NASA's launch of the space shuttle Atlantis has slipped to late January, with a push to early February likely, as engineers work to replace a faulty fuel tank connector, a top official said Thursday.
John Shannon, NASA's deputy shuttle program manager, said Atlantis will not fly until Jan. 24 at the earliest, a two-week slip from an earlier Jan. 10 target, to allow tests and modifications of a vital fuel tank connector.
"Everything has to go exactly right for us to make the 24th," Shannon told reporters.
More likely launch targets are Feb. 2 or Feb. 7, which allows time for extra tests but no major unexpected surprises, Shannon said.
Atlantis' planned 11-day mission to deliver a new European laboratory to the International Space Station (ISS) has been delayed since early December, when vital fuel gauge-like sensors failed standard countdown checks. Known as engine cutoff sensors, the fuel gauges serve as a backup system to shutdown an orbiter's three main engines before its fuel supply runs out.
NASA tracked the glitch to a suspect electrical connector near the bottom of Atlantis' 15-story external tank, where sporadic open circuits may form as the tank is filled with its super-cold liquid hydrogen propellant.
The three-part connector consists of an interior electrical socket, a glass-and-metal pin bridge and an exterior electrical socket that work together to transmit signals from four liquid hydrogen fuel gauges to a computer aboard Atlantis.
Engineers have already removed exterior portions of the electrical connector and will replace it next week with a modified version with wires soldered directly to their corresponding pins to avoid open circuits, NASA said.
"It's fairly simple," said Shannon. "It's a fairly elegant change and we feel very confident that, if the problem is where we think it is?that this will solve that."
NASA requires at least a five-week breather between shuttle launches, which pushes the planned Feb. 14 launch of the Endeavour orbiter and the first part of Japan's massive Kibo laboratory beyond its initial target, he added.
The space agency also must not conflict with the planned ISS arrival of the unmanned Russian Progress 28 cargo ship, which is currently slated to launch on Feb. 7.
"The hard constraint today is not to have a shuttle docked while we're trying to dock a Progress," said Mike Suffredini, NASA's ISS program manager.
Suffredini added that ISS managers are also discussing when to add an extra spacewalk to the chore list of the space station's Expedition 16 crew to replace a solar wing motor.
Commanded by veteran spaceflyer Stephen Frick, Atlantis' seven astronauts expect to install the European Space Agency's Columbus laboratory and stage at least three spacewalks slated for their shuttle mission.
"They did get the holidays off. I think that was a good thing," Shannon said of the shuttle astronauts. "They're, from all I can tell, very excited and ready to go whenever the shuttle is."
