The external tank for the final planned shuttle mission was rolled out of Lockheed Martin's Michoud Assembly Facility Thursday to begin the 900-mile voyage to the Kennedy Space Center for launch next February.

Wrapping up 37 years of tank deliveries in support of the shuttle program, Lockheed Martin employees, joined by senior NASA managers, lawmakers and company officials, gathered for a departure ceremony to mark the completion of ET-138. Many of the workers were wearing black T-shirts with the words "Finish Strong" on the back.

"Everyone of you should be proud, as I know you are," said Joanne Maguire, Lockheed Martin executive vice president for space systems. "The accomplishments of the external tank team are the stuff of legend. The challenges and hardships you've overcome have been monumental and our respect for, and gratitude to you, is immeasurable.

"We have two more missions to fly before we bring to a close one of America's most iconic human spaceflight programs. I have every confidence this team will rally together, as they have through thick and thin, to safely and successfully conclude the space shuttle program even as we prepare for what comes next. Whatever that might be. This team is a team we have counted on for decades to do the heavy lifting, figuratively and literally, and it is my firm commitment and hope that we can continue to rely on you going forward."

The tank will travel by barge across the Gulf of Mexico from New Orleans, around the tip of Florida and up the coast to the Kennedy Space Center where it will be prepared for launch Feb. 26 with the shuttle Endeavour.

Sen. David Vitter, a Louisiana Republican, attended the ET-138 rollout and took the opportunity to criticize the Obama administration's post-shuttle space policy, which includes a shift to commercial manned launch operations and a multi-year gap between the shuttle's retirement and the debut of whatever spacecraft replaces it.

"I for one am extremely concerned about those proposals and plans for NASA," Vitter said. "Because quite frankly, if we stay on that radical new path - and it is a radical new plan for NASA - it will mean two things. Here at Michoud, it will turn that gap into a cliff, and I'm fighting to prevent that from happening. And for the nation, I truly think it will give up our leadership in manned spaceflight, probably for the rest of our lifetimes.

"Now, call me old fashioned, but I think NASA should be about space flight," Vitter said, prompting applause. "Call me old fashioned, but I don't want NASA just to be the fourth or the fifth or the sixth climate change research agency. And call me old fashioned, but I certainly don't want its primary purpose to be outreach to Muslim countries to make them feel good about their scientists."

The last comment, loudly cheered by the assembled workers, was a clear dig at NASA Administrator Charles Bolden, who told the Al-Jazeera network last week that President Obama had told him that one of NASA's primary objectives was to "reach out to the Muslim world and engage much more with dominantly Muslim nations to help them feel good about their historic contribution to science, math and engineering."

Vitter concluded his remarks by saying "the good news is there are many folks in Congress, Republicans and Democrats, who feel as I do. So this battle is not over by a long shot."

While Endeavour's flight is the last officially planned shuttle mission, NASA plans to prepare the shuttle Atlantis for launch on a possible rescue flight in case of any major problems with Endeavour that might prevent a safe re-entry.

The tank for the stand-by mission, ET-122, was damaged in Hurricane Katrina, but it has since been repaired and is in the final stages of assembly. Shipment to the Kennedy Space Center is expected in September.

NASA managers are studying the possibility of actually launching Atlantis on a final space station resupply mission if a rescue flight is not needed. By launching the shuttle with a reduced crew of four, Russian Soyuz spacecraft could be used for possible rescue duty, eliminating the need for a second shuttle stand-by mission.

Shuttle program managers are studying cost projections and potential savings to see how far they can stretch current funding. The shuttle program normally costs about $200 million a month to operate and even with projected savings, sources say additional money almost certainly will be required to cover a final mission with Atlantis.

A decision is expected by early August.