The problem is less our ability to make the drives themselves have a high TWR (thrust to weight ratio) so much as that the power generation necessarily required

The problem is less our ability to make the drives themselves have a high TWR (thrust to weight ratio) so much as that the power generation necessarily required to run them is very heavy. See here: http://hopefullyintersting.blogspot.com/2015/03/rockets-electric-propulsion.html http://hopefullyintersting.blogspot.com/2015/03/rockets-elec...