A Russian rocket transporting American astronaut Nick Hague and Russian cosmonaut Alexey Ovchinin to the International Space Station suffered a malfunction shortly after launch on Thursday. The two-man crew separated their capsule from the malfunctioning rocket and initiated a “ballistic descent” back to the surface of the earth.

Ovchinin, the mission commander, made the decision to separate the Soyuz capsule a bit more than three minutes into the rocket’s flight, suggesting that the malfunction occurred after the Soyuz FG rocket separated from its first stage boosters and engaged the second stage. In footage captured inside the Soyuz capsule, the two men can clearly be seen shaking violently as a result of the malfunction. The Russian translator can be heard saying, “failure to booster” twice, before confirming that the capsule had separated. Thus far, what exactly went wrong remains a mystery.

NASA Astronaut and engineer Leroy Chiao posted this analysis to twitter:

The ride back to earth after the abort has been widely glossed over by the international media thanks, in no small part, to the survival of the two-man crew. However, a ballistic descent of this type is no laughing matter. Hague and Ovchinin likely experienced something near to 8 Gs (or eight times the earth’s gravity) as they flew in a barely controlled and extremely steep descent back to earth. Unlike normal Soyuz “controlled reentry” landings, ballistic reentry involves using a steep descent to maximize the air resistance to (hopefully) create enough drag to make landing survivable.

Watch: NASA astronaut Nick Hague explains what it was like to survive aborted Soyuz rocket launch

Read Next: Watch: NASA astronaut Nick Hague explains what it was like to survive aborted Soyuz rocket launch

American record-setting astronaut Peggy Whitson also survived a ballistic reentry in a Soyuz capsule — one of only four to ever occur.

“It was just one big hit and a roll,” she said at the time. “I felt my face getting pulled back. It was hard to breathe, and you kind of have to breathe through your stomach, using your diaphragm instead of expanding your chest.”

Search and rescue teams were dispatched immediately upon Ovchinin ordering the mission abort. The two men were recovered shortly after landing and transported to the Gagarin Cosmonaut Training Center in Star City, Russia for medical evaluation.

“NASA astronaut Nick Hague and Russian cosmonaut Alexey Ovchinin are in good condition following today’s aborted launch,” NASA Administrator Jim Bridenstine tweeted from Kazakhstan. “I’m grateful that everyone is safe. A thorough investigation into the cause of the incident will be conducted.”

Although this incident had a happy ending, with both crew members reportedly in good health, it raises a number of questions about operations aboard in the International Space Station, as well as U.S. and Russian cooperation in future space endeavors. Historically, the United States and Russia have managed to keep diplomatic tensions out of joint space endeavors, but Vladimir Putin’s decision to appoint Dmitry Rogozin as the new head of Roscosmos has complicated things. Rogozin is under U.S. sanctions for his role in the illegal military annexation of Crimea in 2014, meaning he is not authorized to travel to the United States, even for official state duty as the head of Russia’s space program.

As a result, NASA Administrator Jim Bridenstine is currently in Russia to meet with Rogozin, in part to discuss a recent slew of problems Roscosmos has suffered. Currently, Russia’s Soyuz rockets are the only platforms on the planet rated to carry human passengers. If NASA has concerns about the safety or reliability of the Soyuz platforms as a result of Thursday’s incident, it stands to reason that Americans may not reach space again until private corporations like SpaceX begin ferrying them.

Tensions are particularly high after a hole that appeared to be drilled through the side of a Soyuz space capsule was discovered by the crew of the International Space Station a few weeks ago. Rogozin launched an investigation into the incident but said that Russia is not currently ruling out the possibility of sabotage.

As for the International Space Station — astronaut Nick Hague and cosmonaut Alexey Ovchinin were slated to remain on board for six months upon their arrival. It is now unclear how the space station will remain manned through that window of time.

You can watch the dramatic launch and abort, originally broadcast on Russian television, in the video below: