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  • Lightning Strikes Delay Endeavour
    Posted by Frank Morring, Jr. 3:53 PM on Jul 11, 2009

    NASA will try again Sunday to launch the space shuttle Endeavour, pending the outcome of some retesting to ensure a couple of lightning strikes Friday afternoon didn't damage critical systems on the orbiter and its solid-fuel booster rockets.

    Mike Moses, head of the mission management team, said sensors registered 11 strikes within 0.3 nautical miles of Pad 39A during a "pretty spectacular electrical storm" that rolled through at about 3 p.m. EDT. The lightning protection system on the pad worked as advertised on the seven strikes that hit it, he said, but two of those strikes induced voltage and magnetic fields in orbiter and booster systems over the limits that require retesting.

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    As an example, Moses said lightning-induced voltage on some orbiter computer buses reached 110 volts, 10 volts over the threshold that requires retesting. Experts were still analyzing whether that testing will be possible in time to support a Sunday launch.

    "The teams are pretty confident, but they're not quite there this morning," Moses said. "We need to be 100 percent confident."

    One problem involves circuitry to the pyrotechnics that separate and - in a catastrophic loss of control -- destroy the solid-rocket boosters. Because live pyrotechnics are involved, the testing must be sufficient to ensure that the systems will work without actually setting them off. It is possible that retesting on either the orbiter systems or the boosters could require more time than would allow a Sunday launch.

    "We'll make the call tomorrow as to whether we'll be able to try," Moses said, nothing that a further delay was considered unlikely.

    "We don't think we're going to need to go there, but if we do we will," he said.

    If Endeavour can launch Sunday, liftoff would come at 7:14 p.m. EDT. Weather at that time is forecast to permit a 60% chance of launch, an improvement from today's 40% forecast. If Endeavour can't launch on Sunday, Moses said the program will have until Tuesday to get it off the pad before its 16-day assembly mission to the International Space Station conflicts with the planned launch of a Russian Progress resupply vehicle.

    NASA may ask the Russians to delay the Progress launch if Endeavour can't get underway on Sunday, Moses said.

    Tags: os99, sts127, Endeavour, scrub, lightning

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