Escape speed-square is twice circular speed-square at each checked radius. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.
highlighted = computed this step
Escape square doubles circular square at radius 4
Circular speed-square 4 doubles to escape speed-square 8.
2⋅4=8,ϵ=0
Escape square doubles circular square at radius 2
Circular speed-square 8 doubles to escape speed-square 16.
2⋅8=16,ϵ=0
Escape square doubles circular square at radius 1
Circular speed-square 16 doubles to escape speed-square 32.
2⋅16=32,ϵ=0
Escape square stays twice circular square at every checked radius
Changing radius changes both circular and escape speed-square. The zero-energy boundary stays closed because escape speed-square is twice circular speed-square.