Aeronaut wrote: I thought ‘less than friendly neighbor’ meant drastically limiting shielding mass…

For the concept that I wandered off exploring the FF cores are the thrusters. But that involves passing the alpha beams through the shielding

The only hazard in that concept would be if you were directly behind the ship… but that would get very unhealthy very fast. Thus the cost of doing business with that design goes up equally fast.

And with the power available with FF we’re no longer at the stage of trying to reach orbit by any means possible.

The MHD research means that FF-powered supersonic jets can be done for far less MWe than I had thought… but there’s a ways to go from Mach 3 to orbit.