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N_Molson

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However, the craziest of those attempts are Ares I and Boeing SRB-X, whose nasty g-forces make them unreliable for both crew and cargo.

Well SLS is nothing like that, the ascent profile is nothing really out of the ordinary. A very "classic" rocket, and that's why I like it. Maybe too classic, we'll see. That matches my personal representation of what is a rocket : expandable inline stack with boosters.
 

Thunder Chicken

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Not official, but not a surprise either:


If they are just getting to the shake tests now there is no way they are flying in 2021 without the use of a magic wand. On paper they are still targeting a launch date of NET November 26, 2021 which is Black Friday after Thanksgiving. KSC is struggling with COVID personnel issues (thanks DeSantis! /s), weather, and upcoming holidays.
 

N_Molson

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At this point, I'd say if they manage to perform a successful full dress rehersal test with engines firing nominally before the end of the year, it won't be that bad...
 

Thunder Chicken

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I don't believe they are doing a static fire on the pad - that was the reason for the full-duration Green Run at Michaud. They are going to do the shake test, pressure test the tanks, do the closeouts. That's still a lot of punch list items and engineering analysis to work through, and the odds of it being a gremlin-free process are probably zilch. They're not pounding through all that in 3 months.

EDIT: I don't believe deliberate static fires were ever done on the full Saturn V or shuttle stacks either. They basically utilized hold-downs and sensors verifying engine operation before blowing the bolts and sending it.
 
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DaveS

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I don't believe they are doing a static fire on the pad - that was the reason for the full-duration Green Run at Michaud. They are going to do the shake test, pressure test the tanks, do the closeouts. That's still a lot of punch list items and engineering analysis to work through, and the odds of it being a gremlin-free process are probably zilch. They're not pounding through all that in 3 months.
Correction, the Green Run was at Stennis Space Center, Michoud Assembly Facility (MAF) is the manufacturing facility of the Core Stage. The modal test is just a shake test with the tanks at the standard processing pressure (no way to pressurize the tanks in VAB). It will conclude with the Umbilical Release and Retract Test (URRT) which will see the umbilical arms of the Mobile Launcher release and swing away like they would for would for an actual launch.

Once that is done, the stand-in Orion Stage Adapter (OSA) and Orion Mass Simulator will be destacked and removed from the vehicle and replaced with the actual flight hardware. Once the stacking of the actual flight hardware has been completed along with re-mating of the ML umbilicals, the entire ML+SLS stack will head out to 39B for a full up tanking test (also called a Wet Dress-Rehearsal, WDR) before heading back to the VAB for final close-outs and Flight Termination System Linear Shape Charge (FTS LSC) installations ahead of the rollout to 39B for the actual launch countdown.
 

Kyle

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The WDR really seems like an unnecessary step. Wish they'd remove the mass simulator & put Orion/LAS straight into a launch attempt and, should a problem arise, roll it back to the VAB. Else if no problems arise, proceed into terminal count. Reduces the steps to launch while reducing the amount of time SLS will be spending on the launch pad exposed to the elements (a poorly timed hail storm or EMP causing could delay this until late-2022).
 

DaveS

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The WDR really seems like an unnecessary step. Wish they'd remove the mass simulator & put Orion/LAS straight into a launch attempt and, should a problem arise, roll it back to the VAB. Else if no problems arise, proceed into terminal count. Reduces the steps to launch while reducing the amount of time SLS will be spending on the launch pad exposed to the elements (a poorly timed hail storm or EMP causing could delay this until late-2022).
The WDR will be with the full up flight vehicle. The OSA and OMS will be removed after the URRT which happens in the VAB prior to rollout for the WDR. While they're deconfiguring from the modal test and URRT, the OSA and OMS will be destacked and replaced by the real OSA and Orion with the LAS. The LAS is currently being installed on the EM-1 Orion in the LASF right now.

And hail isn't an issue to the vehicle given that A)The CM is protected by the CMA and LAS Boost Protective Cover and B)Orion is located above any debris sources. Also, pad stay time for launch is only planned to be a week. Any serious technical problems will result in a rollback to the VAB as there's no access to change out hardware at the pad.
 
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