Last Launch of Space Shuttle Atlantis Set for May 14
Space shuttle Atlantis rolls out on April 21-22 from the Vehicle Assembly Building at NASA's Kennedy Space Center in Florida.
Credit: collectSPACE. Click here for more photos.

This story was updated at 6:24 p.m. ET.

NASA has cleared the space shuttle Atlantis for its last planned launch on May 14, the first of three final spaceflights planned for the U.S. space agency's storied space plane fleet.

Atlantis is officially set to blast off on May 14 at 2:20 p.m. EDT (1820 GMT) from NASA's Kennedy Space Center in Florida on a 12-day mission to the International Space Station. The shuttle's six-astronaut crew will deliver and install a new Russian science module called Rassvet, which means "Dawn" in Russian.

"We're ready to go next Friday," NASA's shuttle program chief John Shannon told reporters Wednesday. "It's been 15 days since we last landed, nine days until we launch. This is the kind of pace that this team thrives on."

NASA's most recent shuttle mission aboard Atlantis' sister ship Discovery delivered tons of spare parts to the station in April. Discovery landed on April 20, setting the stage for Atlantis' upcoming mission.

Tough mission on tap

Veteran NASA astronaut Ken Ham, a U.S. Navy captain, is commanding the mission, which will mark the 132nd space shuttle flight in NASA history since the reusable space plane fleet began flying in April 1981. It will be the 32nd flight for Atlantis, which made its first spaceflight in 1985.

"This flight has a little bit of everything," Shannon said of Atlantis' last planned spaceflight.

Ham and his crew plan to perform three spacewalks packed with challenging robotic arm work to to install the new Russian module - also known as Mini-Research Module 1 - on the International Space Station, replace old solar array batteries and deliver spare parts for the station and its exterior maintenance robot Dextre.

The station's new Rassvet module is a 23-foot (7-meter) cylinder equipped with a small airlock for experiments that will be attached to an Earth-facing berth on the station's Russian Zarya control module. It weighs about 17,147 pounds (7,777 kg) and will double as a science room and docking port for visiting Russian spacecraft.

NASA has packed the Rassvet module with nearly 1 ton of extra cargo for the station's six-person crew, mission managers said.

Shuttle era's end in sight

Atlantis' final planned mission has the sense of a true beginning of the end for NASA's space shuttle fleet. The orbiter has been flying since Oct. 13, 1985 (the fourth assembled after Columbia, Challenger and Discovery) and has launched several interplanetary and classified missions.

"The whole team has been involved since its first mission in 1985," said NASA launch director Mike Leinbach. "Yeah, she's been around a long time and a lot of us have known that ship for 25 years."

NASA plans to retire its three-shuttle fleet of Atlantis, Discovery and Endeavour in November after nearly 30 years of service. Discovery is slated to deliver a storage closet to the space station in mid-September, with Endeavour to launch a $1.5 billion astrophysics experiment to the orbiting laboratory no earlier than Nov. 26.

These final missions will put the finishing touches on the nearly complete International Space Station, a $100 billion space outpost that has been under construction by 16 different countries since 1998. NASA launched two other shuttle missions earlier this year, in February and April, to continue space station construction.

NASA sans shuttle

After the final space shuttle mission, NASA will have to rely on Russian Soyuz spacecraft to launch American astronauts on round trips to the International Space Station.

In February, U.S. President Barack Obama announced his proposed cancellation of the Constellation program in charge of building NASA's shuttle successor ? the Orion crew capsules and their Ares rockets. Obama has since revived the Orion capsule to launch unmanned and serve as an escape ship for the space station.

Meanwhile, Obama has ordered NASA to support the development of commercial spacecraft capable of launching Americans to the space station.

The U.S. space agency currently has contracts in place with two commercial companies ? SpaceX in California, and Orbital Sciences in Virginia ? to launch unmanned cargo ships to resupply astronauts on the International Space Station in the next few years.

Atlantis, however, will not be mothballed right after its final planned space mission this month. NASA will keep the shuttle spaceworthy and ready to serve as a rescue ship if needed for the final planned shuttle mission ? STS-134 aboard Endeavour ? in the fall.

Some lawmakers have been lobbying to use Atlantis, since it would be ready to come to Endeavour's aid, to fly one last, extra supply flight to the space station, though NASA would have to get approval and funding for that flight by June to make it happen, the agency's space operations chief Bill Gerstenmaier said. That extra mission would likely include just four crewmembers and a payload bay full of station cargo, but no approvals or decisions have been made, he added.

After the last shuttle mission, Atlantis, Discovery and Endeavour are due to be retired to museums for public exhibition.

Leinbach said Atlantis' launch team has never lost focus for this next mission, but there is a bittersweet feeling behind what is expected to be the orbiter's last flight.

"Our mission is coming to an end and our team is coming to grips with that," Leinbach said. "But we're going to do it safely and surely, and we hope to do it next Friday."