CAPE CANAVERAL, Fla. - NASA is preparing to both loft the space shuttle Atlantis Tuesday and pull the spacecraft from the launch pad as flight controllers wrangle lightning-related issues and a hurricane bearing down on Florida's western coast.
"We're kind of hedging our bets both ways," William Gerstenmaier, NASA's associate administrator for space operations, told reporters Sunday. "Tonight is really the night that we've got to decide."
That decision point, Gerstenmaier said, will likely be midnight tonight here at NASA's Kennedy Space Center (KSC) launch site.
NASA will hold a press briefing on Atlantis' launch preparations no earlier than 8:00 p.m. EDT (0000 Aug. 29 GMT) tonight, he added.
Earlier today, NASA postponed Atlantis' planned Monday launch to the International Space Station (ISS) citing the need for more system checks following a Friday lightning strike to the orbtier's Pad 39B launch site. The shuttle's STS-115 mission - already delayed 24 hours due to ongoing spacecraft checks - was slated to rocket spaceward Monday at 4:04:14 p.m. EDT (2014:14 GMT).
If Atlantis rolls back from its launch pad, the earliest it could be ready to launch is around Sept. 7, the end of NASA's target flight window, Gerstenmaier said.
The mission, commanded by veteran shuttle astronaut Brent Jett, will deliver two new solar arrays and a 17.5-ton pair of segments to be attached to the port side of the space station's main truss.
While Atlantis' shipboard electronics were cleared following the lightning strike, which hit the shuttle's launch pad protection system and not the spacecraft itself - more analysis is needed to determine the health of vital pyrotechnics systems aboard the orbiter's twin solid rocket boosters, NASA has said.
At the same time, Hurricane Ernesto - now in the Caribbean - is bearing down on Florida's west coast. While the storm is expected to make landfall on Thursday, there is a 40 percent chance that tropical storm force winds exceeding 34 knots (39 miles per hour) will batter the general area of NASA KSC spaceport before then, according to a 2:00 p.m. EDT (1800 GMT) update from the National Hurricane Center.
NASA rules call for a shuttle rollback when sustained wind speeds higher than 40 knots - or peak winds of 70 knots - are expected at the launch pad. The shuttle's Rotating Service Structure, a shell-like cover that protects orbiters from weather at the launch pad, cannot be rolled clear to allow a rollback in 40-knot winds, NASA said.
Gerstenmaier said shuttle workers are going through the motions required to both launch Atlantis, and haul the spacecraft and its external tank-solid rocket booster launch stack the 4.2-mile to NASA's massive Vehicle Assembly Building, where it will be safe from Ernesto's expected winds.
"When you look at that, you may think we've lost our minds," Gerstenmaier said. "We really haven't lost our minds, we're protecting those two options to the best of our ability."
NASA's top shuttle managers will meet at 6:00 p.m. EDT (2200 GMT) tonight to discuss any new developments in the lightning strike analysis.
Of particular concern, Gerstenmaier said, are any ill effects to electronics associated with the control systems to fire explosive bolts separating Atlantis' boosters from the launch pad at liftoff, and similar systems that blow the rockets free from the external tank about two minutes into the flight.
Atlantis' boosters were not powered up when the 100,000-amp bolt of lighting struck Pad 39B at 1:49 p.m. EDT (1749 GMT) Friday, hence engineers are unsure whether the strike led to a spike in their electrical system, Gerstenmaier said.
Also outstanding is an evaluation of a liquid hydrogen vent arm that runs from the launch pad to Atlantis' external tank, which also registered a power surge during the lighting strike, he added.
Because of daylight lighting constraints and the precision needed to reach the ISS,
NASA's window to launch Atlantis runs though Sept. 13.
But the space agency has set its own cutoff date of about Sept. 7 to allow enough buffer time between Atlantis' complicated space station construction mission and Russia's planned Sept. 14 launch of a Soyuz spacecraft carrying the next ISS crew.
Gerstenmaier said there is some wiggle room in that launch plan - Sept. 8 may be a launch possibility - and that NASA station managers will be in contact with their Russian counterparts later this evening. Russia could also reset their launch for Sept. 18, are reluctant because the move would push the return of another Soyuz spacecraft - carrying the current ISS crew Expedition 13 - into an unfavorable night landing on the steppes of Kazakhstan in Central Asia.
With so many factors in play, Gerstenmaier said the confluence of STS-115 launch challenges does have some positive points.
"If you had to pick a perfect training scenario, this is probably the most awesome scenario we've ever seen," he said. "Even though this is a lot of work for our folks, this is really, really good for our teams."
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