Roscosmos cosmonaut Alexander Misurkin and spaceflight participants Mr Maezawa and Mr Hirano lifted off aboard the Soyuz MS-20 spacecraft and docked to the ISS early morning on Wednesday, Nasa said in a blog post.
This is the first visit to the orbiting outpost by self-funded space tourists in over a decade.
Mr Hirano will be participating in research designed to increase the understanding of the impact of spaceflight on the human body with important biomedical data collected before launch and upon return to Earth, during his 12-day stay aboard the ISS.
The ISS crew of 10 people gathered at the Russian segment for a brief welcoming ceremony for the tourists where they spoke on a live video connection to family.
The three will document their daily life aboard the ISS for Mr Maezawa’s YouTube channel.
“I would like to look at the Earth from space. I would like to experience the opportunity to feel weightlessness,” Mr Maezawa said at a pre-flight conference on Tuesday.
For this trip, Mr Maezawa booked seats for himself and Mr Hirano via the US-based company Space Adventures, which arranges rides for wealthy people.
While the exact ticket costs are unknown, Space Adventures has said they are in the range of $50-60m (£38-45m).
A consortium of scientists, who are part of the Translational Research Institute for Space Health (TRISH), plan to assess research-grade electrocardiogram (ECG) activity, movement, sleep, heart rate and rhythm and blood oxygen saturation data, as well as a set of other information collected during the 12-day trip.
“The work we are doing to study the impact the human body faces in space will help future space explorers safely travel beyond Earth. TRISH is grateful for Mr Hirano’s participation in this research to further human space exploration,” Dorit Donoviel, TRISH executive director and professor of space medicine at Baylor, had said in a statement before the launch.
TRISH is a part of Nasa’s Human Research Programme and is a cooperative agreement with a consortium led by Baylor College of Medicine and includes the California Institute of Technology in Pasadena and Massachusetts Institute of Technology in Cambridge, according to the space agency’s website.
Mr Maezawa, the founder of Zozo, a Japanese online fashion retailer, has also booked a trip with Elon Musk’s SpaceX for a journey around the Moon set for 2023.
This mission, named “Dear Moon,” is expected to take three days to fly to the Moon, loop behind it in orbit, and then spend three days returning.
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