Can the ISS stay in orbit without the support of Russia's engine?

The primary thrust module of the ISS is Russia's.
Brad Bergan
The ISS in low-Earth orbit.NASA

Hours after Russian President Vladimir Putin ordered his military to invade Ukraine on Thursday, the chief of Russia's space program intimated that the International Space Station (ISS) might fall out of the sky.

This scenario, tweeted Director General Dmitry Rogozin of Roscosmos, might happen allegedly because of the new sanctions imposed on Russia by the US and its NATO allies:

"If you block cooperation with us, who will save the International Space Station from an uncontrolled deorbit and fall into the United States or Europe?"

While this sounds like a hyperbolic threat with no grounding in reality — it's not impossible. The ISS is stationed low in low-Earth orbit, making it easier to reach in a flash after a rocket launches. But it also increases atmospheric drag, which slows it down.

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And the slower an object goes in orbit, the closer it comes to re-entry and unspeakably hot plasma. This is why Russia's Progress vehicle is generally used to periodically reboost the ISS to maintain its altitude, saving it with every iteration. If this process were canceled, the ISS would need another way to keep itself aloft.

But, can it?

Russia's space chief hints at ISS crashing into Earth

The ISS moves at incredible speeds to keep above the Earth's horizon as it falls around the surface, in orbit; at roughly 17,500 miles per hour, it circles the planet every 90 minutes. Its average altitude is 248 miles above our heads, but even this high, there are still tiny particles that smack into the surfaces of the ISS, slowing it down with every bump.

Taken together, these particles cause the massive, football field-sized station to lose velocity, which means its orbit decays and approaches re-entry. To combat this, the Russian cargo ship called Progress MS-19 — a Russian-made cargo ship — can perform reboosting maneuvers to keep the ISS in place.

If it were shut down, deactivated, or even parted ways with the ISS, this might reduce the maneuverability of the station, which seems to be what the Roscosmos chief is getting at. "There is also the possibility of a (551-ton) structure falling on India and China. Do you want to threaten them with such a prospect?" continued Rogozin's tweets.

Russia is not happy about new US sanctions

"The ISS does not fly over Russia, therefore all the risks are yours," added Rogozin. "Are you ready for them?" These risks are always there since the ISS is always flying over several continents every 90 minutes. But, while the Progress vehicle is generally the method of reboosting the ISS, it's not the only way.

Other modules on the station have thrusters, which can reboost the ISS if needed. In the past, space shuttles from NASA also performed these maneuvers while docked to the ISS. But this raises the possibility for commercial vehicles — perhaps one of SpaceX's Dragon capsules — to serve as a potential alternative for reboosting the ISS.

But, this probably won't be necessary. Despite new sanctions on Russia by the US, following the former's invasion of Ukraine, NASA has said that cooperation in space between the US and Russia will go on unimpeded.

"NASA continues working with all our international partners, including the State Space Corporation Roscosmos, for the ongoing safe operations of the International Space Station," said an agency spokesperson in a report.

NASA and Roscosmos' partnership will continue on the ISS

"The new export control measures will continue to allow US-Russia civil space cooperation," continued the spokesperson. "No changes are planned in the agency's support for ongoing in orbit and ground station operations."

Unless Russia announces drastic plans to sever its civil partnership with NASA and other space agencies like the ESA, scientific and commercially funded missions on the ISS will continue. There's no denying that when it comes to Russia's substantial shift into wartime policies, not even the exploration of space is off of the table when it comes to idle threats.

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