A scaled-down, two-man US-Russian crew has arrived at the International Space Station, six hours after blasting off from the Baikonur Cosmodrome in Kazakhstan.
A Russian Soyuz capsule carrying Jack Fischer, 43, and Fyodor Yurchikhin, 58, lifted off with a rare empty third seat with Russia scaling back space station staffing until its long-delayed science laboratory is flown to the orbiting outpost next year.
Fischer and Yurchikhin reached the $US100 billion space station, which orbits about 400 km above Earth, arrived on schedule at 10:18pm (AEST).
Fischer suspects the biggest challenge he faces in his first voyage into space will be learning how to use the station's zero-gravity toilet.
'It's all about suction, it's really difficult,' Fischer said in a NASA interview before launch.
The rookie astronaut will be sharing the station with two seasoned veterans, a Russian cosmonaut on his second flight and a first-time French flier.
Station commander Peggy Whitson, 57, in the midst of her third long-duration mission, is due to arrive on Monday to beat the 534-day record for cumulative time spent in space by a US astronaut.
She's expected to receive a congratulatory phone call on Monday from US President Donald Trump, NASA said on Wednesday.
Whitson, who flew to the station in November along with Russian cosmonaut Oleg Novitskiy and French astronaut Thomas Pesquet, will remain aboard with Fischer and Yurchikhin until September.