For the third time, astronauts are ready to dock a private rocket trip into space.

SpaceX, the rocket company founded and operated by Elon Musk, is scheduled to launch its latest mission for NASA early on Friday, bringing two American, one Japanese and one French astronauts to the International Space Station. This will be a continuation of the Space Agency’s successful efforts to turn the business of placing humans into low-earth orbit to the private sector.

SpaceX conducted a demonstration mission with two NASA astronauts, Bob Behnken and Doug Hurley, a year ago. The two men then splashed into the Atlantic in August. They traveled in the same capsule called Endeavor that will fly on Friday.

Months later, SpaceX carried out what NASA called the first routine missions for the Crew Dragon spacecraft with four astronauts on board. That mission, Crew-1, was launched in November and the astronauts are still on the station.

Now comes the second operational mission known as Crew-2.

The launch is scheduled for Friday at 5:49 a.m. Eastern Time from the Kennedy Space Center in Florida. Both NASA and SpaceX will be offering marathon coverage of the mission starting at 1:30 a.m., from the astronauts’ lawsuit to launch.

The Crew-2 launch was set for Thursday morning and the weather on the launchpad was favorable. Mission managers also had to consider the Atlantic conditions under which the Crew Dragon capsule splashed down if something went wrong at launch. There NASA and SpaceX decided that the winds and waves were too high.

The Friday morning weather report predicts a 90 percent chance of favorable conditions at the Kennedy Space Center. Conditions in the Atlantic are expected to be better than on Thursday.

Hours before take-off, the astronauts, with the help of technicians, begin putting on their trademark SpaceX spacesuits. Then they say goodbye to their families and head to the Launchpad in Tesla Model X SUVs (a bit of cross-marketing between SpaceX and Tesla, both operated by Mr. Musk).

After arriving at the launchpad, the astronauts climb into the capsule and work with mission control for hours to confirm that their systems are ready to fly.

The launch is timed to coincide with the space station’s orbit over Florida. When the capsule reaches orbit, it will be right behind the space station, but will move faster in a lower orbit. This allows the Crew Dragon to catch up to dock at 5:10 a.m. on Saturday.

During their 23 hours of flight, the astronauts take off their spacesuits, eat a meal or two, rest and inform about mission control.

Once the capsule is docked at the station – an automated process – it takes a few hours to make sure there are no air leaks before the hatches open and the Crew 2 astronauts disembark.

The Crew 2 astronauts are expected to spend six months on the International Space Station.

Akihiko Hoshide from JAXA, the Japanese space agency. Mr. Hoshide, 52, has already made two trips into space. He was a member of the crew of the space shuttle Discovery in 2008 and spent four months on the space station in 2012.

Shane Kimbrough NASA. Mr. Kimbrough, 53, is the commanding officer for Crew-2. He has made two previous space trips, once on the space shuttle Endeavor in 2008 and then spent more than six months on the space station from October 2016 to April 2017.

K. Megan McArthur NASA. Dr. McArthur, 49, flew the Space Shuttle Atlantis in May 2009 on its final mission to renovate and upgrade the Hubble Space Telescope. During this mission, Dr. McArthur, a trained oceanographer, uses the shuttle’s robotic arm to grab the telescope and place it in the hold.

Dr. McArthur is married to Bob Behnken, one of the astronauts who traveled on the first astronaut flight of the same SpaceX capsule last year. She will sit in the seat he occupied during that flight.

Thomas Pesquet the European Space Agency. Pesquet, 43, previously spent six months on the space station from November 2016 to June 2017, overlapping most of his stay with Mr. Kimbrough. He is from France.