The Kennedy Space Center took receipt of the last space shuttle external fuel tank today, as the massive propellant reservoir for Endeavour's February launch was offloaded from a sea-going barge.

Built by Lockheed Martin in New Orleans, the External Tank No. 122 was damaged when the factory's roof was blown off by Hurricane Katrina in 2005. But workers repaired the hardware and made it worthy for spaceflight again.

The tank was packed aboard the covered barge named Pegasus last week for the 900-mile journey to the Florida spaceport. After arriving at the dock Monday, it was unloaded in a somber-feeling event this morning.

The motorized transporter started rolling at about 9:28 a.m. for the drive across the street to the Vehicle Assembly Building, eventually disappearing into the doorway of the cavernous facility at 9:53 a.m. EDT.

"It's kind of a sentimental day. We're excited to have the tank here and offloaded. It's always such a quick process and gets everybody's adrenaline going. And, at the same, it's kinda of sad because it is the last tank," said Alicia Mendoza, tank and booster vehicle manager at KSC.

Original plans had set this tank aside for use by the shuttle program's STS-335 launch-on-need rescue flight, a mission that NASA never intended to fly. With renewed hope of adding one more International Space Station resupply run to the shuttle manifest, however, NASA officials recently opted to switch assignments and fly ET-122 on Endeavour's STS-134 mission.

Endeavour is scheduled for blastoff February 26 to deliver the Alpha Magnetic Spectrometer particle physics experiment to the space station.

ET-138, once earmarked for Endeavour, arrived at KSC on July 14. Since that tank is the most pristine tank available in inventory, officials decided to keep it for the possible extra shuttle launch next summer. That absolutely-final mission which would have no rescue capability waiting on standby because there won't be any further tanks available.

STS-335 is the emergency response vehicle to bring the Endeavour crew home if there's a major problem with the orbiter. But legislation pending in Congress funds efforts to convert this into STS-135, a real mission by Atlantis to ferry supplies and bolster the International Space Station.

Congress has not yet passed NASA's marching orders, keeping the funding and final decisions in limbo. Shuttle leaders have strived to lay the framework to fly Atlantis on a regular STS-135 with ET-138 next June if, and when, the money arrives.

In any case, all external tank hardware for the remaining launches has been delivered to the Kennedy Space Center.

"It kind of brings home reality that it is the last tank that we will be receiving here at KSC for the shuttle program," Mendoza said.

"So almost kind of nostalgic. We're not going to really see this again."

The foam-covered tanks form the structural core of the space shuttle vehicle for launch and hold the half-million gallons of supercold liquid hydrogen and liquid oxygen consumed by the orbiter's three main engines during the eight-and-a-half-minute trek to space.

They stand 15 stories tall, or 154 feet in length, almost 28 feet in diameter, and weigh about 1.7 million pounds when loaded with propellant. Each have 480,000 separate parts and 38 miles electrical wiring.

The contractor deal for the shuttle tanks was awarded in 1973, the first unit used for ground testing was finished in 1977 and the tank for the maiden shuttle mission was produced in 1979. In all, Lockheed Martin delivered three test tanks and 136 flight tanks over past 37 years.

ET-122 will be hoisted into the checkout cell within the assembly building's High Bay 4 on Wednesday to undergo final pre-flight processing.

Stacking of the twin solid rocket boosters for the mission has been completed aboard the mobile launching platform in High Bay 1. The boosters will be rolled around to High Bay 3 on October 26 in advance of attaching the tank on November 18.

Endeavour is undergoing pre-flight activities at its hangar adjacent. Current plans call for the orbiter's delivery to the Vehicle Assembly Building on January 5 for attachment to the tank and boosters. The fully stacked shuttle vehicle then rolls to pad 39A on January 18.

Liftoff time on February 26 is targeted for 4:04 p.m. EST.

Spaceflight Now photos by Justin Ray

Credit: Justin Ray/Spaceflight Now