2018-07-05 18:36:06 UTC
Gear down the drive and fit them tugs with yuge 30 m diameter props or the propulsion efficiency will result in unnecessary burning of megatons of carbon!
Is this a crank idea? Run the nubbers:
The iceberg is 200 X the size of the largest ship. Ignore efficiencies of scale (possibly to his favor), ignore the horrifically low propulsion efficiency from undersized props and ignore the lousy hydrodynamics of an iceberg (not to his favor).
Assume a 20,000,000 kw engine could get it moving at 20 knots.
Assume the 2 tugs + 1 ship with conventional props only put out 100,000 kw.
By the propeller rule the speed drops by (100,000/20,000,000)^0.33 = 0.17 or 83%
Or 3.4 knots ignoring the horrifically low propulsion efficiency.
Supposing you don't want to ignore the horrifically low propulsion efficiency?
The props were designed to go 3 - 5 times faster than this at maximum propulsion efficiency. Iterate once or twice and the horrifically low propulsion efficiency drops the speed down to maybe 1/2 knot.
He can use ocean currents _if_ they aren't too fast, _if_ he can get in and out of the currents with a top speed of half a knot.
Kind of like how they tell you at the beach to swim perpendicular to a rip tide. Half a knot might not be fast enough before you can no longer see land.