As written, it divides a planets atmosphere into zones ... and the PCs must move up/down through the zones ... with limited speeds to avoid taking "friction" damage (directly to their hull, bypassing shields).
While it limits the speeds it makes no mention of how much movement is needed to move between these "atmospheric zones".
Is it 5 hexes? 10 hexes? or do they simply advance up/down one zone per turn regardless of said speed??
I realize the answer might be more complex like "depends on the size of the planet and the type of atmosphere." sure, but how about an example??
Without distance involved, the max speed is irrelevant and pointless. Why bother moving faster than the listed Max Safe Speed ... if distance has no bearing?!
With the "5 distinct layers of atmosphere" ... how can we calculate a "fair" value that would work?
Perhaps it could be broken down by the density of the atmosphere;
1 layer - no atmosphere, so only need to escape the "lowest" (only) layer.
4 layer - thin atmosphere
5 layers - normal or thick atmospheres
I realize this is all overly simplified and excessively abstracted ... but there must be an intended use for this mechanic for it to be included.
For fairness to my players, I need to define the distance to travel and/or time to orbit ... in a consistent way ... to simulate the players escaping from a thin atmosphere while being chased by a horde of pirate ships.
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For simplicity, I tried using a default of "5 hexes per layer" ... so it took a minimum of 11 turns to escape into orbit before they could accelerate to full speed and loose their pursuers.