A momentum limit for electromagnetic railguns

It is postulated that there is a required velocity of magnetic flux into a plasma-armature railgun to keep the armature from expanding toward the breech and thereby changing the nature of the forward-going force. Data from several guns confirmed this hypothesis, provided the required flux velocity increases with the square of the linear current density. This leads to the conclusion that these guns have a momentum limit while they are operating as true electromagnetic launchers. That limit is derived. High-performance railguns reach this limit during current rise, and most of their momentum comes from a hybrid phase. The hybrid phase has a pressure limitation at high velocity similar to electrothermal, light-gas, and powder guns. The 6 km/s velocity limit is explained by this pressure limitation