Inside the fusion reactor behind their compartment, multiple toroids of plasma formed, began to spin, merge, then intersected and with a sudden roaring crackle burst into a star hot fusion reaction. Electrostatic grids bled off the energy into hungry batteries and uncharged coils, power greedy drives sucking at the immediate abundance of energy, ready to push the forty metre long octagonal cylinder into a higher orbit.
It's just a rough idea of course, but what I conceive is rather like having a Farnsworth type central chamber with a number of accelerator, or Tokamak style coils feeding 'streams' of accelerated plasma into and out of it.
The mathematics of such a device are beyond me, since I am just a wannabe Science Fiction writer with several MSS currently sitting in a number of publishers 'slush piles' awaiting reading. Sometimes in my gloomier moments I wonder if they have not already been put in file 13.