For the second time in less than three weeks, SpaceX has delivered an astronaut crew to the International Space Station (ISS).
The Dragon capsule flying SpaceX's Crew-4 mission for NASA docked with the orbiting lab today (April 27) around 7:37 p.m. EDT (2337 GMT), just under 16 hours after lifting off atop a Falcon 9 rocket — the quickest-ever crewed Dragon trip to the station. The Dragon and station were sailing 261 miles (420 kilometers) above the central Pacific Ocean as they met in orbit.
The hatches between the Dragon, which is named Freedom, opened at about 9:15 p.m. EDT (0115 GMT on April 28). The Crew-4 astronauts — NASA's Kjell Lindgren, Bob Hines and Jessica Watkins and the European Space Agency's (ESA) Samantha Cristoforetti — then floated aboard the ISS, which will be their home for the next six months or so.
The Crew-4 team joined seven astronauts already on the ISS — NASA's Thomas Marshburn, Kayla Barron and Raja Chari, ESA's Matthias Maurer and Russian cosmonauts Oleg Artemyev, Denis Matveev and Sergey Korsakov. Watkins is making history as the first Black woman to fly a long-duration mission to the station.
But the orbiting lab's population will drop again soon. Marshburn, Barron, Chari and Maurer — the astronauts of SpaceX's Crew-3 mission, which launched last November — are scheduled to depart for Earth in their own Dragon on May 4 or thereabouts.
As its name suggests, Crew-4 is the fourth operational astronaut mission that SpaceX is flying to the ISS for NASA. Its arrival at the station was the second that SpaceX has pulled off in less than three weeks.
On April 9, the Dragon capsule Endeavour reached the orbiting complex with an all-private crew — the first time this had ever been done. Endeavour was flying Ax-1, a mission organized by the Houston-based company Axiom Space, and three of its four crewmembers were paying customers. The fourth was former NASA astronaut, and current Axiom employee, Michael López-Alegría.
Ax-1 was supposed to leave the ISS on April 19, but bad weather in the projected splashdown zone pushed its departure back all the way to Sunday (April 24). This delay, in turn, pushed the launch of Crew-4 back from Saturday (April 23) to early Wednesday morning (April 27).
Ax-1's Dragon occupied the same ISS docking port that Crew-4's is now using. And NASA wanted about two days between Ax-1's splashdown and Crew-4's launch to analyze data and make other preparations, agency officials have explained.
Editor's note: This story was updated at 11:05 p.m. EDT on April 27 with news of Dragon's hatch opening.
Mike Wall is the author of "Out There (opens in new tab)" (Grand Central Publishing, 2018; illustrated by Karl Tate), a book about the search for alien life. Follow him on Twitter @michaeldwall (opens in new tab). Follow us on Twitter @Spacedotcom (opens in new tab) or on Facebook (opens in new tab).