NASA is readying the shuttle Atlantis for launch Friday on the iconic program's 135th and final flight, bringing the curtain down on one of the nation's greatest technological triumphs after more than three decades at the apex of manned spaceflight.
Carrying a reduced crew of four to minimize potential post-launch rescue complications, Atlantis is scheduled for liftoff at 11:26 a.m. EDT, roughly the moment Earth's rotation carries launch complex 39A into the plane of the International Space Station's orbit.
NASA said in a briefing this morning that, despite some iffy weather in the forecast, it still expects to have an on-time launch.
Strapped in on Atlantis' upper flight deck will be commander Christopher Ferguson, pilot Douglas Hurley, flight engineer Rex Walheim, and space station veteran Sandra Magnus. All four are spaceflight veterans and all four clearly recognize the historic nature of their voyage.
"That is the most graceful, beautiful vehicle we've had to fly in space, ever, and it's going to be a long time until you see a vehicle roll out to the pad that looks as beautiful as that," Walheim said during Atlantis' move to the launch pad May 31. "How can you beat that? An airplane on the side of a rocket. It's absolutely stunning."
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Huge crowds are expected as space aficionados, tourists and area residents turn out for a final chance to see the world's most powerful manned spaceship blast off for the last time. Brevard County officials expect between a half-million and 750,000 spectators to jam area roads and beaches.
Assuming an on-time liftoff, Ferguson will guide Atlantis to a docking at the space station's forward port at 11:09 a.m. Sunday. The next day, an Italian-built cargo module will be attached to the Earth-facing port of the forward Harmony module and the combined 10-member shuttle-station crew will begin a hectic week of work to move 8,640 pounds of equipment and supplies into the lab complex.
The supplies are critical to the space station program. Two companies, Space Exploration Technologies -- SpaceX -- and Orbital Sciences, are building unmanned cargo ships to take over from the shuttle after the fleet is retired, with initial test flights expected later this year or early next.
Atlantis' mission was added to the shuttle manifest to deliver enough supplies to keep the station provisioned through 2012 as a hedge against development problems that might delay the commercial cargo ships.
"All of these supplies are going to be the lifeline to help us extend the period of time we can go on orbit before our commercial providers start flying regularly to ISS. That's critical to us, to give them the time they need to make sure their vehicles are ready to go fly, finish their development and get their test fights behind them and then start servicing ISS," said Michael Suffredini, the space station program manager at the Johnson Space Center in Houston. "From our perspective, although it doesn't look very sexy, it's one of the most important fights that we've ever had come to ISS."
With a reduced crew of four, only one spacewalk is planned during Atlantis' visit, a 6.5-hour excursion by station flight engineers Ronald Garan and Michael Fossum. Their primary objectives are to move an experimental robotic refueling package from Atlantis to the station and to mount a failed ammonia coolant pump in the shuttle's cargo bay for return to Earth.
NASA did not originally intend to launch Atlantis on an actual mission. Using the agency's final set of solid-fuel boosters and its last external tank, Atlantis was designated for stand-by duty as a "launch on need" rescue flight for the crew of the shuttle Endeavour, which launched in May.
This was in keeping with a post-Columbia decision to process the next shuttle in the launch sequence for a quick-response rescue mission if needed.
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But as the end of the shuttle program approached, NASA managers decided an additional cargo flight would be good insurance against problems launching the new commercial cargo ships.
So there is no second shuttle to rescue Atlantis' crew if things go wrong after launch. For that reason, NASA came up with a plan to bring a four-person crew home aboard Russian Soyuz ferry craft during normal space station crew rotations. While it would take a full year for all four Atlantis astronauts to make it home in a rescue scenario, NASA and the Russians believe it could be safely done.
"We've had a chance in training to go through all the various scenarios, contingency deorbits, different kinds of contingency undocking scenarios, and we have actually found procedures that assume you have five or six or seven crew members," Magnus said. "And so these have been very good exercises for us to go through and figure out, OK, so now we only have four people, how are we going to do it?
"The overall workload is pretty high, we've had to do a lot more cross training than normal for a shuttle crew. It actually feels like a station mission because you end up being a little bit more of a jack of all trades and not so much just a pipeline specialist. And that's been a lot of fun, because we get to dabble in each other's areas."
If Atlantis takes off on time Friday, NASA managers may extend the mission one day to give the crew more time to pack up the cargo module with no-longer-needed equipment and trash. As of this writing, the astronauts plan to undock from the station around 2 a.m. on July 18. Landing back at the Kennedy Space Center is expected around 6:56 a.m. on July 20, the 42nd anniversary of Apollo 11's touchdown on the moon.