The Space Station Is Always Falling. Here's What Keeps It Up.

The International Space Station is falling right now. It has been falling, slowly and continuously, for its entire 26 years in orbit, and the only reason it hasn't come down is that cargo ships keep giving it a push back up.

Why does the space station need to be reboosted?

The ISS flies roughly 370 to 460 kilometers above Earth, low enough that the atmosphere hasn't actually run out. It's thin almost beyond measuring, but individual molecules of oxygen and nitrogen still collide with the station's enormous surface area, its modules, trusses and especially its solar arrays, creating a faint, continuous braking force called atmospheric drag, according to space-industry outlet New Space Economy, which cites NASA's own orbital references. That drag bleeds off orbital energy and steadily lowers the station's altitude.

Left alone, the problem gets worse, not better: a lower orbit runs into denser air, which increases drag further, which lowers the orbit faster. NASA's transition-plan documentation, cited by New Space Economy, says the ISS would naturally reenter the atmosphere within roughly one to two years without any reboosts at all, depending on solar activity. Reboosting counters that by adding a small amount of forward speed. Engine burns from a docked spacecraft push the station along its direction of travel, and in orbital mechanics, more forward speed raises the opposite side of the orbit. It isn't a vertical lift. It's closer to how a slingshot works.

How often does the ISS get reboosted?

Roughly every few weeks to a few months, depending on solar activity and traffic scheduling, according to spaceflight blog Sentinel Mission. Recent burns show how routine, and how brief, the maneuver actually is. On Nov. 19, 2025, a docked Progress 93 cargo craft fired its engines from the aft port of the Zvezda service module for 14 minutes and 7 seconds, lifting the station's altitude by one mile at apogee and 2.3 miles at perigee. On April 16, 2026, the same spacecraft fired again for just over five minutes, this time to set up the station's orbital phase for the arrival of Progress 95.

Russian Progress spacecraft have handled most routine reboosts for decades because their docking port lines up almost exactly with the station's direction of travel, which wastes less thrust. But the job no longer belongs to Russia alone. SpaceX's Cargo Dragon demonstrated a boost-kit capability during its CRS-33 mission: a test burn on Sept. 3, 2025 raised the station about one mile at perigee, and a longer burn on Dec. 29, 2025, more than 19 minutes on two Draco engines, added 1.6 miles at apogee and 1.9 miles at perigee. Dragon performed six reboosts in total during that mission. Northrop Grumman's Cygnus spacecraft completed its own first limited reboost back on June 25, 2022, a five-minute-and-one-second burn that nudged the orbit by a tenth of a mile at apogee and half a mile at perigee.

What happens if the ISS is never reboosted?

The station keeps losing altitude until reentry becomes unavoidable, and unlike the deliberate, controlled reentry NASA is now planning for the station's eventual retirement, an unmanaged descent would be neither timed nor targeted. That's precisely why routine reboosting exists alongside a much larger engineering conversation about the station's age. Reboost burns are gentle compared to launch, but engineers still log every one of them against the station's certified structural limits, a discipline that matters more each year on hardware that has been aloft since core modules Zarya and Unity launched in 1998.

The same physics that requires reboosting also explains why keeping anything in low Earth orbit is a maintenance problem, not a one-time achievement, a pattern that shows up across why satellites fall from orbit and NASA's race to save one and in the tracking system behind the CRASH Clock's measure of how close satellites really are to disaster. NASA has already selected SpaceX to build the dedicated U.S. Deorbit Vehicle that will eventually bring the ISS down on purpose, on a schedule, rather than let atmospheric drag decide the timing on its own. Until then, the reboosts continue — a few minutes of thrust every few weeks, quietly undoing what the atmosphere does to the station every single day.