Art: Solid candidate for Best in Show.
Writing: Strikes the right balance between clarity and vibes. Pretty original setup and fits well in the Mothership universe. Plot-wise, given how sus Delphi is acting and the likelihood that the players are keeping an eye on her, I feel like there needs to be an opportunity to detect and thwart the bomb plot. It also seems weird that the drill is still going after the Reactor has been ruptured, but I guess it's just a fuel line leak or something. It would be nice if there was a way to separate the geographical, Ymir-related stuff that's guaranteed to happen from crew-related subplots that could be thwarted/modified/interfered with/participated in, but I realize that's hard in this limited format.
Game Design: I realize this is kind of personal preference, but I'm not big on "Thing happens at you, make this roll" as a design structure. I strongly prefer that players choose how to respond to a situation and then rolls happen or not based on that decision. That said, I know there's not a lot of space to cover contingencies, and a good Warden will take this and turn each of those scenarios into an interactive scene that may or may not culminate in the given roll (or a different one). I worry that a novice group would take it too literally and just make the roll and move on to the next thing, in which case the players aren't actually doing anything for most of the adventure, just having a story told to them.
Theme: I stupidly didn't Google "Ymir" and was going to give you a lower mark for only doing something that feels like it could be a myth. But you did a myth, good job. Rating revised to a five after reading the other comments.
Layout: Full marks, but one note: I find the map a little hard to read at a glance, because the numbers, structural lines, and interior details are all the same color and of similar weight. I would suggest creating some visual differences between the numbers, walls/ladders/doors, and everything else.
Utility: Full marks because it can be run out of the box for a group that's okay with a linear narrative where stuff happens at you. For me, there would be prep in that I'd want to do some planning ahead to fill in detail for the various scenes and do some contingency planning for if the players decide to intervene with Delphi before she's gone completely off the rails.
Favorability: Should easily be in the top five and possibly win in some individual categories. I dislike linear narratives, but there's enough to work with that I could just make it nonlinear when running it myself.