WASHINGTON — An exercise countdown for NASA’s Space Launch System could delay the launch of a commercial mission to the International Space Station, a move with potential knock-on effects for other missions to the station.
NASA, Axiom Space and SpaceX officials said on March 25 that they have successfully completed a flight readiness check for the Ax-1 mission to the ISS. A Falcon 9 is scheduled to launch the Crew Dragon spacecraft on this mission April 3 from Launch Complex 39A at Kennedy Space Center.
However, NASA also plans to conduct a wet dress rehearsal (WDR) of the first Space Launch System from neighboring Launch Complex 39B that day. During this test, the rocket is loaded with liquid oxygen and liquid hydrogen propellants and undergoes a practice countdown, stopping at approximately T-10 seconds, just before the core stage’s RS-25 engines would ignite.
NASA, at a briefing after reviewing Ax-1’s readiness to fly, said that the Artemis 1 WDR would have priority, provided both stay on their current schedules. “Right now, Artemis 1 Wet Dress has the reach. Our plan is to get this done as soon as possible,” said Kathy Lueders, NASA’s deputy administrator for space operations. “We still have 8 to 10 days of processing time on either side to get there.”
She said there have been daily meetings between the NASA and SpaceX teams working on their respective missions, with another “checkpoint” on March 28. “From a planning perspective, it made a lot of sense for us to just get the wet-clothing mission done,” she said, “and then allow ourselves time for back-to-back launch attempts.”
If Artemis 1 WDR goes ahead as planned, the earliest Ax-1 could launch is April 4 at 12:50 p.m. Eastern Time. Lueders said one of the factors driving the separation between the two missions are raw materials, such as nitrogen gas, that would be needed at both launch sites. At one point, she said that might require a two-day segregation between missions, but that teams were working to shorten that to one day. “If we take off the wet dress on the 3rd, we could possibly start on the 4th.”
Like other Crew Dragon missions to the ISS, Ax-1 has an immediate launch window once a day. A complicating factor is NASA crew’s next rotational mission to the ISS, Crew-4, which will launch on another Crew Dragon on April 19 at the earliest.
“We have a bit of a buffer” in the schedule, said Dana Weigel, NASA ISS deputy program manager. NASA wants two days between Ax-1’s splashdown and Crew-4’s launch so Ax-1 can still launch on April 7 for its 10-day mission without impacting Crew-4’s launch date, she said .
However, a complicating factor is the weather at the splash site, which could delay Ax-1’s return. “I think the real key for us is to get out as early as possible. We’ll want to take those early opportunities, assuming we have good starting weather because we don’t know what we’ll get to undock at the back end,” said Weigel.
Any delays in Ax-1’s return after April 17 would cause Crew-4 to slip up day-to-day. NASA wants the Crew-3 spacecraft Crew Dragon, currently on station, with its four astronauts by May 10, about six months after its launch and after a five-day handover between Crew-3 and Crew-4. let return.
However, the schedule conflict is the only major problem with the Ax-1 mission. This mission, the first of Axiom Space’s series as a precursor to adding a commercial module to the ISS, will carry a former NASA astronaut, Michael López-Alegría, and three customers: Larry Connor, Mark Pathy and Eytan Stibbe. All have completed training and are in quarantine ahead of launch, said Michael Suffredini, the company’s president and chief executive officer.
The Ax-1 mission will be the first for a Dragon spacecraft since a Dragon cargo ship crashed on Jan. 24 after one of its four main parachutes deployed slowly. A similar “trailing” parachute was observed during the Crew-2 splashdown in November.
Bill Gerstenmaier, SpaceX’s vice president of build and flight reliability, said the company investigated the trailing parachutes but couldn’t find a cause for the problem, adding that the safety of either splash would not be compromised.
“We couldn’t find anything that turned out to be the cause,” he said. “We spent a lot of time looking at that to see if we were missing something. We can’t find anything. It’s almost a feature of this design.” He added that SpaceX would dedicate more bandwidth to the cameras on the spacecraft during reentry to get better images of the parachute deployment.