NASA Targets Saturday for Space Shuttle Launch

Discovery's Launch Date Shifts as Engineers Investigate Sensor Glitch
A diagram of the engine cutoff (ECO) sensors inside the external tanks used by NASA's space shuttle.
(Image: © NASA.)

CAPECANAVERAL, Fla. - NASA is now targeting a weekend launch for the space shuttleAtlantis and a new European lab after a fuel tank sensor glitch prevented aThursday liftoff, mission managers said.

Atlantis isslated to launch Europe?sColumbus laboratory and a seven-astronaut crew no earlier than Saturday at3:43 p.m. EST (2043 GMT), but only if mission managers decide tomorrow that therisk of flying without two of four vital fuel tank sensors is acceptable, saidLeRoy Cain, head of Atlantis? STS-122 mission management team.

?We?ve doneeverything we can to maintain the possibility of launching on Saturday,? Caintold reporters in an evening briefing here at NASA?s Kennedy Space Center.

NASAcalled off Atlantis? planned 4:31 p.m. EST (2131 GMT) launch toward theInternational Space Station (ISS) early this morning, when two of the four EngineCut-Off (ECO) sensors in the liquid hydrogen portion of the shuttle?s15-story fuel tank failed a standard countdown test.

NASA flightrules call for three of the four fuel gauge sensors, which serve as a backupsystem to shut down a shuttle?s three main engines before its hydrogen suppliesrun dry, to be working properly in order to launch. Similar sensor issues have afflictedrecent NASA shuttle launches, mostrecently in September 2006.

U.S. space shuttles consume more than500,000 gallons (1.9 million liters) of cryogenic liquid hydrogen and liquidoxygen propellant to make the 8.5-minute launch into orbit.

Cain saidlate Thursday that a set of new instruments which watches over the ECO sensorsmay offer extra data that could allow flight controllers to launch Atlantis andits STS-122 crew Saturday if two of four sensors performing as designed.Engineers currently suspect an open circuit somewhere between an electronicsbox inside Atlantis and its fuel tank, and not the sensors themselves, is thesource of the glitch.

?It wasslightly different than things we?ve seen before,? Cain said of the glitch,adding that analysis teams simply ran out of time today. ?What all that meansto us is, it?s still a little bit new and we want to sleep on it.?

Atlantis?fuel tank sensor glitch marred what appeared to be an otherwise flawlesscountdown, with the weather forecast predicting clear skies and a 90 percentchance of favorable launch conditions.

?The countdownhad been going very smooth,? said NASA shuttle launch director Doug Lyons. ?Theweather was perfect. Everything was lining up for a perfect launch on our firstattempt.?

Atlantis?launch scrub ended NASA?s 2007 streak of on-time shuttle launches thatstretched across three missions that lifted off on the first try in June,August and October, respectively.

Commandedby veteran shuttle flyer Stephen Frick, Atlantis? seven-astronaut crew willdeliver the European Space Agency?s (ESA) Columbuslaboratory to the ISS. The delay disappointed hundreds of ESA officials whohave spent more than two decades building Europe?s first permanent human spaceflightlaboratory to fly.

?In the bigpicture, it?s not a setback,? said Alan Thirkettle, the ESA?s space stationprogram manager, of the delay. ?[But] it is disappointing because we have 750people over here.?

Thevisitors are ESA Columbus program officials and supporters who have toiled overthe module?s 20-year history to see it reach the ISS. They will return to Europe aboard a charter jet late Friday, whether or not Atlantis makes a new launchattempt, Thirkettle said.

NASA mustlaunch Atlantis to the space station by Dec. 13 or else stand down to Jan. 2,when the angles between the orbital laboratory?s expansive solar arrays and thesun are more favorable to support a visiting shuttle crew.

Atlantis?STS-122 mission will mark NASA?s fourth space shuttle flight to the ISS thisyear, and the second to haul a new orbital room to the high-flying orbitallaboratory. If Atlantis cannot launch on Saturday, a third attempt could bemade as early as Sunday at 3:20 p.m. EST (2020 GMT), with current weatherforecasts predicting a 70 percent chance of acceptable flight conditions.

NASAwill broadcast Atlantis' STS-122 mission live on NASA TV. Click here for SPACE.com's shuttle mission coverage and NASATV feed.

  • SPACE.com Video Interplayer: NASA's STS-122: Columbus Sets Sail for ISS
  • IMAGES: Discovery's STS-120 Mission in Pictures
  • VIDEO: ISS Commander Peggy Whitson Takes Charge

 

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