46 thrusters are being built for one job: dragging the space station down

SpaceX’s spacecraft for pulling the International Space Station out of orbit will carry 46 Draco thrusters, 30 dedicated to lowering the station’s altitude and 16 reserved for keeping it pointed the right way during the descent. NASA awarded the contract for the vehicle, formally called the U.S. Deorbit Vehicle, to SpaceX in 2024, with a value of up to $843 million covering development alone. The launch itself will be procured separately, and the spacecraft is not expected to fly until close to the station’s planned 2030 retirement.

NASA will own and operate the vehicle once SpaceX finishes building it, a break from how the agency normally buys cargo and crew flights to the station as a commercial service. Ken Bowersox, NASA’s associate administrator for the Space Operations Mission Directorate, said the choice was meant to set up an orderly handoff rather than an improvised one. “Selecting a U.S. Deorbit Vehicle for the International Space Station will help NASA and its international partners ensure a safe and responsible transition in low Earth orbit at the end of station operations,” Bowersox said, adding that the station “remains a blueprint for science, exploration, and partnerships in space for the benefit of all.”

Thirty thrusters point one way, sixteen point another

The 46-thruster arrangement reflects a two-part job. Most of the bank, 30 Draco engines, exists purely to shove the station’s orbit lower and lower until it is on a path toward the atmosphere; the other 16 exist to fight the wobble that a structure the size of a football field naturally develops as its orbit decays and its solar arrays and modules catch uneven amounts of drag. Without a dedicated attitude-control set, the final burn risked tumbling a spacecraft that NASA’s own solicitation documents describe as needing “sufficient redundancy and anomaly recovery capability to continue the critical deorbit burn” on its first and only flight.

That reliability requirement is also why NASA passed over Northrop Grumman, the other finalist and a company that already flies cargo missions to the station. A government source-selection document said Northrop Grumman’s design carried a higher total cost and a weakness tied to certain “solar beta” angles — the geometry between the station’s orbit and the sun — that could have forced NASA into a costly redesign or a launch that limited how flexibly the agency could schedule the deorbit.

Built on a spacecraft with a decade of docking practice

Rather than design an entirely new spacecraft, SpaceX is basing the deorbit vehicle on its Dragon capsule, which has flown cargo runs to the station since 2012 and carried astronauts since 2020. Sarah Walker, director of Dragon mission management at SpaceX, said the vehicle keeps much of that flight history intact, including a docking system NASA has already certified, while adding what she called an “enhanced trunk section” carrying extra propellant tanks, engines, avionics and power generation built specifically for the deorbit mission.

Reusing a proven docking system and avionics stack, rather than inventing new ones, is the same logic the source-selection document credited for making SpaceX’s proposal the more reliable of the two. The vehicle still has to dock with a station that, by the time it flies, will have operated continuously since 1998 under five space agencies — NASA, Russia’s Roscosmos, Japan’s JAXA, the Canadian Space Agency and Europe’s ESA — each responsible for the hardware it contributed.

A months-long fall, not a single push

The reentry itself will not be a quick maneuver. NASA has said the station will first “drift down” on its own for roughly 12 to 18 months after its final crew departs, shedding altitude gradually before the deorbit vehicle performs the burns that send it into the atmosphere. ISS program manager Dana Weigel told reporters the plan calls for astronauts to leave about six months before that final reentry, once the station has fallen to roughly 136 miles, well below its typical operating altitude of about 250 miles and close to the lower limit NASA considers safe for crewed spacecraft.

NASA and the station’s partners have targeted a remote stretch of ocean, similar to the South Pacific zone used for retiring other large spacecraft, as the reentry’s final destination. Administrator Bill Nelson has separately pointed to the scale of the task as the reason the program needs steady funding, describing the station as “as big as a football stadium” and warning that geopolitical uncertainty makes it important to bring the structure down safely on schedule rather than improvise later.

A deadline that assumes nothing else changes first

The 2030 target is not fixed regardless of circumstances. NASA’s own planning documents note the deorbit vehicle could sit in storage into the mid-2030s if the agency decides to extend station operations, an option it says depends on whether commercial successors funded through NASA’s low Earth orbit program are ready to take over research capacity in time. Companies including Axiom Space, Vast, and a Voyager Space-led partnership with Lockheed Martin and Northrop Grumman are all building candidate replacement stations, but none has flown a crewed outpost yet.

Until one of those replacements is operating, the 46 thrusters on SpaceX’s vehicle remain the backup plan NASA is building specifically so a controlled ending, not an uncontrolled one, is available whenever the agency decides the station’s three-decade run is over. The station has hosted more than 3,300 microgravity experiments in that time, run by researchers on the ground who never set foot aboard it, and NASA has framed the deorbit contract as a safe and responsible transition in low Earth orbit rather than an ending — the goal is a planned handover to commercial successors, not a scramble once funding or hardware runs out.

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This article was produced with the assistance of AI and reviewed by Morning Overview editors prior to publication.