NASA officially extends Discovery mission a day
BY WILLIAM HARWOOD
STORY WRITTEN FOR CBS NEWS "SPACE PLACE" & USED WITH PERMISSION
Posted: October 29, 2007
As expected, NASA's Mission Management Team today agreed with a recommendation from space station officials to extend the shuttle Discovery's flight one day to permit a more thorough inspection of a contaminated solar array rotary joint during a spacewalk Thursday.
The original content of that excursion - a heat shield repair demonstration - will be deferred to a future mission and a fifth and final spacewalk, originally planned for Friday, will slip one day to Saturday. In the meantime, the astronauts are pressing ahead with plans to stage a spacewalk early Tuesday - EVA No. 3 - to re-attach and deploy the P6 solar array truss segment.
Under the revised schedule, Discovery would undock from the space station early Nov. 5 for a landing back at the Kennedy Space Center on Wednesday, Nov. 7. The latest projections show a deorbit rocket firing at 4:09 a.m. EST on Nov. 7 with landing expected around 5:11 a.m.
Below is our original story published this afternoon before the mission extension was decided:
Space station managers today recommended extending the shuttle Discovery's mission by one day to permit a dedicated spacewalk devoted to inspecting an apparently contaminated solar array rotary joint. NASA managers want to track down the source of metallic shavings found inside the joint during a brief inspection Sunday to help figure out what might be needed to fix it.
"We have a lot of ideas. My personal opinion is we're probably still dealing with something that's rubbing that's not supposed to," said Mike Suffredini, space station program manager at the Johnson Space Center in Houston. "I don't think we're in any situation we can't recover from, it's just a matter of time."
The Discovery astronauts have conducted two of five planned spacewalks, helping install a new multi-hatch module Friday and detaching a 35,000-pound solar array truss segment during an excursion Sunday so it can be mounted on the far left end of the station's main power truss Tuesday.
The port-6, or P6 segment was "parked" overnight on the end of the station's robot arm. Early today, arm operators Dan Tani and Clay Anderson "handed" the massive segment to the shuttle's robot arm, operated by Stephanie Wilson and pilot George Zamka.
While the shuttle arm held onto P6, the station arm, mounted atop a tram on the front of the lab's main solar power beam, was moved about 80 feet to a work site on the far left end. From there, the arm re-grappled P6 and the shuttle arm let go, completing the second handoff of the day.
Early Tuesday, astronauts Scott Parazynski and Doug Wheelock plan to stage a six-and-a-half-hour spacewalk - EVA-3 - to attach P6 to the far left end of the power truss and to monitor the re-deployment of its huge solar wings. After releasing a stowed radiator panel, Parazynski now plans to remove one of 22 insulation blankets from the left-side solar alpha rotary joint, or SARJ. The idea is to look for any signs of contamination like the metallic shavings discovered by Tani during an inspection of the right-side SARJ on Sunday.
The massive SARJ joints, one on each side, use a motor-driven 10-foot-wide gear to slowly turn the outboard solar arrays to keep them face on to the sun and ensure maximum power generation. The inspection of the starboard SARJ Sunday was ordered after engineers noticed higher-than-expected vibration levels and power over the past two months or so.
Tani used adhesive tape to collect samples of the contamination and station commander Peggy Whitson used a magnet today to show the material is metallic and not made up of mylar insulation as engineers speculated Sunday.
"The significance of it being ferrous is an indication that it's not aluminized mylar and it's not from the (thermal) covers," Suffredini said. "The covers are aluminum, the aluminized mylar obviously has aluminum in it as well. So that would tell you perhaps it's some of the steel from the bearings or the race or some other area."
To gather additional data, flight controllers decided overnight to have Parazynski carry out a brief inspection of the left-side SARJ during the spacewalk Tuesday. The port SARJ is operating normally and engineers want to get a better idea of how it might differ from the starboard SARJ.
"What we thought we'd do is go look on the (port) side and see what it looks like," Suffredini said today. "And that will give us some indication of what is nominal. You can glean a lot of information from this. It won't necessarily tell you what's good and what's not, but it certainly will tell you more about what the design produces as opposed to (what) we're dealing with on the starboard side."
The shuttle flight plan originally called for a fourth spacewalk Thursday to test a new heat shield repair technique and a final excursion Friday, this one by Whitson and flight engineer Yuri Malenchenko, to continue outfitting the newly installed Harmony module. Staging the spacewalks back to back out of the station's Quest airlock module limited the duration of the tile repair exercise to provide enough turnaround time for Whitson and Malenchenko.
Suffredini said the station project wanted to turn the fourth spacewalk into a dedicated full-duration inspection of the starboard SARJ. That plan would require extending Discovery's mission one day to give Whitson and Malenchenko enough time to prepare for their spacewalk.
"Right now, the team is leaning toward inspecting under every (thermal) panel during EVA-4," Suffredini said. "The plan right now, assuming our shuttle friends agree at the MMT (is) to do a full length EVA-4. That requires us to have a day off between EVAs 4 and 5 so don't be surprised at the end of the MMT today if we formally announce that we'll extend the flight one additional day in order to allow EVA-4 to be its full length."
Suffredini said engineers debated whether the astronauts could carry out an abbreviated tile repair demonstration, but "we are going to recommend that we use the entire full-length EVA to do this inspection. We need the entire EVA to remove every cover and inspect under each cover. We also plan to take samples in any areas where the data might look different."
Until the issue is resolved, the starboard SARJ will remain locked in one position except on the few occasions when it needs to be reoriented due to thruster firings or other operations. With only the port arrays rotating to track the sun, the station's power production will suffer. But Suffredini said today a new analysis shows that if the P6 arrays are redeployed as planned, the lab complex will have enough power to operate normally through the end of the year and into early 2008 and that it should not affect plans to launch Europe's Columbus research module in early December.
But both SARJs eventually must be operational to support a full slate of science operations inside Columbus, the U.S. Destiny lab module and two pressurized Japanese labs scheduled for delivery in February and April.
In a worst-case scenario, Suffredini said, spacewalkers could reposition two drive motors and 12 trundle bearings to use an inboard drive gear in the starboard joint. Assuming the astronauts could clean up the contamination to prevent additional wear and tear, the SARJ would be in a near-new state. But the work is complicated, it would require multiple spacewalks and it would disrupt station assembly.
Engineers are hopeful the inspection of the port SARJ by Parazynski on Tuesday, and a more thorough look at the starboard SARJ later in the week, will give them the insight they need to determine the best course of action.
As of this writing, NASA managers have not yet finalized plans for the fourth and fifth spacewalks or officially approved the mission extension. In the meantime, here is an updated timeline of Tuesday's spacewalk - EVA-3 - including Parazynski's inspection of the left-side SARJ (in EDT and mission elapsed time).
EDT........DD...HH...MM...EVENT 12:38 AM...06...13...00...STS/ISS crew wakeup 01:13 AM...06...13...35...EVA-3: Airlock repressurized to 14.7 psi; hygiene break 02:23 AM...06...14...45...EVA-3; Spacewalk preps 03:53 AM...06...16...15...EVA-3: Spacesuit purge 04:08 AM...06...16...30...EVA-3: Spacesuit oxygen pre-breathe 05:08 AM...06...17...30...EVA-3: Airlock depressurization 05:33 AM...06...17...55...EVA-3: Airlock egress 06:03 AM...06...18...25...EVA-3: Parazynski: Attach P6 to P5 06:18 AM...06...18...40...EVA-3: Wheelock: Attach P6 to P5 08:13 AM...06...20...35...Shuttle robot arm (SSRMS): P6 ungrapple 08:13 AM...06...20...35...EVA-3: Parazynski: P5/P6 umbilical connections 08:48 AM...06...21...10...EVA-3: Wheelock: P5/P6 umbilical connections 08:53 AM...06...21...15...EVA-3: Parazynski: Electronic box shroud removal 09:03 AM...06...21...25...EVA-3: Wheelock: Shroud removal 09:28 AM...06...21...50...EVA-3: Parazynski: Radiator cinch release 10:03 AM...06...22...25...EVA-3: Wheelock: Spare power switching unit transfer to ISS 10:28 AM...06...22...50...EVA-3: Parazynski: Port SARJ inspection 11:08 AM...06...23...30...EVA-3: Parazynski: Radiator squib firing unit activation 11:18 AM...06...23...40...EVA-3: Parazynski: Switching unit transfer 11:58 AM...07...00...20...P6 solar mast 1 deploy operations begin 12:03 PM...07...00...25...EVA-3: Parazynski: Airlock ingress 12:18 PM...07...00...40...EVA-3: Wheelock: Airlock ingress 12:38 PM...07...01...00...EVA-3: Airlock repressurization 12:38 PM...07...01...00...2B array 100 percent deployed 01:28 PM...07...01...50...4B array 100 percent deployed 01:48 PM...07...02...10...Shuttle robot arm (SRMS) powerdown 04:08 PM...07...04...30...ISS crew sleep begins 04:38 PM...07...05...00...STS crew sleep begins
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