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 US$100 billion (NZ$143b) space station, which orbits about 400km above Earth, arrived on schedule at 10:18pm (AEST) (12:18am Friday NZ time).
Mr 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," Mr Fischer said in a NASA interview before launch.
"You just can't train for that on the ground, so I approach my space-toilet activities with respect, preparation and a healthy dose of sheer terror."
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.
Yurchikhin has made four previous space flights.
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.
Ms Whitson, who flew to the station in November along with Russian cosmonaut Oleg Novitskiy and French astronaut Thomas Pesquet, will remain aboard with Mr Fischer and Mr Yurchikhin until September.