Unsure when U.S. companies will be ready to fly astronauts to the International Space Station, NASA has signed up for six more rides with the Russian space agency, at a cost of $70 million apiece.

The contract covers rides on Russian Soyuz spaceships through June 2017 and includes a price hike of $5 million a seat since NASA’s last purchase. In addition to round-trip rides on Soyuz spaceships, the contract includes training and other support services, NASA said.

Docked! Soyuz Takes Shortcut to Space Station

Russia was left the sole provider of crew transport to the station following the retirement of the U.S. space shuttles in 2011.

NASA is supporting efforts by three companies — Space Exploration Technologies, Boeing and Sierra Nevada Corp — to develop seven-person space taxis that also would be available for commercial service.

BIG PIC: Astronauts Get Epic View of Launching Soyuz

The agency is requesting $822 million in the fiscal year that begins Oct. 1 to keep its so-called Commercial Crew program on track to provide an alternative to Russian flight services before the end of 2017.

Image: The Soyuz launches from Baikonur Cosmodrome in Kazakhstan. Credit: Roscosmos