NASA has literally U-turned their decision – for the first time in NASA history – to rollback Atlantis to the Vehicle Assembly Building (VAB), and she is has now arrived back at launch pad 39B.
Forecasts have shown that tropical storm Ernesto is weakening, as it heads towards the Cape – which means Atlantis will be able to cope with the wind and rain, while sat at the launch complex.
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STS-115 will attempt to launch at the end of the current window, taking in two possible attempts on September 6 and 7.
Space Shuttle Program’s Leroy Cain explained the decision to go back to the pad with Atlantis was based on new forecast information, which showed that the orbiter would be ok to stay at the pad, protected by the Rotating Service Structure (RSS), whilst riding out the storm.
‘We came in last night and saw some indication that some of the forecasts were favourable, that the storm wasn’t going to be as intense,’ said Cain. ‘So we came back in this morning to have a look at it again – and by the time we needed to make a decision to rollback, the forecast was not quite good enough.’
‘It was very close, and by that I don’t mean close as in pushing it, it was close to being near the kinda margin we like to have.’
Also key for the U-turn was the ability to change their decision before Atlantis had taken in over half the journey back to the VAB. The trip back to the pad before that point would ultimately ensure that the crawler-transporter she was riding on would not exceed the total journey time by turning around before the half way point.
‘We basically had a lot of discussions, and at one point it was decided the decision time was not when we rolled back, but when we got to a point of no return (in the rollback).
‘Essentially, that’s where we got to. With the kind of forecast we have now, we can have the RSS around the stack, as the wind levels won’t be high enough. Once we got forecast of the storm that was within our criteria for being at the launch pad, I felt comfortable, and thought it was the right thing to do.’
Earlier, Shuttle manager Wayne Hale noted how difficult the decision was to rollback Atlantis.
‘Yes I think it was a difficult decision this time, because there is always uncertainty in the track and intensity of the hurricanes,’ said Hale, who was party to discussions this morning, following new weather forecasts that showed the storm was weakening as it left Cuba.
However, he claimed the risk involved with leaving the multi-billion dollar vehicle on the pad was simply not worth it, as Atlantis was moved away from Pad 39B this morning.
‘There was some talk this morning on whether the storm had degraded, to a level where we’d be better to weather it on the pad,’ added Hale.
‘The professional weather forecasters that we have at the Kennedy Space Center and through the United States Air Force gave their professional opinion that we could see winds of over 70 knots – at least in gusts – and that is the criteria that we don’t want to stay on the pad for.’
Atlantis will target a launch date that will comply with the end of the window, September 7, to carry out her mission to install the P3/P4 truss and solar panels into the International Space Station (ISS) configuration.