With 4 Shuttle Flights Left, Station is 98 Percent Complete

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NEW YORK — With the successful landing of the Space Shuttle Endeavour Feb. 22, the international space station is on the verge of completion after $100 billion and 11 years of construction. NASA plans just four more missions to wrap up its few remaining station deliveries.

For Endeavour, in particular, the evening landing at NASA’s Kennedy Space Center in Florida marked the beginning of the end. The spacecraft is the youngest of NASA’s three aging space shuttles, and engineers quickly began working to prepare it for one final spaceflight in July.

“We’ll go into that with our heads held high,” shuttle launch director Mike Leinbach said after the landing. “It’s a little bit [of a] sad note, but a great ending to a great mission, and we’re looking forward to the next one.”

Endeavour’s 14-day mission delivered a seven-window observation deck and a new room to the international space station.

With the new additions — NASA’s final major pieces for the space station — the orbiting laboratory is 98 percent complete.

NASA plans to retire its three space shuttles — Discovery, Atlantis and Endeavour — by the end of September. After that, American astronauts will have to hitch rides to the space station on Russian Soyuz spacecraft.

In February, U.S. President Barack Obama canceled NASA’s Constellation program, responsible for building new spaceships and rockets to replace the shuttle fleet. The administration is banking on the rise of commercial spacecraft capable of ferrying astronauts to orbit. NASA has contracts in place with companies to provide unmanned launches to deliver cargo to the space station.

Leinbach said there is a “whole series of lasts” coming, and he feels for the engineers responsible for priming each of those final steps.

Endeavour’s STS-130 mission was NASA’s 130th shuttle mission since the fleet began flying in 1981, and the 24th flight for Endeavour.

When the first station crew of three astronauts took up residence in November 2000, the outpost was made up of just three modules. Now, its external truss segments span the length of a football field and the station can easily be seen from Earth by the unaided eye.

The station can now support permanent crews of six astronauts. It has three airlocks and 12 rooms, counting the new bay window compartment delivered by Endeavour. It has enough living space to rival the cabin of a Boeing 747 jumbo jet.

The dome-shaped observation deck gives astronauts stunning panoramic views of the Earth. It also doubles as a lookout during robotic arm operations.

The new room, called Tranquility, will house life-support systems and exercise equipment.

Both compartments were built for NASA by the European Space Agency. Together, they cost nearly $409 million and boosted the space station’s mass to nearly 362,873 kilograms.

The final four shuttle missions include several spare-parts delivery flights as well as the installation of a small Russian module and a $1 billion experiment called the Alpha Magnetic Spectrometer.

Next up on the launch pad will be the Space Shuttle Discovery, the oldest orbiter after Columbia and Challenger, both of which were lost in fatal accidents. Discovery is due to launch April 5 to deliver new science experiment gear and spare parts to the space station.

Mike Moses, NASA’s shuttle integration manager, said Endeavour’s successful mission is a great start to the space shuttle era’s final year. The shuttle launched one day late due to cloudy weather. “We’re off to a great running start with the year here,” Moses said.

Cold weather in Florida has delayed Discovery’s flight from its original March 18 launch target to April. However, barring an unexpected setback or major payload delivery delay, NASA should be able fly all four remaining missions by the end of September as planned, Moses said.

Still, there is a sense of loss for the space shuttle fleet.“The people fall in love with the machines, and it’s going to be hard to let them go,” Leinbach said. “We’re professional about it, so we’re going to prepare and process that last mission, and we’ll move on.”