WASHINGTON — NASA and Roscosmos have extended a seat barter agreement for flights to the International Space Station into 2027 that will feature longer Soyuz missions to the station.
NASA announced April 3 that astronaut Chris Williams had been assigned to the Soyuz MS-28 spacecraft scheduled to launch to the ISS in November, joining Roscosmos cosmonauts Sergey Kud-Sverchkov and Sergei Mikaev. The announcement came ahead of the April 8 launch of fellow astronaut Jonny Kim to the ISS on Soyuz MS-27.
The announcement of the Williams flight assignment was the first public indication by NASA that it has extended an agreement with Roscosmos for “integrated crews” on Soyuz and commercial crew flights to the ISS. Under the no-exchange-of-funds barter agreement, NASA astronauts fly on Soyuz spacecraft and Roscosmos cosmonauts fly on commercial crew vehicles to ensure that there is at least one American and one Russian on the station should either Soyuz or commercial crew vehicles be grounded for an extended period.
Last fall, the future of that seat barter agreement was unclear after Roscosmos released crew assignments for the Soyuz MS-28 and MS-29 missions that included only Russian cosmonauts. Bill Nelson, NASA administrator at the time, said he expected that agreement to be extended “in due course” but offered no details on the timing to do so.
Reports in Russian media in January indicated that the extension had been completed, but at the time NASA declined to confirm it, with a spokesperson telling SpaceNews that the agency would provide an update on the seat barter agreement “in the coming weeks.”
NASA confirmed, after the Williams announcement, that it had extended the integrated crew agreement with Roscosmos into 2027. “NASA and Roscosmos have amended the integrated crew agreement to allow for a second set of integrated crew missions in 2025, one set of integrated crew missions in 2026, and a SpaceX Dragon flight in 2027,” a spokesperson told SpaceNews April 9.
One change with the agreement is the cadence of Soyuz missions. While Roscosmos had been flying Soyuz missions to the ISS every six months, missions starting with Soyuz MS-27 will spend eight months at the station. The NASA announcements about both Kim’s launch to the station and the assignment of Williams to the next mission both mentioned they would each spend eight months at the ISS.
Neither NASA nor Roscosmos offered a reason the change, which means that Roscosmos will fly one fewer Soyuz missions over a two-year period: three instead of four. NASA is averaging commercial crew missions every six months, with some variation due to activity of other visiting vehicles to the station.
Another uncertain aspect of the agreement is if it will include future Boeing Starliner commercial crew missions to the ISS. Last May, NASA officials said it was unlikely Roscosmos would include a cosmonaut on Starliner-1, the first crew rotation mission by that spacecraft, just as Roscosmos waited until 2022 to start flying cosmonauts on Crew Dragon.
NASA has yet to formally schedule Starliner-1, having pushed it back several times because of delays in the Crew Flight Test mission by the spacecraft and subsequent investigation into the problems encountered during that mission. One of the astronauts assigned to Starliner-1, Mike Fincke, was recently reassigned to the Crew-11 mission launching as soon as July on Crew Dragon.