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SCAN 26 SCIENTIFIC AMERICAN OCTOBER 2004 NASA, HO AP Photo news I nside the Orbiter Processing Facility at the Kennedy Space Center, NASA techni- cians are readying the space shuttle Dis- covery, which is expected to be launched next March. Discovery will be the first shuttle to go into orbit since the loss of Columbia in February 2003, and the space agency has re- designed the vehicle to reduce the risk of a similar catastrophe. Yet not all the recom- mended fixes will be in place at the time of the first flight, limiting the kinds of missions the spacecraft can tackle. First and foremost, NASA will remove the foam insulation from the metal struts con- necting the shuttle to its external fuel tank; a 1.7-pound chunk of this foam fell off during Columbia’s launch and punched a hole in the shuttle’s wing, allowing superheated gases to flow into the craft on reentry. And in case foam peels off from another part of the ex- ternal tank, NASA has put sensors in Discov- ery’s wing panels to detect debris impacts and will install a digital camera for viewing the tank after it separates from the shuttle during the ascent. Other safety steps, however, have proved harder to implement. In its August 2003 re- port, the Columbia Accident Investigation Board urged NASA to devise ways to inspect the shuttle while it is in orbit and repair any serious damage that is discovered. The space agency began work on a sensor system locat- ed at the end of a 50-foot-long boom that would be attached to the shuttle’s robotic arm. Equipped with a laser ranger and a tele- vision camera, the system is designed to cap- ture three-dimensional images of the rein- forced carbon-carbon panels on the shuttle’s wings. But a recent report by the Return to Flight Task Group, which is monitoring NASA’s progress, said the inspection effort faced “enormous challenges” because of the tight schedule for developing the sensor sys- tem. The plans for repairing damage are also incomplete: although the astronauts will be able to fill cracks in the wings and plug holes up to four inches wide, they will not be able to fix a gash as large as the six- to 10-inch breach that doomed Columbia. As a stopgap, NASA is preparing alterna- tive measures that do not require as much technology development. Before Discovery docks with the International Space Station, the shuttle’s pilot will flip the craft so that as- tronauts in the station can take photographs of the heat-shield tiles on the shuttle’s under- side from 600 feet away. The crew members may also conduct space walks to get a closer look. If they find a hole that cannot be fixed, the Discovery’s crew will remain in the station until the arrival of the shuttle Atlantis, which could be launched on a rescue mission with- in 45 days. The station should have enough supplies to support the astronauts for that long, assuming there are no breakdowns in critical systems such as oxygen generation or carbon dioxide removal. Because NASA will rely on the station as a safe haven for shuttle crews, agency direc- tor Sean O’Keefe has canceled a planned 2006 mission to service the Hubble Space Telescope, which is expected to cease oper- Readying for a Relaunch NASA MAKES THE SPACE SHUTTLE SAFER BUT LIMITS ITS MISSIONS BY MARK ALPERT SPACEFLIGHT Robots might not have the touch to fix the Hubble Space Telescope, says Jeffrey A. Hoffman, a former NASA astronaut who participated in the first Hubble servicing mission in 1993. Hoffman says installing new gyroscopes would be tricky because they must be placed near the telescope’s center of mass. One strategy would be to incorporate the gyroscopes into the replacement for the Wide Field Planetary Camera (affectionately known as Wiff-Pick) that Hoffman installed a decade ago. “A robot should be able to remove the old Wiff-Pick,” Hoffman says. “But when the new Wiff-Pick goes in, it has to be aligned perfectly. With your hands you can maneuver the thing, you can feel the edge. But robots don’t have that force- feedback capability. They could jam the Wiff-Pick, which would not be good.” HUMAN VS. ROBOT SPACE SHUTTLE DISCOVERY is scheduled to go into orbit in March in the first flight since the loss of Columbia in February 2003. Pictured here in 1998, Discovery is being rebuilt to make it safer. COPYRIGHT 2004 SCIENTIFIC AMERICAN, INC.

Readying for a Relaunch

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Page 1: Readying for a Relaunch

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26 S C I E N T I F I C A M E R I C A N O C T O B E R 2 0 0 4

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Inside the Orbiter Processing Facility atthe Kennedy Space Center, NASA techni-cians are readying the space shuttle Dis-

covery, which is expected to be launched nextMarch. Discovery will be the first shuttle togo into orbit since the loss of Columbia inFebruary 2003, and the space agency has re-designed the vehicle to reduce the risk of asimilar catastrophe. Yet not all the recom-mended fixes will be in place at the time of thefirst flight, limiting the kinds of missions thespacecraft can tackle.

First and foremost, NASA will remove thefoam insulation from the metal struts con-necting the shuttle to its external fuel tank; a1.7-pound chunk of this foam fell off duringColumbia’s launch and punched a hole in theshuttle’s wing, allowing superheated gases toflow into the craft on reentry. And in casefoam peels off from another part of the ex-ternal tank, NASA has put sensors in Discov-ery’s wing panels to detect debris impacts and

will install a digital camera for viewing thetank after it separates from the shuttle duringthe ascent.

Other safety steps, however, have provedharder to implement. In its August 2003 re-port, the Columbia Accident InvestigationBoard urged NASA to devise ways to inspectthe shuttle while it is in orbit and repair anyserious damage that is discovered. The spaceagency began work on a sensor system locat-ed at the end of a 50-foot-long boom thatwould be attached to the shuttle’s roboticarm. Equipped with a laser ranger and a tele-vision camera, the system is designed to cap-ture three-dimensional images of the rein-forced carbon-carbon panels on the shuttle’swings. But a recent report by the Return toFlight Task Group, which is monitoringNASA’s progress, said the inspection effortfaced “enormous challenges” because of thetight schedule for developing the sensor sys-tem. The plans for repairing damage are alsoincomplete: although the astronauts will beable to fill cracks in the wings and plug holesup to four inches wide, they will not be ableto fix a gash as large as the six- to 10-inchbreach that doomed Columbia.

As a stopgap, NASA is preparing alterna-tive measures that do not require as muchtechnology development. Before Discoverydocks with the International Space Station,the shuttle’s pilot will flip the craft so that as-tronauts in the station can take photographsof the heat-shield tiles on the shuttle’s under-side from 600 feet away. The crew membersmay also conduct space walks to get a closerlook. If they find a hole that cannot be fixed,the Discovery’s crew will remain in the stationuntil the arrival of the shuttle Atlantis, whichcould be launched on a rescue mission with-in 45 days. The station should have enoughsupplies to support the astronauts for thatlong, assuming there are no breakdowns incritical systems such as oxygen generation orcarbon dioxide removal.

Because NASA will rely on the station asa safe haven for shuttle crews, agency direc-tor Sean O’Keefe has canceled a planned2006 mission to service the Hubble SpaceTelescope, which is expected to cease oper-

Readying for a RelaunchNASA MAKES THE SPACE SHUTTLE SAFER BUT LIMITS ITS MISSIONS BY MARK ALPERT

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Robots might not have the touch tofix the Hubble Space Telescope,

says Jeffrey A. Hoffman, a formerNASA astronaut who participated in

the first Hubble servicing missionin 1993. Hoffman says installing

new gyroscopes would be trickybecause they must be placed near

the telescope’s center of mass.One strategy would be to

incorporate the gyroscopes intothe replacement for the Wide FieldPlanetary Camera (affectionatelyknown as Wiff-Pick) that Hoffman

installed a decade ago. “A robotshould be able to remove the old

Wiff-Pick,” Hoffman says. “Butwhen the new Wiff-Pick goes in,

it has to be aligned perfectly. With your hands you can maneuver

the thing, you can feel the edge.But robots don’t have that force-

feedback capability. They could jam the Wiff-Pick, which

would not be good.”

HUMAN VS.ROBOT

SPACE SHUTTLE DISCOVERY is scheduled to go intoorbit in March in the first flight since the loss ofColumbia in February 2003. Pictured here in 1998,Discovery is being rebuilt to make it safer.

COPYRIGHT 2004 SCIENTIFIC AMERICAN, INC.

Page 2: Readying for a Relaunch

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ating by 2008 if its batteries and gyro-scopes are not replaced. (Hubble and thestation travel in very different orbits,making it impossible for the shuttle tovisit both.) Instead O’Keefe gave the go-ahead in August for a robotic mission toinstall new batteries, gyroscopes and sci-entific instruments to Hubble, at a costestimated between $1 billion and $1.6billion (about three times as expensive asa shuttle mission). But a robotic missionto Hubble might not prove successful,because much new technology needs tobe developed, according to a July Na-tional Academy of Sciences report.

Ironically, limiting the shuttle tospace station flights might actually beriskier than fixing the Hubble. RobertZubrin, an astronautical engineer whoheads the Mars Society, notes that therisk of fatal impacts with micrometeorsor man-made debris is much lower dur-ing a Hubble mission because the shut-tle can be oriented to minimize its vul-nerability. (While docked at the station,the craft’s belly is exposed.) And finish-ing the assembly of the station will re-quire at least 25 shuttle flights, whereasrepairing Hubble would entail only one.

COUNTING DOWN: NASA technicians work nearthe front landing-wheel well of Discovery inpreparation for the resumption of shuttle flightsnext year. Ceramic tiles on the craft’s undersideprotect it from the heat of reentry.

COPYRIGHT 2004 SCIENTIFIC AMERICAN, INC.