'Very Smooth' New Crane Stars During Spacewalk Tests By Guy Gugliotta Washington Post Staff Writer
Sunday, July 9, 2006; A11 http://www.washingtonpost.com/wp-dyn/content/article/2006/07/08/AR2006070800993_pf.html HOUSTON, July 8 -- Tethered like two lures at the end of a fishing rod, astronauts Piers Sellers and Michael Fossum rode space shuttle Discovery's spindly crane 70 feet into space on Saturday in an unprecedented test to see if the crane would remain stable enough to serve as a repair platform. "Very smooth, very nice," said Sellers, as Discovery's sensor boom lifted him out of the cargo bay. "It's actually like a very slow elevator." For several hours, first Sellers, then Fossum and Sellers together, bent, twisted, pushed and pulled at their restraints and at the side of the international space station to see how much the shuttle's cargo arm and its 50-foot boom extension would whiplash them. Although few trips were as gentle as Sellers's initial liftoff, both astronauts reported sways of only one to two feet in most cases. At the conclusion of the spacewalk, Fossum performed simulated repairs at the end of the station's "P-1" truss, a distance of about 70 feet. When fully extended, the combination of arm and boom reaches 100 feet. At the end of the day, Tomas Gonzalez Torres, NASA's extravehicular activities officer, said engineers were astonished at how effectively the boom performed. He noted that the astronauts got in and out of foot restraints without returning to the cargo bay, and that the boom took only "15 to 20 seconds" -- instead of the anticipated minute -- to stop swaying after it had been disturbed. "Everybody is very happy," Gonzalez Torres told reporters at Houston's Johnson Space Center. He pronounced the boom ready for use as a repair platform: "I think we're set." Saturday was the fifth day in Discovery's 13-day mission, which has unfolded almost without a hitch. Steve Poulos, the Orbiter Project Office manager, said that analysts had "cleared" all but two blemishes on Discovery's heat shield and that the other two should be cleared Sunday. John Shannon, chairman of the mission management team, said this meant that on Sunday he could clear Discovery for reentry, guaranteeing the orbiter's soundness. Shannon said Discovery's heat shielding was in "by far" the best shape of any shuttle he had ever seen. Sellers and Fossum began their trip outside at 9:17 a.m. Eastern time, leaving the space station's Quest air lock for a spacewalk that ended 7 hours 31 minutes later. Their first task -- repairing the station's mobile tramway -- took a bit over an hour. The next hours were devoted to testing the repair techniques. Astronauts are frequently lifted out of the cargo bay on the orbiter's 50-foot robotic arm, but Discovery's mission marked the first time spacewalkers have extended the crane with the 50-foot boom. The boom is a relatively recent innovation. It was developed after the Columbia tragedy in 2003 as a mount for cameras and sensors that could scan the belly of the orbiter during onboard inspections to check for post-launch damage. The boom performed so well last year that NASA planners decided to test it as a repair platform, enabling astronauts for the first time to reach any part of the orbiter by riding on the end of the arm-boom combination. The only question was whether the extension would be too whippy to allow an astronaut to use it without anchoring himself to his work site. With shuttle astronauts Lisa M. Nowak and Stephanie Wilson operating the arm and boom, Sellers guided the crane to a cocked position "above" the orbiter. Fossum watched from the cargo bay. "Pick up the camera, take two pictures and re-stow the camera," ordered shuttle pilot Mark Kelly, supervising the spacewalk from inside Discovery. "I have the camera in my hand," began Sellers. He proceeded to describe his every movement and the effect on the stability of the arm -- "no perceptible motion," "a smooth, gentle sway," "motion stopped." Kelly ordered other motions: "slow layback," "forward lay position -- hold position for five seconds." Sellers stepped out of his foot restraints and climbed around to the end of the boom, then put the restraints back on. "Just a general comment," Sellers remarked after half an hour of this. "It gets easier as you go along, doing all these tasks on the end of a skinny little pole. A little practice makes perfect, or at least adequate." Each movement was designed to mimic something that an astronaut would do if the shuttle needed repair -- taking pictures of damage, leaning forward to inspect, seeking a better vantage point by abandoning foot restraints for a tether. Most important, Gonzalez Torres said, anything but inspections that could happen at the end of the crane-boom would involve two astronauts, so the second half of the test had Fossum in the foot restraints while a tethered Sellers grabbed hold of a tool stanchion. As the shuttle dipped into darkness, leaving the spacewalkers spotlighted by the shuttle in the middle of nothingness, Kelly said, "You guys look lonely out there." "Well, I'm just looking at Mike," Sellers replied. The two astronauts performed a new series of movements on Kelly's command, then migrated to the end of the P-1 truss. There, Fossum mimicked repair techniques, using a simple "strain gauge" to measure force vectors as he pushed against the work surface. Asked to rate the difficulty of each movement on a scale described by Kelly, Fossum relayed positive results, and noted that his technique improved with practice. "This isn't bad," he said at one point. "I got the desired performance. It's a little bit annoying." ================================ George Antunes, Political Science Dept University of Houston; Houston, TX 77204 Voice: 713-743-3923 Fax: 713-743-3927 antunes at uh dot edu Reply with a "Thank you" if you liked this post. _____________________________ MEDIANEWS mailing list medianews@twiar.org To unsubscribe send an email to: [EMAIL PROTECTED]
