KENNEDY SPACE CENTER, FL - For a second time in a week, NASA's efforts to launch space shuttle Endeavour on a mission to deliver hardware to the International Space Station were put on hold due to a leak of flammable hydrogen gas from a launch pad vent line connected to the shuttle's external tank. Endeavour's scrub means the next launch for NASA will be the Lunar Reconnaissance Orbiter and Lunar Crater Observation and Sensing Satellite (LRO / LCROSS) later this week.
VIDEO: POST-SCRUB NEWS CONFERENCE VIDEO: NASA LAUNCH DIRECTOR MIKE LEINBACH SPEAKS AFTER SCRUB VIDEO: LAUNCH OF ENDEAVOUR IS SCRUBBED VIDEO: GH2 LEAK IS FIRST DETECTED VIDEO: GO FOR TANKING AND THE START OF MPS CHILLDOWN VIDEO: RSS RETRACTION ON MONDAY ALL-ACCESS SUBSCRIBERS: WATCH ENTIRE TANKING AND LAUNCH COMMENTARY - PART 1 - 150KBPS ALL-ACCESS SUBSCRIBERS: WATCH ENTIRE TANKING AND LAUNCH COMMENTARY - PART 2 - 150KBPS ALL-ACCESS SUBSCRIBERS: WATCH ENTIRE TANKING AND LAUNCH COMMENTARY - PART 3 - 150KBPS ALL-ACCESS SUBSCRIBERS: WATCH ENTIRE TANKING AND LAUNCH COMMENTARY - PART 4 - 150KBPS ALL-ACCESS SUBSCRIBERS: WATCH ENTIRE TANKING AND LAUNCH COMMENTARY - PART 1 - 1200KBPS ALL-ACCESS SUBSCRIBERS: WATCH ENTIRE TANKING AND LAUNCH COMMENTARY - PART 2 - 1200KBPS ALL-ACCESS SUBSCRIBERS: WATCH ENTIRE TANKING AND LAUNCH COMMENTARY - PART 3 - 1200KBPS ALL-ACCESS SUBSCRIBERS: WATCH ENTIRE TANKING AND LAUNCH COMMENTARY - PART 4 - 1200KBPS ALL-ACCESS SUBSCRIBERS: WATCH ROTATING SERVICE RETRACTION - 1200KBPS The earliest Endeavour can launch now is July 11, assuming engineers find a fix for the leaky seal. That work will be a challenge as NASA has yet to determine a root cause of the problem. "We'll go work this problem and once we get it fixed and we're confident we have a solution that's going to work and allow us to go fly safely, then we'll proceed forward," said LeRoy Cain, deputy shuttle program manager and chairman of NASA's Mission Management Team... We'll fix it and we'll move forward once we have determined we can get in a safe configuration to go fly." Three of the last five times the external tank has been fueled, indicating a possibly systemic design, manufacturing or processing problem that the space agency will have to track down before devising a resolution. While July 11 is the current NET target date, it's entirely possible that it will take longer than that to solve the issue. "The direction we gave to the team today after our scrub was we need to step back from this problem and try to understand what is different in our process, if anything," said Cain. "Somehow, we've introduced some other variable or some change, albeit very small. But our sense is something has changed and something is different and we need to go re-evaluate. "It could be something as simple as a heat treatment to some material part in the system, it could be some change in a vendor that was done years ago that is just now being introduced because of a part number." Fueling operations for Endeavour got underway 2 hours, 40 minutes late, a record delay for the shuttle, with the propulsion system chilldown at about 10:55 p.m. EDT. Slow-fill of hydrogen began at 11:14. The liquid hydrogen engine cutoff sensors that caused frustration for NASA a few years ago went to the "wet" state at 11:49 p.m. The hydrogen tank was supposed to reach the 98% full mark and enter top-off at 1:19 a.m. followed by stable replenish at 2:04. However, at 1:02, fueling was halted after an unacceptable level of gaseous hydrogen was detected leaking from the Ground Umbilical Carrier Plate (GUCP) at the end of the GH2 vent arm. Engineers tried troubleshooting the problem by cycling the vent valve several times, which appeared at first to reduce the leak rate somewhat. However, with a gaseous hydrogen concentration of 40,000 parts per million in the atmosphere, compared to an allowable limit of 10,000, engineers were unable to fix the leak and, at 1:55 p.m., launch director Pete Nickolenko called a scrub of the launch attempt. Even if the leak had been closed, the team would have been hard-pressed to make the 5:40 a.m. launch time. Already three hours down in the count when fueling began, nearly an hour was used up for troubleshooting. In effect, activities morphed into a tanking test while engineers in launch control watched the leak. At one point, they resumed "fast-fill" of the tank to collect more data. The GUCP was replaced after the shuttle's June 13 launch attempt was scrubbed for the same reason. Last March, launch of Discovery was delayed because of a leak around the GUCP. That time, technicians replaced the carrier plate and seal and the shuttle was able to launch successfully on the next attempt. This time, seal replacement was insufficient to correct the problem. Endeavour's delay leaves an opening for NASA's LRO/LCROSS mission to liftoff this week on a United Launch Alliance Atlas 5 rocket from SLC-41. The lunar mission had been set for launch today, but ULA and NASA agreed to move to the right on the range in order to give the shuttle one more launch attempt. LRO was rescheduled for launch Friday to give time for the Air Force to reconfigure the range for the different launch vehicle, a process which takes 24-48 hours. Since Endeavour scrubbed relatively early, a couple hours after midnight, the Atlas mission was moved up one day and is now scheduled to liftoff at 5:41 p.m. EDT on Thursday. (The Spacearium / Space Media Corporation)
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