A few hours after the AMS installation, Feustel and Chamitoff will seal themselves in the space station's Quest airlock and spend the night at a reduced pressure of 10.2 pounds per square inch. The "camp out" procedure is a standard protocol to help remove nitrogen from the spacewalkers' bloodstreams and prevent the bends when working in NASA's low-pressure spacesuits.

Credit: NASA

The primary goals of the first spacewalk are to retrieve a materials science space exposure experiment mounted on ELC-2; to install a replacement; and to hook up ammonia line jumpers to set up a pipeline from an ammonia coolant tank near the center of the power truss to the outboard left-side solar array.

The Materials International Space Station Experiments -- MISSE -- are the size of suitcases.

"It's a space exposure experiment," Chamitoff said in a NASA interview. "Basically they're like large suitcases with lots of samples inside, and those samples can be everything from materials to paints to coatings to electronic equipment to biological samples, and they can come from different organizations.

"The idea is to expose these things to the harsh environment of space for a long period and see what happens -- if the seeds will still germinate, if a paint material will protect what's below it, see if a circuit can still work and to help us design better systems for the future.

"There are two experiments out there that are a part of MISSE 7," Chamitoff said. "We're going to retrieve those, close (them) up, take them back, put them in the shuttle cargo bay, and then we take new ones out of the cargo bay, MISSE 8, and we install them up on the truss. They'll be out there for six months to a year before they come in."

The spacewalkers then will turn their attention to preparations for topping off the ammonia coolant supply in the port six, or P6, solar array segment.

Each of the station's four sets of solar arrays are equipped with radiators that use circulating ammonia to carry away heat generated by batteries and electronics subsystems. Engineers have been monitoring a small leak in the P6 coolant system and during the crew's second spacewalk, the astronauts will top off the coolant in the P6 radiator panels. But first, Feustel and Chamitoff must hook up the jumpers to complete what amounts to a long hose running from an ammonia storage tank on the P1 truss segment all the way out to P6.

"We have to sort of connect a lot of ammonia hoses between a lot of segments including one that jumps across the rotating solar alpha rotary joint, which normally can't have a hose running across (it). It has to spin freely.

"We're going to go out and we're going to connect all these hoses and then vent them basically so that they're filled with N2, the nitrogen. We're going to vent them so that they're ready to be used for the ammonia fill on the next EVA."

After the line is vented, the segment crossing the solar alpha rotary joint -- the P3/P4 jumper -- will be disconnected so the outboard arrays can rotate as required to track the sun. Those jumpers will be reconnected during the second spacewalk when the ammonia fill will take place.

After the jumper work, Chamitoff and Feustel will install a new wireless antenna that can be used by external experiments and other payloads.

"There are experiments and payloads outside the space station (that) need to communicate to the data system and they're installing a couple of antennas and all the wiring for that to enable those pieces of equipment or experiments to communicate to internal systems," Chamitoff said.

"It's a lot of wiring. It's a little messy with long wires and it takes a while but that's going to be in the front of the space station near the shuttle. The thing that's maybe a little interesting about that is just that in order for us to do that, they have to disable some things internally. We may lose communication. We may have to wave through the window and say everything's OK, and then go down and finish the work and come back and say everything's OK. We'll see how that goes but it should be interesting."

The next day -- flight day six -- Johnson and Coleman, operating the space station's robot arm, will pull the shuttle heat shield inspection boom out of Endeavour's cargo bay and hand it off to the shuttle's arm, operated by Feustel and Vittori. The boom will be used later in the misson to inspect the shuttle's heat shield again. After the handoff, the astronauts will take a half day off to relax and catch their collective breath.

Fincke will join Feustel for the second spacewalk on flight day seven. There are two primary objectives: to fill the P6 ammonia radiator with coolant and to lubricate the port solar alpha rotary joint drive gear and bearing race.

"Building on the success of EVA 1, we hope, we're going to go out, and we have two main jobs for EVA No. 2. Both of them are for the long-duration maintenance of the International Space Station," Fincke said in a NASA interview. "Since we're the last shuttle-based EVA, we're doing things in advance for routine preventative maintenance just like with our automobiles."

Feustel will focus on making the final connections to permit six to eight pounds of ammonia to flow outboard from the P1 ammonia tank assembly to the P6 radiator, including reconnecting the P3/P4 jumper across the solar alpha rotary joint, or SARJ. It will take about 10 minutes to top off the radiator. After that, Fuestel will vent the line with nitrogen to remove any residual ammonia. Two ventings are required, one lasting 17 minutes and one about four minutes.

NASA has a history of problems with ammonia quick-disconnect fittings, and there are more than a half-dozen connections required for the P6 radiator fill. If either spacewalker gets ammonia on his suit, NASA will implement a "bake out" protocol to make sure any ammonia ice crystals sublimate away in direct sunlight, before the astronauts re-enter the space station.

"This isn't your household cleaner ammonia," Fincke said, "this is high-grade industrial ammonia so we have to be super careful not to get it on us or to spill it because it's quite dangerous if we brought it back inside. But we're going to recharge the ammonia lines. ... There's a series of jumpers that we have to go across, including the rotating solar alpha rotary joint, so we have some jumpers, a series of hoses that will fully charge our ammonia system.

"While Drew's doing that, I get to do a lubrication job, add some grease, some Braycote, to our solar alpha rotary joint," Fincke said. "We found the original design had some extra friction that we weren't expecting and it started to grind our joint. So since then, every couple years, (we've) started to add some grease on it and it rotates great. However, we won't have that ability so much in the future, so while Drew's working with the ammonia system I'll be lubricating the outside of the solar alpha rotary joint so it can last another five to ten years, no problem."

When the SARJ work is complete and the astronauts have verified that all tools, tethers and jumpers are inboard of the port SARJ, commands will be sent to rotate the solar arrays through 200 degrees. The 45-minute procedure will spread the grease already applied and bring the other side of the gear and race into position for lubrication.

While the array is slowly rotating, Feustel will install a lens cover on a camera used by the Canadian Special Purpose Dexterous Manipulator, or Dextre, a robot arm attachment fitting that in some cases can take the place of a spacewalking astronaut. With the lens cover in place, Feustel plans to lubricate the snares used by Dextre to hold components in place.

While Feustel is working with Dextre, Fincke will install two grapple bar stowage beams that will provide a temporary mounting point for radiator panels if replacement operations are ever required.

Finally, Fincke and Feustel will apply a final bead of grease to the SARJ race ring before re-installing six covers and heading back to the airlock.

The day after the second spacewalk, the astronauts will take another half-day off before Fincke and Feustel prepare for the mission's third spacewalk.

But this time around, the astronauts will not camp out in the Quest airlock to help remove nitrogen from their bloodstreams. Instead, they will test a new protocol known as the "in-suite light exercise" pre-breathe protocol, or ISLE for short.

Extensive testing on the ground indicates spacewalkers can remove nitrogen by simply performing light exercise the morning of the excursion while breathing pure oxygen. By avoiding the overnight campout, astronauts will not be isolated before a spacewalk and a fire alarm or other problem will not force them to open the airlock and delay a long-planned spacewalk.

"It doesn't require the overnight campout that was used for most of the previous EVAs on the last several flights," said Hassmann. "In terms of complexity, in terms of the quality of life for the crew, this ISLE protocol is a pretty significant upgrade because we don't have that point the night before where the two EVA crew has to go in the airlock, and we shut the hatch, and they're forced to spend the night in the airlock.

"With this in-suit light exercise, or ISLE, protocol, the night before an EVA looks exactly like any other night during the mission. They wake up, they don't have to stay on the portable breathing apparatus, they don't have to stay on the oxygen masks. So up until the point where they actually begin the EVA prep the morning of, it looks just like any other day.

"We think this is an improvement over the campout protocol," he said. "And of course, the main thing we're after here is crew safety. All of these crew protocols are designed to prevent the bends. Leading up to this, we put the ISLE protocol through all the standard medical reviews and tests that both the campout and exercise pre-breathe protocols have been subjected to, and everybody's comfortable it's completely safe. We think it offers some significant advantages."

The third spacewalk, on flight day nine, is devoted primarily to attaching a power and data grapple fixture -- a robot arm anchor fitting -- to the side of the Russian Zarya module, along with a video signal conditioner and associated cabling. The equipment will allow the station's robot arm to base itself on the Russian segment of the space station for maintenance work down the road.

"We've just added this EVA, and this involves installing a power and data grapple fixture, or a base, for Canadarm 2," Feustel said. "So the Canadarm space station arm has a capability of walking around the space station from end to end to do different tasks. The Russian segment doesn't really have any of those bases for the arm to walk on to.

"This is an opportunity for us to actually attach one of these base station mechanisms onto what we call the FGB or Functional Cargo Block portion of the space station to allow the arm to walk onto that position and do some tasks in areas that it wouldn't have been able to reach previous to this."

In addition to mounting the PDGF and the video signal conditioner, Fincke and Feustel also will route power and data cables from the U.S. segment of the station to the new equipment.

The day after the third spacewalk -- flight day 10 -- the astronauts will carry out an inspection of the shuttle's nose cap and wing leading edge panels to look for any signs of damage that might have occurred since launch due to impacts with space debris or micrometeoroids.

This so-called late inspection, using the shuttle's robot arm and heat shield inspection boom, normally is carried out after the shuttle undocks from the station. But Endeavour's orbiter boom sensor system, or OBSS, will be left behind aboard the station to give the lab's robot arm an extension, providing the capability to reach areas that would otherwise be inaccessible.

After the late inspection, the crew will review procedures for a fourth and final spacewalk by Fincke and Chamitoff the next day to mount the OBSS on the station's power truss. If the ISLE protocol works and no problems develop, Fincke and Chamitoff may use it again for EVA No. 4. Otherwise, they will use the normal camp out procedure.

After exiting the Quest airlock, the astronauts will set up foot restraints on the power truss and take the OBSS boom from the shuttle's robot arm, operated by Johnson, known by his nickname Box. After mounting the boom on attachment fixtures, Fincke will demate electrical connectors leading to a no-longer-needed laser scanner and heat shield inspection camera.

Then they will remove the grapple fixture on the other end of the boom that was used by the shuttle's robot arm and replace it with a fixture designed for the station arm.

"That boom will be left behind on the space station with the idea that at some point if the space station has to do some work, it would give the robotic arm more reach if it could use this boom as well," Chamitoff said. "We have left it up there before, we have the mechanisms in place to leave it up there.

"We'll be attaching that boom to the truss, locking it in place. Normally the shuttle arm grabs that boom at the end, and the station arm has a grapple fixture in the middle, but if we're going to use it on the station at some future point, you want to be able to grab it from the end. The grapple fixture at the end is not the right kind and we have to change it so it'll be kind of fun for Mike.

"Because we're kind of tearing this thing apart in a way, we're taking off that end, replacing it with a station grapple fixture, and we have to cut some wires and pull this thing off completely and while we're doing that I'll be on the station robotic arm and Box will be flying me around. That'll be an exciting task to do."

After wrapping up work to stow the OBSS, the astronauts will perform minor maintenance on the Dextre manipulator, unlatch a spare arm mounted on ELC-3 and install a protective handling fixture to the spare high-pressure oxygen tank.

The day after the final spacewalk -- flight day 12 -- the combined crews will wrap up equipment transfers, finish moving science samples from the station to the shuttle and hold a joint crew news conference. Then the two crews will bid each other farewell and close the hatches between Endeavour and the space station.

The next morning, Endeavour will undock to wrap up its final station visit.

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