Trump said that referring to electromagnets.

But the news ran with it as "fucking magnets, how do they work?" to own drumpf.

I could tell you about aircraft carriers, where they use electric catapults. They couldn’t go to the steam, which works better for about 1/100th the price, you know? The electric catapult, you know that story? I could tell you about the elevators on a tremendous carrier, the Gerald Ford, and they decided not to use hydraulic like the John Deere tractor, they decided to use magnets, “we’re gonna use magnets!” to lift up the elevators with seven planes. We need them fast, these massive elevators. They used magnets, they wanted to try it for the first time. This was a ship that was supposed to cost 2.5 billion, it cost 19 billion and didn’t work, and still doesn’t work right.

They had a $900 million cost over on these stupid electric catapults that didn’t work. They had almost a billion dollar cost over on the magnetic elevators. Think of it, magnets. Now all I know about magnets is this, give me a glass of water, let me drop it on the magnets, that’s the end of the magnets. Why didn’t they use John Deere? Why didn’t they bring in the John Deere people? Do you like John Deere? I like John Deere

The catapult system hasn't worked after over a decade of tweaks and has ended up costing 10x the initial bid. It's also at below 5% of it's original reliability requirement, eg it breaks 20x as often as it's supposed to. I'm not sure how shit the electromagnet elevators are, but the answer is probably "very".