Granddads attach giant support to space station

A view from astronaut Lee Morin's helmet camera shows a view of the international space station during a televised spacewalk Saturday.

(CNN) -- Two space shuttle Atlantis astronauts wrapped up a nearly eight-hour spacewalk Saturday, bolting then refitting a 27,000-pound girder-like structure to international space station Alpha.

Mission specialists Jerry Ross and Lee Morin -- NASA's first pair of grandfathers to take a spacewalk together -- spent four hours of the mission attaching the 13.5-ton, $600 million truss. The structure will be the backbone for future research and construction projects on the exterior of the space station.

Ross, 54, and Morin, 49 -- called the "Silver Team" by their crewmates -- floated out of the bay of the shuttle Saturday morning attaching struts to hold the 43-foot long-truss to the space station's Destiny science lab.

After they attached the struts, Ross and Morin hooked up a cable system that eventually will allow the space station's robotic arm, Canadarm2, to move along a rail along the truss structure, which will be more than 350 feet long when it's completed. NASA calls the rail system the first space railroad.

"All in all, an extremely successful day," beamed Ben Sellari, the mission's launch package manager.

New segments to come

Ross now has logged eight spacewalks and is on a record-setting seventh space flight, said NASA spokeswoman Eileen Hawley. This was the first spacewalk for Morin.

Morin worked from the end of Canadarm2, which was operated by Ellen Ochoa from inside Atlantis. Using the shuttle's robot arm cameras, shuttle commander Mike Bloomfield and pilot Steve Frick watched over the spacewalkers, taking photographs and video. Rex Walheim acted as spacewalk choreographer.

•  Shuttle mission guide  •  CNN Presents: what makes the shuttle fly Movies:  •  Atlantis returns to earth  •  Atlantis leaves space station  •  CNN's Miles O'Brien talks with shuttle crew  •  CNN's John Zarrella previews the mission  •  Watch the launch from Kennedy Space Center  •   NASA animation of completed space station railroad More resources:  •  Cult 3-D model of the space shuttle  •  Milestones in space shuttle history  •  Space: The final frontier for railroads

The Atlantis crew, which moved the massive truss to the space station on Thursday, will conduct a third spacewalk on Sunday to place a $190 million railcar to the truss.

With the addition of new segments in the coming years, the railroad will stretch the length of a football field, allowing the station's robot arm to glide from one end of the station to the other. The new railcar will be tested on Monday.

Atlantis is scheduled to undock from the station on April 17 and land back at Kennedy Space Center two days later.

Better space food

Besides nearly $1 billion in heavy hardware, the shuttle delivered several experiments to the space station. One, named the Photosynthetic Experiment and System Testing and Operation, or PESTO, could lead to better space food.

The wheat growth project, which will remain on the station at least two months, could help scientists determine how to grow grains in space. If it works, space station crew members could someday bake their own bread.

The three space station residents, Russian commander Yury Onufrienko and NASA astronauts Daniel Bursch and Carl Walz, are scheduled to return home this summer. They have been on Alpha 128 days as of Saturday and will have spent a record-breaking 189 days in space before they come home.