We need radially mounted engine between thrust and weight of 24-77 "Twitch" Liquid Fuel Engine and Mk-55 "Thud" Liquid Fuel Engine
Electric and internal combustion engines for ships and submarines.
With all that hype around hyperloop IMO we should have tracks, trains and hyperloop pressurised tunnel.
I know part counts, but tunnel and tracks could be permanently placed on a desired location, so physics wouldn't apply to it. Of course we should be able to demolish it.