HOW NASA AND SPACEX WILL BRING DOWN THE SPACE STATION WHEN IT'S RETIRED

SpaceX will use a powerful, souped-up capsule to shove the International Space Station out of orbit once time is up for the sprawling lab.

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NASA and Elon Musk's company outlined the plan to burn the space station up on reentry and plunge what's left into the ocean, ideally at the beginning of 2031 when it hits the 32-year mark.

The space agency rejected other options, like taking the station apart and bringing everything home or handing the keys to someone else.

NASA gave SpaceX a $843 million contract to bring down the station - the biggest structure ever built off the planet.

Here's a rundown on the work and challenges ahead:

WHY GET RID OF THE SPACE STATION?

The space station is already is showing signs of age. Russia and the U.S. launched the first pieces in late 1998, and astronauts moved in two years later. Europe and Japan added their own segments, and Canada provided robotic arms. By the time NASA’s shuttles retired in 2011, the station had grown to the size of a football field, with a mass of nearly 1 million pounds (430,000 kilograms). NASA figures the station will last until at least 2030. The goal is for private companies to launch their own space stations by then, with NASA serving as one of many customers. That strategy — already in place for station cargo and crew deliveries — will free NASA up to focus on moon and Mars travel. NASA could decide to extend the station’s life, too, if no commercial outposts are up there yet. The aim is to have an overlap so scientific research is not interrupted.

WHY NOT BRING IT BACK TO EARTH?