[![enter image description here][1]][1]


first of all this code is not mine i am trying to understand how the equation for m_u works. this comes from a master thesis called *Trajectory design for a Titan mission using
the Direct Fusion Drive* as shown it is a different variant of the tsiolkovsky rocket equation i believe for the propellant weight on the rocket in this case it is being used to plot the change in delta V relevant to mission length so Delta-t is total number of seconds in 0 to 15 years. can anyone link to elsewhere this equation can be found

to make it clearer the equation is [![enter image description here][2]][2]


  [1]: https://i.sstatic.net/3fHtR.png
  [2]: https://i.sstatic.net/piCJa.png

where Ve is (Isp * Gravity constant)