Shuttle Atlantis fueled-up in hope of launch

Last Updated at 11:07 a.m. ET

KENNEDY SPACE CENTER, Fla. - NASA is "cautiously optimistic" that weather which threatened the launch of Atlantis will pass, allowing liftoff Friday morning for the space shuttle program's 135th and final mission.

NASA managers early Friday cleared engineers to load the shuttle Atlantis with more than a half-million gallons of rocket fuel and to press ahead for an attempt to launch the orbiter as scheduled, at 11:26:46 a.m. Eastern. With a 70 percent chance of stormy weather, mission managers held open the option of standing down later Friday morning, depending on actual conditions.

The updated forecast improves to 60 percent "go" on Saturday with a 50 percent chance of acceptable weather Sunday.

CBS Space Place: The latest news on shuttle mission

Commander Christopher Ferguson, pilot Douglas Hurley, Sandra Magnus and flight engineer Rex Walheim strapped in shortly after 8:00 a.m. to await launch.

"Mike Moses, the mission management team chair, said some people might call it silly to try and play in the rain this morning, but he said we're going to absolutely try for tanking," said countdown commentator Allard Beutel.

Can the U.S. really endure a manned space hiatus?
Shuttle program's end may cost Fla. 9,000 jobs
Video: The last shuttle mission

"But throughout the overnight and closer to the dawn early morning hours, between six and seven o'clock, they'll keep their eyes on the forecast, of course, all night long, but around that time, they'll start getting a very focused look on the weather and see whether it's the right thing to proceed towards launch or whether the forecast really is getting worse. We'll look at perhaps standing down at that point."

Hoping for the best, engineers began pumping super-cold liquid oxygen and liquid hydrogen through transfer lines to pad 39A at 2:01 a.m. Eastern. Routed through Atlantis' main engine plumbing to condition the hardware to cryogenic temperatures, the propellants then flowed into oxygen and hydrogen reservoirs in the shuttle's huge external tank. Three hours later, the tank was full and engineers transitioned to "stable replenish" mode.

Shuttle legacy: Soaring achievements, high costs
Space Shuttle trivia: 8 key facts to remember
9 of the weirdest things that ever flew on the shuttle

Going into the final launch campaign, NASA managers said Atlantis had to be off the ground by Sunday to avoid a conflict with the launch next week of an Air Force navigation satellite.

But agency officials said Thursday it might be possible to extend the shuttle launch window through Monday if the Air Force agreed to delay the satellite launch by one day. But no final decisions have been made.

[realist2010]

God, these wingnuts are annoying. Newsflash: you can't have it both ways.

[wfw3536]

President Kennedy would be so disappointed the we will now have to beg the Russians for a ride into space for at least 3 to 5 years. He started our country on a track to leadership in space and now we will let a number of other countries take the lead. Obama and his administration have billions to waste on another needless war in Libya, yet will not support our space program. How sad.

[Socialization]

Thanks to Obama, NASA will now focus on "global warming"

What a crock of ^%&^%......

We will now pay the Russians billions to take our people into space.

This is a very sad day for America. Thank you to the fool and chief.

[gschmidt57]

This is a sad day for me. I'm a teacher and have told my students that when I was their age there was no space program. The pictures of the planets and objects in space were either very vague or artist conceptions. Now the pictures are actual photographs and humans have walked on the moon. We've seen Nebulae and other galaxies. We now have a concept of the sheer size of the universe. In my lifetime we've learned SO much thanks to the space program and NASA. I feel like crying that this era is over and we will not be able to go into space on our own for such a long time. It's just sad.

[Kt_Swakker]

It's kind of funny how the weather might prevent the final launch.
It's so well timed...almost like someone wants to stop it from happening...

Kidding aside, let's hope that final four make it back safe.
Good luck;
http://www.youtube.com/watch?v=QHrBhtNCvgY