Hi everyone!

I am trying to model a spacecraft and its propulsion system. Assuming that the spacecraft have four thrusters, and every thruster has its unique fuel tank. So, what I need to achieve is determine the fuel mass inside the fuel tanks after a maneuver. I have tried to achieve it by defining four finite thrust maneuvers at the same time in the same direction. The only difference between these maneuvers are their ISP. The problem is, I do not know how to reach the total mass consumption for every individual maneuver. In conclusion, how can I get the mass depletion for after every maneuver which have the same start time, burn duration and direction, but the isp.

Thank in advance,

Uzay