NASA astronaut Jack Fischer and his Expedition 51-52 crewmate Russian cosmonaut Fyodor Yurchikhin lifted off on Russia's Soyuz MS-04 spacecraft, atop a Soyuz-FG rocket, from the Baikonur Cosmodrome in Kazakhstan at 3:13 a.m. EDT Thursday, April 20 (1:13 p.m. Baikonur time).
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.
The spacecraft is scheduled to dock to the International Space Station in six hours after the launch, while three previous flights were two days long as the Soyuz-MS spacecraft was undergoing tests. This frees up two Soyuz seats a year. She is scheduled to return to Earth in September. It also protects the option for a contingency spacewalk if problems crop up on the US segment of the station.
Fischer, 43, is an Air Force colonel and former test pilot with a master's degree in aeronautics and astronautics from the Massachusetts Institute of Technology.
A camera in the Soyuz crew module shows commander Yurchikhin, left, and Fisher, right during the climb to space. The new avionics box is arriving aboard Orbital ATK's Cygnus cargo craft on Saturday, April 22.
While it is Yurchikin's fifth mission to the space station, Fischer is on his first.
The ISS laboratory, a rare example of American and Russian worldwide cooperation, has been orbiting Earth at about 28,000 kilometres per hour (17,000 miles per hour) since 1998.
She will return to earth in early September with both Fischer and Yurchikhin after NASA made a decision to extend her stay in space by three months.
Whitson, who on Monday (April 24) will surpass the record for the most time spent in space by an American astronaut - 534 days and counting, in the course of her three flights - recently had her own stay extended.