Imagine you have a sealed cylindrical vessel with a given radius with a compressed gas inside. Let's give some numbers, 5 cm radius and 100 atm pressure. You poke a hole in the vessel and the gas will flow out, propelling the vessel in the opposite direction with a given force. Intuition tells me that this force depends on the hole size. Suppose the pressure does not change as time goes by, what's the optimal hole size to deliver the best acceleration ?