran into problems disconnecting one of the ammonia lines during their first spacewalk and were unable to remove the failed pump module before time ran out. They successfully replaced the unit during a second spacewalk, but a third excursion had to be added to make up for the lost time.

NASA managers are hopeful lessons learned will help Mastracchio and Hopkins complete the S1 pump module replacement this time around in two spacewalks. If not, the astronauts are prepared for a third spacewalk on Christmas day.

NASA has conducted six previous spacewalks during the Christmas holiday season and if a third spacewalk is required for Mastracchio and Hopkins, it will come on the 40th anniversary of a Christmas Day outing during the Skylab space station program in 1973.
© 2011 William Harwood/CBS News
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Leaky Spacesuit Fixed For Christmas Spacewalk Blitz On Station, NASA Says
by Elizabeth Howell on December 18, 2013
NASA astronaut Rick Mastracchio during a spacewalk on STS-118. Credit: NASA
When NASA astronaut Mike Hopkins steps into space for the first time this week, he will wear a spacesuit that previously sprung a water leak and forced Italian astronaut Luca Parmitano back to station in July, NASA officials said Wednesday (Dec. 18).
While at first glance this sounds like an extra bit of drama as Hopkins and Rick Mastracchio make contingency spacewalks Dec. 21, 23 and 25 to kickstart a shut-down cooling loop, NASA officials say the suit is ready to go for another trip outside because astronauts (under NASA's direction) have made a bunch of changes to the unit.
Repurposing spacesuit parts, a new pad will be added to the back of all NASA spacesuit helmets to soak up water, should one leak again. Astronauts also velcroed a pipe into each suit — a sort of snorkel — that in the worst case, would give an astronaut with a water leak an alternate route for drawing in air.
Also, the Expedition 38 crew swapped out a fan pump separator that likely malfunctioned and caused the spacesuit leak. The cause is still under investigation, but NASA believes that a problem in the water chemistry caused contamination that plugged a tiny hole inside the water separation part of the unit. This allowed the water to escape, enter the air loop and get into the helmet.
Finally, there are new procedures in place for the astronauts themselves. They will monitor the helmet pad for fluid. NASA additionally plotted out its spacewalk procedures — which include the use of a Canadian robotic arm on station — to make sure the astronauts are always within reasonable reach of an airlock.
NASA astronauts Rick Mastracchio and Mike Hopkins will do spacewalks in December 2013 to swap out a cooling pump on the International Space Station. Credit: NASA
So here's why the spacewalks are happening: a week ago (Dec. 11), a flow control valve inside of a pump — the pump is located outside of the station — stopped regulating ammonia temperatures inside of an external cooling loop. The loop is required to, as the name implies, cool down space station electronics. The loop got too cold, it shut down automatically, and NASA took science experiments and redundant systems offline to deal with the problem. (The main problem is NASA can't run a heat exchanger on Node 2, which affects experiments in the U.S. Columbus laboratory and Japanese Experiment Module. No completed research has been lost to date, however.)
After figuring out that it couldn't control the valve again, NASA shifted its attention to an isolation valve upstream. That valve is only designed to be in two positions — opened or closed — but the hardware vendor said it could be used at spots in between to regulate the ammonia flow. So software engineers created a patch to make this happen, and uploaded it to station.
Throw in another element, however: the station is about to enter what's called an annual "high beta" period, when orbital dynamics mean the sun will be shining on it for longer periods of time than usual. (Read more technical details here.) When the angle exceeds 60 degrees, for safety reasons NASA suspends all cargo flights to station as well as spacewalks. This year, it will happen between about Dec. 30, 2013 and Jan. 9, 2014.
The International Space Station in 2010. Credit: NASA
So if NASA spent time playing with the valve and found out it couldn't work in the long run, a couple of problems could happen. First, it would be harder to do a spacewalk to fix it.
Also, the agency was weighing whether to allow Orbital Sciences to fly a Cygnus cargo flight this month, and felt that they could run into a problem where the spacecraft was ready to go, but NASA needed more time to fix the problem. So that's why the spacewalk is happening.
Here's a diagram of the pump that Mastracchio and Hopkins plan to replace:
A view of a pump module aboard the International Space Station that is used to maintain ammonia at the correct temperature in an external cooling loop. Credit: NASA
The "nominal" plan is for three spacewalks, but it could range anywhere from two to four depending on how things go. To put things simply, here's how the spacewalks would go:
EVA 1: The pump with the broken valve would be disconnected and a spare pump (which is some distance away, but reachable using Canadarm2) would be prepped for the swap.
EVA 2: The pump with the broken valve would be removed and set aside while the spare pump is partially installed (meaning, only the bolts and electrical connections would be put in.)
EVA 3: The spare pump's installation would be finished, and the pump with the broken valve would be stowed more permanently outside. NASA thinks that eventually, it could use that first pump again if astronauts installed a new valve on it, but that isn't a need for the time being.
Flying Canadarm2 would be Japanese astronaut Koichi Wakata, who has operated every type of robotics currently in orbit. Mastracchio has six spacewalks under his belt already, while Hopkins will be on his first go.
If all goes to plan, NASA will not only swap out the pump, but also preserve the option for the Russians to proceed with a planned Dec. 27 spacewalk that is less urgent. In that case, the cosmonauts plan to swap out experiments, put in a foot restraint and install some cameras.
We'll cover the spacewalks as they happen. They're scheduled for Dec. 21, 23 and 25 at 7:10 a.m. EST (12:10 p.m. UTC) and should run about 6.5 hours each. Broadcasts will run live on NASA Television.
By the way, the pump with the problem is just three years old — astronauts had to make three spacewalks in 2010 to install it after a more severe failure. NASA characterized this situation as a more unusual failure and said this is not a symptom of an aging station at all.
Overview of the tasks that Rick Mastracchio and Mike Hopkins will perform during three spacewalks in December 2013 to remove and replace a pump with a faulty valve inside of it. The pump is required to maintain the external cooling system at the right temperature. Credit: NASA
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AmericaSpace
For a nation that explores
December 18th, 2013
Space Station Astronauts Set for Up to Three Challenging EVAs Over Christmas
By Ben Evans
Expedition 38 astronauts Rick Mastracchio (bottom left) and Mike Hopkins (top right) work with their space suits inside the Quest airlock, as preparations for the Christmas EVAs gather momentum. Photo Credit: NASA
For Mike Hopkins it will be a Christmas gift like no other. It has been granted to a little over 200 individuals to walk in space, clad only in a pressurized suit, and to fewer still—just three, in fact—to have walked in space on the traditional date of Christ's birth. On Christmas Day, Hopkins and fellow Expedition 38 crewmate Rick Mastracchio may complete the third in a critical series of EVAs outside the International Space Station (ISS), whose primary objective is to replace the malfunctioning starboard pump module and hopefully resolve a problem with one of two external ammonia coolant loops. Today (Wednesday), NASA unveiled its plans for up to three 6.5-hour spacewalks, currently targeted to begin at about 7:10 a.m. EST on 21, 23, and maybe 25 December.
It was way back in 1973 that U.S. astronauts Gerry Carr and Bill Pogue floated outside Skylab on Christmas Day and performed a lengthy EVA to photograph Comet Kohoutek and replace film aboard the space station's Apollo Telescope Mount. For Pogue, the experience reminded him of his childhood, "doing a mud-crawl in a four-foot-deep stock tank used for watering cows and horses." By the time the two men returned inside Skylab and rejoined crewmate Ed Gibson, they were advised that they had established a new world record for the longest spacewalk to date, at 6 hours and 54 minutes. This duration record has since been broken several times, and others have spacewalked close to the big day—STS-103 astronauts Steve Smith and John Grunsfeld made their final EVA to service the Hubble Space Telescope on Christmas Eve in 1999—but Carr and Pogue's accomplishment at celebrating the traditional date of Christ's birth, unhindered by spacecraft walls, high above Earth, has never been duplicated.
Ed Gibson is pictured outside Skylab during one of the station EVAs in the winter of 1973-1974. The final Skylab mission marked the first occasion on which a spacewalk was conducted on Christmas Day. Photo Credit: NASA
Until now, it seems. "NASA managers have planned for the first spacewalk to begin Saturday, the second on Monday and if necessary a third spacewalk on Christmas Day," the agency revealed today (Wednesday). The situation has drawn some parallels with the August 2010 failure in the starboard-side coolant loop, which left the ISS with barely half of its normal cooling capability and severely restricted the redundancy of several systems. In particular, two of the four Control Moment Gyroscopes were shut down and three EVAs were executed by U.S. astronauts Doug Wheelock and Tracy Caldwell-Dyson to remove the failed pump module and restore the starboard loop to its proper functionality.
For Saturday's opening EVA—the first spacewalk to be conducted from the station's U.S. segment in U.S.-built suits since the terminated EVA-23 by Chris Cassidy and Luca Parmitano on 16 July—the two main participants have spent the past several days readying their equipment, tools, and procedures checklists. Rick Mastracchio is no stranger to spacewalking. Expedition 38 is his fourth space mission, and he has chalked up a cumulative six EVAs, lasting a total of 38 hours and 30 minutes, which currently establishes him as the 27th most experienced spacewalker in history. Mike Hopkins, on the other hand, is making his first space mission on Expedition 38, and although both he and Mastracchio had trained extensively for contingency EVAs before launch, neither of them could have anticipated the suddenness with which the events of the last week have unfolded.
On Wednesday, 11 December, the pump module on one of the space station's two coolant loops automatically shut down when it reached pre-set temperature limits. Suspicion quickly centered on the improper functionality of a regulating flow control valve inside the pump module, and NASA engineers have been hard at work to develop a clearer understanding of the issue through testing over the last week. By regulating the temperature of ammonia in the coolant loop, the valve ensures that when it is re-introduced into the heat exchanger of the station's Harmony node, it does not freeze the water also passing through the exchanger. Although NASA stressed that the Expedition 38 crew was placed in no danger, engineers worked to move certain critical station systems over to the second coolant loop. Some non-critical elements were also powered down inside Harmony, as well as Japan's Kibo and Europe's Columbus laboratory modules.
The Christmas EVAs by Rick Mastracchio and Mike Hopkins will bear close similarities to the three spacewalks performed by Doug Wheelock (pictured) and Tracy Caldwell-Dyson in August 2010. Photo Credit: NASA
Replacing the valve itself is not an option, since its location within the pump module is inaccessible to spacewalkers. Only the removal and replacement of the entire pump module—of which several "spares" were delivered to the ISS by the shuttle and are situated aboard the station's External Stowage Platforms (ESP)—is a realistic option. Yesterday (Tuesday), NASA announced its decision to postpone the scheduled 19 December launch of Orbital Sciences' first dedicated Cygnus cargo mission (ORB-1) until no earlier than 13 January, in order to focus on the repair effort.
Early Saturday, 21 December, after post-sleep and personal hygiene activities, Mastracchio and Hopkins will jump right onto a well-trodden path of 60 minutes of pre-breathing on masks, during which time the Quest airlock's inner "equipment lock" will be depressed from its "ambient" 14.7 psi down to 10.2 psi. Their next step will be the process of donning and purging their bulky Extravehicular Mobility Units (EMUs), after which the atmosphere will be repressurized to 14.7 psi. The astronauts will then enter a nominal pre-breathing period, lasting about 50 minutes, followed by a further 50 minutes of In-Suit Light Exercise (ISLE). This protocol was first debuted on the STS-134 mission in May 2011 and will involve Mastracchio and Hopkins flexing their knees for four minutes, resting for one minute, and repeating over and over until the 50 minutes are up. ISLE serves to remove nitrogen from the spacewalkers' blood in a much shorter time period.
An hour before the EVA's scheduled 7:10 a.m. EST start time, the fully-suited pair and their equipment will be transferred into Quest's outer "crew lock," and Expedition 38 crewmates Koichi Wakata and Commander Oleg Kotov will confirm the closure of hatches between the two locks. Depressurization will be briefly halted at 5 psi for standard leak checks, after which the process will resume and continue until the crew lock is at near-vacuum conditions. EVA-24 will officially commence when Mastracchio and Hopkins transfer their suits' critical life-support utilities onto internal battery power.
Rick Mastracchio (with red stripes on the legs of his suit) manipulates the failed pump module in this NASA graphic. He will ride the end of the space station's Canadarm2 robotic arm, controlled by Japanese astronaut Koichi Wakata. Image Credit: NASA
Principal tasks for Saturday's EVA-24 will be the preparations to remove the failed starboard pump module, which includes the demating of four ammonia fluid quick disconnects, the installation of jumpers, and the removal of five electrical connectors. Mastracchio (designated "EV1," with red stripes on the legs of his space suit) and Hopkins ("EV2," clad in a pure-white suit) will then turn their attention to preparing the replacement pump module—currently located on External Stowage Platform (ESP)-3 and delivered to orbit by the STS-127 shuttle crew, back in July 2009—for movement to its new home. The two men will open multi-layer insulation on the new pump module to ready it for installation during EVA-25 on Monday, 23 December.
The second spacewalk will see the astronauts remove the failed pump module and stow it on the Payload Orbital Replacement Unit (ORU) Accommodation (POA) of the station's Mobile Base System (MBS). They will then install the bolts and electrical connectors for the replacement pump module. Assuming that the historic Christmas Day EVA-26 goes ahead, NASA graphics indicate a change in the roles of the two spacewalkers, with Hopkins now taking on the EV1 duties and Mastracchio serving as EV2. They will finish up the installation of the replacement pump module, securing its ammonia fluid quick disconnects, and will permanently stow its failed counterpart before cleaning up their worksite. With all three EVAs expected to last in the region of 6.5 hours, the New Year should see Hopkins accrue a total of 19.5 hours of spacewalking time, whilst Mastracchio's record will jump to about 58 hours in nine spacewalks. As a result, this will push Mastracchio from 27th place to 5th place (behind Anatoli Solovyov, Mike Lopez-Alegria, Jerry Ross, and John Grunsfeld) in the list of the most experienced spacewalkers of all time.

Copyright © 2013 AmericaSpace - All Rights Reserved

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Astronauts prepare for first spacewalk since helmet leak problem
By Irene Klotz

CAPE CANAVERAL, Florida (Reuters) - Astronauts aboard the International Space Station prepared for an unexpected series of spacewalks by fabricating spacesuit snorkels they can use for breathing in case of another helmet water leak, NASA officials said on Wednesday.
The spacewalks, the first of which is slated to begin at 7:10 a.m. EST (1210 GMT) on Saturday, are needed to replace one of two cooling pumps outside the $100 billion complex, which flies about 250 miles above Earth.
U.S. spacewalks have been suspended since July after a spacesuit helmet worn by Italian astronaut Luca Parmitano filled with water, causing him to nearly drown.
The underlying cause of the leak remains under investigation but engineers have learned enough to make modifications so the problem will not happen again, NASA managers told reporters during a conference call.
"I would be surprised if we have a problem with the suits," said space station program manager Mike Suffredini.
As a contingency, the spacewalkers' helmets will be outfitted with absorbent pads and home-made snorkels to funnel air from the body of the water-cooled suits into an astronaut's mouth, if needed.
The snorkels, which were fabricated by the crew on Sunday, are made from plastic water line vent tubes used in the spacesuits.
"This is your last resort," said Allison Bolinger, lead spacewalk officer. "If water is encroaching your face, similar to what happened to Luca, the crewmember can lean down and use this (the snorkel) to breathe."
First-time spacewalker Michael Hopkins will wear Parmitano's spacesuit, but it has been outfitted with a new fan pump separator, a device that circulates water and air and removes moisture from air.
The fan pump separator from Parmitano's suit was flown back to Earth for analysis and engineers found tiny holes in the water-separator portion of the device were clogged.
That allowed water to back up into the fan portion, get into a vent loop and enter the helmet, said space station flight director Dina Contella.
Still unknown is how the water was contaminated.
"Unfortunately, it's a pretty complicated water chemistry problem," Contella said.
Suffredini said: "We believe the lines we're using today are clean. We've put in new filters and we think the filter system works."
A new fan pump separator is among the cargo aboard Orbital Sciences Corp's first supply ship to the station which had been slated to launch this week. But it is being delayed until mid-January so NASA can tackle the higher-priority work of getting the station's cooling system back in operation.
One of two ammonia cooling systems shut down on December 11, forcing astronauts to turn off unnecessary equipment and suspend some science experiments.
The U.S. side of the station has a second cooling system, but it cannot accommodate all the gear.
Hopkins will be joined by six-time spacewalker Rick Mastracchio for three spacewalks to replace the faulty cooling system with a spare that is in storage outside the station.
In addition to Saturday's 6.5-hour outing, spacewalks are planned for Monday and Wednesday.
(Editing by Kevin Gray and Mohammad Zargham)
Copyright © 2013 Reuters Limited. All rights reserved.

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