Atlantis mission preview:
The new voyage of Columbus
BY WILLIAM HARWOOD
STORY WRITTEN FOR CBS NEWS "SPACE PLACE" & USED WITH PERMISSION
Posted: February 4, 2008
Running two months late, the shuttle Atlantis and its crew are set for blastoff Thursday on a long-awaited flight to attach the European Space Agency's Columbus research lab to the international space station. The module represents Europe's first manned toehold in orbit and promises to open a new era of international research with Japanese lab modules scheduled to follow in March and April.
"I think for Europe, it's the start of manned space flight," said Hans Schlegel, a German astronaut making his second flight aboard a space shuttle. "Because all of the sudden, we have what we are strong in - developing experiments, building experiments to be conducted in space, either in cooperation with NASA or cooperation with the Russian space agency - all of the sudden we have a module of our own which is available to us, to the scientists in Europe, 24 hours (a day), 365 days a year. This will really be the beginning."
Said NASA Administrator Mike Griffin: "Reaching this point is a tremendous milestone for NASA and the space station program. I mean at one stroke, we almost double the laboratory capacity on board. It's a new, modern, state-of-the-art laboratory, several years newer in the end than the U.S. lab. It makes a real international partnership come to fruition in the form of real hardware.
"We want to take this partnership with us back to the moon, and that wasn't going to happen unless and until we finish up our obligations on the space station and made a real working vehicle out of it," Griffin said in an interview. "Columbus (is) a huge step toward making that happen. Until we actually set out for the moon again, this is as good as it gets."
With commander Steve Frick and pilot Alan Poindexter at the controls, Atlantis is scheduled to lift off from pad 39A at the Kennedy Space Center at 2:45:28 p.m. Thursday, roughly the moment when Earth's rotation carries the launch pad into the plane of the space station's orbit. Their crewmates are flight engineer Rex Walheim, Leland Melvin, Stan Love and European astronauts Schlegel and Leopold Eyharts, a French air force general hitching a ride to the space station.
Liftoff originally was planned for Dec. 6, but the flight was delayed because of intermittent electrical continuity in wiring leading to low-level hydrogen fuel sensors in the base of the shuttle's external tank. A second launch try Dec. 9 also ended in failure and the mission was put on hold pending a fueling test Dec. 18 and work to pin down the cause of the engine-cutoff ECO sensor problems.
The four ECO sensors are part of a backup system intended to make sure the shuttle's main engines don't suck a tank dry after some other problem - a leak, for example, or an improper hydrogen-oxygen mixture ratio - used up propellant at faster than normal rates. An engine running out of hydrogen during normal operation likely would suffer a catastrophic failure.
The 10 wires that carry signals from all four ECO sensors and a 5 percent sensor pass through the same connector in the wall of the external tank. The three-part 37-pin connector (27 pins are not used) features a pass-through fitting with gold-plated male pins on both sides.
Wires from the sensors inside the tank terminate in a female connector that is plugged into the male pins of the pass-through. Those pins are imbedded in a glass matrix. A similar female socket plugs into the pass-through on the outside of the tank where the pins are mounted in a Teflon insert.
Data collected during the Dec. 18 fueling test indicated the problem was the result of temperature-induced circuit-breaking gaps in the pins and sockets on the external side of the feed-through connector when the system was chilled to ultra-low temperatures.
To make sure, the feed-through plate with the external connector still attached was removed and shipped to the Marshall Space Flight Center in Huntsville, Ala., for additional testing at cryogenic temperatures. When the hardware was submerged in liquid hydrogen, engineers saw the same sort of open circuits that cropped up during the December launch attempts.
The solution was to solder the external pins and sockets together, eliminating any gaps that could lead to a loss of connectivity. Testing at cryogenic temperatures indicates the fix was successful.
"We had a multi-disciplinary team from a number of NASA centers, as well as a number of contractors, working together in a unified manner and we have come to a root cause, we believe, for our problems that we've been having in those circuits," said shuttle Program Manager Wayne Hale. "There is a good solid repair, or fix, technique which has been implemented and we have a lot of testing that's gone on to prove that this fix is a good fix, does not entail any unanticipated consequences and will provide us with a reliable safety system in the low level cutoff protection world.
"The work is complete on the vehicle at the launch pad and we're beginning to implement that fix on subsequent tanks so that we won't ever have to talk about engine cutoff sensors again," he said.
NASA's original ECO sensor launch commit criteria required three of the four circuits to be operational for a launch to proceed. That rule later was changed to four-of-four because of concern about a common component that, should it fail, could take out two circuits. That design flaw was addressed before Columbia's last flight and NASA managers eventually changed the flight rule back to requiring three of four operational circuits.
That's the rule that was in place for Atlantis's initial launch try, but it was amended to four of four for the second attempt, primarily because engineers did not yet know what was causing the problem.
Now that testing indicates the problem has been resolved, NASA managers have agreed to go back to the three-of-four criteria, "which is the design intention for that system," Hale said.
"On this first tanking with the new system in place we're going to watch it very closely to ensure that we really have eliminated the common cause mechanism," he said. "If there are any funnies that happen, they will be scrutinized very carefully. ... I expect when we go tank up the vehicle next Thursday we'll be in good shape to go fly."
The ECO sensor problem and two-month launch delay came at a critical moment in space station assembly. Going into Atlantis' December launch campaign, Expedition 16 Commander Peggy Whitson, cosmonaut Yuri Malenchenko and astronaut Dan Tani had just wrapped up a grueling few weeks of work to ready the station for arrival of Columbus and two Japanese modules originally scheduled for launch in February and April.
The delay for Atlantis pushed the next flight - shuttle Endeavour and the first of the two Japanese modules - from Feb. 14 to mid March. Launch of the shuttle Discovery with the second Japanese research lab remains on track for April 24, but Atlantis' next flight, a final mission to service the Hubble Space Telescope, is expected to slip from Aug. 7 to around Aug. 28.
The final two flights of the year, a space station logistics and resupply mission by Endeavour and delivery of a final set of solar arrays, are expected to slip about a month, to mid October and early December respectively. But Hale said he is optimistic NASA can pull off a six-mission year and even if even if additional problems crop up, enough margin remains in the schedule to complete the station and retire the shuttle in 2010 as planned.
"We know that it takes continuous vigilance to maintain a safe flight rate, to fly each and every flight as safely as we possibly can," Hale said late last year. "The shuttle is an extraordinary vehicle with a lot of capability and a lot of flexibility, a huge payload capability, but it takes a lot of attention from a lot of people to make sure we fly safely and we have to watch every little anomaly, every little indication to make sure we continue to fly safely.
In 2008, Hale said, "it's a fairly aggressive schedule (but) we have plenty of margin in our schedule to complete the international space station, meet the president's directive to complete flying (the shuttle) by no later than Sept. 30, 2010, so that the agency can then press on and build the moon ship, the Orion and Ares rockets that will take us past low-Earth orbit and back to the moon and on, potentially, to Mars."
The Atlantis astronauts plan to attach the Columbus module to the newly installed Harmony module's right-side port on Feb. 10, the day after docking.
The 22.5-foot-long module weighs some 28,200 pounds and adds 2,600 cubic feet of volume to the station. Built by EADS Space Transportation, Columbus will be launched with four European science racks and one European storage rack in place. NASA later will install five racks of its own. The European Space Agency has spent about $2 billion building Columbus, the experiments that will fly in it and the ground control infrastructure necessary to operate them.
In addition to delivering Columbus, Atlantis also will ferry Eyharts to the station. The European Space Agency astronaut, veteran of a three-week stay aboard the Russian Mir space station in 1998, will replace Tani aboard the ISS. Tani, who was launched to the station Oct. 23 aboard the shuttle Discovery, will return to Earth in Eyharts' place aboard Atlantis.
For Tani, Atlantis' launch delay translated into an unexpected two-month mission extension. Along with missing the Christmas holidays with his family, Tani was off the planet when his mother was killed in a car wreck Dec. 19. For Eyharts, the launch delay resulted in a shortened mission. He will remain aboard the lab complex with Whitson and Malenchenko until late March, when he will be replaced by NASA astronaut Garrett Reisman.
With less time aloft than he originally expected, Eyarts' primary responsibility will be activating and outfitting Columbus and beginning science operations after Atlantis departs.
"Columbus is mainly scientific module," Eyharts said in a NASA interview. "We will have four European scientific racks, which will allow Europe to perform science during, we hope, at least 10 years in the station. But there will be also American scientific racks which be installed a little bit later in the station. So with the arrival of Columbus, and later on of the Japanese module, we will start the full exploitation of the ISS as a scientific laboratory. And with the arrival of Columbus, Europe will become a co-owner of the ISS.
"Columbus is a first for Europe," he said. "This will be the first time Europe will have a permanent base in space. And of course, this is very important and this is very challenging. So in the future, of course, we hope that this first participation will help in reinforcing our technical expertise and our experience of operations to be able to go further and participate with the future of space exploration, too."
NASA's larger Destiny laboratory module "is really the heart of the space station, the U.S. segment of the space station," Frick said. "It's got laboratory (equipment), payloads, it's got all kinds of science resources, but it also has the heart of the U.S. segment: It has our computers, it has our power distribution, it has all the things we need to keep functioning and keep alive. The Columbus laboratory is really more of a pure laboratory - it has the resources it needs to keep its payloads going and to keep the crew members that are working inside of it healthy and able to do their job. But it relies on the other modules in the U.S. segment for resources like power and cooling and air and those kinds of things."
Preparing the station for Columbus has been a major challenge. The station was designed for the six-port Harmony module - the eventual attachment point for Columbus and Japan's Kibo research lab - to be mounted on the front end of the station, between the U.S. Destiny lab module and the shuttle docking port, known as pressurized mating adapter No. 2.
Harmony was delivered to the station in late October aboard the shuttle Discovery and temporarily attached to the central Unity module's left side hatch. After Discovery departed, Whitson and Malenchenko staged a spacewalk Nov. 9 to disconnect electrical cables from PMA-2. Then, on Nov. 12, the crew used the station's robot arm to detach PMA-2 and robotically connect it to Harmony's outboard port.
Two days later, on Nov. 14, the Harmony/PMA-2 "stack" was detached from Unity and bolted to the front end of the Destiny module. Whitson and Tani then staged spacewalks Nov. 20 and 24 to hook up power cables and connect ammonia supply and return lines between Harmony and the station's main cooling system on the lab's solar power truss. That work, along with internal outfitting, set the stage for Atlantis' launch and installation of the Columbus module.
Adding a new research module to the space station is a major milestone in the lab's evolution. So is adding another ground control center, a state-of-the-art complex in Oberfaffenhofen, Germany, near Munich. With the addition of Columbus, station astronauts will be in daily contact with flight controllers at the Johnson Space Center in Houston, Oberfaffenhofen and Russian ground control in Korolev near Moscow.
"We all come into these space shuttle flights looking at the big element in the payload bay and waiting for the action when we actually install it," said station Program Manager Mike Suffredini. "This flight and the following stage and multiple stages after that will be an extra challenge for us.
"We have been working with our Russian counterparts and our Canadian counterparts for the better part of about seven years and in all that time, we evolved in our operations capability, how we work together. And now we're bringing on another partner, multiple countries, multiple control centers to operate this Columbus module.
"So the very small part you'll see during the docked operations of installing the Columbus module really will just be the tip of the iceberg as we work together in a partnership and move on into the next couple of flights," Suffredini said. "By April, we'll have the (Japanese modules) up and we'll have yet another partner in operation with us. So it's a very exciting time for us in the ISS program."
Three spacewalks are planned for the Atlantis mission, two by Walheim and Schlegel and one by Walheim and Love.
During the first excursion Feb. 10, the day after docking, Walheim and Schlegel will attach a robot arm attachment fitting to Columbus, disconnect power cables from the new module, remove docking port covers and make preparations for a second spacewalk two days later. Melvin, meanwhile, will use the station's robot arm to move Columbus from its perch in the shuttle's cargo bay to its mounting point on the right side of Harmony. It will be locked in place by 16 motorized bolts.
If all goes well, Eyharts will float into Columbus for the first time the next day, on Feb. 11, and begin initial outfitting. The day after that, Walheim and Schlegel will venture back outside to replace a spent nitrogen tank in the main solar power truss that was used to push ammonia coolant through the supply and return lines leading to and from Harmony. The old nitrogen tank assembly will be moved to the shuttle's cargo bay for return to Earth.
A third spacewalk by Walheim and Love is planned two days later, on Feb. 14, to mount two European experiment facilities on the outboard bulkhead of the Columbus module and to move a failed control moment gyroscope from a storage platform on the station to Atlantis for return to Earth.
Going into the mission, the flight plan calls for Atlantis to land back at the Kennedy Space Center around 10 a.m. on Feb. 18. But if there are no major problems in orbit, NASA managers likely will extend the mission by one day to allow extra time for Columbus activation.
Going into the original December launch campaign, NASA managers held open the option of adding a fourth spacewalk to Atlantis' mission. The idea was to carry out additional inspections of the station's right-side solar alpha rotary joint, or SARJ, which is used to rotate outboard solar arrays like a giant paddle wheel to track the sun.
The space station is equipped with two such rotary joints, one on each side of the lab's main power truss. Each joint features two redundant 10-foot-wide gear/race rings and two drive motors, only one of which is engaged at any given time. Twelve so-called trundle bearing assemblies are positioned around one of the two gear races and hold in place with 1,000 pounds of force to allow smooth rotary operation.
The left-side SARJ is rotating normally, but earlier this fall flight controllers noticed unusual vibration and slightly higher current levels in the right-side SARJ. Tani looked inside the joint behind thermal panel No. 12 during an already planned shuttle assembly spacewalk Oct. 28.
He spotted metallic contamination and collected samples using adhesive tape. Those samples later were determined to be made up of race ring material itself. At that point, mission managers decided to lock the starboard SARJ in place to prevent additional damage.
During a second inspection by Tani during a spacewalk Nov. 24, additional contamination was spotted in a different area. Going into the initial attempts to launch Atlantis, engineers still did not know what might be causing the damage or what might be needed to fix it.
Then, on Dec. 8, another problem developed: a bearing motor roll ring module, or BMRRM (pronounced "broom"), failed on a right-side array, preventing the station's flight computers from positioning the affected panel as required to maximize electricity production.
While the SARJ joints on each side of the power truss turn the outboard arrays like giant paddle wheels, completing one full revolution per orbit, each set of arrays also is equipped with a beta gimbal assembly, or BGA, that uses BMRRMs to turn the panels about their long axis in a motion similar to changing the pitch of an airplane propeller.
The port-side of the station's power truss is finished and now features four solar array wings. The BGAs on those four wings are working normally, as is the port-side SARJ.
But only one set of arrays is in place on the right side of the truss and one of them - panel S4-1A - suffered a BGA failure Dec. 8. Engineers initially believed a cable or some other component might have been hit by space debris or a micrometeoroid. But during a spacewalk inspection by Whitson and Tani on Dec. 18, no such damage was found. Subsequent tests showed the problem involved a fault inside the BGA motor assembly itself, the BMRRM.
Facing two major problems on the right side of the station's main power truss, NASA managers worried they might not have enough power to support the addition of the European and Japanese research modules. But after extensive analysis, engineers concluded station assembly could proceed if the faulty BMRRM was replaced. Even then, power conservation measures will be required.
Given the delay getting Atlantis ready for a third launch try, station managers opted to stage a spacewalk Jan. 30 so Whitson and Tani could install a spare BGA motor. The spacewalk was successful and with beta angle positioning restored on the right side of the power truss, the station can generate enough electricity to support the new research labs. As such, there are no plans to add a fourth spacewalk to Atlantis' mission.
The bigger problem - the damage to the starboard SARJ - is not yet understood. The current plan is to possibly lubricate the damaged race in the near term to permit periodic repositionings and then, during a shuttle visit later this fall, move the 12 bearing assemblies and two drive motors to a redundant inboard gear. Switching to the inboard race would take four to five spacewalks. But engineers do not want to consider such a drastic step until they figure out what is causing the problem with the active gear and race ring.
"Without understanding exactly what the problem is, it's hard to drive back through the fault tree and say exactly how it is that we got there," said Kenny Todd, space station integration and operations manager at JSC. "So obviously, this will be an activity that will challenge us.
"But replacing bearings is something we know how to do. Replacing the drive lock assembly is something we know how to do. These are what we term ORUs, orbital replacement units, they exist to be able to be changed out on orbit. We're not treading new ground here when it comes to doing these tasks. They are things that we train for and we understand how to do.
"I think what's going to be important for us is to understand this particular failure enough that when we go to perform that repair we do it in a way that doesn't somehow or another exacerbate this condition on the other ring. But I think without getting a better understanding of how it was that this happened, it's going to be hard for us to say for sure here's what we'll change, here's what we'll do different."