The Russians did this with a sort of under water missile. Problem was it was point and shoot. It couldn’t maneuver well. Seems putting people on something like that is suicidal.
I’m no scientist but wouldn’t inertia have an influence, not to mention gravity? Going from “zero” mph to in excess of 3000 mph has got to have some effect.
Likely not at all. It didn't need to. The entire point was to deliver a nuclear weapon just beyond the lethal radius of the SSBN that fired it, straight down the path of the incoming torpedo that they just detected.
That wouldn’t bother the chinese. They have billions to choose from.