Shuttle astronauts set for Wednesday spacewalk
05/24/2011 02:53 PM Filed in: Space Shuttle | STS EVA | Space News | STS-134 | International Space Station
By WILLIAM HARWOOD
CBS News
KENNEDY SPACE CENTER, FL--The Endeavour astronauts helped out with space station maintenance Tuesday, beginning work to service a carbon dioxide scrubber and to install a filter in a U.S. oxygen generator amid preparations for an overnight spacewalk, the third of four planned by the shuttle's crew.
The U.S. segment of the station is equipped with two carbon dioxide removal assemblies, or CDRAs, one in the Destiny lab module and the other in Tranquility, that use a desiccant bed to condition incoming air before it is passed through an absorbent bed to remove CO2.
A replacement for one of the beds in the Tranquility CDRA was carried aloft aboard Endeavour and shuttle commander Mark Kelly, joined by space station flight engineer Ronald Garan, started the repair work Tuesday.
Michael Fincke and Gregory Chamitoff, both veterans of long-duration stays aboard the station, started maintenance work on a U.S. oxygen generator that has had problems with contamination in the water that is broken down to produce oxygen. The astronauts are installing a new filter assembly and associated plumbing that may resolve the issue. After leak checks, the OGA will be activated later in the week for test runs and analysis.
In a bit of unplanned maintenance, Fincke also replaced a remote power control module, or RPCM, that "tripped" overnight, knocking out power to high definition video systems and disabling gear used to transmit science data to the ground. Older-style RPCMs have a known problem with built-in firmware and NASA is in the process of replacing them with upgraded versions. In this case, Fincke installed a replacement and downstream systems were brought back on line without incident.
The astronauts went to bed just before noon EDT (GMT-4). They will begin flight day 10 at 7:56 p.m. and quickly move into preparations for an overnight spacewalk by Fincke and Andrew Feustel. The excursion is scheduled to begin around 1:46 a.m. Wednesday
The primary goals of the spacewalk are to mount a power and data grapple fixture on the left side of the Russian Zarya module that can be used later as a base for the station's Canadian-built robot arm. They also plan to install wiring between the U.S. and Russian segments of the station to improve redundancy in the system that feeds power from the lab's NASA-supplied solar arrays to the Russian segment of the station.
"The Canadarm space station arm has a capability of walking around the space station from end to end to do different tasks," Feustel said in a NASA interview. "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 mechanisms onto (Zarya) 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."
The spacewalkers also plan to install a video signal conditioner for the power and data grapple fixture; to finish connecting wiring needed by new antennas installed during the crew's first spacewalk; and to carry out photo documentation of experiments mounted on the station's power truss.
One item on the crew's original EVA-3 timeline was deleted to make room for the antenna wiring. Installation of a data cable needed before the Zarya robot arm base station can be used was deferred to a future spacewalk.
For the first two spacewalks, and scores that preceded them, spacewalkers used a so-called "campout" protocol to purge nitrogen from their bloodstreams to prevent the bends while working in NASA's low-pressure spacesuits.
The campout protocol required spacewalkers to wear oxygen masks for one hour the night before an EVA and then to spend the night in the station's airlock at a reduced pressure of 10.2 psi. The day of the spacewalk, the astronauts would put the masks back on, repressurize the airlock, eat breakfast and attend to hygiene, depress the airlock back to 10.2 psi, take the masks off and don their spacesuits. Then another 50 minutes breathing pure oxygen was required before the spacewalk could begin.
For EVA No. 3, Fincke and Feustel will test a new protocol known as the "in-suit 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 -- the equivalent of walking a 70-minute mile -- while breathing pure oxygen. By avoiding the overnight campout, astronauts will not be isolated before a spacewalk and a fire alarm or other problem would 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 space station Flight Director Derek 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."
For the first test run of the new protocol, Fincke and Chamitoff will spend 20 minutes on pure oxygen at rest, followed by 50 minutes of light exercise and then 30 more minutes at rest.
Lead spacewalk officer Allison Bolinger said that along with improving the quality of life for spacewalkers, the ISLE protocol will save oxygen.
"Post shuttle retirement, this will be a big deal for station," she said. "The crew members will also spend less time on the oxygen masks, which for some crew members can be uncomfortable. They're not isolated in the airlock overnight, which is also a benefit.
"The one drawback to this protocol, though, it does take longer in the morning to get out the door than it does with the campout protocol. So (airlock) egress we estimate to be about 30 minutes later than if we had done the campout protocol."
Here is an updated timeline of the crew's planned activities for flight day 10 (in EDT and mission elapsed time; includes revision G of the NASA television schedule; best viewed with fixed-width font):
CBS News
KENNEDY SPACE CENTER, FL--The Endeavour astronauts helped out with space station maintenance Tuesday, beginning work to service a carbon dioxide scrubber and to install a filter in a U.S. oxygen generator amid preparations for an overnight spacewalk, the third of four planned by the shuttle's crew.
The U.S. segment of the station is equipped with two carbon dioxide removal assemblies, or CDRAs, one in the Destiny lab module and the other in Tranquility, that use a desiccant bed to condition incoming air before it is passed through an absorbent bed to remove CO2.
 |
| Lead spacewalker Andrew Feustel pretends to play the International Space Station's keyboard in the Japanese Kibo module. (Credit: NASA TV) |
Michael Fincke and Gregory Chamitoff, both veterans of long-duration stays aboard the station, started maintenance work on a U.S. oxygen generator that has had problems with contamination in the water that is broken down to produce oxygen. The astronauts are installing a new filter assembly and associated plumbing that may resolve the issue. After leak checks, the OGA will be activated later in the week for test runs and analysis.
In a bit of unplanned maintenance, Fincke also replaced a remote power control module, or RPCM, that "tripped" overnight, knocking out power to high definition video systems and disabling gear used to transmit science data to the ground. Older-style RPCMs have a known problem with built-in firmware and NASA is in the process of replacing them with upgraded versions. In this case, Fincke installed a replacement and downstream systems were brought back on line without incident.
The astronauts went to bed just before noon EDT (GMT-4). They will begin flight day 10 at 7:56 p.m. and quickly move into preparations for an overnight spacewalk by Fincke and Andrew Feustel. The excursion is scheduled to begin around 1:46 a.m. Wednesday
The primary goals of the spacewalk are to mount a power and data grapple fixture on the left side of the Russian Zarya module that can be used later as a base for the station's Canadian-built robot arm. They also plan to install wiring between the U.S. and Russian segments of the station to improve redundancy in the system that feeds power from the lab's NASA-supplied solar arrays to the Russian segment of the station.
"The Canadarm space station arm has a capability of walking around the space station from end to end to do different tasks," Feustel said in a NASA interview. "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 mechanisms onto (Zarya) 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."
The spacewalkers also plan to install a video signal conditioner for the power and data grapple fixture; to finish connecting wiring needed by new antennas installed during the crew's first spacewalk; and to carry out photo documentation of experiments mounted on the station's power truss.
One item on the crew's original EVA-3 timeline was deleted to make room for the antenna wiring. Installation of a data cable needed before the Zarya robot arm base station can be used was deferred to a future spacewalk.
For the first two spacewalks, and scores that preceded them, spacewalkers used a so-called "campout" protocol to purge nitrogen from their bloodstreams to prevent the bends while working in NASA's low-pressure spacesuits.
 |
| In this computer graphic, astronauts Andrew Feustel and Michael Fincke attach a space station robot arm mounting fixture on the Russian Zarya module. (Credit: NASA TV) |
The campout protocol required spacewalkers to wear oxygen masks for one hour the night before an EVA and then to spend the night in the station's airlock at a reduced pressure of 10.2 psi. The day of the spacewalk, the astronauts would put the masks back on, repressurize the airlock, eat breakfast and attend to hygiene, depress the airlock back to 10.2 psi, take the masks off and don their spacesuits. Then another 50 minutes breathing pure oxygen was required before the spacewalk could begin.
For EVA No. 3, Fincke and Feustel will test a new protocol known as the "in-suit 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 -- the equivalent of walking a 70-minute mile -- while breathing pure oxygen. By avoiding the overnight campout, astronauts will not be isolated before a spacewalk and a fire alarm or other problem would 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 space station Flight Director Derek 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."
For the first test run of the new protocol, Fincke and Chamitoff will spend 20 minutes on pure oxygen at rest, followed by 50 minutes of light exercise and then 30 more minutes at rest.
Lead spacewalk officer Allison Bolinger said that along with improving the quality of life for spacewalkers, the ISLE protocol will save oxygen.
"Post shuttle retirement, this will be a big deal for station," she said. "The crew members will also spend less time on the oxygen masks, which for some crew members can be uncomfortable. They're not isolated in the airlock overnight, which is also a benefit.
"The one drawback to this protocol, though, it does take longer in the morning to get out the door than it does with the campout protocol. So (airlock) egress we estimate to be about 30 minutes later than if we had done the campout protocol."
Here is an updated timeline of the crew's planned activities for flight day 10 (in EDT and mission elapsed time; includes revision G of the NASA television schedule; best viewed with fixed-width font):
DATE/EDT...DD...HH...MM...SS...EVENT
05/24
01:00 PM...08...04...04...00...Daily video highlights reel on NASA TV
05:45 PM...08...08...49...00...Flight director update on NASA TV
05:45 PM...08...09...49...00...Flight director update replay on NASA TV
07:56 PM...08...11...00...00...STS/ISS crew wakeup (begin flight day 10)
09:11 PM...08...12...15...00...EVA-3: ISLE EVA prep (new in-suit light exercise protocol)
09:26 PM...08...12...30...00...ISS daily planning conference
11:21 PM...08...14...25...00...EVA-3: Spacesuit purge
11:36 PM...08...14...40...00...EVA-3: ISLE spacesuit pre-breathe
05/25
01:16 AM...08...16...20...00...EVA-3: Crew lock depressurization
01:46 AM...08...16...50...00...EVA-3: Spacesuits to battery power (official start time)
01:51 AM...08...16...55...00...EVA-3: Egress and setup
02:31 AM...08...17...35...00...EVA-3: PDGF setup
03:01 AM...08...18...05...00...EVA-3: Retrieve PDGF and attachment fitting
03:21 AM...08...18...25...00...EVA-3: Install PDGF on Zarya
03:36 AM...08...18...40...00...EVA-3: Install video signal conditioner
04:06 AM...08...19...10...00...EVA-3: FGB Y jumper install (channel 1/4)
04:51 AM...08...19...55...00...EVA-3: EWC antenna cable install (from EVA-1)
05:51 AM...08...20...55...00...EVA-3: Zarya Y jumper (channel 2/3)
06:56 AM...08...22...00...00...EVA-3: EV-1: PDGF/Zarya thruster photos
06:56 AM...08...22...00...00...EVA-3: EV-2: Zarya cleanup
07:11 AM...08...22...15...00...EVA-3: EV-1: STP-H3 IR experiment imagery
07:11 AM...08...22...15...00...EVA-3: EV-2: High pressure gas tank grapple fixture insulation install
07:51 AM...08...22...55...00...EVA-3: Cleanup and ingress
08:21 AM...08...23...25...00...EVA-3: Airlock repressurization
08:31 AM...08...23...35...00...Spacesuit servicing
09:11 AM...09...00...15...00...ISS daily planning conference
10:00 AM...09...01...04...00...Mission status briefing on NASA TV
11:26 AM...09...02...30...00...ISS crew sleep begins
11:56 AM...09...03...00...00...STS crew sleep begins