NASA moves Artemis II static test to Saturday

Nothing is quite as vivid a reminder that the earliest possible launch date for Artemis II is near as realizing that the checkout of the Artemis II SLS launch vehicle is nearly to complete and going into the final tests before launch. 

The rocket's last major hurdle before launch is the SLS wet dress rehearsal, and this week NASA moved that test forward to Saturday, January 31. The previous schedule was "no later than February 2nd." 

If the vehicle passes that test, and the smoother the test goes, the more likely it becomes that Artemis II launches Friday night, in the two hour launch window of 9:41 to 11:41 PM. 

"Engineers have remained on track or ahead of schedule as they work through planned activities at the launch pad and are getting ready to conduct a wet dress rehearsal, leading up to a simulated 'launch,'" the agency wrote in an update on Monday (Jan. 26).
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The upcoming wet dress rehearsal will officially kick off about two full days ahead of its simulated T-0 liftoff time, as launch teams begin tending their stations. The most critical portion of the test will take place on Saturday, when cryogenic fuel loading of the rocket's two main stages will commence. In total, SLS will take on more than 700,000 gallons (2,650,000 liters) of cryogenic propellant and weigh approximately 5.75 million pounds (about 2.6 million kilograms) once fully fueled.

The goal will be to run the SLS mission clock down to T-33 seconds, the point at which the rocket's computer would take over system monitoring during an actual launch attempt. If all goes according to plan, after SLS' T-33 second countdown hold, mission operators will reset the simulated clock to T-10 minutes and run it down a second time, to T-30 seconds.

NASA plans to put SLS and ground teams through their paces during the test, with several "runs" during the T-10 minute terminal count period to assess operating procedures for holding, resuming and recycling the mission clock, according to the agency's update.

NOTE: Stating the start time of the test as "two full days ahead of its simulated" liftoff time means tonight, Jan. 29. at 9:41 PM Eastern. 

The Artemis I wet dress rehearsal was plagued by fuel leaks - I remember asking rhetorically if NASA had forgotten everything about working with liquid hydrogen. Aside from the fueling leaks there were other issues that forced SLS to be rolled back to the Vehicle Assembly Building (VAB) three times for repairs. NASA officials have voiced confidence that they have solved those issues, but even a perfect wet dress rehearsal may not result in a Feb. 6 launch. I think we can confidently say that if they have to roll the SLS back to the VAB at all, even once, Feb. 6th is out. 

NASA has published the same sort of calendar of acceptable launch days for this launch as they did for Artemis I. Note that there are only 5 days available per month - except for April, which seems to have pulled a day out of May. 

Since the vast majority of you readers aren't here near the KSC, I'm betting you aren't aware that our weather forecasts for this weekend are not just record-breaking, they're pretty much completely record shattering. Granted this forecast is a few days in advance, our overnight low temperature forecast, 40-ish miles south of Pad 39B is that Sunday morning will be 25. The existing record low for February 1 is 32 degrees. Monday morning's forecast of 30 is lower than the February 2nd record of 33. About the accuracy of the forecasts, I feel I should point out for both yesterday and today, the forecast low was 40 degrees but the actual temperature was 36. 

The point of this side note is that the SLS has components that can be affected by these unusually low temperatures. NASA says they've taken preliminary steps to safeguard the rocket from the inclement weather. The big picture is that if the launch actually goes Friday night in that launch window, the temperatures appear to be in the range of 50 +/- "a few". 

That out of the way, while missions can always be changed or aborted, the broad brush look at the mission is that it will last 10 days. It will spend time in Earth orbit to verify important systems that haven't been tested yet, like the crew's air supply, before doing its translunar orbit injection. The published look at the mission has been tweaked a bit to look like this:

Not visible in this is that in the lunar space, it could be a Near Rectilinear Halo Orbit (NRHO) that is something core to the Artemis approach to getting to the moon. It's not mentioned here. That NRHO could take the four astronauts farther from Earth than any human has ever been - depending on launch time and how well the mission unfolds.

A major difference between this mission and Apollo 8, for example, this is a trajectory that can't allow Artemis II to go into orbit around the moon - it's called a free-return trajectory. 

The main purpose of the mission, though, is to thoroughly check out the Artemis hardware and verify it can do everything required for the lunar landing mission, Artemis III, currently estimated to be in 2028.