Yea certainly looks non-zero to me.

He gave another equation for Ve in message 34741, and allowed Po=Pe, but I'm not sure you can do that. For any nozzle shape there'll be more pressure on the inside than the outside - and thus some gas expansion. Without a pressure difference there wouldn't be any flow.

But we'll see better when he returns.

Anyway, how does this show that momentum isn't conserved? Or how does it show that you can get sustained propulsion of a closed cylinder?