SpaceX has successfully static fired a Falcon 9 rocket scheduled to launch another batch of NASA and ESA astronauts after the crew “completed a full rehearsal of launch day activities.”
However, poor weather and strict operational limits have prevented a separate group of private astronauts known as Axiom-1 from boarding a different Crew Dragon and returning to Earth as planned, delaying Crew-4 from April 23rd to no earlier than (NET) April 26th.
In a twist of fate that can be partially blamed on SpaceX, the ISS only has two docking ports (parking spots) capable of receiving Crew Dragon. NASA technically contracted Boeing to build three such ports but the first was destroyed when Falcon 9 failed catastrophically while attempting to launch Cargo Dragon’s CRS-7 space station resupply mission in June 2015. For unknown reasons, close to seven years later, NASA still hasn’t so much as attempted to build or launch a replacement docking adapter. As a result, most NASA cargo or crew missions have become more sensitive to the delays of other spacecraft and missions as NASA and its providers attempt to juggle a packed manifest with just two parking spots.
The lack of a third docking port and constraints on the use of one of the two remaining ports has forced NASA to repeatedly undock and redock Crew Dragons to set the stage for new arrivals and also limits the number of launch opportunities available to certain crew and cargo missions. Now, following the start of a series of Axiom Space Crew Dragon missions carrying private astronauts to the space station, NASA has yet another class of visiting vehicle to plan around.
Somewhat unsurprisingly, the close proximity of Axiom-1 and Crew-4, the presence of just two docking ports, and Crew Dragon’s fairly strict operational limits have combined to create added pressure and cause a mess of delays. Following Axiom-1’s April 8th launch, the Ax-1 Crew Dragon joined Crew-3’s Crew Dragon at the International Space Station (ISS).
To ensure a continuous US/European presence aboard the station amid Russian threats against the outpost it co-operates with NASA and other international partners, Crew-3 can’t (or shouldn’t) leave until Crew-4 arrives. Crew-4 thus can’t launch until Axiom-1 departs and frees up a docking port. Originally planned to spend around 10 days in space after their April 8th launch, the Axiom-1 crew is still aboard the ISS 12 days later after concerns about safe recovery weather have repeatedly delayed their departure. Only late on April 20th did NASA, SpaceX, and Axiom settle on a new undocking date for Ax-1, slipping from the latest target of April 20th to no earlier than 8:35 pm EDT (00:35 UTC) on April 23rd with a splashdown now on April 24th. As a result, Crew-4 has been delayed to April 26th – 11 days after the original April 15th target.
It’s unclear what particular weather concerns caused such a delay; if this is a “perfect storm” event and just a matter of bad luck; or if this situation was made worse (or possible) by apparent Crew Dragon recovery restrictions that require extremely calm seas. Regardless, it’s hard to imagine that NASA and SpaceX will attempt another private space station mission so close to an operational Crew launch after the challenges and close to two weeks of delays Axiom-1 has caused Crew-4.