Two people en route to the International Space Station had to make an emergency detour on Thursday after their rocket’s booster suffered a fault. NASA astronaut Nick Hague and Roscosmos cosmonaut Alexey Ovchinin returned to earth in a “ballistic descent” in a Soyuz capsule, with rescue teams deployed to the landing site.

The pair took off from the Baikonur Cosmodrome in Kazakhstan at 4:40 a.m. Eastern time on board a Russian Soyuz MS-10 spacecraft. The launch was intended as a six-hour journey to dock with the station at 10:44 a.m. However, shortly after takeoff, an issue with the booster caused the launch team to abandon the ascent. The pair then undertook a “ballistic descent,” a return to earth at a particularly sharp angle. The capsule landed east of Dzhezkazgan in Kazakhstan, a city around 250 miles north-east of the cosmodrome. A search and recovery team reached the site and brought them onto a helicopter to return to the cosmodrome. The pair are now being transported to the Gagarin Cosmonaut Training Center in Star City, Russia, outside of Moscow. NASA administrator Jim Bridenstine said the pair are in “good condition.”

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The two are working as part of NASA’s Expedition 57, and expected to join the other three members that arrived at the station on June 6, including commander Alexander Gerst from the ESA. The five are tasked with undertaking a number of experiements in biology, earth science, physical science and biotechnology. The launch was Hague’s first space mission, having joined the astronaut corps in 2013.

Ballistic descents can be tense. Astronaut Peggy Whitson was involved in a 2008 incident where the Soyuz capsule returned to earth at staggering speed, with crushing forces over eight times that of gravity pressing the crew for over 60 seconds. The capsule landed around 300 miles from its target in Kazakhstan at an angle over 30 degrees. Whitson, who likened the descent to a car crash, described the incident as “just one big hit and a roll.”

It is unclear what caused Thursday’s failure. Brindenstine said in his statement that “a thorough investigation into the cause of the incident will be conducted,” and “NASA is working closely with Roscosmos to ensure the safe return of the crew.”

The issue has come at a tough time for the International Space Station. Earlier this month, astronauts announced a spacewalk to find out more about a pressure leak that has caused tension between the United States and Russia.