Superconducting ship wrecked

One of the dangers of being a science writer is that I'm not a working scientist in the fields I write about, and though I try to make sure my facts are up to scratch, there will always be errors that slip through the net. Luckily, readers are good at spotting these, and email me to point them out.

I've had an email from a reader who say that he enjoyed reading my book on quantum physics and its applications, The Quantum Age, but identified an error when I was talking about the use of electric motors in ships.

In the book, I said existing electric motors simply can’t be scaled up to the size required to power a full-sized ocean-going ship. I had misread an Institute of Physics report, saying that its not possible to have low transmission loss motors at this scale, not that it’s not possible to have them at all. As my correspondent pointed out:
Electric motors have been used for ship propulsion since the 19th century.
  • In 1987 the QE2 was fitted with 2 x 44MW electric motors driving variable pitch propellers. The motors were built at the GEC factory in Rugby .
  • The Type 45 destroyers for the Royal Navy all have integrated full electric propulsion (IFEP) as do the new Queen Elizabeth Class aircraft carriers.
  • Most cruise liners use podded electric motors with full azimuthing capability to provide both propulsion and steering. 
  • The QM2 has 4 x 21.5MW podded electric motors built by ALSTOM. 
  • All submarines use electric propulsion.
  • In Rugby we developed a 5MW superconducting motor, and made a contribution to the development of a 36MW superconducting motor for the US Navy for ship propulsion.
What I should have said is that existing electric motors suffer from high transmission losses when scaled up to the size required for a full-sized ocean-going ship.

Thanks again to my correspondent for pointing this out.