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Friday, February 25, 2011

Discovery Soars On Final Mission

Shuttle Discovery thundered away from NASA’s Kennedy Space Center for the last time on Feb. 24, piercing the sunny Florida skies with the final pieces of the International Space Station (ISS) and a legacy already rich in achievement.
NASA’s oldest orbiter at 27 years, Discovery lifted off on her 39th flight at 4:53 p.m. EST and climbed steeply on a northeasterly trajectory that will lead to a 13th docking with the orbiting science laboratory on Feb. 26 at 2:16 p.m. EST.
Liftoff came slightly later than planned after U.S. Air Force technicians corrected a glitch in a range safety computer at the last minute.
“We are clean on all systems,” Mission Control Center-Houston radioed the crew at 5:06 p.m. “We are not tracking anything.”
Over the 11- to 12-day STS-133 mission, Discovery’s six astronauts plan to equip the station with a storage compartment and an external platform securing a spare thermal control system radiator. The shuttle carries five tons of cargo, including Robonaut 2, an experimental humanoid developed by NASA in partnership with General Motors.
Mission commander Steve Lindsey’s crew includes pilot Eric Boe, Mike Barratt, Nicole Stott, Alvin Drew and Steve Bowen.
Within hours of their linkup, the shuttle crew plans to secure the logistics carrier on the lab’s starboard truss using the station’s robot arm. On Feb. 28, Drew and Bowen are slated to embark on the first of two spacewalks to retrieve and vent a station pump motor that failed in late July, crippling half the cooling system.
The 21-ft.-long equipment compartment will be hoisted from Discovery’s payload bay and attached to the Earth-facing docking port of the station’s Unity module on March 1, also using robot arm operations.
The second spacewalk is scheduled for a day later, and Discovery’s crew will aim for a March 5 departure and return to Kennedy on March 7.
Midway through the shuttle’s stay at the station, mission managers may add a day to the flight. The extension would permit three of the Expedition 27 crew members to board their 24S Soyuz spacecraft with cameras and back away for a space station portrait. Using cameras and high-definition camcorders, the Soyuz crew would record the outpost with a full house of docked spacecraft. The visitors include Russian Soyuz and Progress spacecraft, the newly arrived Automated Transfer Vehicle, Japan’s H-II Transfer Vehicle as well as Discovery (Aerospace DAILY, Feb. 23).
Europe’s ATV-2, the Johannes Kepler, docked with the station’s aft docking port six hours before Discovery’s departure, removing a potential obstacle to the liftoff. The freighter launched from Kourou, French Guiana, on Feb. 16, with seven tons of propellant, dry goods and other supplies.
Discovery followed Columbia and Challenger off the Rockwell International assembly line in Palmdale, Calif., in late 1983.
Named for a pair of historic sailing ships, one commanded by Henry Hudson in the early 1600s to examine Hudson Bay and the other captained by James Cook to explore the South Pacific in the 1770s, Discovery took flight for the first time on Aug. 30, 1984.
Discovery and her crews led the United States back into space following the Columbia and Challenger tragedies in 2003 and 1986. During a 1990 mission, Discovery launched the Hubble Space Telescope. In 1994, Russian Sergei Krikalev joined Discovery’s crew for a mission that symbolized a post Cold War thaw in relations between the U.S. and the former Soviet Union.
In 1998, Discovery ushered 77-year-old U.S. Sen. John Glenn back into space. Glenn became the first American to orbit the Earth as a Mercury astronaut in 1962.
A dozen previous station assembly flights have occupied Discovery’s twilight years. The STS-133 mission was stalled by a launch pad hydrogen leak on Nov. 5 and the subsequent discovery of a separation in the insulating foam that jackets the top of the external tank (ET). Additional troubleshooting revealed small cracks in the underlying metal on the ET’s stringer section.
Engineers traced the damage to an unusually brittle decade-old stock of metal alloy, forces resident in the assembly of the tank’s subcomponents and the structural contractions that accompanied the chilled propellant flow on Nov. 5. The cracks were repaired and the stringers fortified with “radius blocks” to prevent future cracking. The fuel tanks assigned to the final flights of Endeavour and Atlantis are receiving the same modifications.
Currently, Endeavour is set to lift off for the station in late April on STS-134, a two week mission to deliver the Alpha Magnetic Spectrometer. Though unfunded, NASA plans to launch Atlantis between late June and August on STS-135, an 11-day station supply mission.

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