NASA hails solar array repair as complete success
BY WILLIAM HARWOOD
STORY WRITTEN FOR CBS NEWS "SPACE PLACE" & USED WITH PERMISSION
Posted: November 3, 2007
Physician-astronaut Scott Parazynski, working on the end of a boom carried by the space station's robot arm, successfully repaired a mangled solar array today, cutting away a snarled guidewire, installing five suture-like braces and then standing by while his crewmates extended the array its full 110-foot length.
Working with deliberate care, astronaut Dan Tani, sending commands from a computer inside the shuttle-station complex, extended the array's central mast a half bay at a time, stopping and letting Parazynski assess the health of the repairs as tension slowly built up on the just-installed braces.
There were no problems and as the last bay of the array's mast extended and locked into place, sensors indicated full extension and Tani exclaimed, "Oh, we've got deploy discretes, two deploy discretes!"
"Yay, all right!" someone yelled.
"Great news," Parazynski said. "What an accomplishment."
"Nice teamwork," congratulated station commander Peggy Whitson.
"Phenomenal," Parazynski agreed.
"Excellent work, guys, excellent," Whitson said.
"But it's not over yet," Discovery commander Pam Melroy said. "We've still got to get you inside."
"That would be nice," Parazynski said.
"Those are the minor details, but thank you guys very much," astronaut Steve Swanson radioed from Houston.
A successful repair was critical to NASA's plans for continuing space station assembly. At the Kennedy Space Center in Florida on Saturday, engineers moved the shuttle Atlantis from its hangar to the Vehicle Assembly Building for attachment to a set of boosters and an external tank. Launch on the next space station assembly mission, a high-profile flight to deliver Europe's Columbus research module, is targeted for Dec. 6.
Because of problems with the station's right-side solar array rotary joint, NASA needed to get the P6 array repaired and fully extended to provide the power necessary to support the attachment of Columbus next month as well as Japanese research modules scheduled for launch early next year.
With today's successful repair job, the December flight should remain on track.
"There is quite a bit of work that has to be done from this point to the point of launch," Suffredini said of Atlantis and the Columbus module. "We are currently asking the shuttle program to hold the sixth of December as a launch date. My guess is we may not quite make the sixth, but we're going to give it a good go. ... We have a good chance of having several (launch) attempts before the (launch window closes) on Dec. 13. And that's outstanding news."
But the schedule is tight and it will be up to station commander Peggy Whitson, Tani and flight engineer Yuri Malenchenko to complete a long list of chores to clear the way for Atlantis' long-awaited mission.
First, Whitson and Malenchenko plan a spacewalk Nov. 9 to finish rigging the newly delivered Harmony module for its move to the front of the space station. Harmony was temporarily attached to the Unity module's left port. On Nov. 12, the crew will use the station's robot arm to move the shuttle docking port from the front of the Destiny lab module to Harmony. Two days later, the Harmony/docking port assembly will be moved to the front of Destiny and bolted in place.
Whitson and Tani plan two more spacewalks, on Nov. 20 and 24, to connect Harmony to the space station's main power and cooling systems. That will set the stage for the Columbus module's attachment to Harmony's right-side port in December. Japanese modules will be attached to Harmony's upper and left-side ports in February and April.
Here is a schedule of major upcoming events (in EST):
DATE.......TIME.......EVENT 11/05/07...05:32 AM...Discovery undocks from space station 11/07/07...01:02 PM...Discovery lands at the Kennedy Space Center 11/09/07...06:00 AM...Whitson, Malenchenko spacewalk; Harmony outfitting 11/10/07...04:00 AM...Atlantis is moved to launch pad 39A 11/12/07...05:40 AM...Shuttle docking port moved from Destiny to Harmony 11/14/07...04:55 AM...Harmony/docking port moved to Destiny 11/14/07..............Shuttle program flight readiness review concludes 11/20/07...TBD........Whitson, Tani EVA; Harmony connected to ISS power/cooling 11/20/07..............Shuttle practice countdown; headquarters review concludes 11/24/07...TBD........Whitson, Tani EVA; Harmony connected to ISS power/cooling 12/03/07...TBD........Start of countdown to Atlantis launch 12/06/07...04:32 PM...Launch of Atlantis and Columbus module (time approx.) 12/09/07...03:12 PM...Columbus module attached to space station (time approx.) 12/15/07...08:22 AM...Atlantis undocks from space station (time approximate) 12/17/07...12:02 PM...Atlantis lands at the Kennedy Space Center (time approx.)
"We're in great shape," Suffredini said today. The repaired P6 solar array "doesn't quite look like we'd expected, but you know it's just like anybody, you have your baby, your baby's beautiful to you, and our baby is still beautiful to us. Best of all, we're ready to get on with the work to get us to the launch of the Columbus."
Parazynski and Wheelock ended today's spacewalk at 1:22 p.m., seven hours and 19 minutes after they switched their spacesuits to battery power to officially kick off the fourth and final spacewalk of Discovery's mission. Duration of all four EVAs was 27 hours and 14 minutes, moving Parazynski to fifth in the world in cumulative spacewalk time with 47 hours and five minutes over seven EVAs.
"I tell you what, I'm not sure I believe it when I look at this video of what we just did," Melroy said later, narrating footage shot by the astronauts from Discovery's flight deck.
Working at the end of the shuttle's heat shield inspection boom, Parazynski installed a suture-like strap to help stabilize the damaged blanket and cut away a snarled guide wire that hung up during deployment Tuesday. After installing four more so-called cufflinks to hold the damaged blanket together, the array was successfully extended.
"The spacewalk to repair the 4B solar array was just a complete success," said Derek Hassmann, lead space station flight director. "We installed the cufflinks, we completed the deploy of the 4B solar array and we put it in what we call high-tension mode, which puts it in a completely nominal configuration. ... Just a fabulous day, a fabulous shift and one of the greatest things that I personally have ever been involved in in my career here at NASA.
"How smooth today's spacewalk went is a tribute to all the people on the engineering and operations teams who've been working 24/7 since we first tried the 4B deploy and saw the tear in the solar array.
The 17-ton P6 solar array truss segment was launched in 2000 to provide power during the initial stages of assembly. The lab's main power truss is now built and equipped with huge sets of solar panels on each end: starboard 4 (S4) on the right side and port 4 (P4) on the left. The outermost right side S6 arrays, scheduled for launch next fall, will be attached to a short spacer segment known as S5.
During two recent shuttle flights, astronauts retracted the two wings of the P6 array and disconnected it from the station's power system. Spacewalkers had problems retracting the 4B panel, however, encountering a frayed guidewire that repeatedly hung up on grommets during the retraction process.
On Tuesday, P6 was unbolted from its initial mounting point and moved to the far left end of the power truss and bolted to the P5 spacer segment. The first of its two solar array wings, known as P6-2B, extended a full 110 feet as required, but the crew aborted deployment of the 4B wing when one section of hinged blanket slats hung up due to a guide wire snag. Two seams between adjacent slats pulled open, resulting in separate tears, and the edges of several nearby slats were crumpled. The largest rip measured some two-and-a-half feet long.
Eighty percent deployed, the P6-4B array was able to generate more than 95 percent percent of the electricity of a fully extended wing. But without being fully extended, the array did not have the structural stability required for sun tracking. As a result, the station's left-side solar alpha rotary joint, or SARJ, was locked in place until the damage could be fixed.
With today's repair, the left side arrays can once again be turned to track the sun. While a few solar cells in the 4B wing apparently were damaged in the initial hang up Tuesday, Suffredini said the panel would provide all the power the station needs.
"This was just a fabulous effort," he said. "The idea of this was to regain the functionality of the solar array, it wasn't about looking good when it was over with, it just had to provide the power. And in fact, we're under high tension and so we've got full structural capability back.
"When I left the mission evaluation room, they told me the array was providing about 217 amps," he said. "That's about 3 amps from what we normally expect to get from an array, which is much, much higher than what we need to provide the required power to the space station as a whole. That would indicate that perhaps we had some damage, minor damage, to some of the cells. But we're certainly getting more than enough power out of the array, as much as the design requires.
"From a functionality standpoint, we've recovered the array, we can go on to normal operations and expect to get the normal amount of power we had planned for in the ISS program for the life of the program."
With P6 and P4 rotating normally to track the sun, NASA will have a bit of breathing room to troubleshoot a problem with the right-side solar alpha rotary joint, or SARJ. Two massive rotary joints, one on each side of the station's main power truss, slowly turn the port and starboard solar arrays to track the sun as the lab complex circles the globe.
During a spacewalk last Sunday, Tani discovered metallic contamination inside the right-side SARJ, indicating a potentially serious bearing or alignment problem. A planned heat-shield repair demonstration spacewalk originally planned for Thursday was called off to permit a more thorough inspection of the starboard SARJ. Then on Tuesday, the P6 array was damaged during deployment and NASA managers ultimately scrapped the SARJ inspection to make way for today's repair work.
Suffredini said the SARJ issue will be addressed during a future flight, but no decisions have been made about where it might fit into the station assembly sequence. As of today, he said, engineers believe the station will have enough power for normal operations through February, when NASA plans to launch the first of two Japanese modules.
But it's not yet clear whether the starboard SARJ must be operational by the time Japan's large Kibo research lab is launched in April.