I'm assuming (as is megameklab) that it requires an engine big enough to correspond to a movement rate of 0.
Which for a tech E fusion engine would be 0.025*(4 + (0*0))*.75*200=15.
(Where 0.025 is the base engine value, (4+(0*0)) is the movement factor, 0.75 is the weight multiplier for a tech E fusion engine, and 200 is the total vehicle mass)
full disclosure, I designed the tractor entirely in mml, but I could only partially make the trailer in that program, as it doesn't yet have an option for putting a subcapital weapon on a support vehicle, so the trailer readout is hand edited.