Artemis to Roll Back to VAB

On Friday, we covered that the Artemis Wet Dress Rehearsal never completed and the next step  was uncertain.  On Saturday, the agency held a teleconference to discuss the progress and announced they will roll the vehicle back to the VAB.  

The decision comes after three tries during the last two weeks. Each fueling attempt was scuttled by one or more technical issues with the rocket, its mobile launch tower, or ground systems that supply propellants and gases. During the most recent attempt, on Thursday April 14, NASA succeeded in loading 49 percent of the core-stage liquid oxygen fuel tank and 5 percent of the liquid hydrogen tank.

While this represents progress, it did not include the most dynamic portion of the test, during which the rocket is fully fueled and pressurized; and it, the ground systems, and computer systems are put into a terminal countdown when every variable is closely monitored. NASA had hoped to complete this wet dress rehearsal test to work out the kinks in the complicated launch system so that, when the rocket is rolled out later this year for its actual launch, the countdown will proceed fairly smoothly.

NASA said that they and their contractors will use the next several weeks to address the problems found during the test.  Something I hadn't read before was that some issues were found with nitrogen system contractor Air Liquide's hardware, which will have to upgrade its capabilities.  Technicians will replace the faulty check valve on the upper stage of the rocket, as well as fix a leak on the mobile launch tower's "tail service mast umbilical," a 10-meter-tall structure that provides propellant and electricity lines to the rocket on the pad.  

Under the "nothing happens quickly" rule of thumb, it seems like a reasonable guess to say it will take them a week to prepare and roll the mobile launch tower and Artemis back to the VAB.  Under the same assumption, I expect the work to take the month of May.  

At some point, NASA has to decide if they roll Artemis back out to the pad and complete the WDR successfully, roll it back to the VAB for some tasks typically done between WDR and then roll it to the pad for the third time to launch, or if they take a riskier approach and roll it to the pad essentially ready to fly.  If they do that, once the WDR passes, they could conceivably launch within days.  

There's a gotcha here.  The "tasks typically done" in the VAB between WDR and launch include arming the flight termination system or FTS.  All vehicles are required to carry such a system to destroy the vehicle if it threatens other people or places, and everyone who has listened to launch coverage of Falcon 9s or other launches have heard call-outs about the FTS being armed or being made safe.  

During a teleconference on Friday, Artemis Launch Director Charlie Blackwell-Thompson confirmed that there is a 20-day timeline once the flight safety system is armed. (This is a range safety mechanism used by all orbital rockets that destroys the booster in case it veers off course.) After the system is activated, it will take about a week to make final preparations in the Vehicle Assembly Building and a week to roll to the launch pad and make preparations there. That would leave just a single week for a fueling test, recycling of commodities, and perhaps one or two launch attempts before the 20-day window closes.

With a 20-day window, the system would have to be virtually flawless and it seems like a large bet they could approach flawless.  Which implies the earliest they could possibly launch the unmanned test flight would be around the start of July, but from August into the fall might be more realistic.  

Artemis SLS rollout on March 17th.  You can just mentally move the stack left (back into the VAB) or right (back out to pad 39B) and use the same image for the next few months.