WASHINGTON — NASA says it’s gearing up for a rapid-fire series of events on the International Space Station that includes the return of a private astronaut mission and the launch of a new long-duration crew of American and European astronauts.
NASA announced April 15 that Axiom Space’s Ax-1 mission to the station, which launched April 8 and docked to the station the next day, will conclude with an undocking scheduled for 10:35 a.m. Eastern April 19. That would lead to a splashdown off the Florida coast at 7:19 a.m. Eastern April 20.
That schedule means the Ax-1 crew will spend a couple extra days on the ISS than originally advertised. Axiom Space originally stated that they Ax-1 mission would last 10 days, including eight at the ISS. Under the current schedule, they will be on the station for 10 days and spend nearly 12 days in space. Neither NASA nor Axiom disclosed the reason for the extended stay, but weather considerations for splashdown have been a major factor for past returns to Earth of ISS crews on SpaceX Crew Dragon spacecraft.
A splashdown on April 20 will allow NASA to proceed with the launch of the Crew-4 mission to the ISS as soon as April 23. NASA held a flight readiness review April 15 for that Crew Dragon mission to the station, approving plans to proceed with a launch attempt April 23 at 5:26 a.m. Eastern from Kennedy Space Center’s Launch Complex 39A.
Crew-4 will deliver NASA astronauts Kjell Lindgren, Bob Hines and Jessica Watkins, and European Space Agency astronaut Samantha Cristoforetti, to the station for a mission lasting to at least September. NASA plans to return the four Crew-3 astronauts currently on the station — Raja Chari, Thomas Marshburn and Kayla Barron of NASA and Matthias Maurer of ESA — about five days after the arrival of Crew-4.
Kathy Lueders, NASA associate administrator for space operations, said in a call with reporters after the Crew-4 flight readiness review that it was a “busy time ahead” for the station. “We all talked about how we’re needing to stay vigilant and we’re doing this one step at a time.”
That vigilance includes at least 48 hours between the Ax-1 splashdown and the Crew-4 launch to perform post-flight reviews. “Our team has been flight-following that mission,” said Steve Stich, NASA commercial crew program manager, calling the Ax-1 spacecraft “very clean” in terms of no technical issues. “We’ll have time to do a review between that landing and the Crew-4 launch.”
Joel Montalbano, NASA ISS program manager, said NASA will use the same tracking assets, such as an aircraft equipped with an infrared camera, to monitor the Ax-1 splashdown as it would for a NASA commercial crew mission.
“We follow all the Dragon flights,” Stich said, including cargo and private astronaut missions. “We’ll follow that flight all the way to splashdown.”
The upcoming Crew-4 launch comes as NASA continues to work on the countdown rehearsal for the Space Launch System at neighboring Launch Complex 39B. At a briefing earlier April 15, SLS managers said the earliest they would be ready to attempt another tanking of the rocket and go through a practice countdown is April 21, pending work to track down and fix a hydrogen leak found in the latest test April 14.
However, Lueders said the Crew-4 launch would have priority on the range over any SLS tests. “Jim Free and I early on in this flow agreed that getting our crews up to the ISS is really the most important mission out there,” she said, referring to the associate administrator for exploration systems development. “There’s a difference between a test and getting a crew on orbit to maintain the on-orbit vehicle and get Crew-3 down.”
NASA does have some slack in the schedule if Crew-4 is delayed. Stich said they want to have Crew-3 back by May 10, when a “beta cutout” caused by sun angles restricts undocking operations at the station. However, he added that the Crew-3 spacecraft is in good health and rated to remain at the station until mid-June.
A return of Crew-3 by May 10, though, would allow NASA and Boeing to proceed with a second uncrewed test flight of the CST-100 Starliner commercial crew vehicle, currently scheduled for launch May 19. That will be followed by a SpaceX cargo Dragon mission to the station in June.
At a separate media event April 15, the four Crew-3 astronauts said they were looking forward to returning to Earth soon but enjoying their time on the station. That included working with the four Ax-1 private astronauts.
“It’s been a really exciting week,” said Marshburn of the Ax-1 crew. “We’ve had a lot of fun showing them around, showing them how to live and work in the space station. They’ve been great crew mates. They’ve been very kind and gracious with us as well. So, it’s been a wonderful week.”
Chari added that it has not been crowded on the station with 11 people on board, including the Crew-4 and Ax-1 crews and three Russian cosmonauts. “This is definitely the dawn of a new era.”