Discovery mission takes construction to new heights
BY WILLIAM HARWOOD
STORY WRITTEN FOR CBS NEWS "SPACE PLACE" & USED WITH PERMISSION
Posted: October 21, 2007
Nine years after the United States and Russia began building the international space station, NASA is poised for what many agency insiders consider the most difficult assembly mission attempted to date, one that will test the limits of orbital construction.
The space shuttle Discovery, carrying an international crew of seven and an Italian-built multi-port station module, is scheduled for liftoff from launch complex 39A at the Kennedy Space Center at 11:38:20 a.m. Tuesday. In a strange coincidence, the launch time and day of week are identical to those of Challenger's final flight.
At the controls aboard Discovery will be Pam Melroy, the second woman to command a space shuttle, and rookie pilot George Zamka, a colonel in the Marine Corps. Their crewmates are flight engineer Stephanie Wilson, Italian astronaut Paolo Nespoli and spacewalkers Scott Parazynski, a physician, Doug Wheelock, a veteran Army helicopter pilot, and Dan Tani, who is hitching a ride to the lab complex to join the Expedition 16 crew.
Forecasters are predicting a 60 percent chance of acceptable weather Tuesday and Wednesday, improving to 70 percent "go" by Thursday. But depending on when an expected frontal system moves through the area, the outlook could change dramatically, with low clouds, rain and thunderstorms. Complicating the issue, the weather at two of NASA's three emergency runways in Spain and France are predicted to be "no go" Tuesday and all three are expected to be out of limits Wednesday and Thursday. At least one overseas landing site must be available for launch.
Hoping for the best, NASA's Mission Management Team met Sunday and Chairman LeRoy Cain said there were no technical issues of any significance. He also vigorously defended an earlier decision to press ahead with launch despite mixed interpretation of subtle test data indicating possible problems with the coating that protects the ship's critical wing leading edge panels.
While there are no data indicating any imminent failure with three panels aboard Discovery that have areas of degraded coating, engineers do not understand what causes the coating to break down. As such, they cannot predict how degraded areas might change from flight to flight. NASA managers decided last week to clear Discovery for flight based on the crew's ability to detect and repair coating damage in orbit, along with past flight history that indicates the areas of concern are relatively stable.
"We believe, to the best of our ability to know today, this risk is certainly lower than some of the more significant risks that we take because of the inherent nature of this vehicle," Cain said. "We feel very confident we have a vehicle that's safe to go fly. We would not launch if we didn't think that was true."
The primary goal of the 120th shuttle mission is delivery of node 2, or Harmony, a roomy 31,500-pound module measuring 23.6 feet long and 14.5 feet wide that will serve as the gateway to European and Japanese research modules that will form the scientific heart of the space station and permit the crew's eventual expansion from three to six.
"Harmony has six different ports that we can add modules onto to build the station," said Expedition 16 commander Peggy Whitson, the first woman to command the station. "So it's, it's our next big connecting piece in our puzzle of putting this huge station together on orbit.
"Node 2 is required to power and provide the thermal heat rejection for the science laboratory modules that'll be coming up, the one built by the European Space Agency and the one built by the Japanese space agency. So it's a pretty key module for us, for the continued development of the station. It's an important step."
Harmony, providing an additional 1,230 cubic feet of habitable volume, will be temporarily attached to the left side of the station's central Unity module, which connects the U.S. and Russian segments of the complex. After Discovery departs, Whitson, Tani and Expedition 16 flight engineer Yuri Malenchenko will use the station's robot arm to detach the lab's main shuttle docking port so it can be bolted onto Harmony. Then Harmony will be detached and permanently mounted on the front end of the U.S. Destiny laboratory module.
Attaching a new pressurized module would have been the highlight of many past assembly missions. But for Discovery's crew, it is just the beginning. The second major objective of the flight is the long-awaited disconnection and relocation of a huge set of solar arrays known as P6. Designed as the sixth and final segment of the port, or left, side of the station's main power truss, P6 was mounted at the center of the station in December 2000 to provide power to the U.S. segment during the initial stages of assembly.
Now, with identical solar panels in place on the left and right sides of the main power truss, NASA needs to move P6 to its permanent position on the far left end of the beam. The 35,000-pound segment's huge arrays, stretching 240 feet from tip to tip, were stowed during shuttle missions last December and June. Power and cooling lines were disconnected during an August flight, setting the stage for the massive truss's detachment, relocation and re-extension during Discovery's mission.
Complicating the work, the station's robot arm cannot reach far enough on its own to make the move. So the station arm, after handing P6 off to the shuttle's space crane, will be moved by the station's mobile transporter to the far end of the power truss. At that point, the shuttle arm will hand the truss segment back to the station arm and Parazynski and Wheelock, making their third spacewalk by that point, will oversee its attachment to the P5 truss segment.
"Moving the P6 solar array will be a major activity," Melroy said in a NASA interview. "On our second spacewalk - our first spacewalk is all about node 2 - we'll be using the robotic arm in one location to actually reach around and pull P6 off ... with the assistance of our spacewalkers.
"Once the P6 has been detached from the space station, then the robotic arm will move it around to the port side of the shuttle, at which point it will be handed off to the shuttle arm. The shuttle robotic arm will take control of the P6 truss while the space station robotic arm is reconfigured and rolled out on the mobile transporter, the mobile platform, all the way to the far end of the port truss. And then, we'll use the station arm to take it back and install it in its final location.
"This is pretty nearly the design-limiting case for the robotic arm of the space station, so it's out at its full extension, trying to get that truss out there," Melroy said. "We'll have the help of the spacewalkers on the third spacewalk to do that. So, all these activities will actually span three days, three full days, two spacewalks with robotics in the middle."
Last December, attempts to stow the folding blankets making up one side of the P6 array ran into problems when several of the slats making up the blankets folded the wrong way along their creases. The astronauts ultimately were successful and engineers don't anticipate major problems re-extending the arrays.
They'd better be right. The station's robot arm will be fully extended just to attach P6 to P5. It will not have the reach necessary to position a spacewalker beyond the lowest few feet of the huge arrays if any major problems are encountered.
"One of perhaps the most audacious things we've ever done in space is this P6 solar array truss relocation," said Parazynski, an emergency room physician and veteran spacewalker making his fifth shuttle flight. "We're powering down this major element, something that we've never done before, basically shutting off the lights, shutting off the computers, turning off the cooling, unbolting it, disconnecting all the fluid and electrical and data lines and then via a process of EVA and very complex robotics we're going to take it to the very tip of the space station and then reverse the process: bolt it together, hook up connectors, deploy solar arrays, deploy a radiator.
"One of the things I love about NASA is we plan for success but we prepare for failure. And so we are very well prepared. A lot of people, a lot of smart rocket scientists around the Johnson Space Center ... have spent a lot of time figuring out what could go wrong and what we might do to address those things. We have a very long list of procedures we can run if things don't go exactly to plan."
A fourth and final set of solar arrays - S6 - will be mounted on the starboard, or right, side of the main truss during a shuttle flight next year.
Five spacewalks are planned during Discovery's mission: One to temporarily install the Harmony module on Unity's left port; two to move and redeploy P6 and continue Harmony outfitting; and one by Whitson and Malenchenko to continue Harmonyıs activation and outfitting.
In September, NASA managers decided to add a fifth spacewalk to the mission that will be sandwiched between the P6 redeployment work and the Harmony outfitting by Whitson and Malenchenko: An excursion by Parazynski and Wheelock to test a heat shield repair technique that could prove useful in the event of damage like that seen during a shuttle flight in August.
The idea is to use a device similar to a pressurized caulk gun to first mix two components and then squirt out the resulting concoction, a thick reddish material known as Shuttle Tile Ablator 54, or STA-54, to fill in small holes or cracks in shuttle heat shield tiles. NASA originally planned to test the so-called "T-RAD" gun ("tile repair ablator dispenser") during a flight next year, but moved the demonstration up to Discovery's mission after experiencing tile damage during the August shuttle flight.
In that case, engineers ultimately concluded the shuttle could safely re-enter without repairs. But the incident prompted extensive discussions about how much confidence to place in an untested repair technique. One concern is the formation of bubbles in the material as the mixture sets up that could degrade its ability to perform.
"We've done all the testing we can do on the ground," said shuttle Program Manager Wayne Hale. "It looks very good on the ground, we've used it in the vacuum glove boxes and it looks very good there. But until we actually do a demonstration in orbit with several simulated damaged tiles and bring those back and see how well it filled, what size the bubbles were, how well it adhered, all those kinds of questions, we don't know for sure.
"So this test is actually a confidence builder. We think the tile repair capability will work as we have it today, but we'd like to be able to go forward in the future with a higher degree of confidence than perhaps we have had to date. And that's why we ordered these tests."
Assuming an on-time liftoff, Melroy will guide Discovery to a linkup with the space station on Oct. 25. Waiting to welcome the shuttle crew aboard will be Whitson, Malenchenko and NASA astronaut Clay Anderson, who was launched to the station last June aboard the shuttle Atlantis.
At that time, Anderson replaced Sunita Williams, joining Expedition 15 commander Fyodor Yurchikhin and flight engineer Oleg Kotov, who were launched to the outpost aboard a Russian Soyuz spacecraft last April. Yurchikhin and Kotov were replaced by Whitson and Malenchenko, who were launched to the station aboard a Soyuz on Oct. 10 along with Malaysian guest cosmonaut Sheikh Muszaphar Shukor.
Yurchikhin, Kotov and Shukor returned to Earth early Oct. 21 aboard the Soyuz TMA-10 capsule. The day Discovery docks, Tani will replace Anderson as an Expedition 16 crew member and Anderson will return to Earth in his place aboard the shuttle.
Discovery's docking and the usual welcome aboard ceremony will have an unusual flavor this time around as the station's first female commander welcomes Melroy, probably the final woman to command a shuttle before the program is retired in 2010. Both women flew together in 2002 when Whitson served as flight engineer of the fifth station expedition and Melroy visited as pilot of the shuttle Atlantis during mission STS-112.
"It is coincidental that it is happening," Whitson told CBS News. "But I do think it is special, not only special just for Pam and I because, you know, we have flown in space before, but the experience of having two women up there at the same time will hopefully be an inspiration to somebody. I was inspired when I was young by the Apollo era astronauts and in particular, I was motivated to become an astronaut when they selected the first female astronauts. I would hope that we could be a role model like that."
Melroy agreed, saying "I remember (astronaut) Sally Ride coming to speak in college and it was just amazing inspiration. I think the part about this that makes me the happiest is that it happened by accident. I really like that. In no way could this be misinterpreted as some major effort on the part of someone to set a special milestone or do something like that. it just happened to be those of our turns."
Coincidence or not, both women looked forward to working together in space on one of the most complex and critical space station assembly missions yet attempted.
"There are things that you feel and see and hear in space that you don't experience anywhere else," Melroy said. "And so it creates this incredible bond between the crew members. And one of the moments I'm looking forward to the most is when the hatch opens and I see Peggy's face on the other side and we reach through for the traditional handshake. That will be a really special moment for me."
For Whitson, Malenchenko and Tani, Discovery's flight kicks off a critical period in the station's assembly. The day the shuttle lands - Nov. 6 - the station crew will detach the station's main shuttle docking port, pressurized mating adapter No. 2, from the Destiny module and bolt it to Harmony. The next day, Whitson and company will use the lab's robot arm to move Harmony and PMA-2 to the front of Destiny, the most critical piece of robotic assembly yet attempted in the absence of a shuttle crew.
"After shuttle undocks, pulling off PMA-2 from the front of the lab, moving it over to the node and then re-installing the node on the front of the lab, that's huge," said Paul Hill, deputy director of mission operations at the Johnson Space Center in Houston. "Because first, there's no shuttle there so there's only three crew members to get all that done with very limited views outside. And, from the time we pull the PMA off until the whole thing is complete, there's not a shuttle docking port. So that'll be sporty."
With Harmony safely in place on the front end of Destiny, Whitson and Tani will stage two spacewalks Nov. 14 and 18 to route power, data and ammonia coolant lines from the main power truss to the new module.
"We bring up the Harmony, this node 2, and the complexity of the shuttle mission is astounding," Tani said in an interview with CBS News. "Even a few years ago, any one of the major things we're doing, any one of them would have been a full shuttle's worth of activities. Bringing the node up, attaching it to the station in a temporary location, starting the outfitting - that's a huge task - moving the P6 from its temporary initial location out to the side location, huge, that's a big robotic operation, a big EVA.
Throwing in a tile repair demonstration spacewalk, "the significance of this particular mission is big, we're doing many, many complex things and again, allowing the international partners to then bring their hardware up and join the station. ... Once the shuttle leaves, we do some very complex robotic operations and maneuver the node over to its final location. ... and then I would say the big technical part of my stay on station is the EVAs that will follow, where we take fluid trays that have been stored on the station for years and we install them on the lab to provide cooling and power to the node so it can offer it to the Columbus module and the Japanese Experiment Module.
"We talk about this as a 45-day shuttle mission in terms of pace," Tani said. "Shuttle missions are scheduled down to 10-minute increments and generally, usually station timelines are a bit more relaxed. But we are not, we are all 'go' from the moment of launch to probably until (Atlantis) comes to get me to bring me home, we are go, go, go."
The shuttle Atlantis - Tani's ride home - is scheduled for launch Dec. 6 to carry the European Space Agency's Columbus research module into orbit. Columbus will be attached to Harmony's right-side port and European Space Agency astronaut Leopold Eyharts, a French air force general, will replace Tani as an Expedition 16 crew member.
Whitson, Malenchenko and Eyharts then will accept delivery of the first of two Japanese research modules next February, which will be temporarily attached to Harmony's upward-facing zenith port. The huge Japanese Experiment Module, known as Kibo, will be attached to Harmony's left-side port next April. The pressurized experiment module launched in February later will be moved from Harmony's zenith port to an upward-facing port on the far end of Kibo.
"Every phase of exploration involves some stepping-stones," Whitson said in a NASA interview. "I think ISS is a key stepping-stone, not only for the development of an international relationship that allows us to extend as a world beyond our planet, which I think is a key thing, but also just the nuts and the bolts of figuring out what types of hardware fail on orbit, what do we need to do in the next phase to engineer something that will be better, what things did work, what didn't work, what surprised us.
"There have been a lot of surprises we've seen in constructing such a big facility on orbit, and those are some important lessons that have to be learned that we wouldn't have learned otherwise. It's a key, I think, a stepping-stone to allowing us to go beyond Earth, hopefully minimizing some of the risks of doing that. Obviously there is always risk associated with exploration, which is what makes it so exciting."