Last-minute glitches continued to plague NASA's space shuttle Atlantis after an errant fuel tank sensor prevented the orbiter and its six-astronaut crew from heading for the International Space Station (ISS) on Friday.
For the second time in three days, Atlantis stood down from a planned mid-day liftoff due to technical problems.
"We had a lot discussion ... and we follow the rules," NASA launch director Michael Leinbach told Atlantis' commander Brent Jett, adding that the scrub falls in line with shuttle flight restrictions.
After plenty of delays, Atlantis must lift off on Saturday or wait until the end of September at the earliest so as not to interfere with a Russian Soyuz trip to the space station. The Soyuz launch to ferry two new station crew members and the first female space tourist is slated for September 18.
However, if NASA attempts a mission later this month or early October, it will have to waive a post-Columbia rule that says launches must be done in daylight so that the spaceship can be photographed for signs of damage. The rule was implemented for thfirst few flights after the Columbia accident, so NASA could check if foam comes off the external fuel tank and could damage the shuttle's heat shield as it did to Columbia.
Atlantis has suffered a series of inopportune delays from its initial August 27 launch date. The flight has been postponed due to a lightning strike to the shuttle's launch pad, weather threats from tropical storm Ernesto and -- on Wednesday -- a power glitch in a pump motor that helps cool one of the spacecraft's three vital fuel cells.
Atlantis' STS-115 mission plans to deliver a US$371.8 million pair of new trusses and solar arrays to the ISS. The spaceflight will mark NASA's third shuttle mission since the 2003 Columbia accident and the first major ISS construction flight since late 2002.
NASA is eager to go ahead with the construction mission since it has just four years to finish building ISS, before the fleet ofthree shuttles on active service retire by 2010. The station's structural trusses, modules and other major components were designed to be launched only on the shuttles.
(Xinhua News Agency September 9, 2006)
