The problem with the 'newtonian physics' for the impulse drive, TGT, is that Roddenberry ALSO says that they're fusion engines, and fusion doesn't work that way.
Where did Roddenberry state that the impulse engines were fusion-powered? In TMoST, Whitfield and Roddenberry
tell us the impulse drive can run for a month before their fuel is exhausted, but nothing about their power source. I vaguely remember reading them described as "atomic powered" and the sheet accompanying the AMT model said they employed the same principal of propulsion as "rockets". But I don't recall ever seeing Roddenberry
describe the original ship as having a fusion-powered impulse drive.