How NASA and SpaceX Will Decommission the International Space Station When It Retires

CAPE CANAVERAL, Fla. — SpaceX will use a powerful, booster capsule to push the International Space Station out of orbit once the sprawling laboratory’s allotted time is up.

NASA and Elon Musk’s company on Wednesday announced a plan to burn up the International Space Station when it re-enters the atmosphere and dump what’s left of it into the ocean, ideally by early 2031 when it reaches its 32nd birthday. The space agency has rejected other options, such as dismantling the station and returning everything to Earth or handing over the keys to someone else.

NASA has awarded SpaceX an $843 million contract to demolish the station — the largest structure ever built outside Earth.

Below is a summary of the work and challenges ahead:

The International Space Station is starting to show signs of its age. Russia and the United States launched its first pieces in late 1998, and astronauts moved in two years later. Europe and Japan added their own pieces, and Canada provided robotic arms. By the time NASA retired its spacecraft in 2011, the station had grown to the size of a football field and weighed about a million pounds.

NASA expects the station to 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 several customers. This strategy — already in place for transporting cargo and crew to the station — would allow NASA to focus on travel to the moon and Mars. NASA may decide to extend the station’s lifespan as well, if no commercial sites are established there yet. The goal is to have overlap so that scientific research is not interrupted.

NASA considered dismantling the space station and shipping its parts to Earth, or letting private companies salvage the parts for use in their planned locations. But NASA said the station was never intended to be dismantled in orbit, and that any such effort would be expensive and risky for the astronauts who would be doing the dismantling. There was also no spacecraft as large as NASA’s old shuttles to drop everything on. Another option was to push the empty station into a higher, more stable orbit. But that too was rejected due to logistical issues and the increased risk of space debris.

Visiting spacecraft periodically boost the space station so it stays in an orbit about 260 miles high. Otherwise, they keep dropping lower and lower until they fall out of orbit out of control. NASA wants to ensure a safe reentry over a remote part of the South Pacific or perhaps the Indian Ocean, which means launching a spacecraft that will dock with the station and steer it toward a watery grave.

NASA expects some of the denser pieces, ranging in size from a microwave oven to a sedan, to remain in a narrow debris field 1,200 miles long. NASA and its partners considered using three Russian supply ships for the mission, but a more powerful vehicle would have been required. Industry was invited, and in June, SpaceX won a contract for a deorbit vehicle.

SpaceX plans to use a regular Dragon capsule — the kind that carries supplies and astronauts to the space station — but with a much larger box containing 46 engines and more than 35,000 pounds of fuel. SpaceX’s Sarah Walker said the challenge will be to create a spacecraft strong enough to steer the space station while dealing with the drag and forces caused by increased atmospheric drag during the final descent.

According to NASA, the spacecraft will require a particularly powerful rocket to reach orbit. The capsule will launch a year and a half before the station is scheduled to be destroyed. The astronauts will remain on board as it gradually descends. Six months before the station is destroyed, the crew will abandon the ship and return home. Once the station is down to about 137 miles, Dragon will drop it four days later.

In 1979, NASA’s first space station, Skylab, broke apart, sending debris raining down on Australia and the surrounding Pacific Ocean. The space agency had hoped that one of the first shuttle crews could attach a rocket to control Skylab’s descent or boost its orbit. But the shuttle wasn’t ready by then, and it didn’t make its first flight until 1981. Ground controllers managed to send Skylab into a slow fall, aiming for the Indian Ocean. But some pieces also landed in Western Australia. Russia has more experience with future space stations. Mir operated for 15 years before being directed to a fiery reentry over the Pacific in 2001. Several Salyut stations had died before that.

NASA wants to bring back some of the smaller items from inside the space station for museum display, such as the ship’s bell, wood, patch panels and other memorabilia. Those items could be dropped off on SpaceX supply ships in the next year or two. “Unfortunately, we can’t bring the really big stuff home,” said NASA’s Ken Bowersox. “The emotional part of me would like to try to salvage some of it,” he said, but the more practical approach would be to drop everything off in one devastating blow.