NASA reveals how it will plunge the space station into Earth's ocean

The International Space Station, weighing in at nearly 1 million pounds, will meet a dramatic death.

After breaking apart and largely vaporizing while falling through Earth's atmosphere, the leftover charred chunks will plunge into a remote ocean, and then sink to the seafloor. The grand deorbit of the aging laboratory will happen around 2030, and NASA has revealed how.

The agency picked the successful rocket and space exploration company SpaceX to develop and deliver the "U.S. Deorbit Vehicle" that will attach to the station — which is the largest single structure in space ever built. The hefty $843 million contract requires that the vehicle bring the ISS down to Earth in a controlled, safe manner, specifically avoiding populated regions.

Taking the whole behemoth structure down at once is necessary. A piece-by-piece deconstruction would be highly complex, likely dangerous for crew, and present a host of engineering hurdles.

"The station wasn't designed to be taken apart," Ken Bowersox, the associate administrator of NASA’s Space Operations Mission Directorate, said at a press conference on July 17.

In retiring the space station, NASA is looking ahead to the next decade and well beyond, particularly human missions to the moon and Mars. The agency, for example, plans to return astronauts to the moon as soon as late 2026. Rather than continuing to assume the 24-7 responsibility of running a space station with its international partners, NASA plans to use commercially owned and operated Earth-orbiting modules for ongoing research endeavors.

How to bring the space station back to Earth

The major goal is to use a spacecraft, capable of producing potent thrust, to push the space station down through Earth's atmosphere and result in a controlled splashdown. This means keeping the falling pieces from landing over a wide or unexpected swath of Earth.

"You minimize how far the parts can be distributed," Dana Weigel, the manager of NASA’s International Space Station Program, said at the conference. "A tight and small footprint, that's the goal."

"The station wasn't designed to be taken apart."

To achieve this, Elon Musk–founded SpaceX will build a modified version of its Dragon cargo spacecraft, shown in the first graphic below. (The Dragon craft currently supply both crew and cargo to the space station.) The new, elongated vehicle will need to carry bounties of propellant to move the giant space station — some 16,000 kilograms, or 35,000 pounds, of propellant.

Here's what will generally happen:

- Launch of SpaceX deorbit vehicle: A rocket capable of lifting a heavy payload will be required to ferry the heavy, propellant-packed U.S. Deorbit Vehicle to the space station. It will weigh in the range of some 30,000 kilograms, or 66,000 pounds.

- Space Station drift down: Between 1 to 1.5 years before the end of 2030, NASA will allow the station to naturally lose altitude. (The structure maintains an altitude of some 400 kilometers, or 250 miles, above Earth, but this requires regularly reboosting the station.) Once the station descends to 220 kilometers (137 miles), the SpaceX craft will start thrusting.

- SpaceX deorbit vehicle brings space station down: The SpaceX vehicle will first fire its thrusters to push the space station into the desired orbit around Earth. Then comes the big push. Over the final week, before reentering, the craft will fire multiple burns. Ultimately, the final thrust must be powerful enough to fly the entire station and ensure it terminates in the desired remote location, NASA's Weigel said.

- Splashdown: The remnants of the space station may plummet into the ocean around January 2031.

With an object the size of the space station breaking apart while traveling at blistering speeds, the actual footprint of falling objects — ranging in size from a microwave to a sedan — can't exactly be tiny. But it can be relatively narrow and controlled. If all goes as planned, the debris will fall into a slim band some 2,000 kilometers (1,240 miles) over the ocean. That's why choosing a remote ocean region is essential. Fortunately, oceans dominate Earth's surface.

Enjoy the space station while you still can. The orbiting laboratory makes 16 orbits around Earth every day, and at night you can glimpse the station moving rapidly across the dark sky.

"I'm glad it's going to be flying for a while longer," Bowersox, also a former NASA astronaut, said.