Having a cylindrical iron container with wall thickness of 20 cm, and a total weight of 50 tons when filled with its cargo, how would you be able to calculate its required voltage and current input in a vertical railgun system, with a needed exit velocity of 12km/s? For example, the rail diameter would be 80cm. There would be 4 in total, 2 positive terminals and 2 negative terminals, connected to each other independently, through an 'insulated channel', so it doesn't make contact with the container itself.
Also, is there any formula that can be used for calculating current and voltage required for a certain exit velocity, or exit speed having a certain current and voltage input? Would it depend on many other factors, if so, which?
If any more specifications would be required for such a calculation, please make some as an example, it would be very helpful.