Shuttle Endeavour readied for rollout to launch pad
BY WILLIAM HARWOOD
STORY WRITTEN FOR CBS NEWS "SPACE PLACE" & USED WITH PERMISSION
Posted: July 8, 2007
Engineers are readying the shuttle Endeavour for rollout to pad 39A early Tuesday and launch Aug. 7 on a space station assembly and resupply mission. The flight features NASA's first educator-astronaut, Barbara Morgan, who served as backup to Christa McAuliffe in the original Teacher-in-Space program. There are no major technical problems with the shuttle or the space station, but NASA managers could opt to delay Endeavour's launch a few days if the agency's next Mars probe - the Phoenix polar lander - runs into problems getting off its pad as planned on Aug. 3.
Either way, Morgan and her crewmates - commander Scott Kelly, pilot Charles Hobaugh, Tracy Caldwell, flight engineer Rick Mastracchio, Canadian flier Dafydd Williams and Benjamin "Al" Drew - plan to participate in media briefings next Wednesday at the Johnson Space Center in Houston before flying to Florida the evening of July 16 for final emergency procedures training and a dress-rehearsal countdown July 19.
Aboard the international space station, meanwhile, astronaut Clay Anderson and Expedition 15 commander Fyodor Yurchikhin plan to stage a spacewalk July 23 to replace a failed electrical component needed to restore redundant power to the mobile transporter used to move the lab's robot arm from one work site to another.
In one of the more dramatic moments of the excursion, Anderson plans to jettison a no-longer-needed 1,400-pound ammonia tank that was part of the station's early power-and-cooling system. The spacewalkers also will clean the mating surfaces of the common berthing mechanism on the downward facing hatch of the Unity module. After Endeavour departs, a pressurized mating adapter currently mounted on Unity's left-side port will be moved to the downward facing hatch to make way for upcoming assembly work and engineers want to ensure a good seal.
"It won't be a problem," Anderson said of the ammonia tank in a pre-launch interview. "It's about 1,500 pounds, I believe. I tell everybody it's about the size of a refrigerator. (In training), I've been relatively consistent with being able to chuck it at around 40 centimeters per second (0.9 mph) and we really only need five centimeters a second. So I think I can send it on its way."
To clear the way for the spacewalk, Russian flight controllers plan to carry out a test reboost maneuver July 21 to make sure computers in the Russian segment are up to the task of controlling the lab's orientation and position.
During a shuttle mission last month to install a new set of solar arrays, secondary power supply switches, presumably detecting minor power quality changes in the station's electrical grid, triggered major problems, preventing critical guidance computers and command-and-control computers from rebooting. Yurchikhin and flight engineer Oleg Kotov eventually installed jumper cables to bypass the suspect switches and the computers powered back up normally.
The July 21 test will serve as another test of the hot-wired system's ability to control the station's attitude. A longer reboost maneuver is planned a few hours after the July 23 spacewalk to ensure plenty of clearance between the lab complex and the jettisoned ammonia tank. The reboost also will set up docking opportunities for a Progress supply ship as well as for Endeavour.
A Progress vehicle loaded with trash and no-longer-needed equipment is scheduled to undock from the Pirs airlock and docking module Aug. 1. The Progress 26P spacecraft, carrying replacement computer gear and other supplies, is scheduled to blast off from the Baikonur Cosmodrome in Kazakhstan at 1:33 p.m. EDT on Aug. 2. Docking is expected on Aug. 5, two days before Endeavour's launching on mission STS-118.
In the midst of space station activity and shuttle launch preparations, NASA is gearing up to launch the Mars Phoenix polar lander atop a Delta 2 rocket at 5:35 a.m. on Aug. 3, the day before Endeavour's countdown is scheduled to begin. This is a high-priority $414 million mission with a limited 22-day launch window that won't reopen for another two years. As such, shuttle managers could be asked to put Endeavour's countdown on hold if Phoenix runs into problems getting off the ground.
Concern, in part, about a possible conflict with Phoenix prompted NASA Administrator Mike Griffin to approve a decision to delay launch of NASA's Dawn asteroid exploration mission from this month to September after a series of problems pushed launch, also aboard a Delta 2 rocket, toward the end of its July launch window.
Endeavour, making its first flight since November 2002, is fresh out of a lengthy overhaul. It is equipped with a new station-to-shuttle power transfer system that will enable the orbiter to use electricity generated by the station's solar panels, easing the load on the shuttle's three fuel cells.
Going into the STS-118 mission, the approved flight plan calls for an 11-day mission with three spacewalks. But if the station-to-shuttle power transfer system works, Endeavour's mission will be extended three days and a fourth spacewalk will be added to the timeline. The SSPTS will be activated shortly after docking, but it will be shut down just before the first spacewalk on flight day 4 because the array it draws power from cannot track the sun during the assembly work. The power transfer system will be reactivated after the spacewalk. At some point after that, if there are no problems, the flight will be extended three days.
The primary goal of Endeavour's mission is to install a short spacer segment on the right end of the station's main solar power truss; to install a refurbished control moment gyroscope to replace one that has shown signs of impending failure; to attach an external equipment stowage platform; and to deliver needed supplies and equipment.
The flight will receive more public attention than most because of Morgan's presence as the first educator-astronaut, a designation approved by former Administrator Dan Goldin when he announced in 1998 that Morgan had been accepted as a full-time astronaut.
Morgan served as backup to high school social studies teacher Christa McAuliffe in the original Teacher in Space program and was looking on from the Kennedy Space Center press site on Jan. 28, 1986, when Challenger took off on its final mission. Morgan never gave up her dream of flying in space and on Aug. 7, she will strap into the center seat on Endeavour's lower deck - the same seat position used by McAuliffe aboard Challenger - to finally fulfill the legacy of the first teacher in space.
"Christa McAuliffe's legacy is open-ended," Morgan said in a NASA interview. "Every teacher's legacy is open-ended. I know people will be looking at this and remembering Challenger, and that's a good thing. They will also be thinking about all the people - teachers and other people - who have been working really hard and will continue working really hard to carry on the work that Christa was doing. I'm happy about that."
Assuming an on-time liftoff, Endeavour will dock with the space station around 3:50 p.m. on Thursday, Aug. 9. SSPTS activation is targeted for 7:47 p.m. that evening, just after the S5 spacer segment is unberthed by the shuttle's robot arm and handed off to the station's arm.
The next day, around 2 p.m., Mastracchio and Williams plan to begin a busy spacewalk to bolt S5 onto the end of the main truss; to relocate a grapple fixture and, if time permits, to connect electrical cables between S5 and the S4 solar panel segment and to prepare S5 for the eventual attachment of a final set of solar arrays, known as S6. They also will monitor the retraction of a folding radiator on the P6 solar array segment to prepare it for relocation to the left end of the main truss later this year.
The S4 solar array will be locked in place for the S5 attachment and as such, unable to track the sun. Because of that, the SSPTS must be deactivated before the spacewalk begins. Once S5 is in place and S4 resumes its normal rotation to track the sun, the SSPTS will be reactivated. A decision to extend the mission is expected after engineers verify the system is working normally.
Mastracchio and Williams plan to venture outside again two days later, around 1:30 p.m. on Aug. 12, to install the new control moment gyroscope. The station uses four massive CMGs to control the lab's orientation without using hard-to-replace rocket fuel. One of them, CMG No. 3, acted up last year and was taken off line on Oct. 10, 2006. The refurbished unit being installed during Endeavour's mission will restore full redundancy to the critical orientation system.
The external stowage platform will be attached to the station's truss structure the day after the second spacewalk using the lab's robot arm. That will set the stage for the third spacewalk of the mission, this one by Mastracchio and Anderson, to upgrade the station's S-band communications; to relocate two logistics carts attached to the mobile transporter; and to retrieve two experiment packages.
Anderson originally was scheduled to take off aboard Endeavour to replace astronaut Sunita Williams. But after the shuttle Atlantis was delayed three months, from March to June, because of hail damage to the ship's external tank, NASA managers decided to launch Anderson aboard Atlantis and to bring Williams home in June as originally planned. Anderson's place in Endeavour's crew was given to Drew.
"Once those guys arrive, I'll pretty much do the same jobs with them that I was planning on doing had I launched with that crew, and that includes EVAs No. 3 and 4, one with Rick Mastracchio and one with Dave Williams, and then I'll also be helping Charlie Hobaugh when he manipulates the arm to install the S5 truss," Anderson said in an interview.
Assuming the SSPTS is working properly, mission managers are expected to extend Endeavour's flight to permit a fourth spacewalk by Anderson and Williams that would begin around noon on Aug. 16. The goals of the final excursion are to install supports that eventually will permit a shuttle heat shield sensor boom to be stored on the station; to install two wireless instrumentation antennas on the U.S. lab module; to retrieve a failed Global Positioning System satellite antenna; and to install a wireless video transceiver on the S3 truss segment.
Under the extended mission scenario, Endeavour would undock from the station around 10 a.m. on Aug. 19 and return to Earth around 1:13 p.m. on Aug. 21.